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# Chapter 2: Loads on Buildings and Structures
2.1
Introduction
2.1.1
Scope
This Chapter specifies the minimum design forces including dead load, live load,
wind and earthquake loads, miscellaneous loads and their various combinations.
These loads shall be applicable for the design of buildings and structures in
conformance with the general design requirements provided in Chapter 1.
2.1.2
Limitations
Provisions of this Chapter shall generally be applied to majority of buildings and
other structures covered in this Code subject to normally expected loading
conditions. For those buildings and structures having unusual geometrical shapes,
response characteristics or site locations, or for those subject to special loading
including tornadoes, special dynamic or hydrodynamic loads etc., site-specific or
case-specific data or analysis may be required to determine the design loads on them.
In such cases, and all other cases for which loads are not specified in this Chapter,
loading information may be obtained from reliable references or specialist advice
may be sought. However, such loads shall be applied in compliance with the
provisions of other Parts or Sections of this Code.
2.1.3
Terminology
The following definitions apply only to the provisions of this Chapter:
ALLOWABLE
STRESS DESIGN
METHOD (ASD)
A method for proportioning structural members such that
the maximum stresses due to service loads obtained from an
elastic analysis does not exceed a specified allowable value.
This is also called Working Stress Design Method (WSD).
APPROVED
Acceptable to the authority having jurisdiction.
BASE
The level at which the earthquake motions are considered to
be imparted to the structures or the level at which the
structure as a dynamic vibrator is supported.
BASE SHEAR
Total design lateral force or shear due to earthquake at the
base of a structure.
BASIC WIND
SPEED, V
Three-second gust speed at 10 m above the ground in
Exposure B (Sec 2.4.6.3) having a return period of 50 years.
BEARING WALL
SYSTEM
A structural system without a complete vertical load
carrying space frame.
BRACED FRAME
An essentially vertical truss system of the concentric or
eccentric type provided to resist lateral forces.
BUILDING,
ENCLOSED
A building that does not comply with the requirements for
open or partially enclosed buildings.
BUILDING
ENVELOPE
Cladding, roofing, exterior walls, glazing, door assemblies,
window assemblies, skylight assemblies, and other
components enclosing the building.
BUILDING, LOW-
RISE
Enclosed or partially enclosed buildings that comply with
the following conditions
1. Mean roof height h less than or equal to 18.3 m.
2. Mean roof height h does not exceed least horizontal
dimension.
BUILDING, OPEN
A building having each wall at least 80 percent open. This
condition is expressed for each wall by the equation ≥
0.8 where,
= total area of openings in a wall that receives positive
external pressure (m2).
= the gross area of that wall in which is identified
(m2).
BUILDING,
PARTIALLY
ENCLOSED
A building that complies with both of the following
conditions:
3. The total area of openings in a wall that receives positive
external pressure exceeds the sum of the areas of openings
in the balance of the building envelope (walls and roof) by
more than 10 percent.
4. The total area of openings in a wall that receives positive
external pressure exceeds 0.37 m2 or 1 percent of the area of
that wall, whichever is smaller, and the percentage of
openings in the balance of the building envelope does not
exceed 20 percent.
These conditions are expressed by the following equations:
1. > 1.10
2. > 0.37m or > 0.01, whichever is smaller, and
/ ≤0.20
Where, , are as defined for open building
= the sum of the areas of openings in the building
envelope (walls and roof) not including , in m2.
= the sum of the gross surface areas of the building
envelope (walls and roof) not including , in m2.
BUILDING,
SIMPLE
DIAPHRAGM
A building in which both windward and leeward wind loads
are transmitted through floor and roof diaphragms to the
same vertical MWFRS (e.g., no structural separations).
BUILDING
FRAME SYSTEM
An essentially complete space frame which provides
support for gravity loads.
BUILDING OR
OTHER
STRUCTURE,
FLEXIBLE
Slender buildings or other structures that have a
fundamental natural frequency less than 1 Hz.
BUILDING OR
OTHER
STRUCTURE,
REGULAR
SHAPED
A building or other structure having no unusual geometrical
irregularity in spatial form.
BUILDING OR
OTHER
STRUCTURES,
RIGID
A building or other structure whose fundamental frequency
is greater than or equal to 1 Hz.
CAPACITY
CURVE
A plot of the total applied lateral force, , versus the lateral
displacement of the control point, , as determined in a
nonlinear static analysis.
COMPONENTS
AND CLADDING
Elements of the building envelope that do not qualify as
part of the MWFRS.
CONTROL POINT
A point used to index the lateral displacement of the
structure in a nonlinear static analysis.
CRITICAL
DAMPING
Amount of damping beyond which the free vibration will
not be oscillatory.
CYCLONE
PRONE REGIONS
Areas vulnerable to cyclones; in Bangladesh these areas
include the Sundarbans, southern parts of Barisal and
Patuakhali, Hatia, Bhola, eastern parts of Chittagong and
ঈড়্থীং ইধুধৎ
DAMPING
The effect of inherent energy dissipation mechanisms in a
structure (due to sliding, friction, etc.) that results in
reduction of effect of vibration, expressed as a percentage
of the critical damping for the structure.
DESIGN
ACCELERATION
RESPONSE
SPECTRUM
Smoothened idealized plot of maximum acceleration of a
single degree of freedom structure as a function of structure
period for design earthquake ground motion.
DESIGN
EARTHQUAKE
The earthquake ground motion considered (for normal
design) as two-thirds of the corresponding Maximum
Considered Earthquake (MCE).
DESIGN FORCE, F Equivalent static force to be used in the determination of
wind loads for open buildings and other structures.
DESIGN
PRESSURE, p
Equivalent static pressure to be used in the determination of
wind loads for buildings.
DESIGN
STRENGTH
The product of the nominal strength and a resistance factor.
DIAPHRAGM
A horizontal or nearly horizontal system of structures acting
to transmit lateral forces to the vertical resisting elements.
The term "diaphragm" includes reinforced concrete floor
slabs as well as horizontal bracing systems.
DUAL SYSTEM
A combination of a Special or Intermediate Moment
Resisting Frame and Shear Walls or Braced Frames
designed in accordance with the criteria of Sec 1.3.2.4
DUCTILITY
Capacity of a structure, or its members to undergo large
inelastic deformations without significant loss of strength or
stiffness.
EAVE HEIGHT, h
The distance from the ground surface adjacent to the
building to the roof eave line at a particular wall. If the
height of the eave varies along the wall, the average height
shall be used.
ECCENTRIC
BRACED FRAME
(EBF)
A steel braced frame designed in conformance with Sec
10.20.15.
EFFECTIVE
WIND AREA, A
The area used to determine GCp. For component and
cladding elements, the effective wind area as mentioned in
Sec 2.4.11 is the span length multiplied by an effective
width that need not be less than one-third the span length.
For cladding fasteners, the effective wind area shall not be
greater than the area that is tributary to an individual
fastener.
EPICENTRE
The point on the surface of earth vertically above the focus
(point of origin) of the earthquake.
ESCARPMENT
Also known as scarp, with respect to topographic effects in
Sec 2.4.7, a cliff or steep slope generally separating two
levels or gently sloping areas (see Figure 6.2.4).
ESSENTIAL
FACILITIES
Buildings and structures which are necessary to remain
functional during an emergency or a post disaster period.
FACTORED
LOAD
The product of the nominal load and a load factor.
FLEXIBLE
DIAPHRAGM
A floor or roof diaphragm shall be considered flexible, for
purposes of this provision, when the maximum lateral
deformation of the diaphragm is more than two times the
average storey drift of the associated storey. This may be
determined by comparing the computed midpoint in-plane
deflection of the diaphragm under lateral load with the
storey drift of adjoining vertical resisting elements under
equivalent tributary lateral load.
FLEXIBLE
ELEMENT OR
SYSTEM
An element or system whose deformation under lateral load
is significantly larger than adjoining parts of the system.
FREE ROOF
Roof (monoslope, pitched, or troughed) in an open building
with no enclosing walls underneath the roof surface.
GLAZING
Glass or transparent or translucent plastic sheet used in
windows, doors, skylights, or curtain walls.
GLAZING,
IMPACT
RESISTANT
Glazing that has been shown by testing in accordance with
ASTM E1886 and ASTM E1996 or other approved test
methods to withstand the impact of wind-borne missiles
likely to be generated in wind-borne debris regions during
design winds.
HILL
With respect to topographic effects in Sec 2.4.7, a land
surface characterized by strong relief in any horizontal
direction (Figure 6.2.4).
HORIZONTAL
BRACING
SYSTEM
A horizontal truss system that serves the same function as a
floor or roof diaphragm.
IMPACT
RESISTANT
COVERING
A covering designed to protect glazing, which has been
shown by testing in accordance with ASTM E1886 and
ASTM E1996 or other approved test methods to withstand
the impact of wind-borne debris missiles likely to be
generated in wind-borne debris regions during design
winds.
IMPORTANCE
FACTOR, WIND
LOAD
A factor that accounts for the degree of hazard to human
life and damage to property.
IMPORTANCE
FACTOR,
EARTHQUAKE
LOAD
It is a factor used to increase the design seismic forces for
structures of importance.
INTENSITY OF
EARTHQUAKE
It is a measure of the amount of ground shaking at a
particular site due to an earthquake
INTERMEDIATE
MOMENT
FRAME (IMF)
A concrete or steel frame designed in accordance with Sec
#### 8.3.10 or Sec 10.20.10 respectively.
LIMIT STATE
A condition in which a structure or component becomes
unfit for service and is judged either to be no longer useful
for its intended function (serviceability limit state) or to be
unsafe (strength limit state).
LIQUEFACTION
State in saturated cohesionless soil wherein the effective
shear strength is reduced to negligible value due to pore
water pressure generated by earthquake vibrations, when
the pore water pressure approaches the total confining
pressure. In this condition, the soil tends to behave like a
liquid.
LOAD EFFECTS
Forces, moments, deformations and other effects produced
in structural members and components by the applied loads.
LOAD FACTOR
A factor that accounts for unavoidable deviations of the
actual load from the nominal value and for uncertainties in
the analysis that transforms the load into a load effect.
LOADS
Forces or other actions that arise on structural systems from
the weight of all permanent constructions, occupants and
their
possessions,
environmental
effects,
differential
settlement, and restrained dimensional changes. Permanent
loads are those loads in which variations in time are rare or
of small magnitude. All other loads are variable loads.
MAGNITUDE OF
EARTHQUAKE
The magnitude of earthquake is a number, which is a
measure of energy released in an earthquake.
MAIN WIND-
FORCE
RESISTING
SYSTEM
(MWFRS)
An assemblage of structural elements assigned to provide
support and stability for the overall structure. The system
generally receives wind loading from more than one
surface.
MAXIMUM
CONSIDERED
EARTHQUAKE
(MCE)
The most severe earthquake ground motion considered by
this Code.
MEAN ROOF
HEIGHT, h
The average of the roof eave height and the height to the
highest point on the roof surface, except that, for roof
angles of less than or equal to 10o, the mean roof height
shall be the roof heave height.
MODAL MASS
Part of the total seismic mass of the structure that is
effective in mode k of vibration.
MODAL
PARTICIPATION
FACTOR
Amount by which mode k contributes to the overall
vibration of the structure under horizontal and vertical
earthquake ground motions.
MODAL SHAPE
COEFFICIENT
When a system is vibrating in a normal mode, at any
particular instant of time, the vibration amplitude of mass
expressed as a ratio of the vibration amplitude of one of
the masses of the system, is known as modal shape
coefficient
MOMENT
RESISTING
FRAME
A frame in which members and joints are capable of
resisting lateral forces primarily by flexure. Moment
resisting frames are classified as ordinary moment frames
(OMF), intermediate moment frames (IMF) and special
moment frames (SMF).
NOMINAL
LOADS
The magnitudes of the loads such as dead, live, wind,
earthquake etc. specified in Sections 2.2 to 2.6 of this
Chapter.
NOMINAL
STRENGTH
The capacity of a structure or component to resist the
effects of loads, as determined by computations using
specified material strengths and dimensions and formulas
derived from accepted principles of structural mechanics or
by field tests or laboratory tests of scaled models, allowing
for modelling effects and differences between laboratory
and field conditions.
NUMBER OF
STOREYS (n)
Number of storeys of a building is the number of levels
above the base. This excludes the basement storeys, where
basement walls are connected with ground floor deck or
fitted between the building columns. But, it includes the
basement storeys, when they are not so connected.
OPENINGS
Apertures or holes in the building envelope that allow air to
flow through the building envelope and that are designed as
ুড়ঢ়বহচ্ ফঁৎরহম ফবংরমহ রিহফং ধং ফবভরহবফ নু:যবংব ঢ়ৎড়ারংরড়হং.
ORDINARY
MOMENT
FRAME (OMF)
A moment resisting frame not meeting special detailing
requirements for ductile behaviour.
PERIOD OF
BUILDING
Fundamental period (for 1st mode) of vibration of building
for lateral motion in direction considered.
P-DELTA EFFECT
It is the secondary effect on shears and moments of frame
members due to action of the vertical loads due to the
lateral displacement of building resulting from seismic
forces.
RATIONAL
ANALYSIS
An analysis based on established methods or theories using
mathematical formulae and actual or appropriately assumed
data.
RECOGNIZED
LITERATURE
Published research findings and technical papers that are
approved.
RESISTANCE
FACTOR
A factor that accounts for unavoidable deviations of the
actual strength from the nominal value and the manner and
consequences of failure. This is also known as strength
reduction factor.
RESPONSE
REDUCTION
FACTOR
It is the factor by which the actual base shear force that
would develop if the structure behaved truly elastic during
earthquake, is reduced to obtain design base shear. This
reduction is allowed to account for the beneficial effects of
inelastic deformation (resulting in energy dissipation) that
can occur in a structure during a major earthquake, still
ensuring acceptable response of the structure.
RIDGE
With respect to topographic effects in Sec 2.4.7, an
elongated crest of a hill characterized by strong relief in two
directions (Figure 6.2.4).
SEISMIC DESIGN
CATEGORY
A classification assigned to a structure based on its
importance factor and the severity of the design earthquake
ground motion at the site.
SEISMIC-FORCE-
RESISTING
SYSTEM
That part of the structural system that has been considered
in the design to provide the required resistance to the
seismic forces.
SHEAR WALL
A wall designed to resist lateral forces acting in its plane
(sometimes referred to as a vertical diaphragm or a
structural wall).
SITE CLASS
Site is classified based on soil properties of upper 30 m.
SITE-SPECIFIC
DATA
Data obtained either from measurements taken at a site or
from substantiated field information required specifically
for the structure concerned.
SOFT STOREY
Storey in which the lateral stiffness is less than 70 percent
of the stiffness of the storey above or less than 80 percent of
the average lateral stiffness of the three storeys above.
SPACE FRAME
A three-dimensional structural system without bearing walls
composed of members interconnected so as to function as a
complete self-contained unit with or without the aid of
horizontal diaphragms or floor bracing systems.
SPECIAL
MOMENT
FRAME (SMF)
A moment resisting frame specially detailed to provide
ductile behaviour complying with the seismic requirements
provided in Chapters 8 and 10 for concrete and steel frames
respectively.
STOREY
The space between consecutive floor levels. Storey-x is the
storey below level-x.
STOREY DRIFT
The horizontal deflection at the top of the story relative to
bottom of the storey.
STOREY SHEAR
The total horizontal shear force at a particular storey (level).
STRENGTH
The usable capacity of an element or a member to resist the
load as prescribed in these provisions.
STRENGTH
DESIGN
METHOD
A method of proportioning structural members using load
factors and resistance factors satisfying both the applicable
limit state conditions. This is also known as Load Factor
Design Method (LFD) or Ultimate Strength Design Method
(USD).
TARGET
DISPLACEMENT
An estimate of the maximum expected displacement of the
control point calculated for the design earthquake ground
motion in nonlinear static analysis.
VERTICAL LOAD-
CARRYING
FRAME
A space frame designed to carry all vertical gravity loads.
WEAK STOREY
Storey in which the lateral strength is less than 80 percent
of that of the storey above.
WIND-BORNE
DEBRIS
REGIONS
Areas within cyclone prone regions located:
1. Within 1.6 km of the coastal mean high water line
where the basic wind speed is equal to or greater than
180 km/h or
2. In areas where the basic wind speed is equal to or
greater than 200 km/h.
WORKING
STRESS DESIGN
METHOD (WSD)
See ALLOWABLE STRESS DESIGN METHOD.
2.1.4
Symbols and Notation
The following symbols and notation apply only to the provisions of this Chapter:
=
Effective wind area, in m2
==
Area of open buildings and other structures either normal to the wind
direction or projected on a plane normal to the wind direction, in m2.
==
Gross area of that wall in which is identified, in m2.
==
Sum of gross surface areas of the building envelope (walls and roof)
not including , in m2
==
Total area of openings in a wall that receives positive external
pressure, in m2.
==
Sum of the areas of openings in the building envelope (walls and
roof) not including , in m2
===
Total area of openings in the building envelope in m2
==
Gross area of the solid freestanding wall or solid sign, in m2
==
Torsion amplification factor at level- .
\=
Horizontal dimension of building measured normal to wind direction,
in m.
\=
Deflection amplification factor.
=
Force coefficient to be used in determination of wind loads for other
structures
\=
Net pressure coefficient to be used in determination of wind loads for
open buildings
!
=
External pressure coefficient to be used in determination of wind
loads for buildings
=
Normalized acceleration response spectrum.
"
=
Numerical coefficient to determine building period
#
\=
Diameter of a circular structure or member in m (as used in Sec 2.4).
#
\=
Dead loads, or related internal moments and forces, Dead load
consists of: a) weight of the member itself, b) weight of all materials
of construction incorporated into the building to be permanently
supported by the member, including built-in partitions, c) weight of
permanent equipment (as used in Sec 2.7).
# #\$
Depth of protruding elements such as ribs and spoilers in m.
%
=
Total load effects of earthquake that include both horizontal and
vertical, or related internal moments and forces. The horizontal
seismic load effect shall include system overstrength factor, o, if
applicable. For specific definition of the earthquake load effect, %,
see Sec 2.5.
Eh
==
Horizontal seismic load effect when the effect of system overstrength
factor, o, is not included.
Emh
===
Horizontal seismic load effect when the effect of system overstrength
factor, o, is included.
Ev
==
Vertical effect of seismic load.
&
=
Design wind force for other structures, in N (as used in Sec 2.4).
&
=
Loads due to weight and pressures of fluids with well-defined
densities and controllable maximum heights or related internal
moments and forces (as used in Sec 2.7).
&'
==
Loads due to flood or tidal surge or related internal moments and
forces.
& , &),&
=========
Design lateral force applied to level-, -\*, or - respectively.
&+
==
Lateral forces on an element or component or on equipment supports.
,
=
Gust effect factor
,
==
Gust effect factor for MWFRSs of flexible buildings and other
structures
, !
===
Product of external pressure coefficient and gust effect factor to be
used in determination of wind loads for buildings
, !
====
Product of the equivalent external pressure coefficient and gust-
effect factor to be used in determination of wind loads for MWFRS
of low-rise buildings
, !
===
Product of internal pressure coefficient and gust effect factor to be
used in determination of wind loads for buildings
, !)
====
## Combined net pressure coefficient for a parapet
\=
Height of hill or escarpment in Figure 6.2.4 in m.
*
\=
Loads due to weight and pressure of soil, water in soil, or other
materials, or related internal moments and forces (as used in Sec 2.7)
.
=
Importance factor
./
==
Intensity of turbulence from Eq. 6.2.7
01, 0, 02 =
Multipliers in Figure 6.2.4 to obtain 0/"
=========================================
# Wind directionality factor in Table 6.2.12
Velocity pressure exposure coefficient evaluated at height 4 5 ℎ
0/
==
Velocity pressure exposure coefficient evaluated at height 4
0/"
===
# Topographic factor as defined in Sec 2.4.7
Horizontal dimension of a building measured parallel to the wind
direction, in m (as used in Sec 2.4)
====================================
Live loads due to intended use and occupancy, including loads due to
movable objects and movable partitions and loads temporarily
supported by the structure during maintenance, or related internal
moments and forces, 6 includes any permissible reduction. If
resistance to impact loads is taken into account in design, such
effects shall be included with the live load 6. (as used in Sec 2.7).
=====================================================================
Distance upwind of crest of hill or escarpment in Figure 6.2.4 to
where the difference in ground elevation is half the height of hill or
escarpment, in m.
=================
Roof live loads, or related internal moments and forces. (as used in
Sec 2.7)
========
Horizontal dimension of return corner for a solid freestanding wall or
solid sign from Figure 6.2.20, in m. (as used in Sec 2.4)
6/̌
===
Integral length scale of turbulence, in m.
Level-
=======
Floor level of the structure referred to by the subscript , e.g., 5 1
designates the first level above the base.
Level- \*
=========
Uppermost level in the main portion of the structure.
9
==
Overturning moment at level-
# :1
Reduced frequency from Eq. 6.2.14
:
=
Standard Penetration Number of soil layer
# ;)\<"
Net design wind pressure from Eq. 6.2.4, in N/m2
;)\<"2=
=======
Net design wind pressure for Exposure A at h = 9.1 m and I = 1.0
from Figure 6.2.3, in N/m2.
;!
==
Combined net pressure on a parapet from Eq. 6.2.22, in N/m2.
;
==
Net design wind pressure from Eq. 6.2.3, in N/m2.
;2=
====
Simplified design wind pressure for Exposure A at h = 9.1 m and I =
### 1.0 from Figure 6.2.2, in N/m2.
# ;
Total vertical design load at level-
# ;>
Wind pressure acting on windward face in Figure 6.2.9, in N/m2.
?
=
Background response factor from Eq. 6.2.8
@
=
Resonant response factor from Eq. 6.2.12
@
=
Response reduction factor for structural systems. (as used in Sec 2.5)
@
=
Rain load, or related internal moments and forces. (as used in Sec
2.7)
@A,@3, @B =
Values from Eq. 6.2.15
@
=
Reduction factor from Eq. 6.2.18
@)
==
Value from Eq. 6.2.13
C
=
Soil factor.
C'
==
Design Spectral Acceleration (in units of g)
CD
==
Undrained shear strength of cohesive layer
E
=
Fundamental period of vibration of structure, in seconds, of the
structure in the direction under consideration. (as used in Sec 2.5)
E
=
Self-straining forces and cumulative effect of temperature, creep,
shrinkage, differential settlement, and shrinkage-compensating
concrete, or combinations thereof, or related internal moments and
forces. (as used in Sec 2.7)
E\<
===
Effective fundamental period of the structure in the direction under
consideration, as determined for nonlinear static analysis
=
Basic wind speed obtained from Figure 6.2.1 or Table 6.2.8, in m/s.
The basic wind speed corresponds to a 3-s gust speed at 10 m above
ground in Exposure Category B having an annual probability of
occurrence of 0.02.
#
Total design base shear calculated by equivalent static analysis. (as
used in Sec 2.5)
=
Unpartitioned internal volume m3
F/̅
====
mean hourly wind speed at height 4̅, m/s.
1
==
Total applied lateral force at the first increment of lateral load in
nonlinear static analysis.
H
==
Effective yield strength determined from a bilinear curve fitted to the
capacity curve
7
===
Total design base shear calculated by response spectrum analysis
"3
===
Total design base shear calculated by time history analysis
==
Shear wave velocity of soil layer
==
Design storey shear in storey
I
=
Width of building in Figures 6.2.12, 6.2.14(a) and 6.2.14(b), and
width of span in Figures 6.2.13 and 6.2.15 in m.
I
=
Total seismic weight of building. (as used in Sec 2.5)
I
=
Wind load, or related internal moments and forces. (as used in Sec
2.7)
J
=
Distance to center of pressure from windward edge in Figure 6.2.18,
in m.
K
=
Seismic zone coefficient.
L
=
Width of pressure coefficient zone, in m.
M
=
Mean hourly wind speed factor in Eq. 6.2.16 from Table 6.2.10
MN
==
3-s gust speed factor from Table 6.2.10
O
=
Turbulence intensity factor in Eq. 6.2.7 from Table 6.2.10
P'
==
Accidental eccentricity of floor mass at level-
Q
=
Acceleration due to gravity.
QR
==
Peak factor for background response in Equations 6.2.6 and 6.2.10
QS
==
Peak factor for resonant response in Eq. 6.2.10
QT
==
Peak factor for wind response in Equations 6.2.6 and 6.2.10
# ℎ
Mean roof height of a building or height of other structure, except
that eave height shall be used for roof angle of less than or equal to
10o, in m.
ℎ\<
===
Roof eave height at a particular wall, or the average height if the
eave varies along the wall
ℎ , ℎ),ℎ
=========
Height in metres above the base to level ,-\* or - respectively
ℎ
===
Storey Height of storey (below level- )
V
=
Integral length scale factor from Table 6.2.10 in m.
\*1
===
Building natural frequency, Hz
W
=
Design pressure to be used in determination of wind loads for
buildings, in N/m2
WB
==
Wind pressure acting on leeward face in Figure 6.2.9, in N/m2
X
=
Velocity pressure, in N/m2.
X3
==
Velocity pressure evaluated at height 4 5 ℎ, in N/m2
X
=
Velocity pressure for internal pressure determination, in N/m2.
X!
==
Velocity pressure at top of parapet, in N/m2.
X/
==
Velocity pressure evaluated at height z above ground, in N/m2.
Y
=
Rise-to-span ratio for arched roofs.
Z
=
Vertical dimension of the solid freestanding wall or solid sign from
Figure 6.2.20, in m.
\[ , \[
========
Portion of I which is assigned to level and respectively
\=
Distance upwind or downwind of crest in Figure 6.2.4, in m.
===========================================================
Height above ground level, in m.
4̅
==
Equivalent height of structure, in m.
4
==
Nominal height of the atmospheric boundary layer used in this
standard. Values appear in Table 6.2.10
4\ )
====
Exposure constant from Table 6.2.10
∆'
==
Maximum allowable storey drift
∆
==
Design storey drift of storey
# ∈
Ratio of solid area to gross area for solid freestanding wall, solid
sign, open sign, face of a trussed tower, or lattice structure
∈\_
===
Integral length scale power law exponent in Eq. 6.2.9 from Table
6.2.10
Ω
==
Horizontal seismic overstrength factor from Table 6.2.19
a
=
3-s gust-speed power law exponent from Table 6.2.10
ab
==
Reciprocal of L from Table 6.2.10
aF
==
Mean hourly wind-speed power law exponent in Eq. 6.2.16 from
Table 6.2.10
c
=
Damping ratio, percent critical for buildings or other structures
=
Horizontal displacement at level-i relative to the base due to applied
lateral forces.
==
The displacement of the control point at load increment d.
e
==
The target displacement of the control point.
1
==
The displacement of the control point at the first increment of lateral
load.
H
==
The effective yield displacement of the control point determined
from a bilinear curve fitted to the capacity curve
f
=
Value used in Eq. 6.2.15 (see Sec 2.4.8.2)
f
=
Damping correction factor
g
=
Angle of plane of roof from horizontal, in degrees. (as used in Sec
2.4)
g
=
Stability coefficient to assess P-delta effects. (as used in Sec 2.5)
h
=
Adjustment factor for building height and exposure from Figures
#### 6.2.2 and 6.2.3
# i
Height-to-width ratio for solid sign
j
=
Viscous damping ratio of the structure
k l
===
Modal shape coefficient at level for mode m
2.2
Dead Loads
2.2.1
General
The minimum design dead load for buildings and portions thereof shall be
determined in accordance with the provisions of this Section. In addition, design of
the overall structure and its primary load-resisting systems shall conform to the
general design provisions given in Chapter 1.
2.2.2
Definition
Dead Load is the vertical load due to the weight of permanent structural and non-
structural components and attachments of a building such as walls, floors, ceilings,
permanent partitions and fixed service equipment etc.
2.2.3
Assessment of Dead Load
Dead load for a structural member shall be assessed based on the forces due to:
weight of the member itself,
weight of all materials of construction incorporated into the building to be
supported permanently by the member,
weight of permanent partitions,
weight of fixed service equipment, and
net effect of prestressing.
2.2.4
Weight of Materials and Constructions
In estimating dead loads, the actual weights of materials and constructions shall be
used, provided that in the absence of definite information, the weights given in
Tables 6.2.1 and 6.2.2 shall be assumed for the purposes of design.
Table 6.2.1: Unit Weight of Basic Materials
Material
Unit Weight
(kN/m3)
Material
Unit Weight
(kN/m3)
Aluminium
27.0
Granite, Basalt
26.4
Asphalt
21.2
Iron - cast
70.7
Brass
83.6
* wrought
75.4
Bronze
87.7
Lead
111.0
Brick
18.9
Limestone
24.5
Cement
14.7
Marble
26.4
Coal, loose
8.8
Sand, dry
15.7
| Table 6.2.1: Unit Weight of Basic Materials | Col2 |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Material**
**Unit Weight**
\*\*(kN/m3) \*\* | **Material**
**Unit Weight**
\*\*(kN/m3) \*\* |
| Aluminium
27.0
Asphalt
21.2
Brass
83.6
Bronze
87.7
Brick
18.9
Cement
14.7
Coal, loose
8.8 | Granite, Basalt
26.4
Iron - cast
70.7
- wrought
75.4
Lead
111.0
Limestone
24.5
Marble
26.4
Sand, dry
15.7 |
Material
Unit Weight
(kN/m3)
Material
Unit Weight
(kN/m3)
Concrete -stone aggregate
(unreinforced)
22.8\*
Sandstone
22.6
-brick aggregate
(unreinforced)
20.4\*
Slate
28.3
Copper
86.4
Steel
77.0
Cork, normal
1.7
Stainless Steel
78.75
Cork, compressed
3.7
Timber
5.9-11.0
Glass, window (soda-lime)
25.5
Zinc
70.0
* for reinforced concrete, add 0.63 kN/m3 for each 1% by volume of main reinforcement
Table 6.2.2: Weight of Construction Materials.
Material/Component/Member
Weight per
Unit Area
(kN/m2)
Material/Component/Member
Weight per
Unit Area
(kN/m2)
Floor
Asphalt, 25 mm thick
Clay tiling, 13 mm thick
Concrete slab (stone aggregate)\*:
solid, 100 mm thick
solid, 150 mm thick
Galvanized steel floor deck (excl.
topping)
Magnesium oxychloride:
normal (sawdust filler), 25 mm
thick
heavy
duty
(mineral
filler),
25 mm thick
Terrazzo paving 16 mm thick
0.526
0.268
2.360
3.540
0.147-
0.383
0.345
0.527
0.431
Walls and Partitions
Acrylic resin sheet, flat, per
mm thickness
Asbestos cement sheeting:
### 4.5 mm thick
### 6.0 mm thick
Brick masonry work, excl.
plaster:
burnt clay, per 100 mm
thickness
sand-lime, per 100 mm
thickness
Concrete (stone aggregate)\*:
100 mm thick
0.012
0.072
0.106
1.910
1.980
2.360
| Material Unit Weight
(kN/m3) | Material Unit Weight
(kN/m3) |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| Concrete -stone aggregate
(unreinforced)
22.8\*
-brick aggregate
(unreinforced)
20.4\*
Copper
86.4
Cork, normal
1.7
Cork, compressed
3.7
Glass, window (soda-lime)
25.5 | Sandstone
22.6
Slate
28.3
Steel
77.0
Stainless Steel
78.75
Timber
5.9-11.0
Zinc
70.0 |
| Material/Component/Member Weight per
Unit Area
(kN/m2) | Material/Component/Member Weight per
Unit Area
(kN/m2) |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Floor**
Asphalt, 25 mm thick
Clay tiling, 13 mm thick
Concrete slab (stone aggregate)\*:
solid, 100 mm thick
solid, 150 mm thick
Galvanized steel floor deck (excl.
topping)
Magnesium oxychloride:
normal (sawdust filler), 25 mm
thick
heavy
duty
(mineral
filler),
25 mm thick
Terrazzo paving 16 mm thick
0.526
0.268
2.360
3.540
0.147-
0.383
0.345
0.527
0.431 | **Walls and Partitions**
Acrylic resin sheet, flat, per
mm thickness
Asbestos cement sheeting:
4.5 mm thick
6.0 mm thick
Brick masonry work, excl.
plaster:
burnt clay, per 100 mm
thickness
sand-lime, per 100 mm
thickness
Concrete (stone aggregate)\*:
100 mm thick
0.012
0.072
0.106
1.910
1.980
2.360 |
Material/Component/Member
Weight per
Unit Area
(kN/m2)
Material/Component/Member
Weight per
Unit Area
(kN/m2)
Roof
Acrylic resin sheet, corrugated:
3 mm thick, standard corrugations
3 mm thick, deep corrugations
Aluminium, corrugated sheeting:
(incl. lap and fastenings)
### 1.2 mm thick
### 0.8 mm thick
### 0.6 mm thick
Aluminium sheet(plain):
### 1.2 mm thick
### 1.0 mm thick
### 0.8 mm thick
Bituminous felt (5 ply) and gravel
Slates:
### 4.7 mm thick
### 9.5 mm thick
Steel sheet, flat galvanized:
### 1.00 mm thick
### 0.80 mm thick
### 0.60 mm thick
Steel, galvanized std. corrugated
sheeting:
(incl. lap and fastenings)
### 1.0 mm thick
### 0.8 mm thick
### 0.6 mm thick
Tiles :
terra-cotta tiles (French pattern)
concrete , 25 mm thick
clay tiles
0.043
0.062
0.048
0.028
0.024
0.033
0.024
0.019
0.431
0.335
0.671
0.082
0.067
0.053
0.120
0.096
0.077
0.575
0.527
0.6-0.9
150 mm thick
250 mm thick
Fibre insulation board, per
10 mm thickness
Fibrous plaster board, per
10 mm thickness
Glass, per 10 mm thickness
Hardboard, per 10 mm
thickness
Particle or flake board, per
10 mm thickness
Plaster board, per 10 mm
thickness
Plywood, per 10 mm
thickness
Ceiling
Fibrous plaster, 10 mm thick
Cement plaster, 13 mm thick
Suspended metal lath and
plaster
(two faced incl. studding)
Miscellaneous
Felt (insulating), per 10 mm
thickness
Plaster:
Cement plaster, per 10
mm thickness
Lime plaster, per 10 mm
thickness
PVC sheet, per 10 mm
thickness
Rubber paving, per 10 mm
thickness
Terra-cotta Hollow Block
Masonry:
75 mm thick
100 mm thick
150 mm thick
3.540
5.900
0.034
0.092
0.269
0.961
0.075
0.092
0.061
0.081
0.287
0.480
0.019
0.230
0.191
0.153
0.151
0.671
0.995
1.388
* For brick aggregate, 90% of the listed values may be used.
| Material/Component/Member Weight per
Unit Area
(kN/m2) | Material/Component/Member Weight per
Unit Area
(kN/m2) |
| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Roof**
Acrylic resin sheet, corrugated:
3 mm thick, standard corrugations
3 mm thick, deep corrugations
Aluminium, corrugated sheeting:
(incl. lap and fastenings)
1.2 mm thick
0.8 mm thick
0.6 mm thick
Aluminium sheet(plain):
1.2 mm thick
1.0 mm thick
0.8 mm thick
Bituminous felt (5 ply) and gravel
Slates:
4.7 mm thick
9.5 mm thick
Steel sheet, flat galvanized:
1.00 mm thick
0.80 mm thick
0.60 mm thick
Steel, galvanized std. corrugated
sheeting:
(incl. lap and fastenings)
1.0 mm thick
0.8 mm thick
0.6 mm thick
Tiles :
terra-cotta tiles (French pattern)
concrete , 25 mm thick
clay tiles
0.043
0.062
0.048
0.028
0.024
0.033
0.024
0.019
0.431
0.335
0.671
0.082
0.067
0.053
0.120
0.096
0.077
0.575
0.527
0.6-0.9 | 150 mm thick
250 mm thick
Fibre insulation board, per
10 mm thickness
Fibrous plaster board, per
10 mm thickness
Glass, per 10 mm thickness
Hardboard, per 10 mm
thickness
Particle or flake board, per
10 mm thickness
Plaster board, per 10 mm
thickness
Plywood, per 10 mm
thickness
**Ceiling**
Fibrous plaster, 10 mm thick
Cement plaster, 13 mm thick
Suspended metal lath and
plaster
(two faced incl. studding)
**Miscellaneous**
Felt (insulating), per 10 mm
thickness
Plaster:
Cement plaster, per 10
mm thickness
Lime plaster, per 10 mm
thickness
PVC sheet, per 10 mm
thickness
Rubber paving, per 10 mm
thickness
Terra-cotta Hollow Block
Masonry:
75 mm thick
100 mm thick
150 mm thick
3.540
5.900
0.034
0.092
0.269
0.961
0.075
0.092
0.061
0.081
0.287
0.480
0.019
0.230
0.191
0.153
0.151
0.671
0.995
1.388 |
2.2.5
Weight of Permanent Partitions
When partition walls are indicated on the plans, their weight shall be considered as
dead load acting as concentrated line loads in their actual positions on the floor. The
loads due to anticipated partition walls, which are not indicated on the plans, shall be
treated as live loads and determined in accordance with Sec 2.3.6.
2.2.6
Weight of Fixed Service Equipment
Weights of fixed service equipment and other permanent machinery, such as
electrical feeders and other machinery, heating, ventilating and air-conditioning
systems, lifts and escalators, plumbing stacks and risers etc. shall be included as dead
load whenever such equipment are supported by structural members.
2.2.7
Additional Loads
In evaluating the final dead loads on a structural member for design purposes,
allowances shall be made for additional loads resulting from the (i) difference
between the prescribed and the actual weights of the members and construction
materials; (ii) inclusion of future installations; (iii) changes in occupancy or use of
buildings; and (iv) inclusion of structural and non-structural members not covered in
Sections 2.2.2 and 2.2.3.
2.3
Live Loads
2.3.1
General
The live loads used for the structural design of floors, roof and the supporting
members shall be the greatest applied loads arising from the intended use or
occupancy of the building, or from the stacking of materials and the use of
equipment and propping during construction, but shall not be less than the minimum
design live loads set out by the provisions of this Section. For the design of structural
members for forces including live loads, requirements of the relevant Sections of
Chapter 1 shall also be fulfilled.
2.3.2
Definition
Live load is the load superimposed by the use or occupancy of the building not
including the environmental loads such as wind load, rain load, earthquake load or
dead load.
2.3.3
Minimum Floor Live Loads
The minimum floor live loads shall be the greatest actual imposed loads resulting
from the intended use or occupancy of the floor, and shall not be less than the
uniformly distributed load patterns specified in Sec 2.3.4 or the concentrated loads
specified in Sec 2.3.5 whichever produces the most critical effect. The live loads
shall be assumed to act vertically upon the area projected on a horizontal plane.
2.3.4
Uniformly Distributed Loads
The uniformly distributed live load shall not be less than the values listed in Table
6.2.3, reduced as may be specified in Sec 2.3.13, applied uniformly over the entire
area of the floor, or any portion thereof to produce the most adverse effects in the
member concerned.
2.3.5
Concentrated Loads
The concentrated load to be applied non-concurrently with the uniformly distributed
load given in Sec 2.3.4, shall not be less than that listed in Table 6.2.3. Unless
otherwise specified in Table 6.2.3 or in the following paragraph, the concentrated
load shall be applied over an area of 300 mm 300 mm and shall be located so as to
produce the maximum stress conditions in the structural members.
In areas where vehicles are used or stored, such as car parking garages, ramps, repair
shops etc., provision shall be made for concentrated loads consisting of two or more
loads spaced nominally 1.5 m on centres in absence of the uniform live loads. Each
load shall be 40 percent of the gross weight of the maximum size vehicle to be
accommodated and applied over an area of 750 mm 750 mm. For the storage of
private or pleasure-type vehicles without repair or fuelling, floors shall be
investigated in the absence of the uniform live load, for a minimum concentrated
wheel load of 9 kN spaced 1.5 m on centres, applied over an area of 750 mm 750
mm. The uniform live loads for these cases are provided in Table 6.2.3. The
condition of concentrated or uniform live load producing the greater stresses shall
govern.
Table 6.2.3: Minimum Uniformly Distributed and Concentrated Live Loadsa
Occupancy or Use
Uniform
kN/m2
Concentrated
kN
Apartments (see Residential)
Access floor systems
Office use
Computer use
2.40
4.80
9.0
9.0
Armories and drill rooms
7.20
----
| Occupancy or Use | Uniform
kN/m2 | Concentrated
kN |
| -------------------------------------------------------- | ------------------ | -------------------- |
| Apartments (see Residential) | | |
| Access floor systems
Office use
Computer use | 2.40
4.80 | 9.0
9.0 |
| Armories and drill rooms | 7.20 | -- |
Occupancy or Use
Uniform
kN/m2
Concentrated
kN
Assembly areas and theaters
Fixed seats (fastened to floor)
Lobbies
Movable seats
Platforms (assembly)
Stage floors
2.90
4.80
4.80
4.80
7.20
## --
## --
\--
Balconies (exterior)
On one- and two-family residences only, and not
exceeding 19.3 m2
4.80
2.90
----
\--
Bowling alleys, poolrooms, and similar recreational areas
3.60
----
Catwalks for maintenance access
2.00
1.33
Corridors
First floor
Other floors, same as occupancy served except as indicated
4.80
\--
Dance halls and ballrooms
4.80
----
Decks (patio and roof)
Same as area served, or
for the type of occupancy
accommodated
Dining rooms and restaurants
4.80
----
## Dwellings (see Residential)
## Elevator machine room grating (on area of 2,580 mm2 )
1.33
Finish light floor plate construction (on area of 645 mm2)
----------------------------------------------------------
0.90
Fire escapes
On single-family dwellings only
4.80
2.00
----
\--
Fixed ladders
See Sec 2.3.11
Garages (passenger vehicles only), Trucks and buses
2.0b,c
Grandstands
See Stadiums and arenas,
Bleachers
এুসহধংরঁসং্তসধরহ ভষড়ড়ৎং ধহফ নধষপড়হরবং
4.80
----
Handrails, guardrails, and grab bars
See Sec 2.3.11
Hospitals
Operating rooms, laboratories
Patient rooms
Corridors above first floor
2.90
2.00
3.80
4.50
4.50
4.50
| Occupancy or Use | Uniform
kN/m2 | Concentrated
kN |
| ---------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------ | ------------------------------------------------------------------------ |
| Assembly areas and theaters
Fixed seats (fastened to floor)
Lobbies
Movable seats
Platforms (assembly)
Stage floors | 2.90
4.80
4.80
4.80
7.20 | --
--
--
--
-- |
| Balconies (exterior)
On one- and two-family residences only, and not
exceeding 19.3m2 | 4.80
2.90 | --
-- |
| Bowling alleys, poolrooms, and similar recreational areas | 3.60 | -- |
| Catwalks for maintenance access | 2.00 | 1.33 |
| Corridors
First floor
Other floors, same as occupancy served except as indicated | 4.80 | -- |
| Dance halls and ballrooms | 4.80 | -- |
| Decks (patio and roof) | Same as area served, or
for the type of occupancy
accommodated | Same as area served, or
for the type of occupancy
accommodated |
| Dining rooms and restaurants | 4.80 | -- |
| Dwellings (see\_Residential\_) | -- | |
| Elevator machine roomgrating (on area of 2,580mm2 ) | -- | 1.33 |
| Finish light floor plateconstruction(on area of 645mm2) | -- | 0.90 |
| Fire escapes
On single-family dwellings only | 4.80
2.00 | --
-- |
| Fixed ladders | See Sec 2.3.11 | See Sec 2.3.11 |
| Garages (passenger vehicles only), Trucks and buses | 2.0\_b,c\_ | 2.0\_b,c\_ |
| Grandstands | See\_Stadiums and arenas,\_
*Bleachers* | See\_Stadiums and arenas,\_
*Bleachers* |
| Gymnasiums—main floors and balconies | 4.80 | -- |
| Handrails, guardrails, and grab bars | See Sec 2.3.11 | See Sec 2.3.11 |
| Hospitals
Operating rooms, laboratories
Patient rooms
Corridors above first floor | 2.90
2.00
3.80 | 4.50
4.50
4.50 |
Occupancy or Use
Uniform
kN/m2
Concentrated
kN
Hotels
See Residential
Libraries
Reading rooms
Stack rooms
Corridors above first floor
2.90
### 7.20 d
3.80
4.50
4.50
4.50
Manufacturing\*
Light
Medium
Heavy
Garments manufacturing floor except stacking or storage
area
Stacking or storage area of garments manufacturing
industry
4.00
6.00
12.00
4.00e
### 6.00 f
6.00
9.00
13.40
-----
### 10.00 f
Marquees
3.60
----
Office Buildings
File and computer rooms shall be designed for
heavier loads based on anticipated occupancy
Lobbies and first-floor corridors
Offices
Corridors above first floor
4.80
2.40
3.80
9.00
9.00
9.00
Penal Institutions
Cell blocks
Corridors
2.00
4.80
## --
Residential
Dwellings (one- and two-family)
Uninhabitable attics without storage
Uninhabitable attics with storage
Habitable attics and sleeping areas
All other areas except stairs and balconies
Hotels and multifamily houses
Private rooms and corridors serving them
Public rooms and corridors serving them
0.50
1.00
1.50
2.00
2.00
4.80
## --
## --
## --
Reviewing stands, grandstands, and bleachers
### 4.80 g
\--
| Occupancy or Use | Uniform
kN/m2 | Concentrated
kN |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------ | ---------------------------------------------------- |
| Hotels | See\_Residential\_ | See\_Residential\_ |
| Libraries
Reading rooms
Stack rooms
Corridors above first floor | 2.90
7.20\_d\_
3.80 | 4.50
4.50
4.50 |
| Manufacturing\*
Light
Medium
Heavy
Garments manufacturing floor except stacking or storage
area
Stacking or storage area of garments manufacturing
industry | 4.00
6.00
12.00
4.00e
6.00\_f\_ | 6.00
9.00
13.40
--
10.00\_ f\_ |
| Marquees | 3.60 | -- |
| OfficeBuildings
File and computer rooms shall be designed for
heavier loads based on anticipated occupancy
Lobbies andfirst-floorcorridors
Offices
Corridors above first floor | 4.80
2.40
3.80 | 9.00
9.00
9.00 |
| Penal Institutions
Cell blocks
Corridors | 2.00
4.80 | --
-- |
| Residential
Dwellings (one- and two-family)
Uninhabitable attics without storage
Uninhabitable attics with storage
Habitable attics and sleeping areas
All other areas except stairs and balconies
Hotels and multifamily houses
Private rooms and corridors serving them
Public rooms and corridors serving them | 0.50
1.00
1.50
2.00
2.00
4.80 | --
--
--
--
--
-- |
| Reviewing stands, grandstands, and bleachers | 4.80\_g\_ | -- |
Occupancy or Use
Uniform
kN/m2
Concentrated
kN
Roofs
Ordinary flat roof
### 1.00 h
\--
Pitched and curved roofs
See Table 6.2.4
Roofs used for promenade purposes
2.90
----
Roofs used for roof gardens or assembly purposes
4.80
----
Roofs used for other special purposes
See Note i below
Awnings and canopies
Fabric construction supported by a lightweight rigid
skeleton structure
0.24
(nonredu-
ceable)
-------
All other construction
1.00
----
Primary roof members exposed to a work floor
Single panel point of lower chord of roof trusses or
any
point along primary
structural members
supporting
roofs
over
manufacturing,
storage
warehouses, and repair garages
------------------------------
9.00
## All other occupancies
1.33
All roof surfaces subject to maintenance workers
------------------------------------------------
1.33
Schools
Classrooms
Corridors above first floor
First-floor corridors
2.00
3.80
4.80
4.50
4.50
4.50
Scuttles, skylight ribs, and accessible ceilings
0.90
Sidewalks, vehicular driveways, and yards subject to
trucking
### 12.00 j
### 35.60 k
Stadiums and arenas
Bleachers
Fixed seats (fastened to floor)
4.80
g
2.90
g
## --
Stairs and exit ways
One- and two-family residences only
4.80
2.00
See Notel
below
-----
| Occupancy or Use | Uniform
kN/m2 | Concentrated
kN |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Roofs
Ordinary flat roof
Pitched and curved roofs
Roofs used for promenade purposes
Roofs used for roof gardens or assembly purposes
Roofs used for other special purposes
Awnings and canopies
Fabric construction supported by a lightweight rigid
skeleton structure
All other construction
Primary roof members exposed to a work floor
Single panel point of lower chord of roof trusses or
any
point along primary
structural members
supporting
roofs
over
manufacturing,
storage
warehouses, and repairgarages
All other occupancies
All roof surfaces subject to maintenance workers | 1.00\_h\_
--
See Table 6.2.4
2.90
--
4.80
--
See Note\_i \_below
0.24
(nonredu-
ceable)
--
1.00
--
--
9.00
--
1.33
--
1.33 | 1.00\_h\_
--
See Table 6.2.4
2.90
--
4.80
--
See Note\_i \_below
0.24
(nonredu-
ceable)
--
1.00
--
--
9.00
--
1.33
--
1.33 |
| Schools
Classrooms
Corridors above first floor
First-floor corridors | 2.00
3.80
4.80 | 4.50
4.50
4.50 |
| Scuttles, skylight ribs, and accessible ceilings | | 0.90 |
| Sidewalks, vehicular driveways, and yards subject to
trucking | 12.00\_j\_ | 35.60\_k\_ |
| Stadiums and arenas
Bleachers
Fixed seats (fastened to floor) | 4.80
*g*
2.90
*g* | --
-- |
| Stairs and exit ways
One- and two-family residences only | 4.80
2.00 | See Note\_l \_
below
-- |
Occupancy or Use
Uniform
kN/m2
Concentrated
kN
Storage areas above ceilings
1.00
----
Storage warehouses (shall be designed for
heavier loads if required for anticipated
storage)
Light
Heavy
6.00
12.00
## --
Stores
Retail
First floor
Upper floors
Wholesale, all floors
4.80
3.60
6.00
4.50
4.50
4.50
Vehicle barriers
See Sec 2.3.11
Walkways and elevated platforms (other than exit ways)
2.90
----
Yards and terraces, pedestrian
4.80
----
Notes:
a It must be ensured that the average weight of equipment, machinery, raw materials
and products that may occupy the floor is less than the specified value in the Table.
In case the weight exceeds the specified values in the Table, actual maximum
probable weight acting in the actual manner shall be used in the analysis and
design.
b Floors in garages or portions of a building used for the storage of motor vehicles
shall be designed for the uniformly distributed live loads of Table 6.2.3 or the
following concentrated load: (1) for garages restricted to passenger vehicles
accommodating not more than nine passengers, 13.35 kN acting on an area of 114
mm by 114 mm footprint of a jack; and (2) for mechanical parking structures
without slab or deck that are used for storing passenger car only, 10 kN per wheel.
c Garages accommodating trucks and buses shall be designed in accordance with an
approved method, which contains provisions for truck and bus loadings.
d The loading applies to stack room floors that support non-mobile, double-faced
library book stacks subject to the following limitations: (1) The nominal book
stack unit height shall not exceed 2290 mm; (2) the nominal shelf depth shall not
exceed 300 mm for each face; (3) parallel rows of double-faced book stacks shall
be separated by aisles not less than 900 mm wide.
| Occupancy or Use | Uniform
kN/m2 | Concentrated
kN |
| ---------------------------------------------------------------------------------------------------------------------------- | ------------------------ | -------------------------- |
| Storage areas above ceilings | 1.00 | -- |
| Storage warehouses (shall be designed for
heavier loads if required for anticipated
storage)
Light
Heavy | 6.00
12.00 | --
-- |
| Stores
Retail
First floor
Upper floors
Wholesale, all floors | 4.80
3.60
6.00 | 4.50
4.50
4.50 |
| Vehicle barriers | See Sec 2.3.11 | See Sec 2.3.11 |
| Walkways and elevated platforms (other than exit ways) | 2.90 | -- |
| Yards and terraces, pedestrian | 4.80 | -- |
e Subject to the provisions of reduction of live load as per Sec 2.3.13
f Uniformly distributed and concentrated load provisions are applicable for a
maximum floor height of 3.5 m. In case of higher floor height, the load(s) must be
proportionally increased.
g In addition to the vertical live loads, the design shall include horizontal swaying
forces applied to each row of the seats as follows: 0.350 kN per linear meter of
seat applied in a direction parallel to each row of seats and 0.15 kN per linear
meter of seat applied in a direction perpendicular to each row of seats. The
parallel and perpendicular horizontal swaying forces need not be applied
simultaneously.
h Where uniform roof live loads are reduced to less than 1.0 kN/m2 in accordance
with Sec 2.3.14.1 and are applied to the design of structural members arranged so
as to create continuity, the reduced roof live load shall be applied to adjacent spans
or to alternate spans, whichever produces the greatest unfavorable effect.
i Roofs used for other special purposes shall be designed for appropriate loads as
approved by the authority having jurisdiction.
j Other uniform loads in accordance with an approved method, which contains
provisions for truck loadings, shall also be considered where appropriate.
k The concentrated wheel load shall be applied on an area of 114 mm by 114 mm
footprint of a jack.
l Minimum concentrated load on stair treads (on area of 2,580 mm2 ) is 1.33 kN.
* The loading in industrial buildings varies considerably and so the loadings under
ঃযব:বৎসং ্তুষরমযঃ,্থ ্তুসবফরঁস্থ ধহফ ্তুযবধা্থু ধৎব রহঃৎড়ফঁপবফ রহ ড়ৎফবৎ:ড় ধষষড়ি ভড়ৎ যিরপয
the relevant floor is designed. It is however important to assess the actual loads to
ensure that they are not in excess of the stipulated load, in case where they are in
excess, the design shall be based on the actual loadings.
2.3.6
Provision for Partition Walls
When partitions, not indicated on the plans, are anticipated to be placed on the floors,
their weight shall be included as an additional live load acting as concentrated line
loads in an arrangement producing the most severe effect on the floor, unless it can
be shown that a more favourable arrangement of the partitions shall prevail during
the future use of the floor.
In the case of light partitions, wherein the total weight per metre run is not greater
than 5.5 kN, a uniformly distributed live load may be applied on the floor in lieu of
the concentrated line loads specified above. Such uniform live load per square metre
shall be at least 33% of the weight per metre run of the partitions, subject to a
minimum of 1.2 kN/m2.
2.3.7
More than One Occupancy
Where an area of a floor is intended for two or more occupancies at different times,
the value to be used from Table 6.2.3 shall be the greatest value for any of the
occupancies concerned.
2.3.8
Minimum Roof Live Loads
Roof live loads shall be assumed to act vertically over the area projected by the roof
or any portion of it upon a horizontal plane, and shall be determined as specified in
Table 6.2.4.
Table 6.2.4: Minimum Roof Live Loads(1)
Type and Slope of Roof
Distributed
Load, kN/m2
Concentrated
Load, kN
I
Flat roof (slope = 0)
See Table 6.2.3
II
(A) Pitched or sloped roof (0 \< slope \< 1/3)
(B) Arched roof or dome (rise \< 1/8 span)
1.0
0.9
III
(A) Pitched or sloped roof (1/3 ≤ slope \< 1.0)
(B) Arched roof or dome (1/8 ≤ rise \< 3/8 span)
0.8
0.9
IV
(A) Pitched or sloped roof (slope ≥ 1.0)
(B) Arched roof or dome (rise ≥ 3/8 span)
0.6
0.9
V
Greenhouse, and agriculture buildings
0.5
0.9
VI Canopies and awnings, except those with cloth
covers
Same as given in I to IV
above based on the type
and slope.
Note:
(1) Greater of this load and rain load as specified in Sec 2.6.2 shall be taken as
the design live load for roof. The distributed load shall be applied over the
area of the roof projected upon a horizontal plane and shall not be applied
simultaneously with the concentrated load. The concentrated load shall be
assumed to act upon a 300 mm 300 mm area and need not be considered for
roofs capable of laterally distributing the load, e.g. reinforced concrete slabs.
2.3.9
Loads not Specified
Live loads, not specified for uses or occupancies in Sections 2.3.3, 2.3.4 and 2.3.5,
shall be determined from loads resulting from:
(a)
weight of the probable assembly of persons;
(b)
weight of the probable accumulation of equipment and furniture, and
(c)
weight of the probable storage of materials.
#### 2.3.10 Partial Loading and Other Loading Arrangements
The full intensity of the appropriately reduced live load applied only to a portion of
the length or area of a structure or member shall be considered, if it produces a more
unfavourable effect than the same intensity applied over the full length or area of the
structure or member.
Where uniformly distributed live loads are used in the design of continuous members
and their supports, consideration shall be given to full dead load on all spans in
combination with full live loads on adjacent spans and on alternate spans whichever
produces a more unfavourable effect.
#### 2.3.11 Other Live Loads
Live loads on miscellaneous structures and components, such as handrails and
supporting members, parapets and balustrades, ceilings, skylights and supports, and
the like, shall be determined from the analysis of the actual loads on them, but shall
not be less than those given in Table 6.2.5.
#### 2.3.12 Impact and Dynamic Loads
The live loads specified in Sec 2.3.3 shall be assumed to include allowances for
impacts arising from normal uses only. However, forces imposed by unusual
vibrations and impacts resulting from the operation of installed machinery and
equipment shall be determined separately and treated as additional live loads. Live
loads due to vibration or impact shall be determined by dynamic analysis of the
supporting member or structure including foundations, or from the recommended
values supplied by the manufacture of the particular equipment or machinery. In
absence of definite information, values listed in Table 6.2.6 for some common
equipment, shall be used for design purposes.
Table 6.2.5: Miscellaneous Live Loads
Structural Member or Component
Live Load(1)
(kN/m)
A. Handrails, parapets and supports:
(a) Light access stairs, gangways etc.
(i) width ≤ 0.6 m
(ii) width > 0.6 m
0.25
0.35
(b) Staircases other than in (a) above, ramps, balconies:
(i) Single dwelling and private
(ii) Staircases in residential buildings
(iii) Balconies or portion thereof, stands etc. having fixed seats
within 0.55 m of the barrier
(iv) Public assembly buildings including theatres, cinemas,
assembly halls, stadiums, mosques, churches, schools etc.
(v) Buildings and occupancies other than (i) to (iv) above
0.35
0.35
1.5
3.0
0.75
B. Vehicle barriers for car parks and ramps:
(a) For vehicles having gross mass ≤ 2500 kg
100(2)
(b) For vehicles having gross mass > 2500 kg
165(2)
(c) For ramps of car parks etc.
see note(3)
Notes: (1) These loads shall be applied non-concurrently along horizontal and vertical
directions, except as specified in note (2) below.
(2) These loads shall be applied only in the horizontal direction, uniformly
distributed over any length of 1.5 m of a barrier and shall be considered to
act at bumper height. For case 2(a) bumper height may be taken as 375
mm above floor level.
(3) Barriers to access ramps of car parks shall be designed for horizontal
forces equal to 50% of those given in 2(a) and 2(b) applied at a level of
610 mm above the ramp. Barriers to straight exit ramps exceeding 20 m in
length shall be designed for horizontal forces equal to twice the values
given in 2(a) and 2(b).
Table 6.2.6: Minimum Live Loads on Supports and Connections of Equipment due
to Impact(1)
Equipment or Machinery
Additional load due to impact as percentage
of static load including self-weight
Vertical
Horizontal
1. Lifts, hoists and related
operating machinery
100%
Not applicable
2. Light machinery (shaft or
motor driven)
20%
Not applicable
3. Reciprocating machinery, or
power driven units.
50%
Not applicable
4. Hangers supporting floors and
balconies
33%
Not applicable
5. Cranes :
(a) Electric overhead
cranes
25% of
maximum
wheel load
(i) Transverse to the rail :
20% of the weight of trolley
and lifted load only, applied
one-half at the top of each rail
(ii) Along the rail :
10% of maximum wheel load
applied at the top of each rail
| to Impact(1) | Col2 |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- |
| **Equipment or Machinery** | **Additional load due to impact as percentage**
**of static load including self-weight** |
| **Equipment or Machinery** | **Vertical**
**Horizontal** |
| 1. Lifts, hoists and related
operating machinery
2. Light machinery (shaft or
motor driven)
3. Reciprocating machinery, or
power driven units.
4. Hangers supporting floors and
balconies | 100%
Not applicable
20%
Not applicable
50%
Not applicable
33%
Not applicable |
Equipment or Machinery
Additional load due to impact as percentage
of static load including self-weight
Vertical
Horizontal
(b) Manually operated
cranes
50% of the
values in (a)
above
50% of the values in (a) above
(c) Cab-operated travelling
cranes
25%
Not applicable
(1) All these loads shall be increased if so recommended by the manufacturer. For
machinery and equipment not listed, impact loads shall be those recommended by the
manufacturers, or determined by dynamic analysis.
#### 2.3.13 Reduction of Live Loads
Except for roof uniform live loads, all other minimum uniformly distributed live
loads, Lo in Table 6.2.3, may be reduced according to the following provisions.
##### 2.3.13.1 General
Subject to the limitations of Sections 2.3.13.2 to 2.3.13.5, members for which a value
of KLLAT is 37.16 m2 or more are permitted to be designed for a reduced live load in
accordance with the following formula:
oL
L
n0.25 +
q.rs
tuvvwxy
(6.2.1)
Where, L = reduced design live load per m2 of area supported by the member; L0=
unreduced design live load per m2 of area supported by the member (Table 6.2.3);
KLL= live load element factor (Table 6.2.7); AT = tributary area in m2, L shall not be
less than 0.50L0 for members supporting one floor and L shall not be less than 0.40L0
for members supporting two or more floors.
Table 6.2.7: Live Load Element Factor, }\~\~
Element
}\~\~\*
Interior columns
Exterior columns without cantilever slabs
Edge columns with cantilever slabs
Corner columns with cantilever slabs
Edge beams without cantilever slabs
Interior beams
| Equipment or Machinery | Additional load due to impact as percentage
of static load including self-weight |
| ------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------- |
| **Equipment or Machinery** | **Vertical**
**Horizontal** |
| (b) Manually operated
cranes
(c) Cab-operated travelling
cranes | 50% of the
values in (a)
above
50% of the values in (a) above
25%
Not applicable |
All other members not identified including:
Edge beams with cantilever slabs
Cantilever beams
One-way slabs
Two-way slabs
Members without provisions for continuous shear transfer
normal to their span
* In lieu of the preceding values, 0BB is permitted to be calculated.
##### 2.3.13.2 Heavy live loads
Live loads that exceed 4.80 kN/m2 shall not be reduced.
Exception: Live loads for members supporting two or more floors may be
reduced by 20 percent.
##### 2.3.13.3 Passenger car garages
The live loads shall not be reduced in passenger car garages.
Exception: Live loads for members supporting two or more floors may be reduced by
20 percent.
##### 2.3.13.4 Special occupancies
(a) Live loads of 4.80 kN/m2 or less shall not be reduced in public assembly
occupancies.
(b) There shall be no reduction of live loads for cyclone shelters.
##### 2.3.13.5 Limitations on one-way slabs
The tributary area, AT, for one-way slabs shall not exceed an area defined by the slab
span times a width normal to the span of 1.5 times the slab span.
#### 2.3.14 Reduction in Roof Live Loads
The minimum uniformly distributed roof live loads, Lo in Table 6.2.3, are permitted
to be reduced according to the following provisions.
##### 2.3.14.1 Flat, pitched, and curved roofs.
Ordinary flat, pitched, and curved roofs are permitted to be designed for a reduced
roof live load, as specified in Eq. 6.2.2 or other controlling combinations of loads, as
discussed later in this Chapter, whichever produces the greater load. In structures
such as greenhouses, where special scaffolding is used as a work surface for
workmen and materials during maintenance and repair operations, a lower roof load
than specified in Eq. 6.2.2 shall not be used unless approved by the authority having
jurisdiction. On such structures, the minimum roof live load shall be 0.60 kN/m2.
67 5 6@1@ (0.60 ≤67 ≤1.00)
(6.2.2)
Where,
67 5 reduced roof live load per m2 of horizontal projection in kN/m2
The reduction factors @1 and @ shall be determined as follows:
@1 5 1 for " ≤ 18.58 m2
5 1.2 − 0.011" for 18.58 m2 \< " \< 55.74 m2
5 0.6 for "≥ 55.74 m2
" 5 tributary area in m2 supported by any structural member and
@ 5 1 for & ≤ 4
5 1.2 − 0.05F for 4 \< & \< 12
5 0.6 for & ≥ 12
For a pitched roof, & 5 0.12 × slope, with slope expressed in percentage points
and, for an arch or dome, & 5 rise-to-span ratio multiplied by 32.
##### 2.3.14.2 Special purpose roofs.
Roofs that have an occupancy function, such as roof gardens, assembly purposes, or
other special purposes are permitted to have their uniformly distributed live load
reduced in accordance with the requirements of Sec 2.3.13.
2.4
Wind Loads
2.4.1
General
Scope: Buildings and other structures, including the Main Wind-Force Resisting
System (MWFRS) and all components and cladding thereof, shall be designed and
constructed to resist wind loads as specified herein.
Allowed Procedures: The design wind loads for buildings and other structures,
including the MWFRS and component and cladding elements thereof, shall be
determined using one of the following procedures:
Method 1: Simplified Procedure as specified in Sec 2.4.2 for buildings and
structures meeting the requirements specified therein;
Method 2: Analytical Procedure as specified in Sec 2.4.3 for buildings and
structures meeting the requirements specified therein;
Method 3: Wind Tunnel Procedure as specified in Sec 2.4.16.
Wind Pressures Acting on opposite faces of each building surface. In the calculation
of design wind loads for the MWFRS and for components and cladding for buildings,
the algebraic sum of the pressures acting on opposite faces of each building surface
shall be taken into account.
Minimum Design Wind Loading
The design wind load, determined by any one of the procedures specified in Sec
2.4.1, shall be not less than specified in this Section.
Main Wind-Force Resisting System: The wind load to be used in the design of the
MWFRS for an enclosed or partially enclosed building or other structure shall not be
less than 0.5 kN/m2 multiplied by the area of the building or structure projected onto
a vertical plane normal to the assumed wind direction. The design wind force for
open buildings and other structures shall be not less than 0.5 kN/m2 multiplied by the
area .
Components and Cladding: The design wind pressure for components and cladding
of buildings shall not be less than a net pressure of 0.5 kN/m2 acting in either
direction normal to the surface.
2.4.2
Method 1: Simplified Procedure
##### 2.4.2.1 Scope
A building whose design wind loads are determined in accordance with this Section
shall meet all the conditions of Sec 2.4.2.2 or Sec 2.4.2.3. If a building qualifies only
under Sec 2.4.2.3 for design of its components and cladding, then its MWFRS shall
be designed by Method 2 or Method 3.
Limitations on Wind Speeds: Variation of basic wind speeds with direction shall not
be permitted unless substantiated by any established analytical method or wind
tunnel testing.
##### 2.4.2.2 Main wind-force resisting systems
For the design of MWFRSs the building must meet all of the following conditions:
(1) The building is a simple diaphragm building as defined in Sec 2.1.3.
(2) The building is a low-rise building as defined in Sec 2.1.3.
(3) The building is enclosed as defined in Sec 2.1.3 and conforms to the wind-
borne debris provisions of Sec 2.4.9.3.
(4) The building is a regular-shaped building or structure as defined in Sec 2.1.3.
(5) The building is not classified as a flexible building as defined in Sec 2.1.3.
(6) The building does not have response characteristics making it subject to a
cross wind loading, vortex shedding, instability due to galloping or flutter;
and does not have a site location for which channeling effects or buffeting
in the wake of upwind obstructions warrant special consideration.
(7) The building has an approximately symmetrical cross-section in each
direction with either a flat roof or a gable or hip roof with g ≤45.
(8) The building is exempted from torsional load cases as indicated in Note 5
of Figure 6.2.10, or the torsional load cases defined in Note 5 do not
control the design of any of the MWFRSs of the building.
##### 2.4.2.3 Components and cladding
For the design of components and cladding the building must meet all the
following conditions:
(1) The mean roof height ℎ must be less than or equal to 18.3 m (ℎ≤18.3 m).
(2) The building is enclosed as defined in Sec 2.1.3 and conforms to wind-
borne debris provisions of Sec 2.4.9.3.
(3) The building is a regular-shaped building or structure as defined in Sec
2.1.3.
(4) The building does not have response characteristics making it subject to
across-wind loading, vortex shedding, instability due to galloping or
flutter; and does not have a site location for which channeling effects or
buffeting in the wake of upwind obstructions warrant special
consideration.
(5) The building has either a flat roof, a gable roof with g ≤45, or a hip roof
with g ≤27.
##### 2.4.2.4 Design procedure
(1) The basic wind speed shall be determined in accordance with Sec 2.4.4.
The wind shall be assumed to come from any horizontal direction.
(2) An importance factor . shall be determined in accordance with Sec 2.4.5.
(3) An exposure category shall be determined in accordance with Sec 2.4.6.3.
(4) A height and exposure adjustment coefficient, h shall be determined from
Figure 6.2.2.
###### 2.4.2.4.1 Main wind-force resisting system: Simplified design wind pressures,
W, for the MWFRSs of low-rise simple diaphragm buildings represent the net
pressures (sum of internal and external) to be applied to the horizontal and
vertical projections of building surfaces as shown in Figure 6.2.2. For the
horizontal pressures (zones A, B, C, D), W is the combination of the windward
and leeward net pressures. W shall be determined by the following equation:
W 5 h0/".W2=
(6.2.3)
Where,
h 5 adjustment factor for building height and exposure from Figure
6.2.2
0/" 5 topographic factor as defined in Sec 2.4.7 evaluated at mean roof
height, ℎ
. 5 importance factor as defined in Sec 2.4.5
W2= 5 simplified design wind pressure for Exposure , at ℎ5 9.1 m,
and for . 5 1.0, refer to Figure 6-2 of ASCE 7-05.
Minimum Pressures: The load effects of the design wind pressures from this
Section shall not be less than the minimum load case from Sec 2.4.2.1 assuming
the pressures, W, for zones A, B, C, and D all equal to + 0.5 kN/m2, while
assuming zones E, F, G, and H all equal to zero kN/m2.
###### 2.4.2.4.2 Components and cladding: Net design wind pressures, W)\<", for the
components and cladding of buildings designed using Method 1 represent the
net pressures (sum of internal and external) to be applied normal to each
building surface as shown in Figure 6.2.3. W)\<" shall be determined by the
following equation:
W)\<" 5 h0/".W)\<"2=
(6.2.4)
Where,
h 5 adjustment factor for building height and exposure from Figure
6.2.3
0/" 5 topographic factor as defined in Sec 2.4.7 evaluated at mean roof
height, h
. 5 importance factor as defined in Sec 2.4.5
W)\<"2= 5 net design wind pressure for Exposure , at ℎ5 9.1 m, and for
. 5 1.0, refer to Figure 6-3 of ASCE 7-05.
Minimum Pressures: The positive design wind pressures, W\*P±, from this Section
shall not be less than +0.5 kN/m2, and the negative design wind pressures, W)\<",
from this Section shall not be less than −0.5 kN/m2.
###### 2.4.2.4.3 Air permeable cladding
Design wind loads determined from Figure 6.2.3 shall be used for all air
permeable cladding unless approved test data or the recognized literature
demonstrate lower loads for the type of air permeable cladding being
considered.
2.4.3
Method 2: Analytical Procedure
##### 2.4.3.1 Scopes and limitations
A building or other structure whose design wind loads are determined in
accordance with this Section shall meet all of the following conditions:
(1) The building or other structure is a regular-shaped building or structure
as defined in Sec 2.1.3.
(2) The building or other structure does not have response characteristics
making it subject to across-wind loading, vortex shedding, instability due
to galloping or flutter; or does not have a site location for which
channeling effects or buffeting in the wake of upwind obstructions
warrant special consideration.
The provisions of this Section take into consideration of the load magnification
effect caused by gusts in resonance with along-wind vibrations of flexible
buildings or other structures. Buildings or other structures not meeting the
requirements of Sec 2.4.2, or having unusual shapes or response characteristics
shall be designed using recognized literature documenting such wind load
effects or shall use the wind tunnel procedure specified in Sec 2.4.16.
##### 2.4.3.2 Shielding
There shall be no reductions in velocity pressure due to apparent shielding
afforded by buildings and other structures or terrain features.
##### 2.4.3.3 Air permeable cladding
Design wind loads determined from Sec 2.4.3 shall be used for air permeable
cladding unless approved test data or recognized literature demonstrate lower
loads for the type of air permeable cladding being considered.
##### 2.4.3.4 Design procedure
(1) The basic wind speed and wind directionality factor 0 shall be
determined in accordance with Sec 2.4.4.
(2) An importance factor . shall be determined in accordance with Sec 2.4.5.
(3) An exposure category or exposure categories and velocity pressure
exposure coefficient 0/ or 03, as applicable, shall be determined for each
wind direction in accordance with Sec 2.4.6.
(4) A topographic factor 0/" shall be determined in accordance with Sec 2.4.7.
(5) A gust effect factor , or ,, as applicable, shall be determined in
accordance with Sec 2.4.8.
(6) An enclosure classification shall be determined in accordance with Sec
2.4.9.
(7) Internal pressure coefficient , ! shall be determined in accordance with
Sec 2.4.10.1.
(8) External pressure coefficients ! or , !, or force coefficients , as
applicable, shall be determined in accordance with Sections 2.4.10.2 or
2.4.10.3, respectively.
(9) Velocity pressure X/ or X3, as applicable, shall be determined in accordance
with Sec 2.4.9.5.
(10) Design wind load ; or & shall be determined in accordance with Sec
2.4.11.
2.4.4
Basic Wind Speed
The basic wind speed, used in the determination of design wind loads on
buildings and other structures shall be as given in Figure 6.2.1 except as
provided in Sec 2.4.4.1. The wind shall be assumed to come from any horizontal
direction.
##### 2.4.4.1 Special wind regions
The basic wind speed shall be increased where records or experience indicate
that the wind speeds are higher than those reflected in Figure 6.2.1.
Mountainous terrain, gorges, and special regions shall be examined for unusual
wind conditions. The authority having jurisdiction shall, if necessary, adjust the
values given in Figure 6.2.1 to account for higher local wind speeds. Such
adjustment shall be based on adequate meteorological information and other
necessary data.
##### 2.4.4.2 Limitation
Tornadoes have not been considered in developing the basic wind-speed
distributions.
##### 2.4.4.3 Wind directionality factor
The wind directionality factor, 0 shall be determined from Table 6.2.12. This
factor shall only be applied when used in conjunction with load combinations
specified in this Chapter.
Figure 6.2.1 Basic wind speed (V, m/s) map of Bangladesh
2.4.5
Importance Factor
An importance factor, . for the building or other structure shall be determined
from Table 6.2.9 based on building and structure categories listed in Sec 1.2.4.
2.4.6
Exposure
For each wind direction considered, the upwind exposure category shall be based on
ground surface roughness that is determined from natural topography, vegetation,
and constructed facilities.
##### 2.4.6.1 Wind directions and sectors
For each selected wind direction at which the wind loads are to be evaluated, the
exposure of the building or structure shall be determined for the two upwind sectors
extending 45o either side of the selected wind direction.
The exposures in these two sectors shall be determined in accordance with Sections
##### 2.4.6.2 and 2.4.6.3 and the exposure resulting in the highest wind loads shall be used
to represent the winds from that direction.
##### 2.4.6.2 Surface roughness categories
A ground surface roughness within each 45o sector shall be determined for a distance
upwind of the site as defined in Sec 2.4.6.3 from the categories defined in the
following text, for the purpose of assigning an exposure category as defined in
Sec 2.4.6.3.
Surface Roughness A: Urban and suburban areas, wooded areas, or other terrain with
numerous closely spaced obstructions having the size of single-family dwellings or
larger.
Surface Roughness B: Open terrain with scattered obstructions having heights
generally less than 9.1 m. This category includes flat open country, grasslands, and
all water surfaces in cyclone prone regions.
Surface Roughness C: Flat, unobstructed areas and water surfaces outside cyclone
prone regions. This category includes smooth mud flats and salt flats.
##### 2.4.6.3 Exposure categories
Exposure A: Exposure A shall apply where the ground surface roughness condition,
as defined by Surface Roughness A, prevails in the upwind direction for a distance of
at least 792 m or 20 times the height of the building, whichever is greater.
Exception: For buildings whose mean roof height is less than or equal to 9.1 m, the
upwind distance may be reduced to 457 m.
Exposure B: Exposure B shall apply for all cases where Exposures A or C do not
apply.
Exposure C: Exposure C shall apply where the ground surface roughness, as
defined by Surface Roughness C, prevails in the upwind direction for a distance
greater than 1,524 m or 20 times the building height, whichever is greater.
Exposure C shall extend into downwind areas of Surface Roughness A or B for a
distance of 200 m or 20 times the height of the building, whichever is greater.
For a site located in the transition zone between exposure categories, the
category resulting in the largest wind forces shall be used.
Exception: An intermediate exposure between the preceding categories is
permitted in a transition zone provided that it is determined by a rational
analysis method defined in the recognized literature.
##### 2.4.6.4 Exposure category for main wind-force resisting system
Buildings and Other Structures: For each wind direction considered, wind loads
for the design of the MWFRS determined from Figure 6.2.6 shall be based on the
exposure categories defined in Sec 2.4.6.3.
Low-Rise Buildings: Wind loads for the design of the MWFRSs for low-rise
buildings shall be determined using a velocity pressure X3 based on the
exposure resulting in the highest wind loads for any wind direction at the site
where external pressure coefficients , ! given in Figure 6.2.10 are used.
##### 2.4.6.5 Exposure category for components and cladding
Components and cladding design pressures for all buildings and other
structures shall be based on the exposure resulting in the highest wind loads for
any direction at the site.
##### 2.4.6.6 Velocity pressure exposure coefficient
Based on the exposure category determined in Sec 2.4.6.3, a velocity pressure
exposure coefficient 0/ or 03, as applicable, shall be determined from Table
6.2.11. For a site located in a transition zone between exposure categories that is near
to a change in ground surface roughness, intermediate values of 0/ or 03 between
those shown in Table 6.2.11, are permitted, provided that they are determined by a
rational analysis method defined in the recognized literature.
2.4.7
Topographic Effects
##### 2.4.7.1 Wind speed-up over hills, ridges and escarpments
Wind speed-up effects at isolated hills, ridges, and escarpments constituting
abrupt changes in the general topography located in any exposure category
shall be included in the design when buildings and other site conditions and
locations of structures meet all of the following conditions:
(i) The hill, ridge, or escarpment is isolated and unobstructed upwind by
other similar topographic features of comparable height for 100 times
the height of the topographic feature (100 H) or 3.22 km, whichever is
less. This distance shall be measured horizontally from the point at
which the height H of the hill, ridge, or escarpment is determined.
(ii) The hill, ridge, or escarpment protrudes above the height of upwind
terrain features within a 3.22 km radius in any quadrant by a factor of
two or more.
(iii) The structure is located as shown in Figure 6.2.4 in the upper one-half of
a hill or ridge or near the crest of an escarpment.
(iv) -/63 ≥0.2
(v) - is greater than or equal to 4.5 m for Exposures B and C and 18.3 m for
Exposure A.
##### 2.4.7.2 Topographic factor
The wind speed-up effect shall be included in the calculation of design wind
loads by using the factor 0/":
0/" 5 (1 + 01002)
(6.2.5)
Where, 01, 0, and 02 are given in Figure 6.2.4. If site conditions and locations of
structures do not meet all the conditions specified in Sec 2.4.7.1 then 0/"5 1.0.
2.4.8
Gust Effect Factor
##### 2.4.8.1 Rigid structures
For rigid structures as defined in Sec 2.1.3, the gust-effect factor shall be taken
as 0.85 or calculated by the formula:
, 5 0.925
1³1.s´µ¶FR
1³1.s·µ¶F
(6.2.6)
./̅ 5 O ¸
1=
/̅ ¹
1 º
»
(6.2.7)
Where, ./̅5 the intensity of turbulence at height 4̅ where 4̅ 5 the equivalent
height of the structure defined as 0.6h, but not less than 4\ ) for all building
heights ℎ. 4\ ) and c are listed for each exposure in Table 6.2.10; QR and the
value of Q¼ shall be taken as 3.4. The background response Q is given by
? 5 ¾
1³=.º2n¿ÀÁ
v¶F y
Â.ÃÄ
(6.2.8)
Where, B, h are defined in Sec 2.1.4; and 6/̅ 5 the integral length scale of
turbulence at the equivalent height given by
6/̅ 5 V ¸
/̅
1=¹
ÅF
(6.2.9)
In which l and ∈\_ are constants listed in Table 6.2.10.
##### 2.4.8.2 Flexible or dynamically sensitive structures
For flexible or dynamically sensitive structures as defined in Sec 2.1.3 (natural
period greater than 1.0 second), the gust-effect factor shall be calculated by
, 5 0.925 Æ
1³1.sµ¶FÇ´
ÈRȳÉ
ÈSÈ
1³1.s·µ¶F
Ê
(6.2.10)
The value of both QR and QT shall be taken as 3.4 and QS is given by
QS 5 t2 ln(3600*1) +
\=.rss
t ËÌ(2º==)Í)
(6.2.11)
@, the resonant response factor, is given by
@ 5 Ç
Î @)@3\@A(0.53 + 0.47\@B)
(6.2.12)
@) 5
s.qs Í
(1³1=.2 Í)
Ï Ä
»
(6.2.13)
:1 5
)ÍB¶F
T\_¶F
(6.2.14)
@Ð 5
Ñ −
ÑÈ (1 −PÒÑ) for f > 0
(6.2.15a)
@Ð 5 1 for f 5 0
(6.2.15b)
Where, the subscript V in Eq. 6.2.15 shall be taken as ℎ, , and 6, respectively,
where ℎ, , and 6 are defined in
Sec 2.1.4.
*1 5 building natural frequency
@Ð 5 @3 setting f 5 4.6*1ℎ/F/̅
@Ð 5 @A setting f 5 4.6*1 /F/̅
@Ð 5 @B setting f 5 15.4\*16/F/̅
c 5 damping ratio, percent of critical
F/̅ 5 mean hourly wind speed at height 4̅ determined from Eq. 6.2.16.
F/̅ 5 MF ¸
/̅
1=¹
∝\_
(6.2.16)
Where, MF and ∝\_ are constants listed in Table 6.2.10.
##### 2.4.8.3 Rational analysis
In lieu of the procedure defined in Sections 2.4.8.1 and 2.4.8.2, determination of
the gust-effect factor by any rational analysis defined in the recognized
literature is permitted.
##### 2.4.8.4 Limitations
Where combined gust-effect factors and pressure coefficients Ô, !, , ! , , !Õ
are given in figures and tables, the gust-effect factor shall not be determined
separately.
2.4.9
Enclosure Classifications
##### 2.4.9.1 General
For the purpose of determining internal pressure coefficients, all buildings shall
be classified as enclosed, partially enclosed, or open as defined in Sec 2.1.3.
##### 2.4.9.2 Openings
A determination shall be made of the amount of openings in the building
envelope to determine the enclosure classification as defined in Sec 2.4.9.3.
##### 2.4.9.3 Wind-borne debris
Glazing in buildings located in wind-borne debris regions shall be protected
with an impact-resistant covering or be impact-resistant glazing according to
the requirements specified in ASTM E1886 and ASTM E1996 or other approved
test methods and performance criteria. The levels of impact resistance shall be a
function of Missile Levels and Wind Zones specified in ASTM E1886 and ASTM
E1996.
Exceptions:
(i) Glazing in Category II, III, or IV buildings located over 18.3 m above the
ground and over 9.2 m above aggregate surface roofs located within 458
m of the building shall be permitted to be unprotected.
(ii) Glazing in Category I buildings shall be permitted to be unprotected.
##### 2.4.9.4 Multiple classifications
ওভ ধ নঁরষফরহম নু ফবভরহরঃরড়হ পড়সঢ়ষরবং রিঃয নড়ঃয:যব ুড়ঢ়বহচ্ ধহফ ুঢ়ধৎঃরধষষু বহপষড়ংবফচ্
ফবভরহরঃরড়হং, রঃ ংযধষষ নব পষধংংরভরবফ ধং ধহ ুড়ঢ়বহচ্ নঁরষফরহম. অ নঁরষফরহম:যধঃ ফড়বং হড়ঃ
পড়সঢ়ষু রিঃয বরঃযবৎ:যব ুড়ঢ়বহচ্ ড়ৎ ুঢ়ধৎঃরধষষু বহপষড়ংবফচ্ ফবভরহরঃরড়হং ংযধষষ নব
পষধংংরভরবফ ধং ধহ ুবহপষড়ংবফচ্ নঁরষফরহম.
##### 2.4.9.5 Velocity pressure
Velocity pressure, X/ evaluated at height z shall be calculated by the following
equation:
X/ 5 0.0006130/0/"0 . ; (kN/m2), V in m/s
(6.2.17)
Where 0 is the wind directionality factor, 0/ is the velocity pressure exposure
coefficient defined in Sec 2.4.6.6, 0/" is the topographic factor defined in Sec
2.4.7.2, and X/ is the velocity pressure calculated using Eq. 6.2.17 at mean roof
height ℎ. The numerical coefficient 0.000613 shall be used except where
sufficient climatic data are available to justify the selection of a different value of
this factor for a design application.
#### 2.4.10 Pressure And Force Coefficients
2.4.10.1
Internal pressure coefficients
Internal Pressure Coefficient. Internal pressure coefficients, , ! shall be
determined from Figure 6.2.5 based on building enclosure classifications
determined from Sec 2.4.9.
Reduction Factor for Large Volume Buildings, @ : For a partially enclosed
building containing a single, unpartitioned large volume, the internal pressure
coefficient, , ! shall be multiplied by the following reduction factor, @ :
@ 5 1.0 or, @ 5 0.5 Æ1 +
Ç1³
ÙÚ
ÃÛÏÍÜÝÞ
Ê ≤1.0
(6.2.18)
Where, 5 total area of openings in the building envelope (walls and roof, in
m2)
5 unpartitioned internal volume, in m3
##### 2.4.10.2 External pressure coefficients
Main Wind-Force Resisting Systems: External pressure coefficients for MWFRSs
! are given in Figures 6.2.6 to 6.2.8. Combined gust effect factor and external
pressure coefficients, , ! are given in Figure 6.2.10 for low-rise buildings. The
pressure coefficient values and gust effect factor in Figure 6.2.10 shall not be
separated.
Components and Cladding: Combined gust effect factor and external pressure
coefficients for components and cladding , ! are given in Figures 6.2.11 to
6.2.17. The pressure coefficient values and gust-effect factor shall not be
separated.
##### 2.4.10.3 Force coefficients
Force coefficients are given in Figures 6.2.20 to 6.2.23.
##### 2.4.10.4 Roof overhangs
Main Wind-Force Resisting System: Roof overhangs shall be designed for a
positive pressure on the bottom surface of windward roof overhangs
corresponding to ! 5 0.8 in combination with the pressures determined from
using Figures 6.2.6 and 6.2.10.
Components and Cladding: For all buildings, roof overhangs shall be designed
for pressures determined from pressure coefficients given in Figure 6.2.11.
##### 2.4.10.5 Parapets
Main Wind-Force Resisting System: The pressure coefficients for the effect of
parapets on the MWFRS loads are given in Sec 2.4.12.2.
Components and Cladding: The pressure coefficients for the design of parapet
component and cladding elements are taken from the wall and roof pressure
coefficients as specified in Sec 2.4.12.3.
#### 2.4.11 Design Wind Loads on Enclosed and Partially Enclosed Buildings
##### 2.4.11.1 General
Sign Convention: Positive pressure acts toward the surface and negative
pressure acts away from the surface.
Critical Load Condition: Values of external and internal pressures shall be
combined algebraically to determine the most critical load.
Tributary Areas Greater than 65 m2: Component and cladding elements with
tributary areas greater than 65 m2 shall be permitted to be designed using the
provisions for MWFRSs.
##### 2.4.11.2 Main wind-force resisting systems
Rigid Buildings of All Heights: Design wind pressures for the MWFRS of
buildings of all heights shall be determined by the following equation:
W 5 X, ! −X Ô, ! Õ (kN m
⁄
)
(6.2.19)
Where,
X 5 X/ for windward walls evaluated at height 4 above the ground
X 5 X3 for leeward walls, side walls, and roofs, evaluated at height ℎ
X 5 X3 for windward walls, side walls, leeward walls, and roofs of
enclosed buildings and for negative internal pressure evaluation
in partially enclosed buildings.
X 5 X/ for positive internal pressure evaluation in partially enclosed
buildings where height 4 is defined as the level of the highest opening in
the building that could affect the positive internal pressure. For
buildings sited in wind-borne debris regions, glazing that is not impact
resistant or protected with an impact resistant covering, shall be treated
as an opening in accordance with Sec 2.4.9.3. For positive internal
pressure evaluation, X may conservatively be evaluated at height ℎ5
(X 5 X3)
, 5 gust effect factor from Sec 2.4.8
! 5 external pressure coefficient from Figures 6.2.6 or 6.2.8
, ! 5 internal pressure coefficient from Figure 6.2.5
X and X shall be evaluated using exposure defined in Sec 2.4.6.3. Pressure shall
be applied simultaneously on windward and leeward walls and on roof surfaces
as defined in Figures 6.2.6 and 6.2.8.
Low-Rise Building: Alternatively, design wind pressures for the MWFRS of low-
rise buildings shall be determined by the following equation:
W 5 X3àÔ, !Õ −Ô, ! Õá (kN m
⁄
)
(6.2.20)
Where,
X3 5 velocity pressure evaluated at mean roof height h using exposure
defined in Sec 2.4.6.3
, ! 5 external pressure coefficient from Figure 6.2.10
, ! 5 internal pressure coefficient from Figure 6.2.5
Flexible Buildings: Design wind pressures for the MWFRS of flexible buildings
shall be determined from the following equation:
W 5 X, ! −X Ô, ! Õ (k N m
⁄
)
(6.2.21)
Where, X, X , !, and , ! are as defined in Sec 2.4.11.2 and ,5 gust effect
factor is defined as in Sec 2.4.8.
Parapets: The design wind pressure for the effect of parapets on MWFRSs of
rigid, low-rise, or flexible buildings with flat, gable, or hip roofs shall be
determined by the following equation:
W! 5 X!, !) (kN m
⁄
)
(6.2.22)
Where,
W! 5 Combined net pressure on the parapet due to the combination of
the net pressures from the front and back parapet surfaces. Plus
(and minus) signs signify net pressure acting toward (and away
from) the front (exterior) side of the parapet
X! 5 Velocity pressure evaluated at the top of the parapet
, !) 5 Combined net pressure coefficient
5 +1.5 for windward parapet
5 −1.0 for leeward parapet
2.4.11.3
Design wind load cases
The MWFRS of buildings of all heights, whose wind loads have been determined
under the provisions of Sec 2.4.11.2, shall be designed for the wind load cases as
defined in Figure 6.2.9. The eccentricity e for rigid structures shall be measured
from the geometric center of the building face and shall be considered for each
principal axis ÔP, PHÕ. The eccentricity P for flexible structures shall be
determined from the following equation and shall be considered for each
principal axis ÔP , PâÕ:
P 5
\<´³1.sµ¶FÇÔ´R\<´Õ
ȳ(ÉS\<É)È
1³1.sµ¶FÇÔ´RÕ
ȳ(ÉS)È
(6.2.23)
Where,
PR 5 Eccentricity e as determined for rigid structures in Figure 6.2.9
PS 5 Distance between the elastic shear center and center of mass of
each floor
./̅, QR, ?, QS, @ shall be as defined in Sec 2.1.4
The sign of the eccentricity P shall be plus or minus, whichever causes the more
severe load effect.
Exception: One-story buildings with h less than or equal to 9.1 m, buildings two
stories or less framed with light-frame construction, and buildings two stories
or less designed with flexible diaphragms need only be designed for Load Case 1
and Load Case 3 in Figure 6.2.9.
##### 2.4.11.4 Components and cladding.
Low-Rise Buildings and Buildings with ℎ≤18.3 m: Design wind pressures on
component and cladding elements of low-rise buildings and buildings with ℎ≤
### 18.3 m shall be determined from the following equation:
W 5 X3àÔ, !Õ −Ô, ! Õá (kN m
⁄
)
(6.2.24)
Where,
X3 5 Velocity pressure evaluated at mean roof height ℎ using exposure
defined in Sec 2.4.6.5
, ! 5 External pressure coefficients given in Figures 6.2.11 to 6.2.16
, ! 5 Internal pressure coefficient given in Figure 6.2.5
Buildings with ℎ> 18.3 m: Design wind pressures on components and cladding
for all buildings with ℎ> 18.3 m shall be determined from the following
equation:
W 5 XÔ, !Õ −X Ô, ! Õ (kN/m)
(6.2.25)
Where,
X 5 X/ for windward walls calculated at height 4 above the ground
X 5 X3 for leeward walls, side walls, and roofs, evaluated at height ℎ
X 5 X3 for windward walls, side walls, leeward walls, and roofs of
enclosed buildings and for negative internal pressure evaluation in
partially enclosed buildings
X 5 X/ for positive internal pressure evaluation in partially enclosed
buildings where height 4 is defined as the level of the highest opening in
the building that could affect the positive internal pressure. For
buildings sited in wind-borne debris regions, glazing that is not impact
resistant or protected with an impact-resistant covering, shall be
treated as an opening in accordance with Sec 2.4.9.3. For positive
internal pressure evaluation, qi may conservatively be evaluated at
height ℎ (X 5 X3)
Ô, !Õ 5 external pressure coefficient from Figure 6.2.17.
Ô, ! Õ 5 internal pressure coefficient given in Figure 6.2.5. X and X
shall be evaluated using exposure defined in Sec 2.4.6.3.
2.4.11.5
Alternative design wind pressures for components and cladding in
buildings with 18.3 m \< ℎ\< 27.4 m.
Alternative to the requirements of Sec 2.4.11.2, the design of components and
cladding for buildings with a mean roof height greater than 18.3 m and less than
### 27.4 m values from Figures 6.2.11 to 6.2.17 shall be used only if the height to
width ratio is one or less (except as permitted by Notes of Figure 6.2.17) and Eq.
#### 6.2.24 is used.
Parapets: The design wind pressure on the components and cladding elements
of parapets shall be designed by the following equation:
W 5 X!Ô, ! −, ! Õ
(6.2.26)
Where,
X! 5 Velocity pressure evaluated at the top of the parapet
, ! 5 External pressure coefficient from Figures 6.2.11 to 6.2.17
, ! 5 Internal pressure coefficient from Figure 6.2.5, based on the
porosity of the parapet envelope.
Two load cases shall be considered. Load Case A shall consist of applying the
applicable positive wall pressure from Figures 6.2.11 or 6.2.17 to the front
surface of the parapet while applying the applicable negative edge or corner
zone roof pressure from Figures 6.2.11 to 6.2.17 to the back surface. Load Case
B shall consist of applying the applicable positive wall pressure from Figures
#### 6.2.11 or 6.2.17 to the back of the parapet surface, and applying the applicable
negative wall pressure from Figures 6.2.11 or 6.2.17 to the front surface. Edge
and corner zones shall be arranged as shown in Figures 6.2.11 to 6.2.17. , !
shall be determined for appropriate roof angle and effective wind area from
Figures 6.2.11 to 6.2.17. If internal pressure is present, both load cases should
be evaluated under positive and negative internal pressure.
#### 2.4.12 Design Wind Loads on Open Buildings with Monoslope, Pitched, or
Troughed Roofs
##### 2.4.12.1 General
Sign Convention: Plus and minus signs signify pressure acting toward and away
from the top surface of the roof, respectively.
Critical Load Condition: Net pressure coefficients CN include contributions from
top and bottom surfaces. All load cases shown for each roof angle shall be
investigated.
2.4.12.2
Main wind-force resisting systems
The net design pressure for the MWFRSs of monoslope, pitched, or troughed
roofs shall be determined by the following equation:
W 5 X3,
(6.2.27)
Where,
X3 5 Velocity pressure evaluated at mean roof height h using the
exposure as defined in Sec 2.4.6.3 that results in the highest wind
loads for any wind direction at the site
, 5 Gust effect factor from Sec 2.4.8
5 Net pressure coefficient determined from Figures 6.2.18(a) to
6.2.18(d).
For free roofs with an angle of plane of roof from horizontal g less than or equal
to 5o and containing fascia panels, the fascia panel shall be considered an
inverted parapet. The contribution of loads on the fascia to the MWFRS loads
shall be determined using Sec 2.4.11.5 with X! equal to X3 .
2.4.12.3
Component and cladding elements
The net design wind pressure for component and cladding elements of
monoslope, pitched, and troughed roofs shall be determined by the following
equation:
W 5 X3,
(6.2.28)
Where,
X3 5 Velocity pressure evaluated at mean roof height ℎ using the
exposure as defined in Sec 2.4.6.3 that results in the highest wind
loads for any wind direction at the site
, 5 Gust-effect factor from Sec 2.4.8
5 Net pressure coefficient determined from Figures 6.2.19(a) to
6.2.19(c).
#### 2.4.13 Design Wind Loads on Solid Free Standing Walls and Solid Signs
The design wind force for solid freestanding walls and solid signs shall be
determined by the following formula:
& 5 X3, (kN)
(6.2.29)
Where,
X3 5 Velocity pressure evaluated at height ℎ (Figure 6.2.20) using
exposure defined in Sec2.4.6.3
, 5 Gust-effect factor from Sec 2.4.8
5 Net force coefficient from Figure 6.2.20
5 Gross area of the solid freestanding wall or solid sign, in m2
#### 2.4.14 Design Wind Loads on Other Structures
The design wind force for other structures shall be determined by the following
equation:
& 5 X/, (kN)
(6.2.30)
Where,
X/ 5 Velocity pressure evaluated at height 4 of the centroid of area
using exposure as in Sec 2.4.6.3
, 5 Gust-effect factor from Sec 2.4.8
5 Force coefficients from Figures 6.2.21 to 6.2.23.
5 Projected area normal to the wind except where is specified for
the actual surface area, m2
#### 2.4.15 Rooftop Structures and Equipment for Buildings with ã ≤äå.æ ç
The force on rooftop structures and equipment with less than (0.1 ℎ)
located on buildings with ℎ≤18.3 m shall be determined from Eq. 6.2.30,
increased by a factor of 1.9. The factor shall be permitted to be reduced linearly
from 1.9 to 1.0 as the value of is increased from (0.1 ℎ) to ( ℎ).
#### 2.4.16 Method 3 - Wind Tunnel Procedure
##### 2.4.16.1 Scope
Wind tunnel tests shall be used where required by Sec 2.4.3.1. Wind tunnel
testing shall be permitted in lieu of Methods 1 and 2 for any building or
structure.
##### 2.4.16.2 Test conditions
Wind tunnel tests, or similar tests employing fluids other than air, used for the
determination of design wind loads for any building or other structure, shall be
conducted in accordance with this Section. Tests for the determination of mean
and fluctuating forces and pressures shall meet all of the following conditions:
(i)
Natural atmospheric boundary layer has been modeled to account for
the variation of wind speed with height.
(ii) The relevant macro- (integral) length and micro-length scales of the
longitudinal component of atmospheric turbulence are modeled to
approximately the same scale as that used to model the building or
structure.
(iii) The modeled building or other structure and surrounding structures
and topography are geometrically similar to their full-scale
counterparts, except that, for low-rise buildings meeting the
requirements of Sec 2.4.3.1, tests shall be permitted for the modeled
building in a single exposure site as in Sec 2.4.6.
(iv) The projected area of the modeled building or other structure and
surroundings is less than 8 percent of the test section cross-sectional
area unless correction is made for blockage.
(v) The longitudinal pressure gradient in the wind tunnel test section is
accounted for.
(vi) Reynolds number effects on pressures and forces are minimized.
(vii) Response characteristics of the wind tunnel instrumentation are
consistent with the required measurements.
#### 2.4.17 Dynamic Response
Tests for the purpose of determining the dynamic response of a building or
other structure shall be in accordance with Sec 2.4.16.2. The structural model
and associated analysis shall account for mass distribution, stiffness, and
damping.
Enclosed Buildings: Walls & Roofs
Notes:
1. Pressures shown are applied to the horizontal and vertical projections, for exposure
A, at h=9.1m, I=1.0, and Kzt = 1.0. Adjust to other conditions using Equation 6.2.3.
2. The load patterns shown shall be applied to each corner of the building in turn as the reference
corner. (See Figure 6.2.10)
3. For the design of the longitudinal MWFRS use θ = 0°, and locate the zone E/F, G/H boundary at
the mid-length of the building.
4. Load cases 1 and 2 must be checked for 25° \< θ ≤ 45°. Load case 2 at 25° is provided only for
interpolation between 25° to 30°.
5. Plus and minus signs signify pressures acting toward and away from the projected surfaces,
respectively.
6. For roof slopes other than those shown, linear interpolation is permitted.
7. The total horizontal load shall not be less than that determined by assuming ps = 0 in zones B & D.
8. The zone pressures represent the following:
Horizontal pressure zones – Sum of the windward and leeward net (sum of internal and external)
pressures on vertical projection of:
A - End zone of wall
C - Interior zone of wall
B - End zone of roof
D - Interior zone of roof
Vertical pressure zones – Net (sum of internal and external) pressures on horizontal projection of:
E - End zone of windward roof G - Interior zone of windward roof
F - End zone of leeward roof H - Interior zone of leeward roof
9\. Where zone E or G falls on a roof overhang on the windward side of the building, use EOH and
GOH for the pressure on the horizontal projection of the overhang. Overhangs on the leeward
and side edges shall have the basic zone pressure applied.
10\. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than
either 4% of least horizontal dimension or 0.9 m.
h: Mean roof height, in feet (meters), except that eave height shall be used for roof angles \<10°.
θ: Angle of plane of roof from horizontal, in degrees.
Adjustment Factor for Building Height and Exposure,
Mean roof height (m)
Exposure
A
B
C
4.6
1.00
1.21
1.47
6.0
1.00
1.29
1.55
7.6
1.00
1.35
1.61
9.1
1.00
1.40
1.66
10.7
1.05
1.45
1.70
12.2
1.09
1.49
1.74
13.7
1.12
1.53
1.78
15.2
1.16
1.56
1.81
16.8
1.19
1.59
1.84
18.3
1.22
1.62
1.87
Figure 6.2.2 Design wind pressure for main wind force resisting system- Method 1
(h ≤ 18.3 m)
Enclosed Buildings: Walls & Roofs
Notes:
1. Pressures shown are applied normal to the surface, for exposure A, at h = 9.1m, I = 1.0, and Kzt =
1.0. Adjust to other conditions using Equation 6.2.4.
2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.
3. For hip roofs with θ ≤ 25°, Zone 3 shall be treated as Zone 2.
4. For effective wind areas between those given, value may be interpolated, otherwise use the value
associated with the lower effective wind area.
5. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4%
of least horizontal dimension or 0.9 m.
h: Mean roof height, in feet (meters), except that eave height shall be used for roof angles \<10°.
θ: Angle of plane of roof from horizontal, in degrees.
| Adjustment Factor for Building Height and Exposure, | Col2 |
| ------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Mean roof height (m)** | **Exposure** |
| **Mean roof height (m)** | \*\*A \*\*
\*\*B \*\*
\*\*C \*\* |
| 4.6
6.0
7.6
9.1
10.7
12.2
13.7
15.2
16.8
18.3 | 1.00
1.21
1.47
1.00
1.29
1.55
1.00
1.35
1.61
1.00
1.40
1.66
1.05
1.45
1.70
1.09
1.49
1.74
1.12
1.53
1.78
1.16
1.56
1.81
1.19
1.59
1.84
1.22
1.62
1.87 |
Roof Overhang Net Design Wind Pressure, Pnet30 (kN/m2)
(Exposure A at h = 9.1 m with l= 1.0)
Roof
Pitch
Zone
Effective
Wind area (m2)
Basic Wind Speed V (m/s)
40.23
44.7
49.17
53.64 58.11 62.58
67.05
75.99
Roof 0 to 7 degrees
0.930
-1.005 -1.239 -1.502 -1.785 -2.096 -2.431 -2.790 -3.584
1.860
-0.986 -1.220 -1.473 -1.756 -2.058 -2.388 -2.742 -3.522
4.648
-0.962 -1.191 -1.440 -1.713 -2.010 -2.330 -2.675 -3.436
9.296
-0.947 -1.168 -1.412 -1.680 -1.971 -2.287 -2.627 -3.373
0.930
-1.656 -2.043 -2.470 -2.943 -3.450 -4.005 -4.594 -5.905
1.860
-1.297 -1.603 -1.938 -2.311 -2.708 -3.144 -3.609 -4.632
4.648
-0.828 -1.024 -1.240 -1.474 -1.727 -2.005 -2.302 -2.957
9.296
-0.479 -0.584 -0.708 -0.842 -0.986 -1.144 -1.311 -1.684
Figure 6.2.3 Design wind pressure for components and cladding - Method 1 (h ≤ 18.3 m)
Roof Overhang Net Design Wind Pressure, Pnet30 (kN/m2)
(Exposure A at h = 9.1 m with l= 1.0)
Roof
Pitch
Zone
Effective
Wind area
(m2)
Basic Wind Speed V (m/s)
40.23
44.7
49.17 53.64 58.11
62.58
67.05
75.99
Roof > 7 to 27 degrees
0.930
-1.302 -1.603 -1.943 -2.311 -2.713 -3.144
-3.613
-4.637
1.860
-1.302 -1.603 -1.943 -2.311 -2.713 -3.144
-3.613
-4.637
4.648
-1.302 -1.603 -1.943 -2.311 -2.713 -3.144
-3.613
-4.637
9.296
-1.302 -1.603 -1.943 -2.311 -2.713 -3.144
-3.613
-4.637
0.930
-2.187 -2.699 -3.268 -3.885 -4.560 -5.292
-6.072
-7.800
1.860
-1.971 -2.436 -2.948 -3.507 -4.115 -4.775
-5.479
-7.039
4.648
-1.689 -2.086 -2.526 -3.005 -3.526 -4.091
-4.694
-6.034
9.296
-1.479 -1.823 -2.206 -2.627 -3.082 -3.574
-4.106
-5.268
| Roof
Pitch | Zone | Effective
Wind area (m2) | Basic Wind Speed V (m/s) | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 |
| ------------------------ | ---------- | ------------------------------------- | ------------------------ | -------- | --------- | --------- | -------------- | --------------- | --------- | --------- |
| **Roof**
**Pitch** | **Zone** | **Effective**
**Wind area (m2)** | **40.23** | **44.7** | **49.17** | **53.64** | \*\* 58.11\*\* | \*\* 62.58\*\* | **67.05** | **75.99** |
| **Roof 0 to 7 degrees** | \*\*2 \*\* | 0.930 | -1.005 | -1.239 | -1.502 | -1.785 | -2.096 | -2.431 | -2.790 | -3.584 |
| **Roof 0 to 7 degrees** | \*\*2 \*\* | 1.860 | -0.986 | -1.220 | -1.473 | -1.756 | -2.058 | -2.388 | -2.742 | -3.522 |
| **Roof 0 to 7 degrees** | \*\*2 \*\* | 4.648 | -0.962 | -1.191 | -1.440 | -1.713 | -2.010 | -2.330 | -2.675 | -3.436 |
| **Roof 0 to 7 degrees** | \*\*2 \*\* | 9.296 | -0.947 | -1.168 | -1.412 | -1.680 | -1.971 | -2.287 | -2.627 | -3.373 |
| **Roof 0 to 7 degrees** | \*\*3 \*\* | 0.930 | -1.656 | -2.043 | -2.470 | -2.943 | -3.450 | -4.005 | -4.594 | -5.905 |
| **Roof 0 to 7 degrees** | \*\*3 \*\* | 1.860 | -1.297 | -1.603 | -1.938 | -2.311 | -2.708 | -3.144 | -3.609 | -4.632 |
| **Roof 0 to 7 degrees** | \*\*3 \*\* | 4.648 | -0.828 | -1.024 | -1.240 | -1.474 | -1.727 | -2.005 | -2.302 | -2.957 |
| **Roof 0 to 7 degrees** | \*\*3 \*\* | 9.296 | -0.479 | -0.584 | -0.708 | -0.842 | -0.986 | -1.144 | -1.311 | -1.684 |
| Roof
Pitch | Zone | Effective
Wind area
(m2) | Basic Wind Speed V (m/s) | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 |
| -------------------------- | ---------- | ---------------------------------------------- | ------------------------ | -------- | --------- | --------- | --------- | --------- | --------- | --------- |
| **Roof**
**Pitch** | **Zone** | **Effective**
**Wind area**
**(m2)** | **40.23** | **44.7** | **49.17** | **53.64** | **58.11** | **62.58** | **67.05** | **75.99** |
| **Roof > 7 to 27 degrees** | \*\*2 \*\* | 0.930 | -1.302 | -1.603 | -1.943 | -2.311 | -2.713 | -3.144 | -3.613 | -4.637 |
| **Roof > 7 to 27 degrees** | \*\*2 \*\* | 1.860 | -1.302 | -1.603 | -1.943 | -2.311 | -2.713 | -3.144 | -3.613 | -4.637 |
| **Roof > 7 to 27 degrees** | \*\*2 \*\* | 4.648 | -1.302 | -1.603 | -1.943 | -2.311 | -2.713 | -3.144 | -3.613 | -4.637 |
| **Roof > 7 to 27 degrees** | \*\*2 \*\* | 9.296 | -1.302 | -1.603 | -1.943 | -2.311 | -2.713 | -3.144 | -3.613 | -4.637 |
| **Roof > 7 to 27 degrees** | \*\*3 \*\* | 0.930 | -2.187 | -2.699 | -3.268 | -3.885 | -4.560 | -5.292 | -6.072 | -7.800 |
| **Roof > 7 to 27 degrees** | \*\*3 \*\* | 1.860 | -1.971 | -2.436 | -2.948 | -3.507 | -4.115 | -4.775 | -5.479 | -7.039 |
| **Roof > 7 to 27 degrees** | \*\*3 \*\* | 4.648 | -1.689 | -2.086 | -2.526 | -3.005 | -3.526 | -4.091 | -4.694 | -6.034 |
| **Roof > 7 to 27 degrees** | \*\*3 \*\* | 9.296 | -1.479 | -1.823 | -2.206 | -2.627 | -3.082 | -3.574 | -4.106 | -5.268 |
Roof >27 to 45 degrees
0.930
-1.182 -1.460 -1.766 -2.101 -2.464 -2.861
-3.282
-4.216
1.860
-1.148 -1.416 -1.713 -2.038 -2.393 -2.775
-3.182
-4.091
4.648
-1.101 -1.359 -1.641 -1.952 -2.292 -2.660
-3.052
-3.924
9.296
-1.062 -1.311 -1.587 -1.890 -2.220 -2.574
-2.952
-3.795
0.930
-1.182 -1.460 -1.766 -2.101 -2.464 -2.861
-3.283
-4.216
1.860
-1.148 -1.416 -1.713 -2.038 -2.393 -2.775
-3.182
-4.091
4.648
-1.101 -1.359 -1.641 -1.952 -2.292 -2.660
-3.053
-3.923
9.296
-1.062 -1.311 -1.589 -1.890 -2.220 -2.574
-2.952
-3.795
Adjustment Factor for Building Height and Exposure,
Mean roof height (m)
Exposure
A
B
C
4.6
1.00
1.21
1.47
6.1
1.00
1.29
1.55
7.6
1.00
1.35
1.61
9.15
1.00
1.40
1.66
10.7
1.05
1.45
1.70
12.2
1.09
1.49
1.74
13.7
1.12
1.53
1.78
15.2
1.16
1.56
1.81
16.8
1.19
1.59
1.84
18.3
1.22
1.62
1.87
Unit Conversion – 1.0 ft =0.3048 m; 1.0 ft2 = 0.0929 m2; 1.0 psf = 0.0479 kN/m2
Figure 6.2.3 (Contd.) Design wind pressure for components and cladding-Method 1
(h ≤ 18.3 m)
| Roof >27 to 45 degrees | 2 | 0.930 | Col4 | -1.182 | -1.460 | -1.766 | Col8 | -2.101 | -2.464 | -2.861 | Col12 | -3.282 | -4.216 |
| ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ |
| **Roof >27 to 45 degrees** | \*\*2 \*\* | 1.860 | 1.860 | -1.148 | -1.416 | -1.713 | -1.713 | -2.038 | -2.393 | -2.775 | -2.775 | -3.182 | -4.091 |
| **Roof >27 to 45 degrees** | \*\*2 \*\* | 4.648 | 4.648 | -1.101 | -1.359 | -1.641 | -1.641 | -1.952 | -2.292 | -2.660 | -2.660 | -3.052 | -3.924 |
| **Roof >27 to 45 degrees** | \*\*2 \*\* | 9.296 | 9.296 | -1.062 | -1.311 | -1.587 | -1.587 | -1.890 | -2.220 | -2.574 | -2.574 | -2.952 | -3.795 |
| **Roof >27 to 45 degrees** | \*\*3 \*\* | 0.930 | 0.930 | -1.182 | -1.460 | -1.766 | -1.766 | -2.101 | -2.464 | -2.861 | -2.861 | -3.283 | -4.216 |
| **Roof >27 to 45 degrees** | \*\*3 \*\* | 1.860 | 1.860 | -1.148 | -1.416 | -1.713 | -1.713 | -2.038 | -2.393 | -2.775 | -2.775 | -3.182 | -4.091 |
| **Roof >27 to 45 degrees** | \*\*3 \*\* | 4.648 | 4.648 | -1.101 | -1.359 | -1.641 | -1.641 | -1.952 | -2.292 | -2.660 | -2.660 | -3.053 | -3.923 |
| **Roof >27 to 45 degrees** | \*\*3 \*\* | 9.296 | 9.296 | -1.062 | -1.311 | -1.589 | -1.589 | -1.890 | -2.220 | -2.574 | -2.574 | -2.952 | -3.795 |
| \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* | \*\*Adjustment Factor for Building Height and Exposure,\*\* |
| **Mean roof height (m)** | **Mean roof height (m)** | **Mean roof height (m)** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** | **Exposure** |
| **Mean roof height (m)** | **Mean roof height (m)** | **Mean roof height (m)** | \*\*A \*\* | \*\*A \*\* | \*\*A \*\* | \*\*A \*\* | \*\*B \*\* | \*\*B \*\* | \*\*B \*\* | \*\*B \*\* | \*\*C \*\* | \*\*C \*\* | \*\*C \*\* |
| 4.6 | 4.6 | 4.6 | 1.00 | 1.00 | 1.00 | 1.00 | 1.21 | 1.21 | 1.21 | 1.21 | 1.47 | 1.47 | 1.47 |
| 6.1 | 6.1 | 6.1 | 1.00 | 1.00 | 1.00 | 1.00 | 1.29 | 1.29 | 1.29 | 1.29 | 1.55 | 1.55 | 1.55 |
| 7.6 | 7.6 | 7.6 | 1.00 | 1.00 | 1.00 | 1.00 | 1.35 | 1.35 | 1.35 | 1.35 | 1.61 | 1.61 | 1.61 |
| 9.15 | 9.15 | 9.15 | 1.00 | 1.00 | 1.00 | 1.00 | 1.40 | 1.40 | 1.40 | 1.40 | 1.66 | 1.66 | 1.66 |
| 10.7 | 10.7 | 10.7 | 1.05 | 1.05 | 1.05 | 1.05 | 1.45 | 1.45 | 1.45 | 1.45 | 1.70 | 1.70 | 1.70 |
| 12.2 | 12.2 | 12.2 | 1.09 | 1.09 | 1.09 | 1.09 | 1.49 | 1.49 | 1.49 | 1.49 | 1.74 | 1.74 | 1.74 |
| 13.7 | 13.7 | 13.7 | 1.12 | 1.12 | 1.12 | 1.12 | 1.53 | 1.53 | 1.53 | 1.53 | 1.78 | 1.78 | 1.78 |
| 15.2 | 15.2 | 15.2 | 1.16 | 1.16 | 1.16 | 1.16 | 1.56 | 1.56 | 1.56 | 1.56 | 1.81 | 1.81 | 1.81 |
| 16.8 | 16.8 | 16.8 | 1.19 | 1.19 | 1.19 | 1.19 | 1.59 | 1.59 | 1.59 | 1.59 | 1.84 | 1.84 | 1.84 |
| 18.3 | 18.3 | 18.3 | 1.22 | 1.22 | 1.22 | 1.22 | 1.62 | 1.62 | 1.62 | 1.62 | 1.87 | 1.87 | 1.87 |
Topographic Multipliers for Exposure B
H/Lh
K1 Multiplier
x/Lh
K2 Multiplier
z/Lh
K3 Multiplier
2-D
Ridge
2-D
Escarp.
3-D
Axisym.
Hill
2-D
Escarp.
All
Other
Cases
2-D
Ridge
2-D
Escarp.
3-D
Axisym.
Hill
0.20
0.29
0.17
0.21
0.00
1.00
1.00
0.00
1.00
1.00
1.00
0.25
0.36
0.21
0.26
0.50
0.88
0.67
0.10
0.74
0.78
0.67
0.30
0.43
0.26
0.32
1.00
0.75
0.33
0.20
0.55
0.61
0.45
0.35
0.51
0.30
0.37
1.50
0.63
0.00
0.30
0.41
0.47
0.30
0.40
0.58
0.34
0.42
2.00
0.50
0.00
0.40
0.30
0.37
0.20
0.45
0.65
0.38
0.47
2.50
0.38
0.00
0.50
0.22
0.29
0.14
0.50
0.72
0.43
0.53
3.00
0.25
0.00
0.60
0.17
0.22
0.09
3.50
0.13
0.00
0.70
0.12
0.17
0.06
4.00
0.00
0.00
0.80
0.09
0.14
0.04
0.90
0.07
0.11
0.03
1.00
0.05
0.08
0.02
1.50
0.01
0.02
0.00
2.00
0.00
0.00
0.00
Notes:
1. For values of H/Lh, x/Lh and z/Lh other than those shown, linear interpolation is permitted.
2. For H/Lh > 0.5, assume H/Lh = 0.5 for evaluating K1 and substitute 2H for Lh for evaluating K2 and
K3.
3. Multipliers are based on the assumption that wind approaches the hill or escarpment along the
direction of maximum slope.
4. Notation:
H: Height of hill or escarpment relative to the upwind terrain, in meters.
Lh: Distance upwind of crest to where the difference in ground elevation is half the height of hill
or escarpment, in meters.
K1: Factor to account for shape of topographic feature and maximum speed-up effect.
K2: Factor to account for reduction in speed-up with distance upwind or downwind of crest.
K3: Factor to account for reduction in speed-up with height above local terrain.
x: Distance (upwind or downwind) from the crest to the building site, in meters.
z: Height above local ground level, in meters.
W: Horizontal attenuation factor.
γ: Height attenuation factor
Equation:
0/" 5 (1 + 01 0 02 ) ; K1 determined from Table below; 0 5 ¸1 −
||
êBÁ¹ ; 02 5
PÒë//BÁ
| Topographic Multipliers for Exposure B | Col2 | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 |
| -------------------------------------- | ---------------------- | ------------------------ | -------------------------------------- | -------------------------------------- | ------------------------ | ------------------------------------- | ------------------------------------- | ---------------------- | ------------------------ | -------------------------------------- |
| **\_H/Lh \_** | ***K1* Multiplier** | ***K1* Multiplier** | ***K1* Multiplier** | **\_x/Lh \_** | ***K2* Multiplier** | ***K2* Multiplier** | **\_z/Lh \_** | ***K3* Multiplier** | ***K3* Multiplier** | ***K3* Multiplier** |
| **\_H/Lh \_** | **2-D**
**Ridge** | **2-D**
**Escarp.** | **3-D**
**Axisym.**
**Hill** | **3-D**
**Axisym.**
**Hill** | **2-D**
**Escarp.** | **All**
**Other**
**Cases** | **All**
**Other**
**Cases** | **2-D**
**Ridge** | **2-D**
**Escarp.** | **3-D**
**Axisym.**
**Hill** |
| 0.20 | 0.29 | 0.17 | 0.21 | 0.00 | 1.00 | 1.00 | 0.00 | 1.00 | 1.00 | 1.00 |
| 0.25 | 0.36 | 0.21 | 0.26 | 0.50 | 0.88 | 0.67 | 0.10 | 0.74 | 0.78 | 0.67 |
| 0.30 | 0.43 | 0.26 | 0.32 | 1.00 | 0.75 | 0.33 | 0.20 | 0.55 | 0.61 | 0.45 |
| 0.35 | 0.51 | 0.30 | 0.37 | 1.50 | 0.63 | 0.00 | 0.30 | 0.41 | 0.47 | 0.30 |
| 0.40 | 0.58 | 0.34 | 0.42 | 2.00 | 0.50 | 0.00 | 0.40 | 0.30 | 0.37 | 0.20 |
| 0.45 | 0.65 | 0.38 | 0.47 | 2.50 | 0.38 | 0.00 | 0.50 | 0.22 | 0.29 | 0.14 |
| 0.50 | 0.72 | 0.43 | 0.53 | 3.00 | 0.25 | 0.00 | 0.60 | 0.17 | 0.22 | 0.09 |
| | | | | 3.50 | 0.13 | 0.00 | 0.70 | 0.12 | 0.17 | 0.06 |
| | | | | 4.00 | 0.00 | 0.00 | 0.80 | 0.09 | 0.14 | 0.04 |
| | | | | | | | 0.90 | 0.07 | 0.11 | 0.03 |
| | | | | | | | 1.00 | 0.05 | 0.08 | 0.02 |
| | | | | | | | 1.50 | 0.01 | 0.02 | 0.00 |
| | | | | | | | 2.00 | 0.00 | 0.00 | 0.00 |
Parameters for Speed-Up Over Hills and Escarpments
Hill Shape
K1/(H/Lh)
γ
μ
Exposure A Exposure B Exposure C
Upwind of
crest
Downwind
of Crest
2-dimensional ridges
(or valleys with negative
H in K1/(H/Lh)
1.30
1.45
1.55
1.5
1.5
2-dimensional
escarpments
0.75
0.85
0.95
2.5
1.5
3-dimensional
axisym.
Hill
0.95
1.05
1.15
1.5
1.5
Figure 6.2.4 Topographic factor, Kzt - Method 2
Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs
Enclosure Classification
GCpi
Notes:
1. Plus and minus signs signify pressures acting
toward and away from the internal surfaces,
respectively.
2. Values of GCpi shall be used with qz or qh as
specified in Sec 2.4.11.
3. Two cases shall be considered to determine the
critical load requirements for the appropriate
condition:
(i) a positive value of GCpi applied to all internal
surfaces
(ii) a negative value of GCpi applied to all internal
surfaces.
Open Building
0.00
Partially Enclosed Building +0.55
-0.55
Enclosed Building
+0.18
-0.18
Figure 6.2.5 Internal pressure coefficient, GCpi main wind force resisting system
component and cladding - Method 2 (All Heights)
| Parameters for Speed-Up Over Hills and Escarpments | Col2 | Col3 | Col4 | Col5 | Col6 | Col7 |
| ---------------------------------------------------------------------------- | ------------------- | ------------------- | ------------------ | -------------- | ---------------------------- | ------------------------------ |
| **Hill Shape** | **\_K1/(H/Lh) \_** | **\_K1/(H/Lh) \_** | **\_K1/(H/Lh) \_** | **\_γ \_** | **\_μ \_** | **\_μ \_** |
| **Hill Shape** | \*\*Exposure A \*\* | \*\*Exposure B \*\* | **Exposure C** | **Exposure C** | **Upwind of**
**crest** | **Downwind**
**of Crest** |
| 2-dimensional ridges
(or valleys with negative
*H* in\_K1/(H/Lh\_) | 1.30 | 1.45 | 1.55 | 3 | 1.5 | 1.5 |
| 2-dimensional
escarpments | 0.75 | 0.85 | 0.95 | 2.5 | 1.5 | 4 |
| 3-dimensional
axisym.
Hill | 0.95 | 1.05 | 1.15 | 4 | 1.5 | 1.5 |
| Figure 6.2.4 Topographic factor, Kzt - Method 2 | Col2 | Col3 | Col4 | Col5 |
| ------------------------------------------------------------------- | ------------------------------------------------------------------- | ------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------- |
| **Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs** | **Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs** | **Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs** | **Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs** | **Enclosed, Partially Enclosed, and Open Buildings: Walls & Roofs** |
| | **Enclosure Classification** | **\_GCpi \_** | Notes:
1. Plus and minus signs signify pressures acting
toward and away from the internal surfaces,
respectively.
2. Values of\_GCpi\_ shall be used with\_qz\_ or\_qh \_as
specified in Sec 2.4.11.
3. Two cases shall be considered to determine the
critical load requirements for the appropriate
condition:
(i) a positive value of\_GCpi \_applied to all internal
surfaces
(ii) a negative value of\_GCpi \_applied to all internal
surfaces. | |
| | Open Building | 0.00 | 0.00 | 0.00 |
| | Partially Enclosed Building | +0.55
-0.55 | +0.55
-0.55 | +0.55
-0.55 |
| | Enclosed Building | +0.18
-0.18 | +0.18
-0.18 | +0.18
-0.18 |
Figure 6.2.6 External Pressure Coefficients, Cp main wind force resisting system -
Method 2 (All Heights)
Enclosed, Partially Enclosed Buildings: Walls & Roofs
Wall Pressure Coefficients, Cp
Surface
L/B
Cp
Use With
Windward Wall
All values
0.8
qz
Leeward Wall
0-1
-0.5
qh
-0.3
> 4
> -0.2
> Side Wall
> All values
> -0.7
> qh
| Wall Pressure Coefficients, Cp | Col2 | Col3 | Col4 |
| ------------------------------ | ---------- | ------- | -------- |
| Surface | *L/B* | \_Cp \_ | Use With |
| Windward Wall | All values | 0.8 | \_qz \_ |
| Leeward Wall | 0-1 | -0.5 | \_qh \_ |
| Leeward Wall | 2 | -0.3 | -0.3 |
| Leeward Wall | > 4 | -0.2 | -0.2 |
| Side Wall | All values | -0.7 | \_qh \_ |
Roof Pressure Coefficients, Cp, for use with qh
Wind
Direction
Windward
Leeward
Angle, θ (degrees)
Angle, θ (degrees)
h/L
> 60#
> 20
> Normal
> To ridge for
> θ >100
\<0.25
-0.7
-0.18
-0.5
0.0\*
-0.3
0.2
-0.2
0.3
-0.2
0.3
0.0\*
0.4
0.4
0.01θ
-0.3
-0.5
-0.6
0.5
-0.9
-0.18
-0.7
-0.18
-0.4
0.0\*
-0.3
0.2
-0.2
0.2
-0.2
0.3
0.0\*
0.4
0.01θ
-0.5
-0.5
-0.6
> 1.0
> -1.3\*\*
> -0.18
> -1.0
> -0.18
> -0.7
> -0.18
> -0.5
> 0.0\*
> -0.3
> 0.2
> -0.2
> 0.2
> 0.0\*
> 0.3
> 0.01θ
> -0.7
> -0.6
> -0.6
> Normal
> To ridge for
> θ \<10o and
> Parallel to
> ridge for all
> θ
\< 0.5
Horizontal distance
from Windward edge
Cp
* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows
0 to h/2
-0.9, -0.18
h/2 to h
-0.9, -0.18
h to 2 h
-0.5, -0.18
> 2h
> -0.3, -0.18
> 1.0
> 0 to h/2
> -1.3\*\*,-0.18
> Area (m2)
> Reduction Factor
> \< 9.3
> 1.0
> h/2
> -0.7, -0.18
> 23.2
> 0.9
> 92.9
> 0.8
> Notes:
1. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.
2. Linear interpolation is permitted for values of L/B, h/L and θ other than shown. Interpolation shall only be carried
out between values of the same sign. Where no value of the same sign is given, assume 0.0 for interpolation
purposes.
3. Where two values of Cp are listed, this indicates that the windward roof slope is subjected to either positive or
negative pressures and the roof structure shall be designed for both conditions. Interpolation for intermediate
ratios of h/L in this case shall only be carried out between Cp values of like sign.
4. For monoslope roofs, entire roof surface is either a windward or leeward surface.
5. For flexible buildings use appropriate Gf as determined by Sec 2.4.8.
6. Refer to Figure 6.2.7 for domes and Figure 6.2.8 for arched roofs.
7. Notation:
B:
Horizontal dimension of building, in meter, measured normal to wind direction.
L:
Horizontal dimension of building, in meter, measured parallel to wind direction.
h:
Mean roof height in meters, except that eave height shall be used for e 10 degrees.
z:
Height above ground, in meters.
G:
Gust effect factor.
qz,qh: Velocity pressure, in N/m2, evaluated at respective height.
θ:
Angle of plane of roof from horizontal, in degrees.
8\. For mansard roofs, the top horizontal surface and leeward inclined surface shall be treated as leeward surfaces
from the table
9\. Except for MWFRS's at the roof consisting of moment resisting frames, the total horizontal shear shall not be less
than that determined by neglecting wind forces on roof surfaces.
\#For roof slopes greater than 80°, use Cp = 0.8
Figure 6.2.6 (Contd.) External pressure coefficients, Cp main wind force resisting system -
Method 2 (All Heights)
| Roof Pressure Coefficients, Cp, for use with qh | Col2 | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 |
| ------------------------------------------------------------------------------------ | ---------------------- | ------------------------------------------- | ------------------------------------------- | ------------------------------------------- | ---------------------- | ---------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Wind**
**Direction** | **Windward** | **Windward** | **Windward** | **Windward** | **Windward** | **Windward** | **Windward** | **Windward** | **Windward** | **Leeward** | **Leeward** | **Leeward** | **Leeward** |
| **Wind**
**Direction** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** | **Angle, θ (degrees)** |
| **Wind**
**Direction** | *h/L* | 10 | 15 | 20 | 25 | 30 | 35 | 45 | >60# | 10 | 10 | 15 | >20 |
| Normal
To ridge for
θ >100 | \<0.25 | -0.7
-0.18 | -0.5
0.0\* | -0.3
0.2 | -0.2
0.3 | -0.2
0.3 | 0.0\*
0.4 | 0.4 | 0.01θ | -0.3 | -0.3 | -0.5 | -0.6 |
| Normal
To ridge for
θ >100 | 0.5 | -0.9
-0.18 | -0.7
-0.18 | -0.4
0.0\* | -0.3
0.2 | -0.2
0.2 | -0.2
0.3 | 0.0\*
0.4 | 0.01θ | -0.5 | -0.5 | -0.5 | -0.6 |
| Normal
To ridge for
θ >100 | >1.0 | -1.3\*\*
-0.18 | -1.0
-0.18 | -0.7
-0.18 | -0.5
0.0\* | -0.3
0.2 | -0.2
0.2 | 0.0\*
0.3 | 0.01θ | -0.7 | -0.7 | -0.6 | -0.6 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | \< 0.5 | Horizontal distance
from Windward edge | Horizontal distance
from Windward edge | Horizontal distance
from Windward edge | \_Cp \_ | \_Cp \_ | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows | \* Value is provided for interpolation
purposes
\*\* Value can be reduced linearly with area
over which it is applicable as follows |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | \< 0.5 | 0 to\_h/2\_ | 0 to\_h/2\_ | 0 to\_h/2\_ | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | \< 0.5 | *h/2* to\_h\_ | *h/2* to\_h\_ | *h/2* to\_h\_ | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 | -0.9, -0.18 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | \< 0.5 | *h* to\_2 h\_ | *h* to\_2 h\_ | *h* to\_2 h\_ | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 | -0.5, -0.18 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | \< 0.5 | > 2h | > 2h | > 2h | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 | -0.3, -0.18 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | > 1.0 | 0 to\_h/2\_ | 0 to\_h/2\_ | 0 to\_h/2\_ | -1.3\*\*,-0.18 | -1.3\*\*,-0.18 | Area (m2) | Area (m2) | Area (m2) | Area (m2) | Reduction Factor | Reduction Factor | Reduction Factor |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | > 1.0 | 0 to\_h/2\_ | 0 to\_h/2\_ | 0 to\_h/2\_ | -1.3\*\*,-0.18 | -1.3\*\*,-0.18 | \< 9.3 | \< 9.3 | \< 9.3 | \< 9.3 | 1.0 | 1.0 | 1.0 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | > 1.0 | > *h/2* | > *h/2* | > *h/2* | -0.7, -0.18 | -0.7, -0.18 | 23.2 | 23.2 | 23.2 | 23.2 | 0.9 | 0.9 | 0.9 |
| Normal
To ridge for
θ \<10o and
Parallel to
ridge for all
θ | > 1.0 | > *h/2* | > *h/2* | > *h/2* | -0.7, -0.18 | -0.7, -0.18 | >92.9 | >92.9 | >92.9 | >92.9 | 0.8 | 0.8 | 0.8 |
Enclosed, Partially Enclosed Buildings and Structures: Domed Roofs
Notes:
1. Two load cases shall be considered:
Case A. Cp values between A and B and between B and C shall be determined by linear
interpolation along arcs on the dome parallel to the wind direction;
Case B. Cp shall be the constant value of A for θ ≤ 25 degrees, and shall be determined by
linear interpolation from 25 degrees to B and from B to C.
2\. Values denote Cp to be used with X3í³ where (hD + f) is the height at the top of the dome.
3\. Plus and minus signs signify pressures acting toward and away from the surfaces,
respectively.
4\. Cp is constant on the dome surface for arcs of circles perpendicular to the wind direction;
for example, the arc passing through B-B-B and all arcs parallel to B-B-B.
5\. For values of hD/D between those listed on the graph curves, linear interpolation shall be
permitted.
6\. 50 degrees on dome springline, θ590 degrees at dome center top point. f is measured
from springline to top.
7\. The total horizontal shear shall not be less than that determined by neglecting wind forces
roof surfaces.
8\. For f/D values less than 0.05, use Figure 6.2.6.
Figure 6.2.7 External pressure coefficients, Cp main wind force resisting system - Method 2
(All Heights)
Enclosed, Partially Enclosed Buildings and Structures: Arched Roofs
Condition
Rise-to-span
ratio, r
Cp
Windward
quarter
Center
half
Leeward
quarter
Roof on elevated
structure
0 \< r \< 0.2
-0.9
-0.7 - r
-0.5
0.2 ≤ r \< 0.3\*
l.5 r - 0.3
-0.7 - r
-0.5
0.3 ≤ r ≤ 0.6
### 2.75 r - 0.7
-0.7 - r
-0.5
Roof springing from
ground level
0 \< r ≤ 0.6
### 1.4 r
-0.7 - r
-0.5
Notes:
* When the rise-to-span ratio is 0.2 ≤ r ≤ 0.3, alternate coefficients given by
(6r- 2.1) shall also be used for the windward quarter.
1. Values listed are for the determination of average load on main wind force
resisting systems.
2. Plus and minus signs signify pressures acting toward and away from the surfaces,
respectively.
3. For wind directed parallel to the axis of the arch, use pressure coefficients from
Figure 6.2.6 with wind directed parallel to ridge.
4. For components and cladding: (1) At roof perimeter, use the external pressure
coefficients in Figure 6.2.11 with e based on spring-line slope and (2) for
remaining roof areas, use external pressure coefficients of this Table multiplied by
0.87.
Figure 6.2.8 External pressure coefficients, Cp main wind force resisting system component
and cladding - Method 2 (All Heights)
| Condition | Rise-to-span
ratio, r | C
p | Col4 | Col5 |
| ------------------------------------- | ------------------------------------------------ | ----------------------------- | ------------------------ | ---------------------------- |
| **Condition** | **Rise-to-span**
\*\*ratio,\*\*\*\**r* \*\* | **Windward**
**quarter** | **Center**
**half** | **Leeward**
**quarter** |
| Roof on elevated
structure | 0 \<*r* \< 0.2 | -0.9 | -0.7 -*r* | -0.5 |
| Roof on elevated
structure | 0.2 ≤*r* \< 0.3\* | l.5\_r\_ - 0.3 | -0.7 -\_ r\_ | -0.5 |
| Roof on elevated
structure | 0.3 ≤*r* ≤ 0.6 | 2.75\_ r\_ - 0.7 | -0.7 -*r* | -0.5 |
| Roof springing from
ground level | 0 \<*r* ≤ 0.6 | 1.4\_ r\_ | -0.7 -\_ r\_ | -0.5 |
Case 1.
Full design wind pressure acting on the projected area perpendicular to
each principal axis of the structure, considered separately along each
principal axis.
Case 2.
Three quarters of the design wind pressure acting on the projected area
perpendicular to each principal axis of the structure in conjunction with a
torsional moment as shown, considered separately for each principal axis.
Case 3.
Wind loading as defined in Case 1, but considered to act simultaneously at
75% of the specified value.
Case 4.
Wind loading as defined in Case 2, but considered to act simultaneously at
75% of the specified value.
Notes:
1. Design wind pressures for windward and leeward faces shall be determined in
accordance with the provisions of Sec 2.4.11 as applicable for building of all heights.
2. Diagrams show plan views of building.
3. Notation:
Pwx, PwY: Windward face design pressure acting in the x, y principal axis,
respectively.
PLX, PLY: Leeward face design pressure acting in the x, y principal axis,
respectively.
e(ex, ey): Eccentricity for the x, y principal axis of the structure, respectively.
MT:
Torsional moment per unit height acting about a vertical axis of the
building.
Figure 6.2.9 Design wind load cases for main wind force resisting system-Method 2
(All Heights)
Enclosed, Partially Enclosed Buildings: Low-rise Walls & Roofs
Figure 6.2.10 External pressure coefficients, GCpf for main wind force resisting
system- Method 2 (h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Low-rise Walls & Roofs
Notes:
1. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively.
2. For values of θ other than those shown, linear interpolation is permitted.
3. The building must be designed for all wind directions using the 8 loading patterns shown. The load
patterns are applied to each building corner in turn as the Reference Corner.
4. Combinations of external and internal pressures (see Figure 6.2.5) shall be evaluated as required
to obtain the most severe loadings.
৫. ঋড়ৎ:যব:ড়ৎংরড়হধষ ষড়ধফ পধংবং ংযড়হি নবষড়,ি:যব ঢ়ৎবংংঁৎবং রহ ুড়হবং ফবংরমহধঃবফ রিঃয ধ ুঞচ্ (১ঞ, ২ঞ, ৩ঞ,
4T) shall be 25% of the full design wind pressures (zones 1, 2, 3, 4).
Exception: One story buildings with h less than or equal to 9.1m, buildings two stories or less
framed with light frame construction, and buildings two stories or less designed with flexible
diaphragms need not be designed for the torsional load cases.
Torsional loading shall apply to all eight basic load patterns using the figures below applied at each
reference corner.
6\. Except for moment-resisting frames, the total horizontal shear shall not be less than that
determined by neglecting wind forces on roof surfaces.
7\. For the design of the MWFRS providing lateral resistance in a direction parallel to a ridge line or for flat
roofs, use θ 5 0° and locate the zone 2/3 boundary at the mid-length of the building.
8\. The roof pressure coefficient GCpf, when negative in Zone 2 or 2E, shall be applied in Zone 2/2E for
a distance from the edge of roof equal to 0.5 times the horizontal dimension of the building parallel
to the direction of the MWFRS being designed or 2.5 times the eave height, he, at the windward
wall, whichever is less; the remainder of Zone 2/2E extending to the ridge line shall use the
pressure coefficient GCpf for Zone 3/3E.
9\. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either
4% of least horizontal dimension or 0.9 m.
h: Mean roof height, in meters, except that eave height shall be used for θ ≤ 10°.
: Angle of plane of roof from horizontal, in degrees.
Roof
Angle θ
(degrees)
Building Surface
1E
2E
3E
4E
0-5
0.40 -0.69 -0.37
-0.29
-0.45
-0.45
0.61
-1.07
-0.53
-0.43
0.53 -0.69 -0.48
-0.43
-0.45
-0.45
0.80
-1.07
-0.69
-0.64
30-45
0.56 0.21 -0.43
-0.37
-0.45
-0.45
0.69
0.27
-0.53
-0.48
0.56 0.56 -0.37
-0.37
-0.45
-0.45
0.69
0.69
-0.48
-0.48
Figure 6.2.10 (Contd.) External pressure coefficients, GCpf for main wind force
resisting system - Method 2 (h ≤ 18.3 m)
| Roof
Angle θ
(degrees) | Building Surface | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 |
| -------------------------------------------- | ---------------- | ---------- | ---------- | ---------- | ---------- | ---------- | ------ | ------ | ------ | ------ |
| **Roof**
**Angle θ**
**(degrees)** | \*\*1 \*\* | \*\*2 \*\* | \*\*3 \*\* | \*\*4 \*\* | \*\*5 \*\* | \*\*6 \*\* | **1E** | **2E** | **3E** | **4E** |
| 0-5 | 0.40 | -0.69 | -0.37 | -0.29 | -0.45 | -0.45 | 0.61 | -1.07 | -0.53 | -0.43 |
| 20 | 0.53 | -0.69 | -0.48 | -0.43 | -0.45 | -0.45 | 0.80 | -1.07 | -0.69 | -0.64 |
| 30-45 | 0.56 | 0.21 | -0.43 | -0.37 | -0.45 | -0.45 | 0.69 | 0.27 | -0.53 | -0.48 |
| 90 | 0.56 | 0.56 | -0.37 | -0.37 | -0.45 | -0.45 | 0.69 | 0.69 | -0.48 | -0.48 |
Enclosed, Partially Enclosed Buildings: Walls
Notes:
1. Vertical scale denotes GCP to be used with qh.
2. Horizontal scale denotes effective wind area, in square meters.
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. Values of GCP for walls shall be reduced by 10% when θ ≤ 100.
6. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller,
but not less than either 4% of least horizontal dimension or 0.9m.
h: Mean roof height, in meters, except that eave height shall be used for θ ≤ 100.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.11(a) External pressure coefficients, GCp for components and cladding–Method
2 (h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Gable Roofs θ ≤ 70
Notes:
1. Vertical scale denotes GCP to be used with qh.
2. Horizontal scale denotes effective wind area, in square meters.
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. If a parapet equal to or higher than 0.9 m is provided around the perimeter of
the roof with θ ≤ 70, the negative values of GCp in Zone 3 shall be equal to
those for Zone 2 and positive values of GCP in Zones 2 and 4 shall be set
equal to those for wall Zones 4 and 5 respectively in Figure 6.2.11(a).
6. Values of GCP for roof overhangs include pressure contributions from both
upper and lower surfaces.
7. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but
not less than either 4% of least horizontal dimension or 0.9 m.
h: Eave height shall be used for θ ≤ 100.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.11(b) External pressure coefficients, GCp for components and cladding–
Method 2 (h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Gable/Hip Roofs 70 \< θ ≤ 270
Notes:
1. Vertical scale denotes GCP to be used with
.
h
q
2. Horizontal scale denotes effective wind area, in square feet (square
meters).
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. Values of GCP for roof overhangs include pressure contributions from
both upper and lower surfaces.
6. For hip roofs with 70 \< θ ≤ 270, edge/ridge strips and pressure
coefficients for ridges of gabled roofs shall apply on each hip.
7. For hip roofs with 70 \< θ ≤ 250, Zone 3 shall be treated as Zone 2.
8. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller,
but not less than either 4% of least horizontal dimension or 0.9 m.
h: Mean roof height, in meters, except that eave height shall be used for θ
≤ 100.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.11(c) External pressure coefficients, GCp for components and cladding–Method 2
(h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Gable Roofs 270 \< θ ≤ 450
Notes:
1. Vertical scale denotes GCP to be used with qh.
2. Horizontal scale denotes effective wind area, in square feet (square
meters).
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. Values of GCP for roof overhangs include pressure contributions from
both upper and lower surfaces.
6. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller,
but not less than either 4% of least horizontal dimension or 0.9m.
h: Mean roof height, in meters.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.11(d) External pressure coefficients, GCp for components and cladding–Method 2
(h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Stepped Roofs
Notes:
On the lower level of flat, stepped roofs shown in Figure 6.2.12, the zone
designations and pressure coefficients shown in Figure 6.2.11(b) shall apply,
except that at the roof-upper wall intersection(s), Zone 3 shall be treated as
Zone 2 and Zone 2 shall be treated as Zone 1. Positive values of GCp equal to
those for walls in Figure 6.2.11(a) shall apply on the cross-hatched areas shown
in Figure 6.2.12.
Notation:
b: 1.5h1 in Figure 6.2.12, but not greater than 30.5 m.
h: Mean roof height, in meters.
hi: h1 or h2 in Figure 6.2.12; h 5 h1 + h2; h1≥ 3.1 m; hi/h 5 0.3 to 0.7.
W: Building width in Figure 6.2.12.
Wi: W1 or W2 or W3 in Figure 6.2.12. W5 W1 + W2 or W1 + W2 + W3; Wi/W5
### 0.25 to 0.75.
e: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.12 External pressure coefficients, GCp for components and cladding–Method 2
(h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Multispan Gable Roofs
Notes:
1. Vertical scale denotes GCP to be used with qh.
2. Horizontal scale denotes effective wind area, in square meters.
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. For θ ≤ 100 Values of GCP from Figure 6.2.11 shall be used.
6. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but
not less than either 4% of least horizontal dimension or 0.9 m.
h: Mean roof height, in feet (meters), except that eave height shall be used for
θ ≤ 100.
W: Building module width, in meters.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.13 External pressure coefficients, GCp for components and cladding–Method 2
(h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Monoslope Roofs 30 \< θ ≤ 100z
Notes:
1. Vertical scale denotes GCP to be used with qh.
2. Horizontal scale denotes effective wind area A, in square meters.
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. For θ ≤ 30 Values of GCP from Figure 6.2.11(b) shall be used.
6. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller,
but not less than either 4% of least horizontal dimension or 0.9 m.
h: Eave height shall be used for θ ≤ 100.
W: Building width, in meters.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.14(a) External pressure coefficients, GCp for components and cladding–
Method 2 (h ≤ 18.3 m)
-3.0
Enclosed, Partially Enclosed Buildings: Monoslope Roofs 100 \< θ ≤ 300
Notes:
1. Vertical scale denotes GCP to be used with qh
2. Horizontal scale denotes effective wind area A, in square feet (square
meters).
3. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4. Each component shall be designed for maximum positive and negative
pressures.
5. Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller,
but not less than either 4% of least horizontal dimension or 0.9 m.
h: Mean roof height in meters.
W: Building width, in meters.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.14(b) External pressure coefficients, GCp for components and cladding–
Method 2 (h ≤ 18.3 m)
-3.0
Enclosed, Partially Enclosed Buildings: Sawtooth Roofs
Notes:
1\.
Vertical scale denotes GCP to be used with qh.
2\.
Horizontal scale denotes effective wind area A, in square feet (square meters).
3\.
Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
4\.
Each component shall be designed for maximum positive and negative pressures.
5\.
For ≤100 Values of GCP from Figure 6.2.11 shall be used.
6\.
Notation:
a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but
not less than either 4% of least horizontal dimension or 0.9 m.
h: Mean roof height in meters except that eave height shall be used for θ ≤ 100.
W: Building width, in meters.
θ: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.15
External pressure coefficients, GCp for components and cladding–
Method 2 (h ≤ 18.3 m)
Enclosed, Partially Enclosed Buildings: Domed Roofs
External Pressure Coefficients for Domes with a circular Base
θ, degrees
Negative Pressures
Positive Pressures
Positive Pressures
0 – 90
0 – 60
61 – 90
GCp
-0.9
+0.9
+0.5
Notes:
1. Values denote Cp to be used with q(hD+f) where hD+f is the height at the
top of the dome.
2. Plus and minus signs signify pressures acting toward and away from the
surfaces, respectively.
3. Each component shall be designed for maximum positive and negative
pressures.
4. Values apply to θ ≤ hDD ≤ 0.5, 0.2≤ f/D ≤0.5.
5.
θ 50o on dome springline, θ 5 90o at dome center top point. f is
measured from springline to top.
Figure 6.2.16 External pressure coefficients, GCp for components and cladding – Method 2
(All heights)
| External Pressure Coefficients for Domes with a circular Base | Col2 | Col3 | Col4 |
| ------------------------------------------------------------- | ---------------------- | ---------------------- | ---------------------- |
| θ, degrees | **Negative Pressures** | **Positive Pressures** | **Positive Pressures** |
| θ, degrees | 0 – 90 | 0 – 60 | 61 – 90 |
| GCp | -0.9 | +0.9 | +0.5 |
Enclosed, Partially Enclosed Buildings: Walls & Roofs
Notes:
1. Vertical scale denotes GCp to be used with appropriate qz or qh.
2. Horizontal scale denotes effective wind area A, in square feet (square meters).
3. Plus and minus signs signify pressures acting toward and away from the surfaces,
respectively.
4. Use qz with positive values of GCp and qh with negative values of GCp
5. Each component shall be designed for maximum positive and negative pressures.
6. Coefficients are for roofs with angle ≤10°. For other roof angles and geometry, use
GCp values from Figure 6.2.11 and attendant qh based on exposure defined in Sec
2.4.6.
7. If a parapet equal to or higher than 0.9 m is provided around the perimeter of the
roof with ≤10° Zone 3 shall be treated as Zone 2.
8. Notation:
a: 10 percent of least horizontal dimension, but not less than 0.9 m.
h: Mean roof height, in meters, except that eave height shall be used for ≤10o.
z: height above ground, in (meters).
: Angle of plane of roof from horizontal, in degrees.
Figure 6.2.17 External pressure coefficients, GCp for components and cladding – Method 2
(h ≤ 18.3 m)
Open Buildings: Monoslope free roofs (q \< 45, = 0, 180)
Roof
Angle
Load
Case
Wind Direction, = 0
Wind Direction, = 180
Clear Wind
Flow
Obstructed
Wind Flow
Clear Wind
Flow
Obstructed Wind
Flow
CNW
CNL
CNW
CNL
CNW
CNL
CNW
CNL
0
A
1.2
0.3
-0.5
-1.2
1.2
0.3
-0.5
-1.2
B
-1.1
-0.1
-1.1
-0.6
-1.1
-0.1
-1.1
-0.6
7.5
A
-0.6
-1
-1
-1.5
0.9
1.5
-0.2
-1.2
B
-1.4
-1.7
-0.8
1.6
0.3
0.8
-0.3
15
A
-0.3
-1.3
-1.1
-1.5
1.3
1.6
0.4
-1.1
B
-1.9
-2.1
-0.6
1.8
0.6
1.2
-0.3
22.5
A
-1.5
-1.6
-1.5
-1.7
1.7
1.8
0.5
-1
B
-2.4
-0.3
-2.3
-0.9
2.2
0.7
1.3
30
A
-1.8
-1.8
-1.5
-1.8
2.1
2.1
0.6
-1
B
-2.5
-0.6
-2.3
-1.1
2.6
1.6
0.1
37.5
A
-1.8
-1.8
-1.5
-1.8
2.1
2.2
0.7
-0.9
B
-2.4
-0.6
-2.2
-1.1
2.7
1.1
1.9
0.3
45
A
-1.6
-1.8
-1.3
-1.8
2.2
2.5
0.8
-0.9
B
-2.3
-0.7
-1.9
-1.2
2.6
1.4
2.1
0.4
Notes:
1. CNW and CNL denote net pressures (contributions from top and bottom surfaces) for
windward and leeward half of roof surfaces, respectively.
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or equal
to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow (>50%
blockage).
3. For values of e between 7.5° and 45°, linear interpolation is permitted. For values of e less
than 7.5°, use Monoslope roof load coefficients.
4. Plus and minus signs signify pressures acting towards and away from the top roof surface,
respectively.
5. All load cases shown for each roof angle shall be investigated.
6. Notation:
L : horizontal dimension of roof, measured in the along wind direction, m
h : mean roof height, m
: direction of wind, degrees
: angle of plane of roof from horizontal, degrees
Figure 6.2.18(a)
Net pressure coefficient, CN for main wind force resisting system
(0.25\< h/L \< 1.0)
| Col1 | Col2 | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 |
| ------------------------------ | ---------------------- | ------------------------------ | ------------------------------ | --------------------------------- | --------------------------------- | ------------------------ | ------------------------ | ------------------------- | ------------------------- |
| **Roof**
**Angle**
| **Load**
**Case** | **Wind Direction, **** = 0** | **Wind Direction, **** = 0** | **Wind Direction, **** = 0** | **Wind Direction, **** = 0** | Wind Direction, = 180 | Wind Direction, = 180 | Wind Direction, = 180 | Wind Direction, = 180 |
| **Roof**
**Angle**
| **Load**
**Case** | **Clear Wind**
**Flow** | **Clear Wind**
**Flow** | **Obstructed**
**Wind Flow** | **Obstructed**
**Wind Flow** | Clear Wind
Flow | Clear Wind
Flow | Obstructed Wind
Flow | Obstructed Wind
Flow |
| **Roof**
**Angle**
| **Load**
**Case** | \*\*CNW \*\* | \*\*CNL \*\* | \*\*CNW \*\* | \*\*CNL \*\* | CNW | CNL | CNW | CNL |
| 0 | A | 1.2 | 0.3 | -0.5 | -1.2 | 1.2 | 0.3 | -0.5 | -1.2 |
| 0 | B | -1.1 | -0.1 | -1.1 | -0.6 | -1.1 | -0.1 | -1.1 | -0.6 |
| 7.5 | A | -0.6 | -1 | -1 | -1.5 | 0.9 | 1.5 | -0.2 | -1.2 |
| 7.5 | B | -1.4 | 0 | -1.7 | -0.8 | 1.6 | 0.3 | 0.8 | -0.3 |
| 15 | A | -0.3 | -1.3 | -1.1 | -1.5 | 1.3 | 1.6 | 0.4 | -1.1 |
| 15 | B | -1.9 | 0 | -2.1 | -0.6 | 1.8 | 0.6 | 1.2 | -0.3 |
| 22.5 | A | -1.5 | -1.6 | -1.5 | -1.7 | 1.7 | 1.8 | 0.5 | -1 |
| 22.5 | B | -2.4 | -0.3 | -2.3 | -0.9 | 2.2 | 0.7 | 1.3 | 0 |
| 30 | A | -1.8 | -1.8 | -1.5 | -1.8 | 2.1 | 2.1 | 0.6 | -1 |
| 30 | B | -2.5 | -0.6 | -2.3 | -1.1 | 2.6 | 1 | 1.6 | 0.1 |
| 37.5 | A | -1.8 | -1.8 | -1.5 | -1.8 | 2.1 | 2.2 | 0.7 | -0.9 |
| 37.5 | B | -2.4 | -0.6 | -2.2 | -1.1 | 2.7 | 1.1 | 1.9 | 0.3 |
| 45 | A | -1.6 | -1.8 | -1.3 | -1.8 | 2.2 | 2.5 | 0.8 | -0.9 |
| 45 | B | -2.3 | -0.7 | -1.9 | -1.2 | 2.6 | 1.4 | 2.1 | 0.4 |
Open Buildings: Pitched Free Roofs ( ≤ 45o, γ = 0o, 180o)
Roof
Angle,
Load
Case
Wind Direction, ð 5 0o , 180o
Clear Wind Flow
Obstructed Wind Flow
CNW
CNL
CNW
CNL
7.5o
A
1.1
-0.3
-1.6
-1
B
0.2
-1.2
-0.9
-1.7
15o
A
1.1
-0.4
-1.2
-1
B
0.1
-1.1
-0.6
-1.6
22.5o
A
1.1
0.1
-1.2
-1.2
B
-0.1
-0.8
-0.8
-1.7
30o
A
1.3
0.3
-0.7
-0.7
B
-0.1
-0.9
-0.2
-1.1
37.5o
A
1.3
0.6
-0.6
-0.6
B
-0.2
-0.6
-0.3
-0.9
45o
A
1.1
0.9
-0.5
-0.5
B
-0.3
-0.5
-0.3
-0.7
Notes:
1. CNW and CNL denote net pressures (contributions from top and bottom surfaces) for
windward and leeward half of roof surfaces, respectively.
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow
(>50% blockage).
3. For values of between 7.5° and 45°, linear interpolation is permitted. For values of
less than 7.5°, use monoslope roof load coefficients.
4. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
5. All load cases shown for each roof angle shall be investigated.
6. Notation:
L : horizontal dimension of roof, measured in the along wind direction, m
h : mean roof height, m
γ : direction of wind, degrees
: angle of plane of roof from horizontal, degrees
Figure 6.2.18(b) Net pressure coefficient, CN for main wind force resisting system (0.25\<
h/L \< 1.0)
| Roof
Angle, | Load
Case | Wind Direction, ð 5 0o , 180o | Col4 | Col5 | Col6 |
| ------------------ | -------------- | ----------------------------- | --------------- | -------------------- | -------------------- |
| Roof
Angle, | Load
Case | Clear Wind Flow | Clear Wind Flow | Obstructed Wind Flow | Obstructed Wind Flow |
| Roof
Angle, | Load
Case | CNW | CNL | CNW | CNL |
| 7.5o | A | 1.1 | -0.3 | -1.6 | -1 |
| 7.5o | B | 0.2 | -1.2 | -0.9 | -1.7 |
| 15o | A | 1.1 | -0.4 | -1.2 | -1 |
| 15o | B | 0.1 | -1.1 | -0.6 | -1.6 |
| 22.5o | A | 1.1 | 0.1 | -1.2 | -1.2 |
| 22.5o | B | -0.1 | -0.8 | -0.8 | -1.7 |
| 30o | A | 1.3 | 0.3 | -0.7 | -0.7 |
| 30o | B | -0.1 | -0.9 | -0.2 | -1.1 |
| 37.5o | A | 1.3 | 0.6 | -0.6 | -0.6 |
| 37.5o | B | -0.2 | -0.6 | -0.3 | -0.9 |
| 45o | A | 1.1 | 0.9 | -0.5 | -0.5 |
| 45o | B | -0.3 | -0.5 | -0.3 | -0.7 |
Open Buildings: Troughed Free Roofs ( ≤ 45o, γ = 0o, 180o)
Roof
Angle,
Load
Case
Wind Direction, γ=0o, 180o
Clear Wind Flow
Obstructed Wind Flow
CNW
CNL
CNW
CNL
7.5o
A
-1.1
0.3
-1.6
-0.5
B
-0.2
1.2
-0.9
-0.8
15o
A
-1.1
0.4
-1.2
-0.5
B
0.1
1.1
-0.6
-0.8
22.5o
A
-1.1
-0.1
-1.2
-0.6
B
-0.1
0.8
-0.8
-0.8
30o
A
-1.3
-0.3
-1.4
-0.4
B
-0.1
0.9
-0.2
-0.5
37.5o
A
-1.3
-0.6
-1.4
-0.3
B
0.2
0.6
-0.3
-0.4
45o
A
-1.1
-0.9
-1.2
-0.3
B
0.3
0.5
-0.3
-0.4
Notes:
1. CNW and CNL denote net pressures (contributions from top and bottom surfaces) for
windward and leeward half of roof surfaces, respectively.
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow
(>50% blockage).
3. For values of between 7.5° and 45°, linear interpolation is permitted. For values of
less than 7.5°, use monoslope roof load coefficients.
4. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
5. All load cases shown for each roof angle shall be investigated.
6. Notation:
L : horizontal dimension of roof, measured in the along wind direction, m
h : mean roof height, m
γ : direction of wind, degrees
: angle of plane of roof from horizontal, degrees
Figure 6.2.18(c) Net pressure coefficient, CN for main wind force resisting system (0.25\< h/L \< 1.0)
| Roof
Angle, | Load
Case | Wind Direction, γ=0o, 180o | Col4 | Col5 | Col6 |
| ----------------------------- | ---------------------- | -------------------------- | ------------------- | ------------------------ | ------------------------ |
| **Roof**
\*\*Angle,\*\* | **Load**
**Case** | **Clear Wind Flow** | **Clear Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** |
| **Roof**
\*\*Angle,\*\* | **Load**
**Case** | **\_CNW \_** | **\_CNL \_** | **\_CNW \_** | **\_CNL \_** |
| 7.5o | A | -1.1 | 0.3 | -1.6 | -0.5 |
| 7.5o | B | -0.2 | 1.2 | -0.9 | -0.8 |
| 15o | A | -1.1 | 0.4 | -1.2 | -0.5 |
| 15o | B | 0.1 | 1.1 | -0.6 | -0.8 |
| 22.5o | A | -1.1 | -0.1 | -1.2 | -0.6 |
| 22.5o | B | -0.1 | 0.8 | -0.8 | -0.8 |
| 30o | A | -1.3 | -0.3 | -1.4 | -0.4 |
| 30o | B | -0.1 | 0.9 | -0.2 | -0.5 |
| 37.5o | A | -1.3 | -0.6 | -1.4 | -0.3 |
| 37.5o | B | 0.2 | 0.6 | -0.3 | -0.4 |
| 45o | A | -1.1 | -0.9 | -1.2 | -0.3 |
| 45o | B | 0.3 | 0.5 | -0.3 | -0.4 |
Open Buildings: Troughed Free Roofs ( ≤ 45o, = 0o, 180o)
Horizontal
Distance from
Windward Edge
Roof
Angle
Load Case
Clear
Wind Flow
Obstructed
Wind Flow
CN
CN
≤ h
All Shapes
A
-0.8
-1.2
≤ 45o
B
0.8
0.5
> h, ≤ 2h
> All Shapes
> A
> -0.6
> -0.9
> ≤ 45o
> B
> 0.5
> 0.5
> 2h
> All Shapes
> A
> -0.3
> -0.6
> ≤ 45o
> B
> 0.3
> 0.3
> Notes:
1. CN denotes net pressures (contributions from top and bottom surfaces).
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow
(>50% blockage).
3. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
4. All load cases shown for each roof angle shall be investigated.
5. For monoslope roofs with theta less than 5 degrees, CN values shown apply also for
cases where gamma 5 0 degrees and 0.05 less than or equal to h/L less than or equal
to 0.25. See Figure 6.2.18(a) for other h/L values.
6. Notation:
L : horizontal dimension of roof, measured in the along wind direction, m
h : mean roof height, m
y : direction of wind, degrees
: angle of plane of roof from horizontal, degrees
Figure 6.2.18(d)
Net pressure coefficient, CN for main wind force resisting system
(0.25\< h/L \< 1.0)
| Horizontal
Distance from
Windward Edge | Roof
Angle | Load Case | Clear
Wind Flow | Obstructed
Wind Flow |
| ----------------------------------------------------------------- | ------------------------ | ------------- | -------------------- | ------------------------- |
| **Horizontal**
**Distance from**
\*\*Windward Edge \*\* | **Roof**
**Angle** | **Load Case** | \*\**CN* \*\* | **\_CN \_** |
| ≤\_ h\_ | All Shapes | A | -0.8 | -1.2 |
| ≤\_ h\_ | ≤ 45o | B | 0.8 | 0.5 |
| > *h*, ≤*2h* | All Shapes | A | -0.6 | -0.9 |
| > *h*, ≤*2h* | ≤ 45o | B | 0.5 | 0.5 |
| > *2h* | All Shapes | A | -0.3 | -0.6 |
| > *2h* | ≤ 45o | B | 0.3 | 0.3 |
Open Buildings: Monoslope Free Roofs ( \< 45)
Roof
Angle
Effective
Wind Area
CN
Clear Wind Flow
Obstructed Wind Flow
Zone 3
Zone 2
Zone 1
Zone 3
Zone 2
Zone 1
0
\< a2
2.4
-3.3
1.8
-1.7
1.2
-1.1
-3.6
0.8
-1.8
0.5
-1.2
> a2, \<4.0a2
> 1.8
> -1.7
> 1.8
> -1.7
> 1.2
> -1.1
> 0.8
> -1.8
> 0.8
> -1.8
> 0.5
> -1.2
> 4.0a2
> 1.2
> -1.1
> 1.2
> -1.1
> 1.2
> -1.1
> 0.5
> -1.2
> 0.5
> -1.2
> 0.5
> -1.2
> 7.5
> \< a2
> 3.2
> -4.2
> 2.4
> -2.1
> 1.6
> -1.4
> 1.6
> -5.1
> 0.5
> -2.6
> 0.8
> -1.7
> a2, \<4.0a2
> 2.4
> -2.1
> 2.4
> -2.1
> 1.6
> -1.4
> 1.2
> -2.6
> 1.2
> -2.6
> 0.8
> -1.7
> 4.0a2
> 1.6
> -1.4
> 1.6
> -1.4
> 1.6
> -1.4
> 0.8
> -1.7
> 0.8
> -1.7
> 0.8
> -1.7
> 15
> \< a2
> 3.6
> -3.8
> 2.7
> -2.9
> 1.8
> -1.9
> 2.4
> -4.2
> 1.8
> -3.2
> 1.2
> -2.1
> a2, \<4.0a2
> 2.7
> -2.9
> 2.7
> -2.9
> 1.8
> -1.9
> 1.8
> -3.2
> 1.8
> -3.2
> 1.2
> -2.1
> 4.0a2
> 1.8
> -1.9
> 1.8
> -1.9
> 1.8
> -1.9
> 1.2
> -2.1
> 1.2
> -2.1
> 1.2
> -2.3
> 30
> \< a2
> 5.2
> -5
> 3.9
> -3.8
> 2.6
> -2.5
> 3.2
> -4.6
> 2.4
> -3.5
> 1.6
> -2.3
> a2, \<4.0a2
> 3.9
> -3.8
> 3.9
> -3.8
> 2.6
> -2.5
> 2.4
> -3.5
> 2.4
> -3.5
> 1.6
> -2.3
> 4.0a2
> 2.6
> -2.5
> 2.6
> -2.5
> 2.6
> -2.5
> 1.6
> -2.3
> 1.6
> -2.3
> 1.6
> -2.3
> 45
> \< a2
> 5.2
> -4.6
> 3.9
> -3.5
> 2.6
> -2.3
> 4.2
> -3.8
> 3.2
> -2.9
> 2.1
> -1.9
> a2, \<4.0a2
> 3.9
> -3.5
> 3.9
> -3.5
> 2.6
> -2.3
> 3.2
> -2.9
> 3.2
> -2.9
> 2.1
> -1.9
> 4.0a2
> 2.6
> -2.3
> 2.6
> -2.3
> 2.6
> -2.3
> 2.1
> -1.9
> 2.1
> -1.9
> 2.1
> -1.9
> Notes:
1. CN denotes net pressures (contributions from top and bottom surfaces).
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50% wind flow denotes objects below roof inhibiting wind flow (>50%
blockage).
3. For values of e other than those shown, linear interpolation is permitted.
4. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
5. Components and cladding elements shall be designed for positive and negative
pressure coefficients shown.
6. Notation:
: 10% of least horizontal dimension or 0.4h, whichever is smaller but not less than
4% of least horizontal dimension or 0.9 m
h : mean roof height, m
L : horizontal dimension of building, measured in along wind direction, m
: angle of plane of roof from horizontal, degrees
Figure 6.2.19(a) Net pressure coefficient, CN for components and cladding (0.25\< h/L \< 1.0)
| Roof
Angle
| Effective
Wind Area | CN | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 |
| ------------------------------ | -------------------------------- | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ----------------------------- | ----------------------------- | ----------------------------- | ----------------------------- | ----------------------------- | ----------------------------- |
| **Roof**
**Angle**
| **Effective**
**Wind Area** | \*\*Clear Wind Flow \*\* | \*\*Clear Wind Flow \*\* | \*\*Clear Wind Flow \*\* | \*\*Clear Wind Flow \*\* | \*\*Clear Wind Flow \*\* | \*\*Clear Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* | \*\*Obstructed Wind Flow \*\* |
| **Roof**
**Angle**
| **Effective**
**Wind Area** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** |
| 0 | \< *a2* | 2.4 | -3.3 | 1.8 | -1.7 | 1.2 | -1.1 | 1 | -3.6 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0 | >*a2*, \<4.0\_a2\_ | 1.8 | -1.7 | 1.8 | -1.7 | 1.2 | -1.1 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0 | >4.0\_a2\_ | 1.2 | -1.1 | 1.2 | -1.1 | 1.2 | -1.1 | 0.5 | -1.2 | 0.5 | -1.2 | 0.5 | -1.2 |
| 7.5 | \< *a2* | 3.2 | -4.2 | 2.4 | -2.1 | 1.6 | -1.4 | 1.6 | -5.1 | 0.5 | -2.6 | 0.8 | -1.7 |
| 7.5 | >*a2*, \<4.0\_a2\_ | 2.4 | -2.1 | 2.4 | -2.1 | 1.6 | -1.4 | 1.2 | -2.6 | 1.2 | -2.6 | 0.8 | -1.7 |
| 7.5 | >4.0\_a2\_ | 1.6 | -1.4 | 1.6 | -1.4 | 1.6 | -1.4 | 0.8 | -1.7 | 0.8 | -1.7 | 0.8 | -1.7 |
| 15 | \< *a2* | 3.6 | -3.8 | 2.7 | -2.9 | 1.8 | -1.9 | 2.4 | -4.2 | 1.8 | -3.2 | 1.2 | -2.1 |
| 15 | >*a2*, \<4.0\_a2\_ | 2.7 | -2.9 | 2.7 | -2.9 | 1.8 | -1.9 | 1.8 | -3.2 | 1.8 | -3.2 | 1.2 | -2.1 |
| 15 | >4.0\_a2\_ | 1.8 | -1.9 | 1.8 | -1.9 | 1.8 | -1.9 | 1.2 | -2.1 | 1.2 | -2.1 | 1.2 | -2.3 |
| 30 | \< *a2* | 5.2 | -5 | 3.9 | -3.8 | 2.6 | -2.5 | 3.2 | -4.6 | 2.4 | -3.5 | 1.6 | -2.3 |
| 30 | >*a2*, \<4.0\_a2\_ | 3.9 | -3.8 | 3.9 | -3.8 | 2.6 | -2.5 | 2.4 | -3.5 | 2.4 | -3.5 | 1.6 | -2.3 |
| 30 | >4.0\_a2\_ | 2.6 | -2.5 | 2.6 | -2.5 | 2.6 | -2.5 | 1.6 | -2.3 | 1.6 | -2.3 | 1.6 | -2.3 |
| 45 | \< *a2* | 5.2 | -4.6 | 3.9 | -3.5 | 2.6 | -2.3 | 4.2 | -3.8 | 3.2 | -2.9 | 2.1 | -1.9 |
| 45 | >*a2*, \<4.0\_a2\_ | 3.9 | -3.5 | 3.9 | -3.5 | 2.6 | -2.3 | 3.2 | -2.9 | 3.2 | -2.9 | 2.1 | -1.9 |
| 45 | >4.0\_a2\_ | 2.6 | -2.3 | 2.6 | -2.3 | 2.6 | -2.3 | 2.1 | -1.9 | 2.1 | -1.9 | 2.1 | -1.9 |
Open Buildings: Monoslope Free Roofs ( ≤ 45o)
Roof
Angle
Effective
Wind Area
CN
Clear Wind Flow
Obstructed Wind Flow
Zone 3
Zone 2
Zone 1
Zone 3
Zone 2
Zone 1
0o
≤a2
2.4
-3.3
1.8
-1.7
1.2
-1.1
-3.6 0.8
-1.8
0.5
-1.2
> a2, ≤4.0a2
> 1.8
> -1.7
> 1.8
> -1.7
> 1.2
> -1.1
> -1.8 0.8
> -1.8
> 0.5
> -1.2
> 4.0a2
> 1.2
> -1.1
> 1.2
> -1.1
> 1.2
> -1.1
> 0.5 -1.2 0.5
> -1.2
> 0.5
> -1.2
> 7.5o
> ≤a2
> 2.2
> -3.6
> 1.7
> -1.8
> 1.1
> -1.2
> -5.1 0.8
> -26
> 0.5
> -1.7
> a2, ≤4.0a2
> 1.7
> -1.8
> 1.7
> -1.8
> 1.1
> -1.2
> 0.8 -2.6 0.8
> ·26
> 0.5
> -1.7
> 4.0a2
> 1.1
> -1.2
> 1.1
> -1.2
> 1.1
> -1.2
> 0.5 -1.7 0.5
> -1.7
> as
> -1.7
> 15o
> ≤a2
> 2.2
> -2.2
> 1.7
> -1.7
> 1.1
> -1.1
> -3.2 0.8
> -2.4
> 0.5
> -1.6
> a2, ≤4.0a2
> 1.7
> -1.7
> 1.7
> -1.7
> 1.1
> -1.1
> 0.8 -2.4 0.8
> -2.4
> 0.5
> -1.6
> 4.0a2
> 1.1
> -1.1
> 1.1
> -1.1
> 1.1
> -1.1
> 0.5 -1.6 0.5
> -1.6
> 0.5
> -1.6
> 30o
> ≤a2
> 2.6
> -1.8
> -1.4
> 1.3
> -0.9
> -2.4 0.8
> -1.8
> 0.5
> -1.2
> a2, ≤4.0a2
> -1.4
> -1.4
> 1.3
> -0.9
> 0.8 -1.8 0.8
> -1.8
> 0.5
> -1.2
> 4.0a2
> 1.3
> -0.9
> 1.3
> -0.9
> 1.3
> -0.9
> 0.5 -1.2 0.5
> .1.2 0.5
> -1.2
> 45o
> ≤a2
> 2.2
> -1.6
> 1.7
> -1.2
> 1.1
> -0.8
> -2.4 0.8
> -1.8
> 0.5
> -1.2
> a2, ≤4.0a2
> 1.7
> -1.2
> 1.7
> -1.2
> 1.1
> -0.8
> 0.8 -1.8 0.8
> -1.8
> 0.5
> -1.2
> 4.0a2
> 1.1
> -0.8
> 1.1
> -0.8
> 1.1
> -0.8
> 0.5 -1.2 0.5
> -1.2
> 0.5
> -1.2
> Notes:
1. CN denotes net pressures (contributions from top and bottom surfaces).
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow
(>50% blockage).
3. For values of other than those shown, linear interpolation is permitted.
4. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
5. Components and cladding elements shall be designed for positive and negative
pressure coefficients shown.
6. Notation:
: 10% of least horizontal dimension or 0.411, whichever is smaller but not less than
4% of least horizontal dimension or 0.9 m
h : mean roof height, m
L : horizontal dimension of building, measured in along wind direction, m
: angle of plane of roof from horizontal, degrees
Figure 6.2.19(b) Net pressure coefficient, CN for components and cladding (0.25\< h/L \< 1.0)
| Roof
Angle
| Effective
Wind Area | CN | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 |
| ------------------------------ | -------------------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ |
| **Roof**
**Angle**
| **Effective**
**Wind Area** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** |
| **Roof**
**Angle**
| **Effective**
**Wind Area** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** |
| 0o | ≤a2 | 2.4 | -3.3 | 1.8 | -1.7 | 1.2 | -1.1 | 1 | -3.6 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0o | >a2, ≤4.0a2 | 1.8 | -1.7 | 1.8 | -1.7 | 1.2 | -1.1 | 08 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0o | >4.0a2 | 1.2 | -1.1 | 1.2 | -1.1 | 1.2 | -1.1 | 0.5 | -1.2 | 0.5 | -1.2 | 0.5 | -1.2 |
| 7.5o | ≤a2 | 2.2 | -3.6 | 1.7 | -1.8 | 1.1 | -1.2 | 1 | -5.1 | 0.8 | -26 | 0.5 | -1.7 |
| 7.5o | >a2, ≤4.0a2 | 1.7 | -1.8 | 1.7 | -1.8 | 1.1 | -1.2 | 0.8 | -2.6 | 0.8 | ·26 | 0.5 | -1.7 |
| 7.5o | >4.0a2 | 1.1 | -1.2 | 1.1 | -1.2 | 1.1 | -1.2 | 0.5 | -1.7 | 0.5 | -1.7 | as | -1.7 |
| 15o | ≤a2 | 2.2 | -2.2 | 1.7 | -1.7 | 1.1 | -1.1 | 1 | -3.2 | 0.8 | -2.4 | 0.5 | -1.6 |
| 15o | >a2, ≤4.0a2 | 1.7 | -1.7 | 1.7 | -1.7 | 1.1 | -1.1 | 0.8 | -2.4 | 0.8 | -2.4 | 0.5 | -1.6 |
| 15o | >4.0a2 | 1.1 | -1.1 | 1.1 | -1.1 | 1.1 | -1.1 | 0.5 | -1.6 | 0.5 | -1.6 | 0.5 | -1.6 |
| 30o | ≤a2 | 2.6 | -1.8 | 2 | -1.4 | 1.3 | -0.9 | 1 | -2.4 | 0.8 | -1.8 | 0.5 | -1.2 |
| 30o | >a2, ≤4.0a2 | 2 | -1.4 | 2 | -1.4 | 1.3 | -0.9 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 30o | >4.0a2 | 1.3 | -0.9 | 1.3 | -0.9 | 1.3 | -0.9 | 0.5 | -1.2 | 0.5 | .1.2 | 0.5 | -1.2 |
| 45o | ≤a2 | 2.2 | -1.6 | 1.7 | -1.2 | 1.1 | -0.8 | 1 | -2.4 | 0.8 | -1.8 | 0.5 | -1.2 |
| 45o | >a2, ≤4.0a2 | 1.7 | -1.2 | 1.7 | -1.2 | 1.1 | -0.8 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 45o | >4.0a2 | 1.1 | -0.8 | 1.1 | -0.8 | 1.1 | -0.8 | 0.5 | -1.2 | 0.5 | -1.2 | 0.5 | -1.2 |
Open Buildings: Troughed Free Roofs ( ≤ 45o)
Roof
Angle
Effective Wind
Area
CN
Clear Wind Flow
Obstructed Wind Flow
Zone 3
Zone 2
Zone 1
Zone 3
Zone 2
Zone 1
0o
≤a2
2.4
-3.3 1.8 -1.7
1.2 -1.1
-3.6 0.8 -1.8 0.5 -1.2
> a2, ≤4.0a2
> 1.8
> -1.7 1.8 -1.7
> 1.1 -1.1
> 0.8 -1.8 0.8 -1.8 0.5 -1.2
> 4.0a2
> 1.2
> -1.1 1.2 -1.1
> 1.2 -1.1
> 0.5 -1.2 0.5 -1.2 0.5 -1.2
> 7.5o
> ≤a2
> 2.4
> -3.3 1.8 -1.7
> 1.2 -1.1
> -4.8 0.8 -2.4 0.5 -1.6
> a2, ≤4.0a2
> 1.8
> -1.7 1.8 -1.7
> 1.2 -1.1
> 0.8 -2.4 0.8 -2.4 0.5 -1.6
> 4.0a2
> 1.2
> -1.1 1.2 -1.1
> 1.2 -1.1
> 0.5 -1.6 0.5 -1.6 0.5 -1.6
> 15o
> ≤a2
> 2.2
> -2.2 1.7 -1.7
> 1.1 -1.1
> -2.4 0.8 -1.8 0.5 -1.2
> a2, ≤4.0a2
> 1.7
> -1.7 1.7 -1.7
> 1.1 -1.1
> 0.8 -1.8 0.8 -1.8 0.5 -1.2
> 4.0a2
> 1.1
> -1.1 1.1 -1.1
> 1.1 -1.1
> 0.5 -1.2 0.5 -12
> 0.5 -1.2
> 30o
> ≤a2
> 1.8
> -2.6 1.4
> -2
> 0.9 -1.3
> -2.8 0.8 -2.1 0.5 -1.4
> a2, ≤4.0a2
> 1.4
> -2
> 1.4
> -2
> 0.9 -1.3
> 0.8 -2.1 0.8 -2.1 0.5 -1.4
> 4.0a2
> 0.9
> -1.3 1.9 -1.3
> 0.9 -1.3
> 0.5 -1.4 0.5 -1.4 0.5 -1.4
> 45o
> ≤a2
> 1.6
> -2.2 1.2 -1.7
> 0.8 -1.1
> -2.4 0.8 -1.8 0.5 -1.2
> a2, ≤4.0a2
> 1.2
> -1.7 1.2 -1.7
> 0.8 -1.1
> 0.8 -1.8 0.8 -1.8 0.5 -1.2
> 4.0a2
> 0.8
> -1.1 1.8 -1.1
> 0.8 -1.1
> 0.5 -1.2 0.5 -1.2 0.5 -1.2
> Notes:
1. CN denotes net pressures (contributions from top and bottom surfaces).
2. Clear wind flow denotes relatively unobstructed wind flow with blockage less than or
equal to 50%. Obstructed wind flow denotes objects below roof inhibiting wind flow
(>50% blockage).
3. For values of other than those shown, linear interpolation is permitted.
4. Plus and minus signs signify pressures acting towards and away from the top roof
surface, respectively.
5. Components and cladding elements shall be designed for positive and negative
pressure coefficients shown.
6. Notation:
: 10% of least horizontal dimension or 0.411, whichever is smaller but not less than
4% of least horizontal dimension or 0.9 m
h : mean roof height, m
L : horizontal dimension of building, measured in along wind direction, m
: angle of plane of roof from horizontal, degrees
Figure 6.2.19(c) Net pressure coefficient, CN for components and cladding (0.25\< h/L \< 1.0)
| Roof
Angle
| Effective Wind
Area | CN | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 |
| ------------------------------ | -------------------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------- | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ | ------------------------ |
| **Roof**
**Angle**
| **Effective Wind**
**Area** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Clear Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** | **Obstructed Wind Flow** |
| **Roof**
**Angle**
| **Effective Wind**
**Area** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** | **Zone 3** | **Zone 3** | **Zone 2** | **Zone 2** | **Zone 1** | **Zone 1** |
| 0o | ≤a2 | 2.4 | -3.3 | 1.8 | -1.7 | 1.2 | -1.1 | 1 | -3.6 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0o | >a2, ≤4.0a2 | 1.8 | -1.7 | 1.8 | -1.7 | 1.1 | -1.1 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 0o | >4.0a2 | 1.2 | -1.1 | 1.2 | -1.1 | 1.2 | -1.1 | 0.5 | -1.2 | 0.5 | -1.2 | 0.5 | -1.2 |
| 7.5o | ≤a2 | 2.4 | -3.3 | 1.8 | -1.7 | 1.2 | -1.1 | 1 | -4.8 | 0.8 | -2.4 | 0.5 | -1.6 |
| 7.5o | >a2, ≤4.0a2 | 1.8 | -1.7 | 1.8 | -1.7 | 1.2 | -1.1 | 0.8 | -2.4 | 0.8 | -2.4 | 0.5 | -1.6 |
| 7.5o | >4.0a2 | 1.2 | -1.1 | 1.2 | -1.1 | 1.2 | -1.1 | 0.5 | -1.6 | 0.5 | -1.6 | 0.5 | -1.6 |
| 15o | ≤a2 | 2.2 | -2.2 | 1.7 | -1.7 | 1.1 | -1.1 | 1 | -2.4 | 0.8 | -1.8 | 0.5 | -1.2 |
| 15o | >a2, ≤4.0a2 | 1.7 | -1.7 | 1.7 | -1.7 | 1.1 | -1.1 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 15o | >4.0a2 | 1.1 | -1.1 | 1.1 | -1.1 | 1.1 | -1.1 | 0.5 | -1.2 | 0.5 | -12 | 0.5 | -1.2 |
| 30o | ≤a2 | 1.8 | -2.6 | 1.4 | -2 | 0.9 | -1.3 | 1 | -2.8 | 0.8 | -2.1 | 0.5 | -1.4 |
| 30o | >a2, ≤4.0a2 | 1.4 | -2 | 1.4 | -2 | 0.9 | -1.3 | 0.8 | -2.1 | 0.8 | -2.1 | 0.5 | -1.4 |
| 30o | >4.0a2 | 0.9 | -1.3 | 1.9 | -1.3 | 0.9 | -1.3 | 0.5 | -1.4 | 0.5 | -1.4 | 0.5 | -1.4 |
| 45o | ≤a2 | 1.6 | -2.2 | 1.2 | -1.7 | 0.8 | -1.1 | 1 | -2.4 | 0.8 | -1.8 | 0.5 | -1.2 |
| 45o | >a2, ≤4.0a2 | 1.2 | -1.7 | 1.2 | -1.7 | 0.8 | -1.1 | 0.8 | -1.8 | 0.8 | -1.8 | 0.5 | -1.2 |
| 45o | >4.0a2 | 0.8 | -1.1 | 1.8 | -1.1 | 0.8 | -1.1 | 0.5 | -1.2 | 0.5 | -1.2 | 0.5 | -1.2 |
Solid Freestanding Walls & Solid Signs
Cf , CASE A & CASE B
Clearance
Ratio, s/h
Aspect Ratio, B/s
≤0.05
0.1
0.2
0.5
≥45
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
Cf, CASE C
Region
(horizontal
distance from
windward
edge)
Aspect Ratio, B/s
Region
(horizontal
distance from
windward
edge)
Aspect
Ratio, B/s
≥45
0 to s
2.25 2.60 2.90 3.10\* 3.30\* 3.40\* 3.55\* 3.65\*
3.75\*
0 to s
4.00\* 4.30\*
s to 2s
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
s to 2s
2.60
2.55
2s to 3s
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
2s to 3s
2.00
1.95
3s to 10s
1.10 1.05
1.05
1.05
1.05
1.00
0.95
3s to 4s
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
Lr/s
Reduction
Factor
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
> 10s
> 0.55
> 0.55
| Solid Freestanding Walls & Solid Signs | Col2 | Col3 | Col4 | Col5 | Col6 | Col7 | Col8 | Col9 | Col10 | Col11 | Col12 | Col13 | Col14 | Col15 | Col16 | Col17 | Col18 | Col19 | Col20 | Col21 | Col22 |
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| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** | **\_Cf, \_CASE A & CASE B** |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **Clearance**
**Ratio\*\*\*\**, s/h*** |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
\*\*Aspect Ratio,\*\*\*\**B/s* \*\* |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **Clearance**
**Ratio\*\*\*\**, s/h*** | **≤0.05** | **≤0.05** | **0.1** | **0.1** | **0.2** | **0.2** | **0.2** | **0.5** | \*\*1 \*\* | \*\*2 \*\* | \*\*4 \*\* | \*\*5 \*\* | **10** | **10** | **20** | **30** | **30** | **≥45** | **≥45** | **≥45** |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 1 | 1.80 | 1.80 | 1.70 | 1.70 | 1.65 | 1.65 | 1.65 | 1.55 | 1.45 | 1.40 | 1.35 | 1.35 | 1.30 | 1.30 | 1.30 | 1.30 | 1.30 | 1.30 | 1.30 | 1.30 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0.9 | 1.85 | 1.85 | 1.75 | 1.75 | 1.70 | 1.70 | 1.70 | 1.60 | 1.55 | 1.50 | 1.45 | 1.45 | 1.40 | 1.40 | 1.40 | 1.40 | 1.40 | 1.40 | 1.40 | 1.40 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0.7 | 1.90 | 1.90 | 1.85 | 1.85 | 1.75 | 1.75 | 1.75 | 1.70 | 1.65 | 1.60 | 1.60 | 1.55 | 1.55 | 1.55 | 1.55 | 1.55 | 1.55 | 1.55 | 1.55 | 1.55 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0.5 | 1.95 | 1.95 | 1.85 | 1.85 | 1.80 | 1.80 | 1.80 | 1.75 | 1.75 | 1.70 | 1.70 | 1.70 | 1.70 | 1.70 | 1.70 | 1.70 | 1.70 | 1.75 | 1.75 | 1.75 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0.3 | 1.95 | 1.95 | 1.90 | 1.90 | 1.85 | 1.85 | 1.85 | 1.80 | 1.80 | 1.80 | 1.80 | 1.80 | 1.80 | 1.80 | 1.85 | 1.85 | 1.85 | 1.85 | 1.85 | 1.85 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0.2 | 1.95 | 1.95 | 1.90 | 1.90 | 1.85 | 1.85 | 1.85 | 1.80 | 1.80 | 1.80 | 1.80 | 1.80 | 1.85 | 1.85 | 1.90 | 1.90 | 1.90 | 1.95 | 1.95 | 1.95 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | ≤0.16 | 1.95 | 1.95 | 1.90 | 1.90 | 1.85 | 1.85 | 1.85 | 1.85 | 1.80 | 1.80 | 1.85 | 1.85 | 1.85 | 1.85 | 1.90 | 1.90 | 1.90 | 1.95 | 1.95 | 1.95 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** | ***Cf*, CASE C** |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | \*\*Aspect Ratio,\*\*\*\**B/s* \*\* | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | **Aspect**
**Ratio, B/s** | **Aspect**
**Ratio, B/s** | **Aspect**
**Ratio, B/s** | **Aspect**
**Ratio, B/s** |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | **Region**
**(horizontal**
**distance from**
**windward**
**edge)** | \*\*2 \*\* | \*\*3 \*\* | \*\*4 \*\* | \*\*4 \*\* | \*\*5 \*\* | \*\*5 \*\* | \*\*6 \*\* | \*\*7 \*\* | \*\*8 \*\* | \*\*9 \*\* | **10** | **10** | **10** | **10** | **10** | **13** | **13** | **≥45** | **≥45** |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | 0 to\_s\_ | 0 to\_s\_ | 2.25 | 2.60 | 2.90 | 2.90 | 3.10\* | 3.10\* | 3.30\* | 3.40\* | 3.55\* | 3.65\* | 3.75\* | 3.75\* | 0 to\_s\_ | 0 to\_s\_ | 0 to\_s\_ | 4.00\* | 4.00\* | 4.30\* | 4.30\* |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | *s* to\_2s\_ | *s* to\_2s\_ | 1.50 | 1.70 | 1.90 | 1.90 | 2.00 | 2.00 | 2.15 | 2.25 | 2.30 | 2.35 | 2.45 | 2.45 | *s* to\_2s\_ | *s* to\_2s\_ | *s* to\_2s\_ | 2.60 | 2.60 | 2.55 | 2.55 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | *2s* to\_3s\_ | *2s* to\_3s\_ | | 1.15 | 1.30 | 1.30 | 1.45 | 1.45 | 1.55 | 1.65 | 1.70 | 1.75 | 1.85 | 1.85 | *2s\_to\_3s* | *2s\_to\_3s* | *2s\_to\_3s* | 2.00 | 2.00 | 1.95 | 1.95 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | *3s* to\_10s\_ | *3s* to\_10s\_ | | | 1.10 | 1.10 | 1.05 | 1.05 | 1.05 | 1.05 | 1.05 | 1.00 | 0.95 | 0.95 | *3\_s to\_4s* | *3\_s to\_4s* | *3\_s to\_4s* | 1.50 | 1.50 | 1.85 | 1.85 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | ***Lr/s*** | ***Lr/s*** | ***Lr/s*** | **Reduction**
**Factor** | **Reduction**
**Factor** | **Reduction**
**Factor** | | | | | 4s to 5s | 4s to 5s | 4s to 5s | 1.35 | 1.35 | 1.85 | |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | ***Lr/s*** | ***Lr/s*** | ***Lr/s*** | **Reduction**
**Factor** | **Reduction**
**Factor** | **Reduction**
**Factor** | | | | | 5s to 10s | 5s to 10s | 5s to 10s | 0.90 | 0.90 | 1.10 | 1.10 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | 0.3 | 0.3 | 0.3 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | 0.3 | 0.3 | 0.3 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 | >10s | >10s | >10s | 0.55 | 0.55 | 0.55 | 0.55 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | 1.0 | 1.0 | 1.0 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 | 0.75 |
| **\_Cf, \_CASE A & CASE B**
**Clearance**
**Ratio\*\*\*\**, s/h***
\*\*Aspect Ratio,\*\*\*\**B/s* \*\*
**≤0.05**
**0.1**
**0.2**
**0.5**
\*\*1 \*\*
\*\*2 \*\*
\*\*4 \*\*
**5 **
**10**
**20**
**30**
**≥45**
1
1.80
1.70
1.65
1.55 1.45 1.40
1.35 1.35 1.30
1.30
1.30
1.30
0.9
1.85
1.75
1.70
1.60 1.55 1.50
1.45 1.45 1.40
1.40
1.40
1.40
0.7
1.90
1.85
1.75
1.70 1.65 1.60
1.60 1.55 1.55
1.55
1.55
1.55
0.5
1.95
1.85
1.80
1.75 1.75 1.70
1.70 1.70 1.70
1.70
1.70
1.75
0.3
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.80
1.85
1.85
1.85
0.2
1.95
1.90
1.85
1.80 1.80 1.80
1.80 1.80 1.85
1.90
1.90
1.95
≤0.16
1.95
1.90
1.85
1.85 1.80 1.80
1.85 1.85 1.85
1.90
1.90
1.95
***Cf*, CASE C**
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect Ratio,\*\*\*\**B/s* **
**Region**
**(horizontal**
**distance from**
**windward**
**edge)**
**Aspect**
**Ratio, B/s**
\*\*2 \*\*
\*\*3 \*\*
\*\*4 \*\*
\*\*5 \*\*
\*\*6 \*\*
\*\*7 \*\*
**8 **
**9 **
**10**
**13**
**≥45**
0 to\_s\_
2.25 2.60 2.90 3.10* 3.30* 3.40* 3.55* 3.65*
3.75*
0 to\_s\_
4.00* 4.30*
*s* to\_2s\_
1.50 1.70 1.90 2.00
2.15
2.25
2.30
2.35
2.45
*s* to\_2s\_
2.60
2.55
*2s* to\_3s\_
1.15 1.30 1.45
1.55
1.65
1.70
1.75
1.85
*2s\_to\_3s*
2.00
1.95
*3s* to\_10s\_
1.10 1.05
1.05
1.05
1.05
1.00
0.95
*3\_s to\_4s*
1.50
1.85
\*Values shall be
multiplied by the
following reduction
factor when a return
corner is present:
***Lr/s***
**Reduction**
**Factor**
0.3
0.9
1.0
0.75
≥2
0.60
4s to 5s
1.35
1.85
5s to 10s
0.90
1.10
>10s
0.55
0.55 | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | \*Values shall be
multiplied by the
following reduction
factor when a return
corner is present: | ≥2 | ≥2 | ≥2 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 |
Notes:
1. The term "signs" in notes below also applies to "freestanding walls".
2. Signs with openings comprising less than 30% of the gross area
are classified as solid signs. Force coefficients for solid signs with
openings shall be permitted to be multiplied by the reduction factor
(1 - (1 - )1.5).
3. To allow for both normal and oblique wind directions, the following
cases shall be considered:
For s/h \< 1:
CASE A: resultant force acts normal to the face of the sign through the
geometric center.
CASE B: resultant force acts normal to the face of the sign at a distance
from the geometric center toward the windward edge equal to
### 0.2 times the average width of the sign.
For B/s ≥ 2, CASE C must also be considered:
CASE C: resultant forces act normal to the face of the sign through the
geometric centers of each region.
For s/h 5 1:
The same cases as above except that the vertical locations of the
resultant forces occur at a distance above the geometric center equal
to 0.05 times the average height of the sign.
4\. For CASE C where s/h > 0.8, force coefficients shall be multiplied by
the reduction factor (1.8 - s/h).
5\. Linear interpolation is permitted for values of s/h, B/s and Lr/s other
than shown.
6\. Notation: B: horizontal dimension of sign, in meters;
h : height of the sign, in meters;
s: vertical dimension of the sign, in meters;
: ratio of solid area to gross area;
Lr: horizontal dimension of return corner, in meters
Figure 6.2.20 Force Coefficient, Cf for other structures - Method 2 (All heights)
Chimneys, Tanks, Rooftop Equipment, & Similar Structures
Cross-Section
Type of Surface
h/D
Square (wind normal to face)
All
1.3
1.4
2.0
Square (wind along diagomal)
All
1.0
1.1
1.5
Hexagonal or octagonal
All
1.0
1.2
1.4
Round
\#tX/ > 5.3, # in m,
X/ in N m
⁄
Moderately smooth
0.5
0.6
0.7
জড়ঁময (উ্থ/উ৫০.০২)
0.7
0.8
0.9
Very rough
(উ্থ/উ৫০.০৮)
0.8
1.0
0.2
Round
\#tX/ ≤5.3, # in m,
X/ in N m
⁄
All
0.7
0.8
1.2
Notes:
1. The design wind force shall be calculated based on the area of the structure
projected on a plane normal to the wind direction. The force shall be assumed
to act parallel to the wind direction.
2. Linear interpolation is permitted for h/D values other than shown.
3. Notation:
D : diameter of circular cross-section and least horizontal dimension of
square, hexagonal or octagonal cross-section at elevation under
consideration, in meters;
উ্থ: ফবঢ়ঃয ড়ভ ঢ়ৎড়ঃৎঁফরহম বষবসবহঃ ংঁপয ধং ৎরনং ধহফ ংঢ়ড়রষবৎং, রহ সবঃবৎং;
H: height of structure, meters and
qz: velocity pressure evaluated at height z above ground, in N/m2
Figure 6.2.21 Force coefficient, Cf for other structures - Method 2 (All heights)
| Cross-Section | Type of Surface | h/D | Col4 | Col5 |
| ------------------------------------------------------ | --------------------------- | --- | ---- | ---- |
| Cross-Section | Type of Surface | 1 | 7 | 25 |
| Square (wind normal to face) | All | 1.3 | 1.4 | 2.0 |
| Square (wind along diagomal) | All | 1.0 | 1.1 | 1.5 |
| Hexagonal or octagonal | All | 1.0 | 1.2 | 1.4 |
| Round
#tX/ > 5.3, # in m,
X/ in N m
⁄ | Moderately smooth | 0.5 | 0.6 | 0.7 |
| Round
#tX/ > 5.3, # in m,
X/ in N m
⁄ | Rough (D’/D50.02) | 0.7 | 0.8 | 0.9 |
| Round
#tX/ > 5.3, # in m,
X/ in N m
⁄ | Very rough
(D’/D50.08) | 0.8 | 1.0 | 0.2 |
| Round
#tX/ ≤5.3, # in m,
X/ in N m
⁄ | All | 0.7 | 0.8 | 1.2 |
Open Signs & Lattice Frameworks
Flat-Sided Members
Rounded Members
Ôôtõö ≤÷. æ, Õ
Ôôtõö > ÷. æ, Õ
\<0.1
2.0
1.2
0.8
### 0.1 to 0.29
1.8
1.3
0.9
### 0.3 to 0.7
1.6
1.5
1.1
Notes:
1. Signs with openings comprising 30% or more of the gross area are classified as
open signs.
2. The calculation of the design wind forces shall be based on the area of all
exposed members and elements projected on a plane normal to the wind
direction. Forces shall be assumed to act parallel to the wind.
3. The area Af consistent with these force coefficients is the solid area projected
normal the wind direction.
4. Notation:
: ratio of solid area to gross area;
D: diameter of a typical round number, in meters
qz: velocity pressure evaluated at height z above ground in N/m2.
Figure 6.2.22 Force coefficient, Cf for other structures - Method 2 (All heights)
| | Flat-Sided Members | Rounded Members | Col4 |
| ----------- | ------------------ | --------------- | -------------- |
| | Flat-Sided Members | Ôôtõö ≤÷. æ,Õ | Ôôtõö > ÷. æ,Õ |
| \<0.1 | 2.0 | 1.2 | 0.8 |
| 0.1 to 0.29 | 1.8 | 1.3 | 0.9 |
| 0.3 to 0.7 | 1.6 | 1.5 | 1.1 |
Table 6.2.8: Basic Wind Speeds, V, for Selected Locations in Bangladesh
Location
Basic Wind
Speed (m/s)
Location
Basic Wind
Speed (m/s)
Angarpota
47.8
Lalmonirhat
63.7
Bagerhat
77.5
Madaripur
68.1
Bandarban
62.5
Magura
65.0
Barguna
80.0
Manikganj
58.2
Barisal
78.7
Meherpur
58.2
Bhola
69.5
Maheshkhali
80.0
Bogra
61.9
Moulvibazar
53.0
Brahmanbaria
56.7
Munshiganj
57.1
Chandpur
50.6
Mymensingh
67.4
Chapai Nawabganj
41.4
Naogaon
55.2
Chittagong
80.0
Narail
68.6
Chuadanga
61.9
Narayanganj
61.1
Comilla
61.4
Narsinghdi
59.7
ঈড়্থীং ইধুধৎ
80.0
Natore
61.9
Dahagram
47.8
Netrokona
65.6
Dhaka
65.7
Nilphamari
44.7
Dinajpur
41.4
Noakhali
57.1
Faridpur
63.1
Pabna
63.1
Feni
64.1
Panchagarh
41.4
Gaibandha
65.6
Patuakhali
80.0
Gazipur
66.5
Pirojpur
80.0
Gopalganj
74.5
Rajbari
59.1
Habiganj
54.2
Rajshahi
49.2
Hatiya
80.0
Rangamati
56.7
Ishurdi
69.5
Rangpur
65.3
Joypurhat
56.7
Satkhira
57.6
Jamalpur
56.7
Shariatpur
61.9
Jessore
64.1
Sherpur
62.5
Jhalakati
80.0
Sirajganj
50.6
Jhenaidah
65.0
Srimangal
50.6
Khagrachhari
56.7
ঝঃ. গধৎঃরহ্থং ওংষধহফ
80.0
Khulna
73.3
Sunamganj
61.1
Kutubdia
80.0
Sylhet
61.1
Kishoreganj
64.7
Sandwip
80.0
Kurigram
65.6
Tangail
50.6
Kushtia
66.9
Teknaf
80.0
Lakshmipur
51.2
Thakurgaon
41.4
| Location Basic Wind
Speed (m/s) | Location Basic Wind
Speed (m/s) |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Angarpota
47.8
Bagerhat
77.5
Bandarban
62.5
Barguna
80.0
Barisal
78.7
Bhola
69.5
Bogra
61.9
Brahmanbaria
56.7
Chandpur
50.6
Chapai Nawabganj
41.4
Chittagong
80.0
Chuadanga
61.9
Comilla
61.4
Cox’s Bazar
80.0
Dahagram
47.8
Dhaka
65.7
Dinajpur
41.4
Faridpur
63.1
Feni
64.1
Gaibandha
65.6
Gazipur
66.5
Gopalganj
74.5
Habiganj
54.2
Hatiya
80.0
Ishurdi
69.5
Joypurhat
56.7
Jamalpur
56.7
Jessore
64.1
Jhalakati
80.0
Jhenaidah
65.0
Khagrachhari
56.7
Khulna
73.3
Kutubdia
80.0
Kishoreganj
64.7
Kurigram
65.6
Kushtia
66.9
Lakshmipur
51.2 | Lalmonirhat
63.7
Madaripur
68.1
Magura
65.0
Manikganj
58.2
Meherpur
58.2
Maheshkhali
80.0
Moulvibazar
53.0
Munshiganj
57.1
Mymensingh
67.4
Naogaon
55.2
Narail
68.6
Narayanganj
61.1
Narsinghdi
59.7
Natore
61.9
Netrokona
65.6
Nilphamari
44.7
Noakhali
57.1
Pabna
63.1
Panchagarh
41.4
Patuakhali
80.0
Pirojpur
80.0
Rajbari
59.1
Rajshahi
49.2
Rangamati
56.7
Rangpur
65.3
Satkhira
57.6
Shariatpur
61.9
Sherpur
62.5
Sirajganj
50.6
Srimangal
50.6
St. Martin’s Island
80.0
Sunamganj
61.1
Sylhet
61.1
Sandwip
80.0
Tangail
50.6
Teknaf
80.0
Thakurgaon
41.4 |
Open Structures: Trussed Tower
Tower Cross Section
Cf
Square
4.0 2 - 5.9 + 4.0
Triangle
3.4 2 - 4.7 + 3.4
Notes:
1\.
For all wind directions considered, the area Af consistent with the specified
force coefficients shall be the solid area of a tower face projected on the plane
of that face for the tower segment under consideration.
2\.
The specified force coefficients are for towers with structural angles or
similar flat-sided members.
3\.
For towers containing rounded members, it is acceptable to multiply the
specified force coefficients by the following factor when determining wind
forces on such members: 0.51 2 + 0.57 1.0
4\.
Wind forces shall be applied in the directions resulting in maximum member
forces and reactions. For towers with square cross-sections, wind forces shall
be multiplied by the following factor when the wind is directed along a tower
diagonal:
1 + 0.75 1.2
5\.
Wind forces on tower appurtenances such as ladders, conduits, lights,
elevators, etc., shall be calculated using appropriate force coefficients for
these elements.
6\. Notation:
: ratio of solid area to gross area of one tower face for the segment under
consideration.
Figure 6.2.23 Force coefficient, Cf for other structures - Method 2 (All heights)
Table 6.2.9: Importance Factor, I (Wind Loads)
Occupancy Category1
or
Importance Class
Non-Cyclone Prone
Regions and Cyclone Prone
Regions with
V 5 38-44 m/s
Cyclone Prone Regions with
V > 44 m/s
I
0.87
0.77
II
1.0
1.00
III
1.15
1.15
IV
1.15
1.15
1 The building and structure classification categories are listed in Table 6.1.1
| Tower Cross Section | Cf |
| ------------------- | ----------------- |
| Square | 4.02 - 5.9+ 4.0 |
| Triangle | 3.42 - 4.7+ 3.4 |
Table 6.2.10: Terrain Exposure Constants
Exposure
ø
öù (m)
úû
üý
þ\_
ü\_
c
(m)
\_
ö (m)\*
A
7.0
365.76 1/7
0.84
1/4.0
0.45
0.30 97.54 1/3.0
9.14
B
9.5
274.32 1/9.5
1.00
1/6.5
0.65
0.20 152.4 1/5.0
4.57
C
11.5 213.36 1/11.5
1.07
1/9.0
0.80
0.15 198.12 1/8.0
2.13
\*4\ )5 Minimum height used to ensure that the equivalent height z is greater of
0.6h or 4\ ).
For buildings with h ≤4\ ), 4̅ shall be taken as 4\ ).
Table 6.2.11: Velocity Pressure Exposure Coefficients, }ã and }ö
Height above
ground level, z
Exposure (Note 1)
A
B
C
(m)
Case 1
Case 2
Case 1 & 2
Case 1 & 2
0-4.6
0.70
0.57
0.85
1.03
6.1
0.70
0.62
0.90
1.08
7.6
0.70
0.66
0.94
1.12
9.1
0.70
0.70
0.98
1.16
12.2
0.76
0.76
1.04
1.22
15.2
0.81
0.81
1.09
1.27
0.85
0.85
1.13
1.31
21.3
0.89
0.89
1.17
1.34
24.4
0.93
0.93
1.21
1.38
27.41
0.96
0.96
1.24
1.40
30.5
0.99
0.99
1.26
1.43
36.6
1.04
1.04
1.31
1.48
42.7
1.09
1.09
1.36
1.52
48.8
1.13
1.13
1.39
1.55
54.9
1.17
1.17
1.43
1.58
61.0
1.20
1.20
1.46
1.61
76.2
1.28
1.28
1.53
1.68
91.4
1.35
1.35
1.59
1.73
106.7
1.41
1.41
1.64
1.78
121.9
1.47
1.47
1.69
1.82
137.2
1.52
1.52
1.73
1.86
152.4
1.56
1.56
1.77
1.89
| Height above
ground level, z | Exposure (Note 1) | Col3 | Col4 | Col5 |
| --------------------------------- | ----------------- | ------ | ---------- | ---------- |
| Height above
ground level, z | A | A | B | C |
| (m) | Case 1 | Case 2 | Case 1 & 2 | Case 1 & 2 |
| 0-4.6 | 0.70 | 0.57 | 0.85 | 1.03 |
| 6.1 | 0.70 | 0.62 | 0.90 | 1.08 |
| 7.6 | 0.70 | 0.66 | 0.94 | 1.12 |
| 9.1 | 0.70 | 0.70 | 0.98 | 1.16 |
| 12.2 | 0.76 | 0.76 | 1.04 | 1.22 |
| 15.2 | 0.81 | 0.81 | 1.09 | 1.27 |
| 18 | 0.85 | 0.85 | 1.13 | 1.31 |
| 21.3 | 0.89 | 0.89 | 1.17 | 1.34 |
| 24.4 | 0.93 | 0.93 | 1.21 | 1.38 |
| 27.41 | 0.96 | 0.96 | 1.24 | 1.40 |
| 30.5 | 0.99 | 0.99 | 1.26 | 1.43 |
| 36.6 | 1.04 | 1.04 | 1.31 | 1.48 |
| 42.7 | 1.09 | 1.09 | 1.36 | 1.52 |
| 48.8 | 1.13 | 1.13 | 1.39 | 1.55 |
| 54.9 | 1.17 | 1.17 | 1.43 | 1.58 |
| 61.0 | 1.20 | 1.20 | 1.46 | 1.61 |
| 76.2 | 1.28 | 1.28 | 1.53 | 1.68 |
| 91.4 | 1.35 | 1.35 | 1.59 | 1.73 |
| 106.7 | 1.41 | 1.41 | 1.64 | 1.78 |
| 121.9 | 1.47 | 1.47 | 1.69 | 1.82 |
| 137.2 | 1.52 | 1.52 | 1.73 | 1.86 |
| 152.4 | 1.56 | 1.56 | 1.77 | 1.89 |
Notes:
1. Case 1:
(a) All components and cladding.
(b) Main wind force resisting system in low-rise buildings designed using
Figure 6.2.10.
Case 2:
(a) All main wind force resisting systems in buildings except those in low-
rise buildings designed using Figure 6.2.10.
(b) All main wind force resisting systems in other structures.
2. The velocity pressure exposure coefficient Kz may be determined from the
following formula:
For 4.57 m ≤ z ≤ zg:
Kz 5 2.01 (z/zg)2/α
For z \< 4.57 m:
Kz 5 2.01 (4.57/zg)2/α
Note: z shall not be taken less than 9.1 m for Case 1 in exposure A.
3\. α and zg are tabulated in Table 6.2.10.
4\. Linear interpolation for intermediate values of height z is acceptable.
5\. Exposure categories are defined in Sec 2.4.6.3.
Table 6.2.12: Wind Directionality Factor, }
Structure Type
Directionality
Factor
0 \*
Structure Type
Directionality
Factor
0 \*
Buildings
Main Wind Force
Resisting System
Components and
Cladding
Arched Roofs
Chimneys, Tanks, and
Similar Structures
Square
Hexagonal
Round
0.85
0.85
0.85
0.90
0.95
0.95
Solid Signs
Open Signs and Lattice
Framework
Trussed Towers
Triangular, square,
rectangular
All other cross section
0.85
0.85
0.85
0.95
* Directionality Factor 0 has been calibrated with combinations of loads
specified in Sec 2.7. This factor shall only be applied when used in conjunction
with load combinations specified in Sections 2.7.2 and 2.7.3.
| Table 6.2.12: Wind Directionality Factor, }� | � |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Structure Type
Directionality
Factor
0 \* | Structure Type
Directionality
Factor
0 \* |
| Buildings
Main Wind Force
Resisting System
Components and
Cladding
Arched Roofs
Chimneys, Tanks, and
Similar Structures
Square
Hexagonal
Round
0.85
0.85
0.85
0.90
0.95
0.95 | Solid Signs
Open Signs and Lattice
Framework
Trussed Towers
Triangular, square,
rectangular
All other cross section
0.85
0.85
0.85
0.95 |
2.5
Earthquake Loads
2.5.1
General
Minimum design earthquake forces for buildings, structures or components
thereof shall be determined in accordance with the provisions of Sec 2.5. Some
definitions and symbols relevant for earthquake resistant design for buildings
are provided in Sections 2.1.3 and 2.1.4. Section 2.5.2 presents basic earthquake
resistant design concepts. Section 2.5.3 describes procedures for soil
investigations, while Sec 2.5.4 describes procedures for determining earthquake
ground motion for design. Section 2.5.5 describes different types of buildings
and structural systems which possess different earthquake resistant
characteristics. Static analysis procedures for design are described in Sections
2.5.6, 2.5.7 and 2.5.12. Dynamic analysis procedures are dealt with in Sections
#### 2.5.8 to 2.5.11. Section 2.5.13 presents how seismic effects are accounted in the
design and combination of earthquake loading effects in different directions and
with other loading effects. Section 2.5.14 deals with allowable drift and
deformation limits. Section 2.5.15 addresses design of non-structural
components in buildings. Section 2.5.16 presents design considerations for
buildings with seismic isolation systems. Design for soft storey condition in
buildings is addressed in Sec 2.5.17.
2.5.2
Earthquake Resistant Design – Basic Concepts
##### 2.5.2.1 General principles
The purpose of earthquake resistant design provisions in this Code is to provide
guidelines for the design and construction of new structures subject to
earthquake ground motions in order to minimize the risk to life for all
structures, to increase the expected performance of higher occupancy structures
as compared to ordinary structures, and to improve the capability of essential
structures to function after an earthquake. It is not economically feasible to
design and construct buildings without any damage for a major earthquake
event. The intent is therefore to allow inelastic deformation and structural
damage at preferred locations in the structure without endangering structural
integrity and to prevent structural collapse during a major earthquake.
The seismic zoning map (Fig. 6.2.24) divides the country into four seismic zones
with different expected levels of intensity of ground motion. Each seismic zone
has a zone coefficient which provides expected peak ground acceleration values
on rock/firm soil corresponding to the maximum considered earthquake (MCE).
The design basis earthquake is taken as 2/3 of the maximum considered
earthquake.
The effects of the earthquake ground motion on the structure is expressed in
terms of an idealized elastic design acceleration response spectrum, which
depends on (a) seismic zone coefficient and local soil conditions defining
ground motion and (b) importance factor and response reduction factor
representing building considerations. The earthquake forces acting on the
structure is reduced using the response modification/reduction factor R in
order to take advantage of the inelastic energy dissipation due to inherent
ductility and redundancy in the structure as well as material over-strength. The
importance factor I increases design forces for important structures. The
provisions of this Code for ductility and detailing need to be satisfied even for
structures and members for which load combinations that do not contain the
earthquake effect indicate larger demands than combinations including
earthquake. The elastic deformations calculated under these reduced design
forces are multiplied by the deflection amplification factor, to estimate the
deformations likely to result from the design earthquake.
The seismic design guidelines presented in this Section are based on the
assumption that the soil supporting the structure will not liquefy, settle or slide
due to loss of strength during the earthquake. Reinforced and prestressed
concrete members shall be suitably designed to ensure that premature failure
due to shear or bond does not occur. Ductile detailing of reinforced concrete
members is of prime importance. In steel structures, members and their
connections should be so proportioned that high ductility is obtained, avoiding
premature failure due to elastic or inelastic buckling of any type.
The building structure shall include complete lateral and vertical force-resisting
systems capable of providing adequate strength, stiffness, and energy
dissipation capacity to withstand the design ground motions within the
prescribed limits of deformation and strength demand. The design ground
motions shall be assumed to occur along any horizontal direction of a building
structure. The adequacy of the structural systems shall be demonstrated
through the construction of a mathematical model and evaluation of this model
for the effects of design ground motions.
##### 2.5.2.2 Characteristics of Earthquake Resistant Buildings
The desirable characteristics of earthquake resistant buildings are described
below:
Structural Simplicity, Uniformity and Symmetry:
Structural simplicity, uniformity and plan symmetry is characterized by an even
distribution of mass and structural elements which allows short and direct
transmission of the inertia forces created in the distributed masses of the
building to its foundation. A building configuration with symmetrical layout of
structural elements of the lateral force resisting system, and well-distributed in-
plan, is desirable. Uniformity along the height of the building is also important,
since it tends to eliminate the occurrence of sensitive zones where
concentrations of stress or large ductility demands might cause premature
collapse.
Some basic guidelines are given below:
(i) With respect to the lateral stiffness and mass distribution, the building
structure shall be approximately symmetrical in plan with respect to
two orthogonal axes.
(ii) Both the lateral stiffness and the mass of the individual storeys shall
remain constant or reduce gradually, without abrupt changes, from the
base to the top of a particular building.
(iii) All structural elements of the lateral load resisting systems, such as
cores, structural walls, or frames shall run without interruption from
the foundations to the top of the building.
(iv) An irregular building may be subdivided into dynamically independent
regular units well separated against pounding of the individual units to
achieve uniformity.
(v) The length to breadth ratio (h 5 6'/6\ )) of the building in plan shall
not be higher than 4, where 6' and 6\ ) are respectively the larger
and smaller in plan dimension of the building, measured in orthogonal
directions.
Structural Redundancy:
A high degree of redundancy accompanied by redistribution capacity through
ductility is desirable, enabling a more widely spread energy dissipation across
the entire structure and an increased total dissipated energy. The use of evenly
distributed structural elements increases redundancy. Structural systems of
higher static indeterminacy may result in higher response reduction factor R.
Horizontal Bi-directional Resistance and Stiffness:
Horizontal earthquake motion is a bi-directional phenomenon and thus the
building structure needs to resist horizontal action in any direction. The
structural elements of lateral force resisting system should be arranged in an
orthogonal (in plan) pattern, ensuring similar resistance and stiffness
characteristics in both main directions. The stiffness characteristics of the
structure should also limit the development of excessive displacements that
might lead to either instabilities due to second order effects or excessive
damages.
Torsional Resistance and Stiffness
Besides lateral resistance and stiffness, building structures should possess
adequate torsional resistance and stiffness in order to limit the development of
torsional motions which tend to stress the different structural elements in a
non-uniform way. In this respect, arrangements in which the main elements
resisting the seismic action are distributed close to the periphery of the building
present clear advantages.
Diaphragm Behaviour
In buildings, floors (including the roof) act as horizontal diaphragms that collect
and transmit the inertia forces to the vertical structural systems and ensure that
those systems act together in resisting the horizontal seismic action. Floor
systems and the roof should be provided with in-plane stiffness and resistance
and with effective connection to the vertical structural systems. Particular care
should be taken in cases of non-compact or very elongated in-plan shapes and in
cases of large floor openings, especially if the latter are located in the vicinity of
the main vertical structural elements, thus hindering such effective connection
between the vertical and horizontal structure. The in-plane stiffness of the
floors shall be sufficiently large in comparison with the lateral stiffness of the
vertical structural elements, so that the deformation of the floor shall have a
small effect on the distribution of the forces among the vertical structural
elements.
Foundation
The design and construction of the foundation and of its connection to the
superstructure shall ensure that the whole building is subjected to a uniform
seismic excitation. For buildings with individual foundation elements (footings
or piles), the use of a foundation slab or tie-beams between these elements in
both main directions is recommended, as described in Chapter 3.
2.5.3
Investigation and Assessment of Site Conditions
##### 2.5.3.1 Site investigation
Appropriate site investigations should be carried out to identify the ground
conditions influencing the seismic action.
The ground conditions at the building site should normally be free from risks of
ground rupture, slope instability and permanent settlements caused by
liquefaction or densification during an earthquake. The possibility of such
phenomena should be investigated in accordance with standard procedures
described in Chapter 3 of this Part.
The intent of the site investigation is to classify the Site into one of types SA, SB,
SC, SD, SE, S1 and S2 as defined in Sec 2.5.3.2. Such classification is based on site
profile and evaluated soil properties (shear wave velocity, Standard Penetration
Resistance, undrained shear strength, soil type). The site class is used to
determine the effect of local soil conditions on the earthquake ground motion.
For sites representing special soil type S1 or S2, site specific special studies for
the ground motion should be done. Soil type S1, having very low shear wave
velocity and low material damping, can produce anomalous seismic site
amplification and soil-structure interaction effects. For S2 soils, possibility of soil
failure should be studied.
For a structure belonging to Seismic Design Category C or D (Sec 2.5.5.2), site
investigation should also include determination of soil parameters for the
assessment of the following:
(a) Slope instability.
(b) Potential for Liquefaction and loss of soil strength.
(c) Differential settlement.
(d) Surface displacement due to faulting or lateral spreading.
(e) Lateral pressures on basement walls and retaining walls due to
earthquake ground motion.
Liquefaction potential and possible consequences should be evaluated for
design earthquake ground motions consistent with peak ground accelerations.
Any Settlement due to densification of loose granular soils under design
earthquake motion should be studied. The occurrence and consequences of
geologic hazards such as slope instability or surface faulting should also be
considered. The dynamic lateral earth pressure on basement walls and retaining
walls during earthquake ground shaking is to be considered as an earthquake
load for use in design load combinations
##### 2.5.3.2 Site classification
Site will be classified as type SA, SB, SC, SD, SE, S1 and S2 based on the provisions
of this Section. Classification will be done in accordance with Table 6.2.13 based
on the soil properties of upper 30 meters of the site profile. Average soil
properties will be determined as given in the following equations:
F 5 ∑
)
∑
Ú
T
Ú
)
»
(6.2.31)
:\_ 5 ∑
)
∑
Ú
Ú
)
»
(6.2.32)
C̅D 5 ∑
\+
l
∑
Ú
Ú
l
»
(6.2.33)
Where,
* 5 Number of soil layers in upper 30 m
5 Thickness of layer
5 Shear wave velocity of layer
: 5 Field (uncorrected) Standard Penetration Value for layer
m 5 Number of cohesive soil layers in upper 30 m
+ 5 Thickness of cohesive layer
ZD 5 Undrained shear strength of cohesive layer
The site profile up to a depth of 30 m is divided into n number of distinct soil or
rock layers. Where some of the layers are cohesive, m is the number of cohesive
layers. Hence ∑
)
5 30 m, while ∑
\+
l
\< 30 m if m \< \* in other words if
there are both cohesionless and cohesive layers. The standard penetration value
N as directly measured in the field without correction will be used.
The site classification should be done using average shear wave velocity F if this
can be estimated, otherwise the value of :\_ may be used.
Table 6.2.13: Site Classification Based on Soil Properties
Site
Class
Description of soil
profile up to 30
meters depth
Average Soil Properties in top 30 meters
Shear wave
velocity, \_ (m/s)
SPT Value, \_
(blows/30cm)
Undrained shear
strength, \_ (kPa)
SA
Rock or other rock-like
geological formation,
including at most 5 m of
weaker material at the
surface.
> 800
> \--
> \--
> SB
> Deposits of very dense
> sand, gravel, or very stiff
> clay, at least several tens
> of metres in thickness,
> characterised by a
> gradual increase of
> mechanical properties
> with depth.
> 360 – 800
> 50
> 250
Site
Class
Description of soil
profile up to 30
meters depth
Average Soil Properties in top 30 meters
Shear wave
velocity, \_ (m/s)
SPT Value, \_
(blows/30cm)
Undrained shear
strength, \_ (kPa)
SC
Deep deposits of dense
or medium dense sand,
gravel or stiff clay with
thickness from several
tens to many hundreds
of metres.
180 – 360
15 - 50
70 - 250
SD
Deposits of loose-to-
medium cohesionless
soil (with or without
some soft cohesive
layers), or of
predominantly soft-to-
firm cohesive soil.
\< 180
\< 15
\< 70
SE
A soil profile consisting
of a surface alluvium
layer with Vs values of
type SC or SD and
thickness varying
between about 5 m and
20 m, underlain by
stiffer material with Vs >
800 m/s.
--------
## --
S1
Deposits consisting, or
containing a layer at
least 10 m thick, of soft
clays/silts with a high
plasticity index (PI >
40\) and high water
content
\< 100
(indicative)
------------
10 - 20
S2
Deposits of liquefiable
soils, of sensitive clays,
or any other soil profile
not included in types SA
to SE or S1
-----------
## --
2.5.4
Earthquake Ground Motion
##### 2.5.4.1 Regional seismicity
Bangladesh can be affected by moderate to strong earthquake events due to its
proximity to the collision boundary of the Northeast moving Indian plate and
Eurasian Plate. Strong historical earthquakes with magnitude greater than 7.0
have affected parts of Bangladesh in the last 150 years, some of them had their
epicenters within the country. A brief description of the local geology, tectonic
features and earthquake occurrence in the region is given in Appendix B.
##### 2.5.4.2 Seismic zoning
The intent of the seismic zoning map is to give an indication of the Maximum
Considered Earthquake (MCE) motion at different parts of the country. In
probabilistic terms, the MCE motion may be considered to correspond to having
a 2% probability of exceedance within a period of 50 years. The country has
been divided into four seismic zones with different levels of ground motion.
Table 6.2.14 includes a description of the four seismic zones. Figure 6.2.24
presents a map of Bangladesh showing the boundaries of the four zones. Each
zone has a seismic zone coefficient (Z) which represents the maximum
considered peak ground acceleration (PGA) on very stiff soil/rock (site class SA)
in units of g (acceleration due to gravity). The zone coefficients (Z) of the four
zones are: Z50.12 (Zone 1), Z50.20 (Zone 2), Z50.28 (Zone 3) and Z50.36
(Zone 4). Table 6.2.15 lists zone coefficients for some important towns of
Bangladesh. The most severe earthquake prone zone, Zone 4 is in the northeast
which includes Sylhet and has a maximum PGA value of 0.36g. Dhaka city falls in
the moderate seismic intensity zone with Z50.2, while Chittagong city falls in a
severe intensity zone with Z50.28.
##### 2.5.4.3 Design response spectrum
The earthquake ground motion for which the building has to be designed is
represented by the design response spectrum. Both static and dynamic analysis
methods are based on this response spectrum. This spectrum represents the
spectral acceleration for which the building has to be designed as a function of
the building period, taking into account the ground motion intensity. The
spectrum is based on elastic analysis but in order to account for energy
dissipation due to inelastic deformation and benefits of structural redundancy,
the spectral accelerations are reduced by the response modification factor R.
For important structures, the spectral accelerations are increased by the
importance factor I. The design basis earthquake (DBE) ground motion is
selected at a ground shaking level that is 2/3 of the maximum considered
earthquake (MCE) ground motion. The effect of local soil conditions on the
response spectrum is incorporated in the normalized acceleration response
spectrum Cs. The spectral acceleration for the design earthquake is given by the
following equation:
s
a
C
R
ZI
S
(6.2.34)
Where,
C' 5 Design spectral acceleration (in units of Q) which shall not be less
than 0.67cK.C
c 5
Coefficient used to calculate lower bound for C'. Recommended
value for c is 0.11
K 5
Seismic zone coefficient, as defined in Sec 2.5.4.2
. 5 Structure importance factor, as defined in Sec 2.5.5.1
@ 5 Response reduction factor which depends on the type of
structural system given in Table 6.2.19. The ratio
µ
S cannot be
greater than one.
5 Normalized acceleration response spectrum, which is a function
of structure (building) period and soil type (site class) as defined
by Equations 6.2.35a to 6.2.35d.
B
T
T
η
B
T
T
S
s
C
for
2.5
(6.2.35a)
C
T
T
B
T
Sη
s
C
for
2.5
(6.2.35b)
D
T
T
C
T
T
C
T
Sη
s
C
for
2.5
(6.2.35c)
sec
T
D
T
T
D
T
C
T
S η
s
C
for
2.5
(6.2.35d)
depends on S and values of TB, TC and TD, (Figure 6.2.25) which are all
functions of the site class. Constant Cs value between periods TB and TC
represents constant spectral acceleration.
S 5 Soil factor which depends on site class and is given in Table 6.2.16
T 5 Structure (building) period as defined in Sec 2.5.7.2
TB 5 Lower limit of the period of the constant spectral acceleration
branch given in Table 6.2.16 as a function of site class.
TC 5 Upper limit of the period of the constant spectral acceleration
branch given in Table 6.2.16 as a function of site class
TD 5 Lower limit of the period of the constant spectral displacement
branch given in Table 6.2.16 as a function of site class
η 5 Damping correction factor as a function of damping with a
reference value of η51 for 5% viscous damping. It is given by the
following expression:
.
)
/(
(6.2.36)
Where, ξ is the viscous damping ratio of the structure, expressed as a percentage
of critical damping. The value of η cannot be smaller than 0.55.
The anticipated (design basis earthquake) peak ground acceleration (PGA) for
rock or very stiff soil (site class SA) is
2 K. However, for design, the ground
motion is modified through the use of response reduction factor R and
importance factor I, resulting in ;,7+l 5
2 ¸
µ
S ¹. Figure 6.2.26 shows the
normalized acceleration response spectrum Cs for 5% damping, which may be
defined as the 5% damped spectral acceleration (obtained by Eq. 6.2.34)
normalized with respect to ;,7+l . This Figure demonstrates the significant
influence of site class on the response spectrum.
Design Spectrum for Elastic Analysis
For site classes SA to SE, the design acceleration response spectrum for elastic
analysis methods is obtained using Eq. 6.2.34 to compute Sa (in units of g) as a
function of period T. The design acceleration response spectrum represents the
expected ground motion (Design Basis Earthquake) divided by the factor R/I.
Design Spectrum for Inelastic Analysis
For inelastic analysis methods, the anticipated ground motion (Design Basis
Earthquake) is directly used. Corresponding real design acceleration response
spectrum is used, which is obtained by using R51 and I51 in Eq. 6.2.34. The
্তুৎবধষ ফবংরমহ ধপপবষবৎধঃরড়হ ৎবংঢ়ড়হংব ংঢ়বপঃৎঁস্থ রং বয়ঁধষ:ড় ্তুফবংরমহ ধপপবষবৎধঃরড়হ
ৎবংঢ়ড়হংব ংঢ়বপঃৎঁস্থ সঁষঃরঢ়ষরবফ নু জ/ও.
Site-Specific Design Spectrum
For site class S1 and S2, site-specific studies are needed to obtain design
response spectrum. For important projects, site-specific studies may also be
carried out to determine spectrum instead of using Eq. 6.2.34. The objective of
such site-specific ground-motion analysis is to determine ground motions for
local seismic and site conditions with higher confidence than is possible using
simplified equations.
Figure 6.2.24 Seismic zoning map of Bangladesh
Table 6.2.14: Description of Seismic Zones
Seismic
Zone
Location
Seismic
Intensity
Seismic Zone
Coefficient, Z
Southwestern part including Barisal, Khulna,
Jessore, Rajshahi
Low
0.12
Lower Central and Northwestern part including
Noakhali, Dhaka, Pabna, Dinajpur, as well as
Southwestern corner including Sundarbans
Moderate
0.20
Upper Central and Northwestern part including
Brahmanbaria, Sirajganj, Rangpur
Severe
0.28
Northeastern part including Sylhet,
Mymensingh, Kurigram
Very Severe
0.36
Table 6.2.15: Seismic Zone Coefficient Z for Some Important Towns of Bangladesh
Town
Z
Town
Z
Town
Z
Town
Z
Bagerhat
0.12
Gaibandha
### 0.28 Magura
0.12
Patuakhali
0.12
Bandarban
0.28
Gazipur
### 0.20 Manikganj
0.20
Pirojpur
0.12
Barguna
0.12
Gopalganj
### 0.12 Maulvibazar
0.36
Rajbari
0.20
Barisal
0.12
Habiganj
### 0.36 Meherpur
0.12
Rajshahi
0.12
Bhola
0.12
Jaipurhat
### 0.20 Mongla
0.12
Rangamati
0.28
Bogra
0.28
Jamalpur
### 0.36 Munshiganj
0.20
Rangpur
0.28
Brahmanbaria
0.28
Jessore
### 0.12 Mymensingh
0.36
Satkhira
0.12
Chandpur
0.20
Jhalokati
### 0.12 Narail
0.12
Shariatpur
0.20
Chapainababganj
0.12
Jhenaidah
### 0.12 Narayanganj
0.20
Sherpur
0.36
Chittagong
0.28
Khagrachari
### 0.28 Narsingdi
0.28
Sirajganj
0.28
Chuadanga
0.12
Khulna
### 0.12 Natore
0.20
Srimangal
0.36
Comilla
0.20
Kishoreganj
### 0.36 Naogaon
0.20
Sunamganj
0.36
Cox's Bazar
0.28
Kurigram
### 0.36 Netrakona
0.36
Sylhet
0.36
Dhaka
0.20
Kushtia
### 0.20 Nilphamari
0.12
Tangail
0.28
Dinajpur
0.20
Lakshmipur
### 0.20 Noakhali
0.20
Thakurgaon
0.20
Faridpur
0.20
Lalmanirhat
### 0.28 Pabna
0.20
Feni
0.20
Madaripur
### 0.20 Panchagarh
0.20
Figure 6.2.25 Typical shape of the elastic response spectrum coefficient Cs
| Town Z | Col2 | Col3 | Town Z | Col5 | Col6 | Town Z | Town Z | Col9 | Col10 |
| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Bagerhat
0.12
Bandarban
0.28
Barguna
0.12
Barisal
0.12
Bhola
0.12
Bogra
0.28
Brahmanbaria
0.28
Chandpur
0.20
Chapainababganj
0.12
Chittagong
0.28
Chuadanga
0.12
Comilla
0.20
Cox's Bazar
0.28
Dhaka
0.20
Dinajpur
0.20
Faridpur
0.20
Feni
0.20 | Bagerhat
0.12
Bandarban
0.28
Barguna
0.12
Barisal
0.12
Bhola
0.12
Bogra
0.28
Brahmanbaria
0.28
Chandpur
0.20
Chapainababganj
0.12
Chittagong
0.28
Chuadanga
0.12
Comilla
0.20
Cox's Bazar
0.28
Dhaka
0.20
Dinajpur
0.20
Faridpur
0.20
Feni
0.20 | Bagerhat
0.12
Bandarban
0.28
Barguna
0.12
Barisal
0.12
Bhola
0.12
Bogra
0.28
Brahmanbaria
0.28
Chandpur
0.20
Chapainababganj
0.12
Chittagong
0.28
Chuadanga
0.12
Comilla
0.20
Cox's Bazar
0.28
Dhaka
0.20
Dinajpur
0.20
Faridpur
0.20
Feni
0.20 | Gaibandha
0.28
Gazipur
0.20
Gopalganj
0.12
Habiganj
0.36
Jaipurhat
0.20
Jamalpur
0.36
Jessore
0.12
Jhalokati
0.12
Jhenaidah
0.12
Khagrachari
0.28
Khulna
0.12
Kishoreganj
0.36
Kurigram
0.36
Kushtia
0.20
Lakshmipur
0.20
Lalmanirhat
0.28
Madaripur
0.20 | Gaibandha
0.28
Gazipur
0.20
Gopalganj
0.12
Habiganj
0.36
Jaipurhat
0.20
Jamalpur
0.36
Jessore
0.12
Jhalokati
0.12
Jhenaidah
0.12
Khagrachari
0.28
Khulna
0.12
Kishoreganj
0.36
Kurigram
0.36
Kushtia
0.20
Lakshmipur
0.20
Lalmanirhat
0.28
Madaripur
0.20 | Gaibandha
0.28
Gazipur
0.20
Gopalganj
0.12
Habiganj
0.36
Jaipurhat
0.20
Jamalpur
0.36
Jessore
0.12
Jhalokati
0.12
Jhenaidah
0.12
Khagrachari
0.28
Khulna
0.12
Kishoreganj
0.36
Kurigram
0.36
Kushtia
0.20
Lakshmipur
0.20
Lalmanirhat
0.28
Madaripur
0.20 | Magura
0.12
Manikganj
0.20
Maulvibazar
0.36
Meherpur
0.12
Mongla
0.12
Munshiganj
0.20
Mymensingh
0.36
Narail
0.12
Narayanganj
0.20
Narsingdi
0.28
Natore
0.20
Naogaon
0.20
Netrakona
0.36
Nilphamari
0.12
Noakhali
0.20
Pabna
0.20
Panchagarh
0.20 | Patuakhali
0.12
Pirojpur
0.12
Rajbari
0.20
Rajshahi
0.12
Rangamati
0.28
Rangpur
0.28
Satkhira
0.12
Shariatpur
0.20
Sherpur
0.36
Sirajganj
0.28
Srimangal
0.36
Sunamganj
0.36
Sylhet
0.36
Tangail
0.28
Thakurgaon
0.20 | Patuakhali
0.12
Pirojpur
0.12
Rajbari
0.20
Rajshahi
0.12
Rangamati
0.28
Rangpur
0.28
Satkhira
0.12
Shariatpur
0.20
Sherpur
0.36
Sirajganj
0.28
Srimangal
0.36
Sunamganj
0.36
Sylhet
0.36
Tangail
0.28
Thakurgaon
0.20 | Patuakhali
0.12
Pirojpur
0.12
Rajbari
0.20
Rajshahi
0.12
Rangamati
0.28
Rangpur
0.28
Satkhira
0.12
Shariatpur
0.20
Sherpur
0.36
Sirajganj
0.28
Srimangal
0.36
Sunamganj
0.36
Sylhet
0.36
Tangail
0.28
Thakurgaon
0.20 |
| | Comilla | | | | | | | | |
| | Cox's Bazar | | | | | | | | |
| | Dhaka | | | Kushtia | | | | | |
| | Dinajpur | | | Lakshmipur | | | | | |
| | Faridpur | | | Lalmanirhat | | | | | |
| | Feni | | | Madaripur | | | | | |
| Col1 | Gazipur | Col3 |
| ---- | ------- | ---- |
| Col1 | Rangamati | Col3 |
| ---- | --------- | ---- |
| | Rangpur | |
| | Satkhira | |
| Col1 | Bogra | Col3 |
| ---- | ------------ | ---- |
| | Brahmanbaria | |
| Col1 | Mymensingh | Col3 |
| ---- | ----------- | ---- |
| | Narail | |
| | Narayanganj | |
| Col1 | Chapainababganj | Col3 |
| ---- | --------------- | ---- |
| | Chittagong | |
| Col1 | Natore | Col3 |
| ---- | ------ | ---- |
| Col1 | Sunamganj | Col3 |
| ---- | --------- | ---- |
| Col1 | Tangail | Col3 |
| ---- | ------- | ---- |
Table 6.2.16: Site Dependent Soil Factor and Other Parameters Defining Elastic Response
Spectrum
Soil type
S
TB(s)
TC (s)
TD (s)
SA
1.0
0.15
0.40
2.0
SB
1.2
0.15
0.50
2.0
SC
1.15
0.20
0.60
2.0
SD
1.35
0.20
0.80
2.0
SE
1.4
0.15
0.50
2.0
Figure 6.2.26 Normalized design acceleration response spectrum for different site classes.
2.5.5
Building Categories
##### 2.5.5.1 Importance factor
Buildings are classified in four occupancy categories in Chapter 1 (Table 6.1.1),
depending on the consequences of collapse for human life, on their importance
for public safety and civil protection in the immediate post-earthquake period,
and on the social and economic consequences of collapse. Depending on
occupancy category, buildings may be designed for higher seismic forces using
importance factor greater than one. Table 6.2.17 defines different occupancy
categories and corresponding importance factor.
Table 6.2.17: Importance Factors for Buildings and Structures for Earthquake design
Occupancy Category
Importance factor I
I, II
1.00
III
1.25
IV
1.50
##### 2.5.5.2 Seismic design category
Buildings shall be assigned a seismic design category among B, C or D based on
seismic zone, local site conditions and importance class of building, as given in
Table 6.2.18. Seismic design category D has the most stringent seismic design
detailing, while seismic design category B has the least seismic design detailing
requirements.
Table 6.2.18: Seismic Design Category of Buildings
Site
Class
Occupancy Category I, II and III
Occupancy Category IV
Zone 1 Zone 2 Zone 3 Zone 4 Zone 1 Zone 2 Zone 3 Zone 4
SA
B
C
C
D
C
D
D
D
SB
B
C
D
D
C
D
D
D
SC
B
C
D
D
C
D
D
D
SD
C
D
D
D
D
D
D
D
SE, S1, S2
D
D
D
D
D
D
D
D
##### 2.5.5.3 Building irregularity
Buildings with irregularity in plan or elevation suffer much more damage in
earthquakes than buildings with regular configuration. A building may be
considered as irregular, if at least one of the conditions given below are
applicable:
###### 2.5.5.3.1 Plan irregularity: Following are the different types of irregularities
that may exist in the plan of a building.
(i)
Torsion irregularity
To be considered for rigid floor diaphragms, when the maximum
storey drift (∆') as shown in Figure 6.2.27(a), computed including
accidental torsion, at one end of the structure is more than 1.2 times
the average ¸∆'¼5
∆ ³∆ Ú
¹ of the storey drifts at the two ends of
the structure. If ∆'> 1.4∆'¼ then the irregularity is termed as
extreme torsional irregularity.
(ii) Re-entrant corners
Both projections of the structure beyond a re-entrant comer \[Figure
6.2.27(b)] are greater than 15 percent of its plan dimension in the
given direction.
| Site
Class | Occupancy Category I, II and III | Occupancy Category IV |
| ------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Site
Class | Zone 1 Zone 2 Zone 3 Zone 4 | Zone 1 Zone 2 Zone 3 Zone 4 |
| SA
SB
SC
SD
SE, S1, S2 | B
C
C
D
B
C
D
D
B
C
D
D
C
D
D
D
D
D
D
D | C
D
D
D
C
D
D
D
C
D
D
D
D
D
D
D
D
D
D
D |
(iii) Diaphragm Discontinuity
Diaphragms with abrupt discontinuities or variations in stiffness,
including those having cut-out \[Figure 6.2.27(c)] or open areas
greater than 50 percent of the gross enclosed diaphragm area, or
changes in effective diaphragm stiffness of more than 50 percent
from one storey to the next.
(iv) Out- of-Plane Offsets
Discontinuities in a lateral force resistance path, such as out-of-plane
offsets of vertical elements, as shown in Figure 6.2.27(d).
(v) Non-parallel Systems
The vertical elements resisting the lateral force are not parallel to or
symmetric \[Figure 6.2.27(e)] about the major orthogonal axes of the
lateral force resisting elements.
###### 2.5.5.3.2 Vertical Irregularity: Following are different types of irregularities
that may exist along vertical elevations of a building.
(i)
Stiffness Irregularity - Soft Storey
A soft storey is one in which the lateral stiffness is less than 70% of that
in the storey above or less than 80% of the average lateral stiffness of
the three storeys above irregularity \[Figure 6.2.28(a)]. An extreme soft
storey is defined where its lateral stiffness is less than 60% of that in the
storey above or less than 70% of the average lateral stiffness of the
three storeys above.
(ii)
Mass Irregularity
The seismic weight of any storey is more than twice of that of its
adjacent storeys \[Figure 6.2.28(b)]. This irregularity need not be
considered in case of roofs.
(iii) Vertical Geometric Irregularity
This irregularity exists for buildings with setbacks with dimensions
given in Figure \[6.2.28(c)].
(iv) Vertical In-Plane Discontinuity in Vertical Elements Resisting Lateral
Force
An in-plane offset of the lateral force resisting elements greater than the
length of those elements \[Figure 6.2.28(d)].
(v)
Discontinuity in Capacity - Weak Storey
A weak storey is one in which the storey lateral strength is less than
80% of that in the storey above. The storey lateral strength is the total
strength of all seismic force resisting elements sharing the storey shear
in the considered direction \[Figure 6.2.28(e)]. An extreme weak storey
is one where the storey lateral strength is less than 65% of that in the
storey above.
##### 2.5.5.4 Type of structural systems
The basic lateral and vertical seismic force–resisting system shall conform to
one of the types A to G indicated in Table 6.2.19. Each type is again subdivided
by the types of vertical elements used to resist lateral seismic forces.
A combination of systems may also be permitted as stated in Sec 2.5.5.5.
The structural system to be used shall be in accordance with the seismic design
category indicated in Table 6.2.18. Structural systems that are not permitted for
ধ পবৎঃধরহ ংবরংসরপ ফবংরমহ পধঃবমড়ৎু ধৎব রহফরপধঃবফ নু ুঘচচ্. ঝঃৎঁপঃঁৎধষ ংুংঃবসং:যধঃ
ফড় হড়ঃ যধাব ধহু যবরমযঃ ৎবংঃৎরপঃরড়হ ধৎব রহফরপধঃবফ নু ুঘখচ্. ডযবৎব:যবৎব রং যবরমযঃ
limit, the maximum height in meters is given.
The response reduction factor, R, and the deflection amplification factor,
indicated in Table 6.2.19 shall be used in determining the design base shear and
design story drift. The selected seismic force-resisting system shall be designed
and detailed in accordance with the specific requirements for the system.
Seismic force resisting systems that are not given in Table 6.2.19 may be
permitted if substantial analytical and test data are submitted that establish the
dynamic characteristics and demonstrate the lateral force resistance and energy
dissipation capacity to be equivalent to the structural systems listed in Table
#### 6.2.19 for equivalent response modification coefficient, R, and deflection
amplification factor, values.
(a) Torsional Irregularity
(b) Re-entrant corners (A/L>0.15)
(c) Diaphragm discontinuity
(d) Out- of-plane offsets of shear wall
(e) Non-parallel systems of shear wall
Figure 6.2.27 Different types of plan irregularities of buildings
(a)
Soft storey
(b) Mass irregularity
(c) Vertical geometric irregularity (setback structures)
(d) Vertical In-Plane Discontinuity in Vertical
(e) Weak storey
Elements Resisting Lateral Force
Figure 6.2.28 Different types of vertical irregularities of buildings
Table 6.2.19: Response Reduction Factor, Deflection Amplification Factor and Height
Limitations for Different Structural Systems
Seismic Force–Resisting System
Response
Reduction
Factor, R
System
Overstrength
Factor, Ω
Deflection
Amplification
Factor, "
Seismic
Design
Category
B
Seismic
Design
Category
C
Seismic
Design
Category
D
Height limit (m)
A. BEARING WALL SYSTEMS
(no frame)
1. Special reinforced
concrete shear walls
2.5
NL
NL
2. Ordinary reinforced
concrete shear walls
2.5
NL
NL
NP
3. Ordinary reinforced
masonry shear walls
2.5
1.75
NL
NP
4. Ordinary plain masonry
shear walls
1.5
2.5
1.25
NP
NP
| Seismic Force–Resisting System | Response
Reduction
Factor, R | System
Overstrength
Factor, Ω
| Deflection
Amplification
Factor, "
| Seismic Seismic Seismic
Design Design Design
Category Category Category
B C D |
| ---------------------------------- | ---------------------------------------------------------------- | ------------------------------------------------------- | -------------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| **Seismic Force–Resisting System** | **Response**
**Reduction**
\*\*Factor,\*\*\*\**R* \*\* | **System**
**Overstrength**
\*\*Factor,\*\*Ω | **Deflection**
**Amplification**
**Factor,**" | **Height limit (m)** |
| 5
4
2
1.5 | 2.5
2.5
2.5
2.5 | 5
4
1.75
1.25 |
| ------------------------ | ------------------------------ | ---------------------------- |
Seismic Force–Resisting System
Response
Reduction
Factor, R
System
Overstrength
Factor, Ω
Deflection
Amplification
Factor, "
Seismic
Design
Category
B
Seismic
Design
Category
C
Seismic
Design
Category
D
Height limit (m)
B. BUILDING FRAME SYSTEMS
(with bracing or shear wall)
1. Steel eccentrically braced
frames, moment resisting
connections at columns
away from links
NL
NL
2. Steel eccentrically braced
frames, non-moment-
resisting, connections at
columns away from links
NL
NL
3. Special steel concentrically
braced frames
NL
NL
4. Ordinary steel
concentrically braced
frames
3.25
3.25
NL
NL
5. Special reinforced concrete
shear walls
2.5
NL
NL
6. Ordinary reinforced
concrete shear walls
2.5
4.25
NL
NL
NP
7. Ordinary reinforced
masonry shear walls
2.5
NL
NP
8. Ordinary plain masonry
shear walls
1.5
2.5
1.25
NP
NP
C. MOMENT RESISTING
FRAME SYSTEMS (no
shear wall)
9. Special steel moment
frames
5.5
NL
NL
NL
10. Intermediate steel moment
frames
4.5
NL
NL
11. Ordinary steel moment
frames
3.5
NL
NL
NP
| Seismic Force–Resisting System | Response
Reduction
Factor, R | System
Overstrength
Factor, Ω
| Deflection
Amplification
Factor, "
| Seismic Seismic Seismic
Design Design Design
Category Category Category
B C D |
| ---------------------------------- | ---------------------------------------------------------------- | ------------------------------------------------------- | -------------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| **Seismic Force–Resisting System** | **Response**
**Reduction**
\*\*Factor,\*\*\*\**R* \*\* | **System**
**Overstrength**
\*\*Factor,\*\*Ω | **Deflection**
**Amplification**
**Factor,**" | **Height limit (m)** |
| 1. Steel eccentrically braced
frames, moment resisting
connections at columns
away from links
2. Steel eccentrically braced
frames, non-moment-
resisting, connections at
columns away from links
3. Special steel concentrically
braced frames
4. Ordinary steel
concentrically braced
frames
5. Special reinforced concrete
shear walls
6. Ordinary reinforced
concrete shear walls
7. Ordinary reinforced
masonry shear walls
8. Ordinary plain masonry
shear walls | 8
7
6
3.25
6
5
2
1.5 | 2
2
2
2
2.5
2.5
2.5
2.5 | 4
4
5
3.25
5
4.25
2
1.25 | NL NL 50
NL NL 50
NL NL 50
NL NL 11
NL NL 50
NL NL NP
NL 50 NP
18 NP NP |
| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------- | ---------------------------------------------------------- | ----------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| 1. Special steel moment
frames
2. Intermediate steel moment
frames
3. Ordinary steel moment
frames | 8
4.5
3.5 | 3
3
3 | 5.5
4
3 | NL NL NL
NL NL 35
NL NL NP |
| --------------------------------------------------------------------------------------------------------------------------- | ------------------- | --------------- | ----------------- | ------------------------------------ |
Seismic Force–Resisting System
Response
Reduction
Factor, R
System
Overstrength
Factor, Ω
Deflection
Amplification
Factor, "
Seismic
Design
Category
B
Seismic
Design
Category
C
Seismic
Design
Category
D
Height limit (m)
4\. Special reinforced concrete
moment frames
5.5
NL
NL
NL
5\. Intermediate reinforced
concrete moment frames
4.5
NL
NL
NP
5\. Ordinary reinforced
concrete moment frames
2.5
NL
NP
NP
D. DUAL SYSTEMS: SPECIAL
MOMENT FRAMES
CAPABLE OF RESISTING AT
LEAST 25% OF
PRESCRIBED SEISMIC
FORCES
(with bracing or shear wall)
1. Steel eccentrically braced
frames
2.5
NL
NL
NL
2. Special steel concentrically
braced frames
2.5
5.5
NL
NL
NL
3. Special reinforced concrete
shear walls
2.5
5.5
NL
NL
NL
4. Ordinary reinforced
concrete shear walls
2.5
NL
NL
NP
E. DUAL SYSTEMS:
INTERMEDIATE MOMENT
FRAMES CAPABLE OF
RESISTING AT LEAST 25%
OF PRESCRIBED SEISMIC
FORCES
(with bracing or shear wall)
5. Special steel concentrically
braced frames
2.5
NL
NL
6. Special reinforced concrete
shear walls
6.5
2.5
NL
NL
7. Ordinary reinforced
masonry shear walls
NL
NP
| Seismic Force–Resisting System | Response
Reduction
Factor, R | System
Overstrength
Factor, Ω
| Deflection
Amplification
Factor, "
| Seismic Seismic Seismic
Design Design Design
Category Category Category
B C D |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------- | ------------------------------------------------------- | -------------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| **Seismic Force–Resisting System** | **Response**
**Reduction**
\*\*Factor,\*\*\*\**R* \*\* | **System**
**Overstrength**
\*\*Factor,\*\*Ω | **Deflection**
**Amplification**
**Factor,**" | **Height limit (m)** |
| 4. Special reinforced concrete
moment frames
5. Intermediate reinforced
concrete moment frames
5. Ordinary reinforced
concrete moment frames | 8
5
3 | 3
3
3 | 5.5
4.5
2.5 | NL
NL
NL
NL
NL
NP
NL
NP
NP |
| 1. Steel eccentrically braced
frames
2. Special steel concentrically
braced frames
3. Special reinforced concrete
shear walls
4. Ordinary reinforced
concrete shear walls | 8
7
7
6 | 2.5
2.5
2.5
2.5 | 4
5.5
5.5
5 | NL NL NL
NL NL NL
NL NL NL
NL NL NP |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------- | ------------------------------ | -------------------------- | -------------------------------------------------- |
| 1. Special steel concentrically
braced frames
2. Special reinforced concrete
shear walls
3. Ordinary reinforced
masonry shear walls | 6
6.5
3 | 2.5
2.5
3 | 5
5
3 | NL NL 11
NL NL 50
NL 50 NP |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------ | ----------------- | ------------------- | --------------- | ------------------------------------ |
Seismic Force–Resisting System
Response
Reduction
Factor, R
System
Overstrength
Factor, Ω
Deflection
Amplification
Factor, "
Seismic
Design
Category
B
Seismic
Design
Category
C
Seismic
Design
Category
D
Height limit (m)
4\. Ordinary reinforced
concrete shear walls
5.5
2.5
4.5
NL
NL
NP
F. DUAL SHEAR WALL-
FRAME SYSTEM:
ORDINARY REINFORCED
CONCRETE MOMENT
FRAMES AND ORDINARY
REINFORCED CONCRETE
SHEAR WALLS
4.5
2.5
NL
NP
NP
G. STEEL SYSTEMS NOT
SPECIFICALLY
DETAILED FOR SEISMIC
RESISTANCE
NL
NL
NP
Notes:
1. Seismic design category, NL 5 No height restriction, NP 5 Not permitted.
Number represents maximum allowable height (m).
2. Dual Systems include buildings which consist of both moment resisting frame
and shear walls (or braced frame) where both systems resist the total design
forces in proportion to their lateral stiffness.
3. See Sec. 10.20 of Chapter 10 of this Part for additional values of R and " and
height limits for some other types of steel structures not covered in this Table.
4. Where data specific to a structure type is not available in this Table, reference
may be made to Table 12.2-1 of ASCE 7-05.
##### 2.5.5.5 Combination of structural systems
###### 2.5.5.5.1 Combinations of Structural Systems in Different Directions: Different
seismic force–resisting systems are permitted to be used to resist seismic forces
along each of the two orthogonal axes of the structure. Where different systems
are used, the respective R and coefficients shall apply to each system,
including the limitations on system use contained in Table 6.2.19.
| Seismic Force–Resisting System | Response
Reduction
Factor, R | System
Overstrength
Factor, Ω
| Deflection
Amplification
Factor, "
| Seismic Seismic Seismic
Design Design Design
Category Category Category
B C D |
| -------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------- | ------------------------------------------------------- | -------------------------------------------------------- | -------------------------------------------------------------------------------------------- |
| **Seismic Force–Resisting System** | **Response**
**Reduction**
\*\*Factor,\*\*\*\**R* \*\* | **System**
**Overstrength**
\*\*Factor,\*\*Ω | **Deflection**
**Amplification**
**Factor,**" | **Height limit (m)** |
| 4. Ordinary reinforced
concrete shear walls | 5.5 | 2.5 | 4.5 | NL
NL
NP |
| F. DUAL SHEAR WALL-
FRAME SYSTEM:
ORDINARY REINFORCED
CONCRETE MOMENT
FRAMES AND ORDINARY
REINFORCED CONCRETE\
SHEAR WALLS | 4.5 | 2.5 | 4 | NL
NP
NP |
| G. STEEL SYSTEMS NOT
SPECIFICALLY
DETAILED FOR SEISMIC
RESISTANCE | 3 | 3 | 3 | NL
NL
NP |
###### 2.5.5.5.2 Combinations of Structural Systems in the Same Direction: Where
different seismic force–resisting systems are used in combination to resist
seismic forces in the same direction of structural response, other than those
combinations considered as dual systems, the more stringent system limitation
contained in Table 6.2.19 shall apply. The value of R used for design in that
direction shall not be greater than the least value of R for any of the systems
utilized in that direction. The deflection amplification factor, in the direction
under consideration at any story shall not be less than the largest value of this
factor for the R factor used in the same direction being considered.
##### 2.5.5.6 Provisions for Using System Overstrength Factor, Ω
###### 2.5.5.6.1 Combinations of Elements Supporting Discontinuous Walls or
Frames.
Columns, beams, trusses, or slabs supporting discontinuous walls or frames of
structures having horizontal irregularity Type IV of Table 6.1.5 or vertical
irregularity Type IV of Table 6.1.4 shall have the design strength to resist the
maximum axial force that can develop in accordance with the load
combinations with overstrength factor of Section 2.5.13.4. The connections of
such discontinuous elements to the supporting members shall be adequate to
transmit the forces for which the discontinuous elements were required to be
designed.
###### 2.5.5.6.2 Increase in Forces Due to Irregularities for Seismic Design Category D.
For structures assigned to Seismic Design Category D and having a horizontal
structural irregularity of Type I.a, I.b, II, III, or IV in Table 6.1.5 or a vertical
structural irregularity of Type IV in Table 6.1.4, the design forces determined
from Section 2.5.7 shall be increased 25 percent for connections of diaphragms
to vertical elements and to collectors and for connections of collectors to the
vertical elements. Collectors and their connections also shall be designed for
these increased forces unless they are designed for the load combinations with
overstrength factor of Section 2.5.5.4, in accordance with Section 2.5.13.4.
###### 2.5.5.6.3 Collector Elements Requiring Load Combinations with Overstrength
Factor for Seismic Design Categories C through D.
In structures assigned to Seismic Design Category C or D, collector elements,
splices, and their connections to resisting elements shall resist the load
combinations with overstrength of Section 2.5.13.4.
###### 2.5.5.6.4 Batter Piles.
Batter piles and their connections shall be capable of resisting forces and
moments from the load combinations with overstrength factor of Section
2.5.13.4. Where vertical and batter piles act jointly to resist foundation forces as
a group, these forces shall be distributed to the individual piles in accordance
with their relative horizontal and vertical rigidities and the geometric
distribution of the piles within the group.
2.5.6
Static Analysis Procedure
Although analysis of buildings subjected to dynamic earthquake loads should
theoretically require dynamic analysis procedures, for certain type of building
structures subjected to earthquake shaking, simplified static analysis
procedures may also provide reasonably good results. The equivalent static
force method is such a procedure for determining the seismic lateral forces
acting on the structure. This type of analysis may be applied to buildings whose
seismic response is not significantly affected by contributions from modes
higher than the fundamental mode in each direction. This requirement is
deemed to be satisfied in buildings which fulfill the following two conditions:
(a) The building period in the two main horizontal directions is smaller
than both 4TC (TC is defined in Sec 2.5.4.3) and 2 seconds.
(b) The building does not possess irregularity in elevation as defined in
Sec 2.5.5.3.
2.5.7
Equivalent Static Analysis
The evaluation of the seismic loads starts with the calculation of the design base
shear which is derived from the design response spectrum presented in
Sec 2.5.4.3. This Section presents different computations relevant to the
equivalent static analysis procedure.
##### 2.5.7.1 Design base shear
The seismic design base shear force in a given direction shall be determined
from the following relation:
W
S
V
a
(6.2.37)
Where,
C' 5 Lateral seismic force coefficient calculated using Eq. 6.2.34
(Sec 2.5.4.3). It is the design spectral acceleration (in units of g)
corresponding to the building period T (computed as per
Sec 2.5.7.2).
W 5 Total seismic weight of the building defined in Sec 2.5.7.3
Alternatively, for buildings with natural period less than or equal to 2.0 sec., the
seismic design base shear can be calculated using ASCE 7-02 with seismic design
parameters as given in Appendix C. However, the minimum value of C' should
not be less than 0.044 SDSI. The values of SDS are provided in Table 6.C.4 of
Appendix C.
##### 2.5.7.2 Building period
The fundamental period T of the building in the horizontal direction under
consideration shall be determined using the following guidelines:
(a) Structural dynamics procedures (such as Rayleigh method or modal
eigenvalue analysis), using structural properties and deformation
characteristics of resisting elements, may be used to determine the
fundamental period T of the building in the direction under
consideration. This period shall not exceed the approximate
fundamental period determined by Eq. 6.2.38 by more than 40 percent.
(b) The building period T (in sec) may be approximated by the following
formula:
E 5 "(ℎ))\
(6.2.38)
Where,
ℎ) 5 Height of building in metres from foundation or from top of
rigid basement. This excludes the basement storeys, where
basement walls are connected with the ground floor deck or
fitted between the building columns. But it includes the
basement storeys, when they are not so connected. " and m
are obtained from Table 6.2.20
(c) For masonry or concrete shear wall structures, the approximate
fundamental period, T (in sec) may be determined as follows:
n
w
h
C
T
0\.
(6.2.39)
i
i
i
x
i
i
n
B
w
D
h
A
h
h
A
C
.
(6.2.40)
| Col1 | C
w |
| ---- | -------- |
Where,
AB = area of base of structure
অর = বিন ধৎবধ ড়ভ ংযবধৎ ধিষষ ুরচ্
উর = ষবহমঃয ড়ভ ংযবধৎ ধিষষ ুরচ্
যর = যবরমযঃ ড়ভ ংযবধৎ ধিষষ ুরচ্
x = number of shear walls in the building
effective in resisting lateral forces in the
direction under consideration.
Table 6.2.20: Values for Coefficients to Estimate Approximate Period
Structure type
Ct
m
Concrete moment-resisting frames
0.0466
0.9
Note:
Consider
moment
resisting frames as frames
which
resist
100%
of
seismic force and are not
enclosed or adjoined by
components that are more
rigid and will prevent the
frames
from
deflecting
under seismic forces.
Steel moment-resisting frames
0.0724
0.8
Eccentrically braced steel frame
0.0731 0.75
All other structural systems
0.0488 0.75
##### 2.5.7.3 Seismic weight
Seismic weight, W, is the total dead load of a building or a structure,
including partition walls, and applicable portions of other imposed loads listed
below:
(a) For live load up to and including 3 kN/m2, a minimum of 25 percent
of the live load shall be applicable.
(b) For live load above 3 kN/m2, a minimum of 50 percent of the live load
shall be applicable.
(c) Total weight (100 percent) of permanent heavy equipment or
retained liquid or any imposed load sustained in nature shall be
included.
Where the probable imposed loads (mass) at the time of earthquake are more
correctly assessed, the designer may go for higher percentage of live load.
| Concrete moment-resisting frames 0.0466 0.9
Steel moment-resisting frames 0.0724 0.8
Eccentrically braced steel frame 0.0731 0.75
All other structural systems 0.0488 0.75 | Note: Consider moment
resisting frames as frames
which resist 100% of
seismic force and are not
enclosed or adjoined by
components that are more
rigid and will prevent the
frames from deflecting
under seismic forces. |
| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
##### 2.5.7.4 Vertical distribution of lateral forces
In the absence of a more rigorous procedure, the total seismic lateral force at
the base level, in other words the base shear V, shall be considered as the sum of
lateral forces & induced at different floor levels, these forces may be calculated
as:
n
i
k
i
i
k
x
x
x
h
w
h
w
V
F
(6.2.41)
Where,
& 5 Part of base shear force induced at level x
\[ and \[ 5 Part of the total effective seismic weight of the structure
(W) assigned to level i or x
ℎ and ℎ 5 the height from the base to level i or x
m 5 1 For structure period 0.5s
5 2 for structure period ≥ 2.5s
5 linear interpolation between 1 and 2 for other periods.
n 5 number of stories
##### 2.5.7.5 Storey shear and its horizontal distribution
The design storey shear , at any storey is the sum of the forces & in that
storey and all other stories above it, given by Eq. 6.2.42:
n
x
i
i
x
F
V
(6.2.42)
Where, & 5 Portion of base shear induced at level i, as determined by Eq. 6.2.41.
If the floor diaphragms can be considered to be infinitely rigid in the horizontal
plane, the shear shall be distributed to the various elements of the lateral
force resisting system in proportion to their relative lateral stiffness. For flexible
diaphragms, the distribution of forces to the vertical elements shall account for
the position and distribution of the masses supported.
Allowance shall also be made for the increased shear arising due to horizontal
torsional moment as specified in Sec 2.5.7.6
##### 2.5.7.6 Horizontal torsional moments
Design shall accommodate increase in storey shear forces resulting from
probable horizontal torsional moments on rigid floor diaphragms. Computation
of such moments shall be as follows:
###### 2.5.7.6.1 In-built torsional effects: When there is in-built eccentricity between
centre of mass and centre of rigidity (lateral resistance) at floor levels, rigid
diaphragms at each level will be subject to torsional moment 9".
###### 2.5.7.6.2 Accidental torsional effects: In order to account for uncertainties in
the location of masses and in the spatial variation of the seismic motion,
accidental torsional effects need to be always considered. The accidental
moment 9"' is determined assuming the storey mass to be displaced from the
calculated centre of mass a distance equal to 5 percent of the building
dimension at that level perpendicular to the direction of the force under
consideration. The accidental torsional moment 9"' at level is given as:
(6.2.43)
Where,
ai
e
accidental eccentricity of floor mass at level i applied in the same
direction at all floors 5 ±0.056
6 5 floor dimension perpendicular to the direction of seismic force
considered.
Where torsional irregularity exists (Sec 2.5.5.3.1) for Seismic Design Category
C or D, the irregularity effects shall be accounted for by increasing the
accidental torsion 9"' at each level by a torsional amplification factor, as
illustrated in Figure 6.2.29 determined from the following equation:
5 %
&
1.& ·Þ'
≤3.0
(6.2.44)
Where,
' 5 Maximum displacement at level-x computed assuming 5 1.
'¼ 5 Average displacements at extreme points of the building at level-x
computed assuming 5 1.
i
ai
tai
F
e
M
The accidental torsional moment need not be amplified for structures of light-
frame construction. Also the torsional amplification factor () should not
exceed 3.0.
###### 2.5.7.6.3 Design for torsional effects: The torsional design moment at a given
storey shall be equal to the accidental torsional moment 9"' plus the inbuilt
torsional moment 9" (if any). Where earthquake forces are applied
concurrently in two orthogonal directions, the required 5 percent displacement
of the center of mass (for accidental torsion) need not be applied in both of the
orthogonal directions at the same time, but shall be applied in only one
direction that produces the greater effect.
Figure 6.2.29 Torsional amplification factor Ax for plan irregularity.
##### 2.5.7.7 Deflection and storey drift
The deflections () of level at the center of the mass shall be determined in
accordance with the following equation:
I
C
xe
d
x
(6.2.45)
Where,
d
C
Deflection amplification factor given in Table 6.2.19
xe
Deflection determined by an elastic analysis
I
Importance factor defined in Table 6.2.17
The design storey drift at storey shall be computed as the difference of the
deflections at the centers of mass at the top and bottom of the story under
consideration:
x
x
x
(6.2.46)
##### 2.5.7.8 Overturning effects
The structure shall be designed to resist overturning effects caused by the
seismic forces determined in Sec 2.5.7.4. At any story, the increment of
overturning moment in the story under consideration shall be distributed to the
various vertical force resisting elements in the same proportion as the
distribution of the horizontal shears to those elements. The overturning
moments at level , 9 shall be determined as follows:
x
i
n
x
i
i
x
h
h
F
M
(6.2.47)
Where,
& 5 Portion of the seismic base shear, induced at level
ℎ , ℎ 5 Height from the base to level or .
The foundations of structures, except inverted pendulum-type structures, shall
be permitted to be designed for three-fourths of the foundation overturning
design moment, 9 determined using above equation.
##### 2.5.7.9 P-delta effects
The P-delta effects on story shears and moments, the resulting member forces
and moments, and the story drifts induced by these effects are not required to
be considered if the stability coefficient (θ) determined by the following
equation is not more than 0.10:
d
sx
x
x
C
h
V
P
(6.2.48)
Where,
; 5 Total vertical design load at and above level ; where
computing ;, no individual load factor need exceed 1.0
∆ 5 Design story drift occurring simultaneously with
5 Storey shear force acting between levels and −1
ℎ 5 Storey height below level
5 Deflection amplification factor given in Table 6.2.19
The stability coefficient g shall not exceed g' determined as follows:
.
.
max
d
C
(6.2.49)
Where, c is the ratio of shear demand to shear capacity for the story between
levels and −1. This ratio is permitted to be conservatively taken as 1.0.
Where, the stability coefficient g is greater than 0.10 but less than or equal
to g', the incremental factor related to P-delta effects on displacements and
member forces shall be determined by rational analysis. Alternatively, it is
permitted to multiply displacements and member forces by
(1−g).
Where, g is greater than g', the structure is potentially unstable and shall be
redesigned.
Where, the P-delta effect is included in an automated analysis, Eq. 6.2.49 shall
still be satisfied, however, the value of g computed from Eq. 6.2.48 using the
results of the P-delta analysis is permitted to be divided by (1 + g) before
checking Eq. 6.2.49.
2.5.8
Dynamic Analysis Methods
Dynamic analysis method involves applying principles of structural dynamics to
compute the response of the structure to applied dynamic (earthquake) loads.
##### 2.5.8.1 Requirement for dynamic analysis
Dynamic analysis should be performed to obtain the design seismic force, and
its distribution to different levels along the height of the building and to the
various lateral load resisting elements, for the following buildings:
(a) Regular buildings with height greater than 40 m in Zones 2, 3, 4 and
greater than 90 m in Zone 1.
(b) Irregular buildings (as defined in Sec 2.5.5.3) with height greater than
12 m in Zones 2, 3, 4 and greater than 40 m in Zone 1.
For irregular buildings, smaller than 40 m in height in Zone 1, dynamic analysis,
even though not mandatory, is recommended.
##### 2.5.8.2 Methods of analysis
Dynamic analysis may be carried out through the following two methods:
(i) Response Spectrum Analysis method is a linear elastic analysis method
using modal analysis procedures, where the structure is subjected to
spectral accelerations corresponding to a design acceleration response
spectrum. The design earthquake ground motion in this case is
represented by its response spectrum.
(ii) Time History Analysis method is a numerical integration procedure
where design ground motion time histories (acceleration record) are
applied at the base of the structure. Time history analysis procedures
can be two types: linear and non-linear.
2.5.9
Response Spectrum Analysis (RSA)
A response spectrum analysis shall consist of the analysis of a linear
mathematical model of the structure to determine the maximum accelerations,
forces, and displacements resulting from the dynamic response to ground
shaking represented by the design acceleration response spectrum (presented
in Sec 2.5.4.3). Response spectrum analysis is also called a modal analysis
procedure because it considers different modes of vibration of the structure and
combines effects of different modes.
##### 2.5.9.1 Modeling (RSA)
A mathematical model of the structure shall be constructed that represents the
spatial distribution of mass and stiffness throughout the structure. For regular
structures with independent orthogonal seismic-force-resisting systems,
independent two-dimensional models are permitted to be constructed to
represent each system. For irregular structures or structures without
independent orthogonal systems, a three-dimensional model incorporating a
minimum of three dynamic degrees of freedom consisting of translation in two
orthogonal plan directions and torsional rotation about the vertical axis shall be
included at each level of the structure. Where the diaphragms are not rigid
compared to the vertical elements of the lateral-force-resisting system, the
সড়ফবষ ংযড়ঁষফ রহপষঁফব ৎবঢ়ৎবংবহঃধঃরড়হ ড়ভ:যব ফরধঢ়যৎধমস্থং ভষবীরনরষরঃু ধহফ ংঁপয
additional dynamic degrees of freedom as are required to account for the
ঢ়ধৎঃরপরঢ়ধঃরড়হ ড়ভ:যব ফরধঢ়যৎধমস রহ:যব ংঃৎঁপঃঁৎব্থং ফুহধসরপ ৎবংঢ়ড়হংব. ঞযব
structure shall be considered to be fixed at the base or, alternatively, it shall be
permitted to use realistic assumptions with regard to the stiffness of
foundations. In addition, the model shall comply with the following:
(a) Stiffness properties of concrete and masonry elements shall consider the
effects of cracked sections
(b) The contribution of panel zone deformations to overall story drift shall be
included for steel moment frame resisting systems.
##### 2.5.9.2 Number of modes (RSA)
An analysis shall be conducted using the masses and elastic stiffnesses of the
seismic-force-resisting system to determine the natural modes of vibration for
the structure including the period of each mode, the modal shape vector k, the
modal participation factor P and modal mass M. The analysis shall include a
sufficient number of modes to obtain a combined modal mass participation of at
least 90 percent of the actual mass in each of two orthogonal directions.
##### 2.5.9.3 Modal story shears and moments (RSA)
For each mode, the story shears, story overturning moments, and the shear
forces and overturning moments in vertical elements of the structural system at
each level due to the seismic forces shall be computed. The peak lateral force
& l induced at level in mode m is given by:
& l 5 lk l;lI
(6.2.50)
Where,
l 5 Design horizontal spectral acceleration corresponding to period of
vibration El of mode m obtained from design response spectrum
(Sec 2.5.4.3)
k l 5 Modal shape coefficient at level in mode m
;l 5 Modal participation factor of mode m
I 5 Weight of floor .
##### 2.5.9.4 Structure response (RSA)
In the response spectrum analysis method, the base shear 7; each of the story
shear, moment, and drift quantities; and the deflection at each level shall be
determined by combining their modal values. The combination shall be carried
out by taking the square root of the sum of the squares (SRSS) of each of the
modal values or by the complete quadratic combination (CQC) technique. The
complete quadratic combination shall be used where closely spaced periods in
the translational and torsional modes result in cross-correlation of the modes.
The distribution of horizontal shear shall be in accordance with the
requirements of Sec 2.5.7.5. It should be noted that amplification of accidental
torsion as per Sec 2.5.7.6 is not required where accidental torsional effects are
included in the dynamic analysis model by offsetting the centre of mass in each
story by the required amount.
A base shear, shall also be calculated using the equivalent static force
procedure in Sec 2.5.7. Where the base shear, 7 is less than 85 percent of , all
the forces but not the drifts obtained by response spectrum analysis shall be
multiplied by the ratio
\=.(rT
T)
.
The displacements and drifts obtained by response spectrum analysis shall be
multiplied by /. to obtain design displacements and drifts, as done in
equivalent static analysis procedure (Sec 2.5.7.7). The P-delta effects shall be
determined in accordance with Sec 2.5.7.9.
#### 2.5.10 Linear Time History Analysis (LTHA)
A linear time history analysis (LTHA) shall consist of an analysis of a linear
mathematical model of the structure to determine its response, through direct
numerical integration of the differential equations of motion, to a number of
ground motion acceleration time histories compatible with the design response
spectrum for the site. The analysis shall be performed in accordance with the
provisions of this Section. For the purposes of analysis, the structure shall be
permitted to be considered to be fixed at the base or, alternatively, it shall be
permitted to use realistic assumptions with regard to the stiffness of
foundations. The acceleration time history (ground motion) is applied at the
base of the structure. The advantage of this procedure is that the time
dependent behavior of the structural response is obtained.
##### 2.5.10.1 Modeling (LTHA)
Mathematical models shall conform to the requirements of modeling described
in Sec 2.5.9.1.
##### 2.5.10.2 Ground motion (LTHA)
At least three appropriate ground motions (acceleration time history) shall be
used in the analysis. Ground motion shall conform to the requirements of this
Section.
Two-dimensional analysis: Where two-dimensional analyses are performed,
each ground motion shall consist of a horizontal acceleration time history
selected from an actual recorded event. Appropriate acceleration histories shall
be obtained from records of events having magnitudes, fault distance, and
source mechanisms that are consistent with those that control the maximum
considered earthquake. Where the required number of appropriate ground
motion records are not available, appropriate simulated ground motion time
histories shall be used to make up the total number required. The ground
motions shall be scaled such that for each period between 0.2T and 1.5T (where
T is the natural period of the structure in the fundamental mode for the
direction considered) the average of the five-percent-damped response spectra
for the each acceleration time history is not less than the corresponding
ordinate of the design acceleration response spectrum, determined in
accordance with Sec 2.5.4.3.
Three-dimensional analysis: Where three-dimensional analysis is performed,
ground motions shall consist of pairs of appropriate horizontal ground motion
acceleration time histories (in two orthogonal horizontal directions) that shall
be selected and scaled from individual recorded events. Appropriate ground
motions shall be selected from events having magnitudes, fault distance, and
source mechanisms that are consistent with those that control the maximum
considered earthquake. Where the required number of recorded ground motion
pairs are not available, appropriate simulated ground motion pairs shall be used
to make up the total number required. For each pair of horizontal ground
motion components, an SRSS spectrum shall be constructed by taking the
square root of the sum of the squares of the five-percent-damped response
spectra for the components (where an identical scale factor is applied to both
components of a pair). Each pair of motions shall be scaled such that for each
period between 0.2T and 1.5T (where T is the natural period of the fundamental
mode of the structure) the average of the SRSS spectra from all horizontal
component pairs is not less than 1.3 times the corresponding ordinate of the
design response spectrum, determined in accordance with Sec 2.5.4.3.
2.5.10.3
Structure response (LTHA)
For each scaled acceleration time history, the maximum values of base shear
and other structure response quantities shall be obtained from the time history
analysis. For three dimensional analysis, orthogonal pair of scaled motions are
applied simultaneously. A base shear, V, shall also be calculated using the
equivalent static force procedure described in Sec 2.5.7.1. Where the maximum
base shear, "3 computed by linear time history analysis, is less than V, all
response quantities (storey shear, moments, drifts, floor deflections, member
forces etc) obtained by time history analysis shall be increased by multiplying
with the ratio,
T
T\*Á. If number of earthquake records (or pairs) used in the
analysis is less than seven, the maximum structural response obtained
corresponding to different earthquake records shall be considered as the design
value. If the number is at least seven, then the average of maximum structural
responses for different earthquake records shall be considered as the design
value.
The displacements and drifts obtained as mentioned above shall be multiplied
by
+,
µ to obtain design displacements and drifts, as done in equivalent static
analysis procedure (Sec 2.5.7.7).
#### 2.5.11 Non-Linear Time History Analysis (NTHA)
Nonlinear time history analysis (NTHA) shall consist of analysis of a
mathematical model of the structure which incorporates the nonlinear
যুংঃবৎবঃরপ নবযধারড়ৎ ড়ভ:যব ংঃৎঁপঃঁৎব্থং পড়সঢ়ড়হবহঃং:ড় ফবঃবৎসরহব রঃং ৎবংঢ়ড়হংব,
through methods of numerical integration, to ground acceleration time histories
compatible with the design response spectrum for the site. The analysis shall be
performed in accordance with the requirements of this Section. For the
purposes of analysis, the structure shall be permitted to be considered to be
fixed at the base or, alternatively, it shall be permitted to use realistic
assumptions with regard to the stiffness of foundations. The acceleration time
history (ground motion) is applied at the base of the structure. The advantage of
this procedure is that actual time dependent behavior of the structural response
considering inelastic deformations in the structure can be obtained.
2.5.11.1
Modeling (NTHA)
A mathematical model of the structure shall be constructed that represents the
spatial distribution of mass throughout the structure. The hysteretic behavior of
elements shall be modeled consistent with suitable laboratory test data and
shall account for all significant yielding, strength degradation, stiffness
degradation, and hysteretic pinching indicated by such test data. Strength of
elements shall be based on expected values considering material over-strength,
strain hardening, and hysteretic strength degradation. As a minimum, a bilinear
force deformation relationship should be used at the element level. In
reinforced concrete and masonry buildings, the elastic stiffness should
correspond to that of cracked sections. Linear properties, consistent with the
provisions of Chapter 5 shall be permitted to be used for those elements
demonstrated by the analysis to remain within their linear range of response.
The structure shall be assumed to have a fixed base or, alternatively, it shall be
permitted to use realistic assumptions with regard to the stiffness and load
carrying characteristics of the foundations consistent with site-specific soils
data and rational principles of engineering mechanics.
For regular structures with independent orthogonal seismic-force-resisting
systems, independent two dimensional models shall be permitted to be
constructed to represent each system. For structures having plan irregularity or
structures without independent orthogonal systems, a three-dimensional model
incorporating a minimum of three dynamic degrees of freedom consisting of
translation in two orthogonal plan directions and torsional rotation about the
vertical axis at each level of the structure shall be used. Where the diaphragms
are not rigid compared to the vertical elements of the lateral-force-resisting
ংুংঃবস,:যব সড়ফবষ ংযধষষ রহপষঁফব ৎবঢ়ৎবংবহঃধঃরড়হ ড়ভ:যব ফরধঢ়যৎধমস্থং ভষবীরনরষরঃু ধহফ
such additional dynamic degrees of freedom as are required to account for the
ঢ়ধৎঃরপরঢ়ধঃরড়হ ড়ভ:যব ফরধঢ়যৎধমস রহ:যব ংঃৎঁপঃঁৎব্থং ফুহধসরপ ৎবংঢ়ড়হংব.
2.5.11.2
Ground motion (NTHA)
The actual time-dependent inelastic deformation of the structure is modeled.
For inelastic analysis method, the real design acceleration response spectrum
(Sec 2.5.4.3) is obtained using Eq. 6.2.34 with R51 and I51. The real design
acceleration response spectrum is the true representation of the expected
ground motion (design basis earthquake) including local soil effects and
corresponds to a peak ground acceleration (PGA) value of
2 KC.
At least three appropriate acceleration time histories shall be used in the
analysis. Ground motion shall conform to the requirements of this Section.
Two-dimensional analysis
Where two-dimensional analyses are performed, each ground motion shall
consist of a horizontal acceleration time history selected from an actual
recorded event. Appropriate acceleration histories shall be obtained from
records of events having magnitudes, fault distance, and source mechanisms
that are consistent with those that control the maximum considered earthquake.
Where the required number of appropriate ground motion records are not
available, appropriate simulated ground motion time histories shall be used to
make up the total number required. The ground motions shall be scaled such
that for each period between 0.2T and 1.5T (where T is the natural period of the
structure in the fundamental mode for the direction considered) the average of
the five-percent-damped response spectra for each acceleration time history is
not less than the corresponding ordinate of the real design acceleration
response spectrum, as defined here.
Three-dimensional analysis
Where three-dimensional analysis is performed, ground motions shall consist of
pairs of appropriate horizontal ground motion acceleration time histories (in
two orthogonal horizontal directions) that shall be selected and scaled from
individual recorded events. Appropriate ground motions shall be selected from
events having magnitudes, fault distance, and source mechanisms that are
consistent with those that control the maximum considered earthquake. Where
the required number of recorded ground motion pairs are not available,
appropriate simulated ground motion pairs shall be used to make up the total
number required. For each pair of horizontal ground motion components, an
SRSS spectrum shall be constructed by taking the square root of the sum of the
squares of the five-percent-damped response spectra for the components
(where an identical scale factor is applied to both components of a pair). Each
pair of motions shall be scaled such that for each period between 0.2T and 1.5T
(where T is the natural period of the fundamental mode of the structure) the
average of the SRSS spectra from all horizontal component pairs is not less than
### 1.3 times the corresponding ordinate of the real design acceleration response
spectrum.
2.5.11.3
Structure response (NTHA)
For each scaled acceleration time history, the maximum values of base shear
and other structure response quantities shall be obtained from the nonlinear
time history analysis. For three dimensional analysis, orthogonal pair of scaled
motions are applied simultaneously. If number of earthquake records (or pairs)
used in the analysis is less than seven, the maximum structural response
obtained corresponding to different earthquake records shall be considered as
the design value. If the number is at least seven, then the average of maximum
structural responses for different earthquake records shall be considered as the
design value. Since real expected earthquake motion input and model
incorporating real nonlinear behavior of the structure is used, the results as
obtained are directly used (no scaling as in LTHA or RSA is required) for
interpretation and design.
2.5.11.4
Structure member design (NTHA)
The adequacy of individual members and their connections to withstand the
design deformations predicted by the analyses shall be evaluated based on
laboratory test data for similar components. The effects of gravity and other
loads on member deformation capacity shall be considered in these evaluations.
Member deformation shall not exceed two thirds of the smaller of: the value that
results in loss of ability to carry gravity loads or the value at which member
strength has deteriorated to less than 67 percent of peak strength.
2.5.11.5
Design review (NTHA)
Special care and expertise is needed in the use of nonlinear dynamic analysis
based design. Checking of the design by competent third party is recommended.
A review of the design of the seismic-force-resisting system and the supporting
structural analyses shall be performed by an independent team consisting of
design professionals with experience in seismic analysis methods and the
theory and application of nonlinear seismic analysis and structural behavior
under extreme cyclic loads. The design review shall include the following: (i)
Review of development of ground motion time histories (ii) Review of
acceptance criteria (including laboratory test data) used to demonstrate the
adequacy of structural elements and systems to withstand the calculated force
and deformation demands (iii) Review of structural design.
#### 2.5.12 Non-Linear Static Analysis (NSA)
Nonlinear static analysis (NSA), also popularly known as pushover analysis, is a
simplified method of directly evaluating nonlinear response of structures to
strong earthquake ground shaking. It is an alternative to the more complex
nonlinear time history analysis (NTHA). The building is subjected to
monotonically increasing static horizontal loads under constant gravity load.
2.5.12.1
Modeling (NSA)
A mathematical model of the structure shall be constructed to represent the
spatial distribution of mass and stiffness of the structural system considering
the effects of element nonlinearity for deformation levels that exceed the
proportional limit. P-Delta effects shall also be included in the analysis.
For regular structures with independent orthogonal seismic-force-resisting
systems, independent two-dimensional models may be used to represent each
system. For structures having plan irregularities or structures without
independent orthogonal systems, a three-dimensional model incorporating a
minimum of three degrees of freedom for each level of the structure, consisting
of translation in two orthogonal plan directions and torsional rotation about the
vertical axis, shall be used. Where the diaphragms are not rigid compared to the
vertical elements of the seismic-force-resisting system, the model should
include representation of the diaphragm flexibility.
Unless analysis indicates that an element remains elastic, a nonlinear force
deformation model shall be used to represent the stiffness of the element before
onset of yield, the yield strength, and the stiffness properties of the element
after yield at various levels of deformation. Strengths of elements shall not
exceed expected values considering material over-strength and strain
hardening. The properties of elements and components after yielding shall
account for strength and stiffness degradation due to softening, buckling, or
fracture as indicated by principles of mechanics or test data.
A control point shall be selected for the model. For normal buildings, the control
point shall be at the center of mass of the highest level (roof) of the structure.
2.5.12.2
Analysis procedure (NSA)
The lateral forces shall be applied at the center of mass of each level and shall be
proportional to the distribution obtained from a modal analysis for the
fundamental mode of response in the direction under consideration. The lateral
loads shall be increased incrementally in a monotonic manner.
At the d"3 increment of lateral loading, the total lateral force applied to the
model shall be characterized by the term . The incremental increases in
applied lateral force should be in steps that are sufficiently small to permit
significant changes in individual element behavior (such as yielding, buckling or
failure) to be detected. The first increment in lateral loading shall result in linear
elastic behavior. At each loading step, the total applied lateral force, the
lateral displacement of the control point, and the forces and deformations in
each element shall be recorded. The analysis shall be continued until the
displacement of the control point is at least 150 percent of the target
displacement determined in accordance with Sec.2.5.12.3. The structure shall be
designed so that the total applied lateral force does not decrease in any load
increment for control point displacements less than or equal to 125 percent of
the target displacement.
2.5.12.3
Effective period and target displacement (NSA)
A bilinear curve shall be fitted to the capacity curve, such that the first segment
of the bilinear curve coincides with the capacity curve at 60 percent of the
effective yield strength, the second segment coincides with the capacity curve at
the target displacement, and the area under the bilinear curve equals the area
under the capacity curve, between the origin and the target displacement. The
effective yield strength, H corresponds to the total applied lateral force at the
intersection of the two line segments. The effective yield displacement, H
corresponds to the control point displacement at the intersection of the two line
segments. The effective fundamental period, E\< of the structure in the direction
under consideration shall be determined using Eq. 6.2.51 as follows:
y
y
e
V
V
T
T
1
(6.2.51)
Where, 1, 1, and E1 are determined for the first increment of lateral load. The
target displacement of the control point, e shall be determined as follows:
g
T
S
C
C
e
a
T
2
(6.2.52)
Where, the spectral acceleration, Sa, is determined at the effective fundamental
period, Te, using Eq. 6.2.34, g is the acceleration due to gravity. The coefficient Co
shall be calculated as :
n
i
i
i
n
i
i
i
o
w
w
C
(6.2.53)
Where,
\[ = the portion of the seismic weight, W, at level i, and
k = the amplitude of the shape vector at level i.
Where the effective fundamental period, Te, is greater than TC (defined in Sec.
2.5.4.3), the coefficient C1 shall be taken as 1.0. Otherwise, the value of the
coefficient C1 shall be calculated as follows:
e
s
d
d
T
T
R
R
C
(6.2.54)
Where, Rd is given as follows:
W
V
S
R
y
a
d
(6.2.55)
2.5.12.4
Structure member design (NSA)
For each nonlinear static analysis the design response parameters, including the
individual member forces and member deformations shall be taken as the values
obtained from the analysis at the step at which the target displacement is reached.
The adequacy of individual members and their connections to withstand the
member forces and member deformations shall be evaluated based on
laboratory test data for similar components. The effects of gravity and other
loads on member deformation capacity shall be considered in these evaluations.
The deformation of a member supporting gravity loads shall not exceed (i) two-
thirds of the deformation that results in loss of ability to support gravity loads,
and (ii) two-thirds of the deformation at which the member strength has
deteriorated to less than 70 percent of the peak strength of the component
model. The deformation of a member not required for gravity load support shall
not exceed two-thirds of the value at which member strength has deteriorated
to less than 70 percent of the peak strength of the component model.
##### 2.5.12.5 Design review (NSA)
Checking of the design by competent third party is recommended. An
independent team composed of at least two members with experience in
seismic analysis methods and the theory and application of nonlinear seismic
analysis and structural behavior under earthquake loading, shall perform a
review of the design of the seismic force resisting system and the supporting
structural analyses. The design review shall include (i) review of any site-
specific seismic criteria (if developed) employed in the analysis (ii) review of
the determination of the target displacement and effective yield strength of the
structure (iii) review of adequacy of structural elements and systems to
withstand the calculated force and deformation demands, together with
laboratory and other data (iv) review of structural design.
#### 2.5.13 Earthquake Load Effects and Load Combinations
The seismic load effect, E, shall be determined in accordance with the following:
1. For use in load combination 5 in Section 2.7.3 or load combination 5 and 6
in Section 2.7.2, E shall be determined in accordance with the following
equation,
E 5 Eh + Ev
2. For use in load combination 7 in Section 2.7.3 or load combination 8 in
Section 2.7.2, E shall be determined in accordance with following equation,
E 5 Eh − Ev
Where,
E 5 total seismic load effect
Eh 5 effect of horizontal seismic forces as defined in Sections 2.5.7 or 2.5.9
Ev 5 effect of vertical seismic forces as defined in Section 2.5.13.2
##### 2.5.13.1 Horizontal earthquake loading, Eh
The horizontal seismic load effect, Eh, shall be taken as the horizontal load
effects of seismic base shear V (Sec 2.5.7 or 2.5.9) or component forces Fc (Sec
2.5.15).
The directions of application of horizontal seismic forces for design shall be
those which will produce the most critical load effects. Earthquake forces act in
both principal directions of the building simultaneously. In order to account for
that,
(a) For structures of Seismic Design Category B, the design horizontal
seismic forces are permitted to be applied independently in each of
two orthogonal directions and orthogonal interaction effects are
permitted to be neglected
(b) Structures of Seismic Design Category C and D shall, as a minimum,
conform to the requirements of (a) for Seismic Design Category B and
in addition the requirements of this Section. The structure of Seismic
Design Category C with plan irregularity type V and Seismic Design
Category D shall be designed for 100% of the horizontal seismic
forces in one principal direction combined with 30% of the
horizontal seismic forces in the orthogonal direction. Possible
combinations are:
ু১০০% রহ ী-ফরৎবপঃরড়হ ৩০% রহ ু-ফরৎবপঃরড়হচ্ ড়ৎ
ু৩০% রহ ী-ফরৎবপঃরড়হ ১০০% রহ ু-ফরৎবপঃরড়হচ্
The combination which produces most unfavourable effect for the
particular action effect shall be considered. This approach may be
applied to equivalent static analysis, response spectrum analysis and
linear time history analysis procedure.
(c) Where three-dimensional analysis of a spatial structure model is
performed as in 3D time history analysis, simultaneous application of
accelerations in two directions shall be considered where the ground
motions shall satisfy the conditions stated in Sections 2.5.10.2 or
2.5.11.2.
##### 2.5.13.2 Vertical earthquake loading, Ev
The maximum vertical ground acceleration shall be taken as 50 percent of the
expected horizontal peak ground acceleration (PGA). The vertical seismic load
effect %¼ may be determined as:
%¼ 5 0.50(L3)#
(6.2.56)
Where,
L3 5 expected horizontal peak ground acceleration (in g) for design 5
(2/3)KC
# 5 effect of dead load, S 5 site dependent soil factor (see Table 6.2.16).
2.5.13.3
Combination of earthquake loading with other loadings
When earthquake effect is included in the analysis and design of a building or
structure, the provisions set forth in Sec 2.7 shall be followed to combine
earthquake load effects, both horizontal and vertical, with other loading effects
to obtain design forces etc.
2.5.13.4
Seismic Load Effect Including Overstrength Factor
Where specifically required, conditions requiring overstrength factor, o,
applications shall be determined in accordance with the following,
1. For use in load combination 5 in Section 2.7.3 or load combinations 5 and 6
in Section 2.7.2, E shall be taken equal to Em as determined in accordance
with the following equation,
Em 5 Emh + Ev
2. For use in load combination 7 in Section 2.7.3 or load combination 8 in
Section 2.7.2, E shall be taken equal to Em as determined in accordance with
the following equation,
Em 5 Emh − Ev
where
Em 5 total seismic load effect including overstrength factor
Emh 5 effect of horizontal seismic forces as defined in Sections 2.5.7 or 2.5.9
including structural overstrength.
Ev 5 effect of vertical seismic forces as defined in Section 2.5.13.2
The horizontal seismic load effect with overstrength factor, Emh, shall be
determined in accordance with the following equation:
Emh 5 oEh
Where, o is the system overstrength factor as defined in Table 6.2.19. Like Eh,
directional combinations as defined in Sec. 2.5.13.1.(b) is also applicable for
calculating Emh. The value of Emh need not exceed the maximum force that can
develop in the structure or element as determined by a rational, plastic
mechanism analysis or nonlinear response analysis (static or dynamic) utilizing
realistic expected values of material strengths.
2.5.13.5
Allowable Stress Increase for Load Combinations with Overstrength
Where allowable stress design methodologies are used with the seismic load
effect defined in Section 2.5.13.4 applied in load combinations 5, 6, or 8 of
Section 2.7.2, allowable stresses are permitted to be determined using an
allowable stress increase of 1.2. This increase shall not be combined with
increases in allowable stresses or load combination reductions otherwise
permitted elsewhere by this standard.
2.5.13.6
Minimum Upward Force for Horizontal Cantilevers for Seismic
Design Category D
In structures assigned to Seismic Design Category D, horizontal cantilever
structural components shall be designed for a minimum net upward force of
### 0.2 times the dead load in addition to the applicable load combinations of
Section 2.7.
#### 2.5.14 Drift and Deformation
2.5.14.1
Storey drift limit
The design storey drift () of each storey, as determined in Sections 2.5.7, 2.5.9
or 2.5.10 shall not exceed the allowable storey drift (a) as obtained from Table
#### 6.2.21 for any story.
For structures with significant torsional deflections, the maximum drift shall
include torsional effects. For structures assigned to Seismic Design Category C or
D having torsional irregularity, the design storey drift, shall be computed as the
largest difference of the deflections along any of the edges of the structure at the
top and bottom of the storey under consideration. For seismic force–resisting
systems comprised solely of moment frames in Seismic Design Categories D, the
allowable storey drift for such linear elastic analysis procedures shall not exceed
Δ'/. where . is termed as a structural redundancy factor. The value of
redundancy factor . may be considered as 1.0 with exception of structures of
very low level of redundancy where . may be considered as 1.3.
For nonlinear time history analysis (NTHA), the storey drift obtained (Sec
2.5.11) shall not exceed 1.25 times the storey drift limit specified above for linear
elastic analysis procedures.
2.5.14.2
Diaphragm deflection
The deflection in the plane of the diaphragm, as determined by engineering
analysis, shall not exceed the permissible deflection of the attached elements.
Permissible deflection shall be that deflection that will permit the attached
element to maintain its structural integrity under the individual loading and
continue to support the prescribed loads.
Table 6.2.21: Allowable Storey Drift Limit (/ú)
Structure
Occupancy Category
I and II
III
IV
Structures, other than masonry shear
wall structures, 4 stories or less with
interior walls, partitions, ceilings and
exterior wall systems that have been
designed to accommodate the story
drifts.
0.025ℎ
0.020ℎ
0.015ℎ
Masonry cantilever shear wall structures
0.010ℎ
0.010ℎ
0.010ℎ
Other masonry shear wall structures
0.007ℎ
0.007ℎ
0.007ℎ
All other structures
0.020ℎ
0.015ℎ
0.010ℎ
Notes:
1. ℎis the story height below Level .
2. There shall be no drift limit for single-story structures with interior walls,
partitions, ceilings, and exterior wall systems that have been designed to
accommodate the storey drifts.
3. Structures in which the basic structural system consists of masonry shear walls
designed as vertical elements cantilevered from their base or foundation
support which are so constructed that moment transfer between shear walls
(coupling) is negligible.
4. Occupancy categories are defined in Table 6.1.1
2.5.14.3
Separation between adjacent structures
Buildings shall be protected from earthquake-induced pounding from adjacent
structures or between structurally independent units of the same building
maintaining safe distance between such structures as follows:
(i)
for buildings, or structurally independent units, that do not belong to
the same property, the distance from the property line to the
potential points of impact shall not be less than the computed
maximum horizontal displacement (Sec 2.5.7.7) of the building at the
corresponding level.
(ii) for buildings, or structurally independent units, belonging to the
same property, if the distance between them is not less than the
square root of the sum of the squares (SRSS) of the computed
maximum horizontal displacements (Sec 2.5.7.7) of the two buildings
or units at the corresponding level.
(iii) if the floor elevations of the building or independent unit under
design are the same as those of the adjacent building or unit, the
above referred minimum distance may be reduced by a factor of 0.7
2.5.14.4
Special deformation requirement for seismic design category D
For structures assigned to Seismic Design Category D, every structural
component not included in the seismic force–resisting system in the direction
under consideration shall be designed to be adequate for the gravity load effects
and the seismic forces resulting from displacement to the design story drift ()
as determined in accordance with Sec 2.5.7.7. Even where elements of the
structure are not intended to resist seismic forces, their protection may be
important. Where determining the moments and shears induced in components
that are not included in the seismic force–resisting system in the direction
under consideration, the stiffening effects of adjoining rigid structural and
nonstructural elements shall be considered and a rational value of member and
restraint stiffness shall be used.
#### 2.5.15 Seismic Design For Nonstructural Components
This Section establishes minimum design criteria for nonstructural components
that are permanently attached to structures and for their supports and
attachments. The following components are exempt from the requirements of
this Section.
(1) Architectural components in Seismic Design Category B, other than
parapets supported by bearing walls or shear walls, where the
component importance factor, .+ is equal to 1.0.
(2) Mechanical and electrical components in Seismic Design Category B.
(3) Mechanical and electrical components in Seismic Design Category C
where the importance factor, .+ is equal to 1.0.
(4) Mechanical and electrical components in Seismic Design Category D
where the component importance factor, .+ is equal to 1.0 and either
(a) flexible connections between the components and associated
ductwork, piping, and conduit are provided, or (b) components are
mounted at 1.2 m or less above a floor level and weigh 1780 N or less.
(5) Mechanical and electrical components in Seismic Design Category C
or D where the component importance factor, .+ is equal to 1.0 and
(a) flexible connections between the components and associated
ductwork, piping, and conduit are provided, and (b) the components
weigh 89 N or less or, for distribution systems, which weigh 73 N/m
or less.
Where the individual weight of supported components and non-building
structures with periods greater than 0.06 seconds exceeds 25 percent of the
total seismic weight W, the structure shall be designed considering interaction
effects between the structure and the supported components.
Testing shall be permitted to be used in lieu of analysis methods outlined in this
Chapter to determine the seismic capacity of components and their supports
and attachments.
2.5.15.1
Component importance factor
All components shall be assigned a component importance factor. The
component importance factor, .+ shall be taken as 1.5 if any of the following
conditions apply:
(1) The component is required to function after an earthquake,
(2) The component contains hazardous materials, or
(3) The component is in or attached to a occupancy category IV building
and it is needed for continued operation of the facility.
All other components shall be assigned a component importance factor, .+ equal
to 1.0.
2.5.15.2
Component force transfer
Components shall be attached such that the component forces are transferred to
the structure. Component attachments that are intended to resist seismic forces
shall be bolted, welded, or otherwise positively fastened without consideration
of frictional resistance produced by the effects of gravity. A continuous load path
of sufficient strength and stiffness between the component and the supporting
structure shall be verified. Local elements of the supporting structure shall be
designed for the component forces where such forces control the design of the
elements or their connections. In this instance, the component forces shall be
those determined in Sec 2.5.15.3, except that modifications to &! and @! due to
anchorage conditions need not be considered. The design documents shall
include sufficient information concerning the attachments to verify compliance
with the requirements of these Provisions.
2.5.15.3
Seismic design force
The seismic design force, Fc, applied in the horizontal direction shall be centered
ধঃ:যব পড়সঢ়ড়হবহঃ্থং পবহঃবৎ ড়ভ মৎধারঃু ধহফ ফরংঃৎরনঁঃবফ ৎবষধঃরাব:ড়:যব পড়সঢ়ড়হবহঃ'ং
mass distribution and shall be determined as follows:
h
z
R
I
W
a
F
c
c
c
h
c
c
(6.2.57)
Where,
0.75L3I+.+ ≤&+ ≤1.5L3I+.+
a+ 5 component amplification factor which varies from 1.0 to 2.5 (Table
#### 6.2.22 or Table 6.2.23).
L3 5 expected horizontal peak ground acceleration (in g) for design 5
0.67ZS
I+ 5 weight of component
@+ 5 component response reduction factor which varies from 1.0 to
12.0 (Table 6.2.22 or Table 6.2.23)
4 5 height above the base of the point of attachment of the component,
but z shall not be taken less than 0 and the value of 4/ℎ need not
exceed 1.0
h 5 roof height of structure above the base
The force &+ shall be independently applied in at least two orthogonal horizontal
directions in combination with service loads associated with the component. In
addition, the component shall also be designed for a concurrent vertical force of
± 0.5ahWc.
Where non-seismic loads on nonstructural components exceed &+ such loads
shall govern the strength design, but the seismic detailing requirements and
limitations shall apply.
2.5.15.4
Seismic relative displacements
The relative seismic displacement, #+ for two connection points on the same
structure A, one at a height ℎ and other at height ℎH, for use in component
design shall be determined as follows:
yA
xA
c
D
(6.2.58)
\#+ shall not exceed #+ ' given by:
sx
aA
y
x
c
h
h
h
D
max
(6.2.59)
Where,
w 5 Deflection at level x of structure A
Hw 5 Deflection at level y of structure A
∆'w 5 Allowable story drift for structure A
hx = Height (above base) of level x to which upper connection point is
attached.
hy = Height (above base) of level y to which lower connection point is
attached.
hsx = Story height used in the definition of the allowable drift a
For two connection points on separate structures, A and B, or separate structural
systems, one at level x and the other at level y, Dc shall be determined as follows:
yB
xA
c
D
(6.2.60)
Dc shall not exceed Dc max given by:
sx
aB
y
sx
aA
x
c
h
h
h
h
D
max
(6.2.61)
Where,
HA = Deflection at level y of structure B
∆'A = Allowable story drift for structure B
The effects of relative seismic relative displacements shall be considered in
combination with displacements caused by other loads as appropriate.
#### 2.5.16 Design For Seismically Isolated Buildings
Buildings that use special seismic isolation systems for protection against
earthquakes shall be called seismically isolated or base isolated buildings.
Seismically isolated structure and every portion thereof shall be designed and
constructed in accordance with the requirements of provisions presented in this
Section.
2.5.16.1
General requirements for isolation system
The isolation system to be used in seismically isolated structures shall satisfy
the following requirements:
(1) Design of isolation system shall consider variations in seismic
isolator material properties over the projected life of structure
including changes due to ageing, contamination, exposure to
moisture, loadings, temperature, creep, fatigue, etc.
(2) Isolated structures shall resist design wind loads at all levels above
the isolation interface. At the isolation interface, a wind restraint
system shall be provided to limit lateral displacement in the isolation
system to a value equal to that required between floors of the
structure above the isolation interface.
(3) The fire resistance rating for the isolation system shall be consistent
with the requirements of columns, walls, or other such elements in
the same area of the structure.
(4) The isolation system shall be configured to produce a lateral
restoring force such that the lateral force at the total design
displacement is at least 0.025 W greater than the lateral force at 50%
of the total design displacement.
(5) The isolation system shall not be configured to include a
displacement restraint that limits lateral displacement due to the
maximum considered earthquake to less than the total maximum
displacement unless it is demonstrated by analysis that such
engagement of restraint does not result in unsatisfactory
performance of the structure.
(6) Each element of the isolation system shall be designed to be stable
under the design vertical load when subjected to a horizontal
displacement equal to the total maximum displacement.
(7) The factor of safety against global structural overturning at the
isolation interface shall not be less than 1.0 for required load
combinations. All gravity and seismic loading conditions shall be
investigated. Seismic forces for overturning calculations shall be
based on the maximum considered earthquake and the vertical
restoring force shall be based on the seismic weight above the
isolation interface.
(8) Local uplift of individual units of isolation system is permitted if the
resulting deflections do not cause overstress or instability of the
isolator units or other elements of the structure.
(9) Access for inspection and replacement of all components of the
isolation system shall be provided.
(10) The designer of the isolation system shall establish a quality control
testing program for isolator units. Each isolator unit before
installation shall be tested under specified vertical and horizontal
loads.
(11) After completion of construction, a design professional shall
complete a final series of inspections or observations of structure
separation areas and components that cross the isolation interface.
Such inspections and observations shall confirm that existing
conditions allow free and unhindered displacement of the structure
to maximum design levels and that all components that cross the
isolation interface as installed are able to accommodate the
stipulated displacements.
(12) The designer of the isolation system shall establish a periodic
monitoring, inspection, and maintenance program for such system.
(13) Remodeling, repair, or retrofitting at the isolation interface, including
that of components that cross the isolation interface, shall be
performed under the direction of a design professional experienced
in seismic isolation systems.
Table 6.2.22: Coefficients ø0 and 10 for Architectural Components
Architectural Component or Element
ø0a
Interior Nonstructural Walls and Partitions
Plain (unreinforced) masonry walls
All other walls and partitions
1.0
1.0
1.5
2.5
Cantilever Elements (Unbraced or braced to structural frame below its
center of mass) Parapets and cantilever interior nonstructural walls
Chimneys and stacks where laterally braced or supported by the structural
frame
2.5
2.5
2.5
2.5
Cantilever Elements (Braced to structural frame above its center of mass)
Parapets
Chimneys and Stacks
Exterior Nonstructural Walls
1.0
1.0
1.0
2.5
2.5
2.5
Architectural Component or Element
ø0a
Exterior Nonstructural Wall Elements and Connections
Wall Element
Body of wall panel connections
Fasteners of the connecting system
1.0
1.0
1.25
2.5
2.5
1.0
Veneer
Limited deformability elements and attachments
Low deformability elements and attachments
1.0
1.0
2.5
1.5
Penthouses (except where framed by an extension of the building frame)
2.5
3.5
Ceilings
All
1.0
2.5
Cabinets
Storage cabinets and laboratory equipment
1.0
2.5
Access Floors
Special access floors
All other
1.0
1.0
2.5
1.5
Appendages and Ornamentations
2.5
2.5
Signs and Billboards
2.5
2.5
Other Rigid Components
High deformability elements and attachments
Limited deformability elements and attachments
Low deformability materials and attachments
Other Flexible Components
High deformability elements and attachments
Limited deformability elements and attachments
Low deformability materials and attachments
1.0
1.0
1.0
2.5
2.5
2.5
3.5
2.5
1.5
3.5
2.5
1.5
a A lower value for c is permitted where justified by detailed dynamic analysis. The value for
c shall not be less than 1.0. The value of c equal to 1.0 is for rigid components and rigidly
attached components. The value of c equal to 2.5 is for flexible components and flexibly
attached components.
Table 6.2.23: Coefficients ø0 and 10 for Mechanical and Electrical Components
Mechanical and Electrical Components
ø0a
Air-side HVAC, fans, air handlers, air conditioning units, cabinet heaters, air
distribution boxes, and other mechanical components constructed of sheet metal
framing.
2.5
6.0
Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers, water
heaters, heat exchangers, evaporators, air separators, manufacturing or process
equipment, and other mechanical components constructed of high-deformability
materials.
1.0
2.5
Engines, turbines, pumps, compressors, and pressure vessels not supported on
skirts and not within the scope of Chapter 15.
1.0
2.5
Skirt-supported pressure vessels
2.5
2.5
Elevator and escalator components.
1.0
2.5
Generators, batteries, inverters, motors, transformers, and other electrical
components constructed of high deformability materials.
1.0
2.5
Motor control centers, panel boards, switch gear, instrumentation cabinets, and
other components constructed of sheet metal framing.
2.5
6.0
Communication equipment, computers, instrumentation, and controls.
1.0
2.5
Roof-mounted chimneys, stacks, cooling and electrical towers laterally braced
below their center of mass.
2.5
3.0
Roof-mounted chimneys, stacks, cooling and electrical towers laterally braced
above their center of mass.
1.0
2.5
Lighting fixtures.
1.0
1.5
Other mechanical or electrical components.
1.0
1.5
Vibration Isolated Components and Systemsb
Components and systems isolated using neoprene elements and neoprene
isolated floors with built-in or separate elastomeric snubbing devices or resilient
perimeter stops.
2.5
2.5
Spring isolated components and systems and vibration isolated floors closely
restrained using built-in or separate elastomeric snubbing devices or resilient
perimeter stops.
2.5
2.0
Internally isolated components and systems.
2.5
2.0
Suspended vibration isolated equipment including in-line duct devices and
suspended internally isolated components.
2.5
2.5
Mechanical and Electrical Components
ø0a
Air-side HVAC, fans, air handlers, air conditioning units, cabinet heaters, air
distribution boxes, and other mechanical components constructed of sheet metal
framing.
2.5
6.0
Wet-side HVAC, boilers, furnaces, atmospheric tanks and bins, chillers, water
heaters, heat exchangers, evaporators, air separators, manufacturing or process
equipment, and other mechanical components constructed of high-
deformability materials.
1.0
2.5
Mechanical and Electrical Components
ø0a
Engines, turbines, pumps, compressors, and pressure vessels not supported on
skirts and not within the scope of Chapter 15.
1.0
2.5
Skirt-supported pressure vessels
2.5
2.5
Distribution Systems
Piping in accordance with ASME B31, including in-line components with joints
made by welding or brazing.
2.5
12.0
Piping in accordance with ASME B31, including in-line components,
constructed of high or limited deformability materials, with joints made by
threading, bonding, compression couplings, or grooved couplings.
2.5
6.0
Piping and tubing not in accordance with ASME B31, including in-line
components, constructed of high-deformability materials, with joints made by
welding or brazing.
2.5
9.0
Piping and tubing not in accordance with ASME B31, including in-line
components, constructed of high- or limited-deformability materials, with joints
made by threading, bonding, compression couplings, or grooved couplings.
2.5
4.5
Piping and tubing constructed of low-deformability materials, such as cast iron,
glass, and non-ductile plastics.
2.5
3.0
Ductwork, including in-line components, constructed of high-deformability
materials, with joints made by welding or brazing.
2.5
9.0
Ductwork, including in-line components, constructed of high- or limited-
deformability materials with joints made by means other than welding or
brazing.
2.5
6.0
Ductwork, including in-line components, constructed of low-deformability
materials, such as cast iron, glass, and non-ductile plastics.
2.5
3.0
Electrical conduit, bus ducts, rigidly mounted cable trays, and plumbing.
1.0
2.5
Manufacturing or process conveyors (non-personnel).
2.5
3.0
Suspended cable trays.
2.5
6.0
a A lower value for c is permitted where justified by detailed dynamic analysis. The value for c
shall not be less than 1.0. The value of c equal to 1.0 is for rigid components and rigidly
attached components. The value of c equal to 2.5 is for flexible components and flexibly
attached components.
b Components mounted on vibration isolators shall have a bumper restraint or snubber in each
horizontal direction. The design force shall be taken as 2Fc if the nominal clearance (air gap)
between the equipment support frame and restraint is greater than 6 mm. If the nominal
clearance specified on the construction documents is not greater than 6 mm, the design force
may be taken as Fc.
2.5.16.2
Equivalent static analysis
The equivalent static analysis procedure is permitted to be used for design of a
seismically isolated structure provided that:
(1)
The structure is located on Site Class SA, SB, SC, SD or SE site;
(2)
The structure above the isolation interface is not more than four stories or
20 m in height
(3)
Effective period of the isolated structure at the maximum displacement,
TM, is less than or equal to 3.0 sec.
(4)
The effective period of the isolated structure at the design displacement,
TD, is greater than three times the elastic, fixed-base period of the
structure above the isolation system as determined in Sec. 2.5.7.2
(5)
The structure above the isolation system is of regular configuration; and
(6)
The isolation system meets all of the following criteria:
(a)
The effective stiffness of the isolation system at the design
displacement is greater than one third of the effective stiffness at 20
percent of the design displacement,
(b)
The isolation system is capable of producing a restoring force as
specified in Sec. 2.5.16.1,
(c)
The isolation system does not limit maximum considered
earthquake displacement to less than the total maximum
displacement.
Where the equivalent lateral force procedure is used to design seismically isolated
structures, the requirements of this Section shall apply.
2.5.16.2.1
Displacement of isolation system: The isolation system shall be
designed and constructed to withstand minimum lateral earthquake displacements
that act in the direction of each of the main horizontal axes of the structure and such
displacements shall be calculated as follows:
D
D
a
D
B
T
g
S
D
4
(6.2.62)
Where,
Sa = Design spectral acceleration (in units of g), calculated using Eq. 6.2.34
for period TD and assuming R=1, I=1, =1 (Sec 2.5.4.3) for the design
basis earthquake (DBE).
g = acceleration due to gravity
BD= damping coefficient related to the effective damping βD of the isolation
system at the design displacement, as set forth in Table 6.2.24.
TD = effective period of seismically isolated structure at the design
displacement in the direction under consideration, as prescribed by Eq.
6.2.63:
g
k
W
T
D
D
min
(6.2.63)
Where,
W = seismic weight above the isolation interface
kDmin = minimum effective stiffness of the isolation system at the design
displacement in the horizontal direction under consideration.
Table 6.2.24: Damping Coefficient, BD or BM
Effective Damping, βD or βM a, b (%)
BD or BM
≤ 2
0.8
1.0
1.2
1.5
1.7
1.9
≥ 50
2.0
a
The damping coefficient shall be based on the effective damping of the isolation system
b
The damping coefficient shall be based on linear interpolation for effective damping values other
than those given.
| Table 6.2.24: Damping Coefficient, BD or | BM |
| ---------------------------------------------------- | --------------------------------------------------------------- |
| **Effective Damping,\*\*\*\**βD or βM a, b (%)*** | ***BD or BM*** |
| ≤ 2
5
10
20
30
40
≥ 50 |
0.8
1.0
1.2
1.5
1.7
1.9
2.0 |
The maximum displacement of the isolation system, DM, in the most critical direction
of horizontal response shall be calculated in accordance with the following formula:
M
M
aM
M
B
T
g
S
D
4
(6.2.64)
Where:
SaM = Maximum spectral acceleration (in units of g), calculated using Eq.
#### 6.2.34 for period TD and assuming R=1, I=1, =1 (Sec 2.5.4.3) for
the maximum considered earthquake (MCE).
BM = numerical coefficient related to the effective damping βM of the
isolation system at the maximum displacement, as set forth in Table
6.2.24.
TM = effective period of seismic-isolated structure at the maximum
displacement in the direction under consideration as prescribed by:
g
k
W
T
M
M
min
(6.2.65)
Where,
m2 \ ) 5 minimum effective stiffness of the isolation system at the
maximum
displacement
in
the
horizontal
direction
under
consideration.
The total design displacement, DTD, and the total maximum displacement, DTM, of
elements of the isolation system shall include additional displacement due to inherent
and accidental torsion calculated considering the spatial distribution of the lateral
stiffness of the isolation system and the most disadvantageous location of eccentric
mass.
2.5.16.2.2
Lateral seismic forces: The structure above the isolation system shall be
designed and constructed to withstand a minimum lateral force, Vs, using all of the
appropriate provisions for a non-isolated structure. The importance factor for all
isolated structures shall be considered as 1.0, also the response reduction factor RI
considered here (for computing design seismic forces) is in the range of 1.0 to 2.0.
Vs shall be determined in accordance with Eq. 6.2.66 as follows:
I
D
D
s
R
D
k
V
max
(6.2.66)
Where,
m3 ' 5 maximum effective stiffness of the isolation system at the design
displacement in the horizontal direction under consideration.
\#3 5
design displacement at the center of rigidity of the isolation system in the
direction under consideration as prescribed by Eq. 6.2.62.
@µ 5
response reduction factor related to the type of seismic-force-resisting
system above the isolation system. RI shall be based on the type of
seismic-force-resisting system used for the structure above the isolation
system and shall be taken as the lesser of
( @ (Table 6.2.19) or 2.0, but
need not be taken less than 1.0.
In no case shall Vs be taken less than the following:
(1)
The lateral force required by Sec 2.5.7 for a fixed-base structure of the
same weight, W, and a period equal to the isolated period, TD;
(2)
The base shear corresponding to the factored design wind load; and
(3)
The lateral force required to fully activate the isolation system (e.g., the
yield level of a softening system, the ultimate capacity of a sacrificial
wind-restraint system, or the break-away friction level of a sliding
system) multiplied by 1.5.
The isolation system, the foundation, and all structural elements below the isolation
system shall be designed and constructed to withstand a minimum lateral force,
4 using all of the appropriate provisions for a non-isolated structure. 4 shall be
determined in accordance with Eq. 6.2.67 as follows:
4 5 m3'#3
(6.2.67)
In all cases, 4 shall not be taken less than the maximum force in the isolation system
at any displacement up to and including the design displacement.
###### 2.5.16.2.3 Vertical distribution of lateral forces: The total lateral force shall be
distributed over the height of the structure above the isolation interface in
accordance with Eq. 6.2.68 as follows:
n
i
i
i
x
x
s
x
h
w
h
w
V
F
(6.2.68)
Where:
5
Total seismic lateral design force on elements above the
isolation system.
ℎ , ℎ 5
Height above the base, to Level i or Level x, respectively.
\[ , \[ 5 Portion of W that is located at or assigned to Level i or Level
x, respectively.
At each Level x the force, & shall be applied over the area of the structure in
accordance with the distribution of mass at the level. Stresses in each structural
element shall be determined by applying the lateral forces, & at all levels above the
base to an analytical model.
2.5.16.2.4
Storey drift: The storey drift shall be calculated as in Sec 2.5.7.7 except
that Cd for the isolated structure shall be taken equal to RI and importance factor
equal to 1.0. The maximum storey drift of the structure above the isolation system
shall not exceed 0.015hsx.
2.5.16.3
Dynamic analysis
Response spectrum analysis may be conducted if the behavior of the isolation system
can be considered as equivalent linear. Otherwise, non-linear time history analysis
shall be used where the true non-linear behaviour of the isolation system can be
modeled. The mathematical models of the isolated structure including the isolation
system shall be along guidelines given in Sections 2.5.9.1 and 2.5.11.1, and other
requirements given in Sec 2.5.16.
The isolation system shall be modeled using deformational characteristics developed
and verified by testing. The structure model shall account for: (i) spatial distribution
of isolator units; (ii) consideration of translation in both horizontal directions, and
torsion of the structure above the isolation interface considering the most
disadvantageous location of eccentric mass; (iii) overturning/uplift forces on
individual isolator units; and (iv) effects of vertical load, bilateral load, and the rate
of loading if the force-deflection properties of the isolation system are dependent on
such attributes.
A linear elastic model of the isolated structure (above isolation system) may be used
provided that: (i) stiffness properties assumed for the nonlinear components of the
isolation system are based on the maximum effective stiffness of the isolation
system, and (ii) all elements of the seismic-force-resisting system of the structure
above the isolation system behave linearly.
2.5.16.3.1
Response Spectrum Analysis: Response spectrum analysis shall be
performed using a modal damping value for the fundamental mode in the direction
of interest not greater than the effective damping of the isolation system or 30
percent of critical, whichever is less. Modal damping values for higher modes shall
be selected consistent with those that would be appropriate for response spectrum
analysis of the structure above the isolation system assuming a fixed base.
Response spectrum analysis used to determine the total design displacement and the
total maximum displacement shall include simultaneous excitation of the model by
100 percent of the ground motion in the critical direction and 30 percent of the
ground motion in the perpendicular, horizontal direction. The design basis
earthquake shall be used for the design displacement, while the maximum
considered earthquake shall be used for the maximum displacement. The maximum
displacement of the isolation system shall be calculated as the vectorial sum of the
two orthogonal displacements.
For the design displacement, structures that do not require site-specific ground
motion evaluation, shall be analyzed using the design acceleration response spectrum
in accordance with Sec 2.5.4.3. The maximum design spectrum to be used for the
maximum considered earthquake shall not be less than 1.5 times the design
acceleration response spectrum.
The response spectrum procedure is based on an equivalent linear model, where the
effective stiffness and effective damping is a function of the displacement, this
formulation is thus an iterative process. The effective stiffness must be estimated,
based on assumed displacement, and then adjusted till obtained displacement agree
with assumed displacement.
The design shear at any story shall not be less than the story shear resulting from
application of the story forces calculated using Eq. 6.2.68 with a value of equal to
the base shear obtained from the response spectrum analysis in the direction of
interest.
2.5.16.3.2
Nonlinear Time History Analysis: Where a time history analysis
procedure is performed, not fewer than three appropriate ground motions shall be
used in the analysis as described below.
Ground motions shall consist of pairs of appropriate horizontal ground motion
acceleration components that shall be selected and scaled from individual recorded
events. Appropriate ground motions shall be selected from events having
magnitudes, fault distance, and source mechanisms that are consistent with those that
control the maximum considered earthquake. If required number of recorded ground
motion pairs are not available, appropriate simulated ground motion pairs shall be
used to make up the total number required. For each pair of horizontal ground-
motion components, a square root of the sum of the squares (SRSS) spectrum shall
be constructed by taking the SRSS of the 5 percent damped response spectra for the
scaled components (where an identical scale factor is applied to both components of
a pair). Each pair of motions shall be scaled such that for each period between 0.5TD
and 1.25TM (where TD and TM are defined in Sec 2.5.16.2.1) the average of the SRSS
spectra from all horizontal component pairs does not fall below 1.3 times the
corresponding ordinate of the design response spectrum (Sec 2.5.16.4), by more than
10 percent.
Each pair of ground motion components shall be applied simultaneously to the model
considering the most disadvantageous location of eccentric mass. The maximum
displacement of the isolation system shall be calculated from the vectorial sum of the
two orthogonal displacements at each time step.
The parameters of interest shall be calculated for each ground motion used for the
time history analysis. If at least seven ground motions are used for the time history
analysis, the average value of the response parameter of interest is permitted to be
used for design. If fewer than seven ground motions are analyzed, the maximum
value of the response parameter of interest shall be used for design.
2.5.16.3.3
Storey drift: Maximum story drift corresponding to the design lateral
force including displacement due to vertical deformation of the isolation system shall
not exceed the following limits:
1. The maximum story drift of the structure above the isolation system
calculated by response spectrum analysis shall not exceed 0.015ℎ.
2. The maximum story drift of the structure above the isolation system
calculated by nonlinear time history analysis shall not exceed 0.020ℎ.
The storey drift shall be calculated as in Sec 2.5.7.7 except that Cd for the isolated
structure shall be taken equal to RI and importance factor equal to 1.0.
2.5.16.4
Testing
The deformation characteristics and damping values of the isolation system used in
the design and analysis of seismically isolated structures shall be based on test results
of isolator units. The tests are for establishing and validating the design properties of
the isolation system and shall not be considered as satisfying the manufacturing
quality control tests.
The following sequence of tests shall be performed on isolator units for the
prescribed number of cycles at a vertical load equal to the average dead load plus
one-half the effects due to live load on all isolator units of a common type and size:
(1)
Twenty fully reversed cycles of loading at a lateral force corresponding to
the wind design force.
(2)
Three fully reversed cycles of loading at each of the following increments
of the total design displacement-0.25DD, 0.5DD, 1.0DD, and 1.0DM where
DD and DM are as determined in Sec 2.5.16.2.1.
(3)
Three fully reversed cycles of loading at the total maximum
displacement, 1.0DTM.
(4)
Not less than ten fully reversed cycles of loading at 1.0 times the total
design displacement, 1.0DTD.
For each cycle of each test, the force-deflection and hysteretic behavior of each
isolator unit shall be recorded. The effective stiffness is obtained as the secant value
of stiffness at design displacement while the effective damping is determined from
the area of hysteretic loop at the design displacement.
2.5.16.5
Design review
A design review of the isolation system and related test programs shall be performed
by an independent team of design professionals experienced in seismic analysis
methods and the application of seismic isolation. Isolation system design review shall
include, but need not be limited to, the following:
(1)
Review of site-specific seismic criteria including the development of site-
specific spectra and ground motion time histories and all other design
criteria developed specifically for the project;
(2)
Review of the preliminary design including the determination of the total
design displacement of the isolation system and the lateral force design
level;
(3)
Overview and observation of prototype (isolator unit) testing
(4)
Review of the final design of the entire structural system and all
supporting analyses; and
(5)
Review of the isolation system quality control testing program.
#### 2.5.17 Buildings with Soft Storey
Buildings with possible soft storey action at ground level for providing open parking
spaces belong to structures with major vertical irregularity \[Figure 6.2.28(a)]. Special
arrangement is needed to increase the lateral strength and stiffness of the soft/open
storey. The following two approaches may be considered:
(1)
Dynamic analysis of such building may be carried out incorporating the
strength and stiffness of infill walls and inelastic deformations in the
members, particularly those in the soft storey, and the members designed
accordingly.
(2)
Alternatively, when system overstrength factor, o, is not included in
determining seismic load effects, the following design criteria are to be
adopted after carrying out the earthquake analysis, neglecting the effect of
infill walls in other storeys. Structural elements (e.g columns and beams)
of the soft storey are to be designed for 2.5 times the storey shears and
moments calculated under seismic loads neglecting effect of infill walls.
Shear walls placed symmetrically in both directions of the building as far
away from the centre of the building as feasible are to be designed
exclusively for 1.5 times the lateral shear force calculated before.
#### 2.5.18 Non-Building Structures
Calculation of seismic design forces on non-building structures (e.g. chimney, self-
supported overhead water/fluid tank, silo, trussed tower, storage tank, cooling tower,
monument and other structures not covered in Sec 2.5) shall be in accordance with
"Chapter 15: Seismic Design Requirements for Non-Building Structures, Minimum
Design Loads for Buildings and Other Structures, ASCE Standard ASCE/SEI 7-05"
complying with the requirements of Sec 2.5 of this Code.
2.6
Miscellaneous Loads
2.6.1
General
The procedures and limitations for the determination of selected miscellaneous loads
are provided in this Section. Loads that are not specified in this Section or elsewhere
in this Chapter, may be determined based on information from reliable references or
specialist advice may be sought.
2.6.2
Rain Loads
Rain loads shall be determined in accordance with the following provisions.
##### 2.6.2.1 Blocked drains
Each portion of a roof shall be designed to sustain the load from all rainwater that
could be accumulated on it if the primary drainage system for that portion is
undersized or blocked. Ponding instability shall be considered in this situation.
##### 2.6.2.2 Controlled drainage
Roofs equipped with controlled drainage provisions shall be designed to sustain all
rainwater loads on them to the elevation of the secondary drainage system plus 0.25
kN/m2. Ponding instability shall be considered in this situation.
2.6.3
Loads Due to Flood and Surge
For the determination of flood and surge loads on a structural member, consideration
shall be given to both hydrostatic and hydrodynamic effects. Required loading shall
be determined in accordance with the established principles of mechanics based on
site specific criteria and in compliance with the following provisions of this Section.
For essential facilities like cyclone and flood shelters and for hazardous facilities
specified in Table 6.1.1, values of maximum flood elevation, surge height, wind
velocities etc., required for the determination of flood and surge load, shall be taken
corresponding to 100-year return period. For structures other than essential and
hazardous facilities, these values shall be based on 50-year return period.
##### 2.6.3.1 Flood loads on structures at inland areas
For structures sited at inland areas subject to flood, loads due to flood shall be
determined considering hydrostatic effects which shall be calculated based on the
flood elevation of 50-year return period. For river-side structures such as that under
Exposure C specified in Sec 2.4.6.3, hydrodynamic forces, arising due to
approaching wind-generated waves shall also be determined in addition to the
hydrostatic load on them. In this case, the amplitude of such wind-induced water
waves shall be obtained from site-specific data.
##### 2.6.3.2 Flood and surge loads on structures at coastal areas
Coastal area of Bangladesh has been delineated as Risk Area (RA) and High Risk
Area (HRA) based on the possible extend of the inland intrusion of the cyclone storm
surge as shown in Figure 6.2.30. To be classified as coastal RISK AREA, the
principal source of flooding must be sea tides, storm surge, and not riverine flood.
The RA extends from the coast line to an inland limit up to which surge water can
reach. The HRA includes a strip of land within the RA. It extends from the coast line
up to the limit where the depth of storm surge inundation may exceed 1m.Entire area
of the off-shore islands except the Maheshkhali area is included in the HRA. A part
of Maheshkhali is covered by hills and therefore free from inundation. However, the
western and northern parts of Maheshkhali are of low elevation and risk inundation.
For structures sited in coastal areas (Risk Areas), the hydrostatic and hydrodynamic
loads shall be determined as follows:
2.6.3.2.1
Hydrostatic Loads
The hydrostatic loads on structural elements and foundations shall be determined
based on the maximum static height of water, Hm, produced by floods or surges as
given by the relation:
-\ 5 5L Ôℎ, ℎÕ
(6.2.69)
ℎ 5 âe −â
(6.2.70)
Where,
ℎ = Maximum surge height as specified in (i) below.
âe = Elevation of the extreme surface water level corresponding to a T-year
return period specified in (ii) below, meters
â = Elevation of ground level at site, meters.
Figure 6.2.30 Coastal risk areas (RA) and high risk areas (HRA) of Bangladesh
(i) Maximum Surge Height, hs : The maximum surge height, hs , associated with
cyclones, shall be that corresponding to a 50-year or a 100-year return period
as may be applicable, based on site specific analysis. In the absence of a
more rigorous site specific analysis, the following relation may be used:
ℎ 5 ℎe −( −1)m
(6.2.71)
Where, hT = design surge height corresponding to a return period of T-years
at sea coast, in metres, given in Table 6.2.25.
x = distance of the structure site measured from the spring tide high-
water limit on the sea coast, in km; x= 1, if x\<1.
k = rate of decrease in surge height in meter/km; the value of k may be
taken as 0.5 for Chittagong-Cox's Bazar-Teknaf coast and as 0.33
for other coastal areas.
(ii) Extreme Surface Water Level, âe: The elevation of the extreme surface
water level, âe for a site, which may not be associated with a cyclonic storm
surge, shall be that obtained from a site specific analysis corresponding to a
50-year or a 100-year return period. Values of âe are given in Table 6.2.26
for selected coastal locations which may be used in the absence of any site
specific data.
Hydrostatic loads caused by a depth of water to the level of the -\ shall be applied
over all surfaces involved, both above and below ground level, except that for
surfaces exposed to free water, the design depth -\ shall be increased by 0.30 m.
Reduced uplift and lateral loads on surfaces of enclosed spaces below the -\ shall
apply only if provision is made for entry and exit of floodwater.
Table 6.2.25: Design Surge Heights at the Sea Coast, hT\*
Coastal Region
Surge Height at the Sea Coast, hT
(m)
T = 50-year(1)
T = 100-year(2)
Teknaf to Cox's Bazar
4.5
5.8
Chakaria to Anwara, and Maheshkhali-Kutubdia
Islands
7.1
8.6
Chittagong to Noakhali
7.9
9.6
Sandwip, Hatiya and all islands in this region
7.9
9.6
Bhola to Barguna
6.2
7.7
Sarankhola to Shyamnagar
5.3
6.4
Notes:
\*
Values prepared from information obtained from Annex-D3, MCSP.
(1)
These values may be used in the absence of site specific data for structures other than
essential facilities listed in Table 6.1.1.
(2)
These values may be used in the absence of site specific data for essential facilities listed in
Table 6.1.1.
Table 6.2.26: Extreme Surface Water Levels above PWD Datum, yT\* at Coastal
Areas during Monsoon
Coastal Area
yT (m)
Location
Thana
T = 50 years(1)
T = 100 years(2)
Teknaf
Cox's Bazar
Shaflapur
Lemsikhali
Banigram
Teknaf
Cox's Bazar
Moheshkhali
Kutubdia
Patiya
2.33
3.84
4.67
4.95
5.05
2.44
3.88
4.87
5.19
5.24
Chittagong
Patenga
Sonapur
Sandwip
Companyganj
Bandar
Bandar
Sonagazi
Sandwip
Companyganj
4.72
4.08
7.02
6.09
7.53
4.88
4.16
7.11
6.2
7.94
Hatiya
Daulatkhan
Dashmina
Galachipa
Patuakhali
Hatiya
Daulatkhan
Dashmina
Galachipa
Patuakhali
5.55
4.62
3.60
3.79
2.87
5.76
4.72
3.73
3.92
3.03
Khepupara
Bamna
Patharghata
Raenda
Chardouni
Mongla
Kobodak (river
estuary)
Kaikhali
Kalapara
Bamna
Patharghata
Sarankhola
Patharghata
Mongla port
Shyamnagar
Shyamnagar
2.93
3.32
3.65
3.66
4.41
3.23
3.51
3.94
3.02
3.37
3.84
3.75
4.66
3.36
3.87
4.12
Notes:
\*
Values prepared from information obtained from Annex -D3, MCSP
(1) These values may be used in the absence of site specific data for structures in
Structure Occupancy Category IV listed Table 6.1.1.
(2) These values may be used in the absence of site specific data for structures in
Structure Occupancy Categories I, II and III listed in Table 6.1.1.
2.6.3.2.2
Hydrodynamic loads
The hydrodynamic load applied on a structural element due to wind-induced local
waves of water, shall be determined by a rational analysis using an established
method of fluid mechanics and based on site specific data. In the absence of a site-
specific data the amplitude of the local wave, to be used in the rational analysis, shall
be taken as ℎ> 5
ℎ
q ≥1 m, where, hs is given in Sec 2.6.3.2.1. Such forces shall be
calculated based on 50-year or 100-year return period of flood or surge. The
corresponding wind velocities shall be 80 m/s or 90 m/s (3-sec gust) respectively.
Exception:
Where water velocities do not exceed 3.0 m/s, dynamic effects of moving water shall
be permitted to be converted into equivalent hydrostatic loads by increasing Hm for
design purposes by an equivalent surcharge depth, dh, on the headwater side and
above the ground level only, equal to
ℎ5
'TÈ
(6.2.72)
Where,
V = average velocity of water in m/s
g = acceleration due to gravity, 9.81 m/s2
a = coefficient of drag or shape factor (not less than 1.25)
In absence of more authentic site specific data, the velocity of water, V, may be
estimated such that ds ≤ V ≤ tQ where g is the acceleration due to gravity and ds is
defined in Sec 2.6.3.4. Selection of the correct value of drag-coefficient a in Eq.
#### 6.2.72 will depend upon the shape and roughness of the object exposed to flood flow,
as well as the flow condition. As a general rule, the smoother and more streamlined
the object, the lower the drag coefficient (shape factor). Drag coefficients for
elements common in buildings and structures (round or square piles, columns, and
rectangular shapes) will range from approximately 1.0 to 2.0, depending upon flow
conditions. However, given the uncertainty surrounding flow conditions at a
particular site, it is recommended that a minimum value of 1.25 be used. Fluid
mechanics texts should be consulted for more information on when to apply drag
coefficients above 1.25.
The equivalent surcharge depth, dh, shall be added to the design depth Hm and the
resultant hydrostatic pressures applied to, and uniformly distributed across, the
vertical projected area of the building or structure that is perpendicular to the flow.
Surfaces parallel to the flow or surfaces wetted by the tail water shall be subject to
the hydrostatic pressures for depths to the Hm only.
2.6.3.3
Breakaway walls
Walls and partitions required to break away, including their connections to the
structure, shall be designed for the largest of the following loads acting perpendicular
to the plane of the wall:
(i)
The wind load specified in Sec. 2.4.
(ii) The earthquake load specified in Sec. 2.5.
(iii) 0.50 kN/m2 pressure.
The loading at which breakaway walls are intended to collapse shall not exceed 1.0
kN/m2 unless the design meets the following conditions:
(i)
Breakaway wall collapse is designed to result from a flood load less than
that which occurs during the base flood.
(ii) The supporting foundation and the elevated portion of the building shall
be designed against collapse, permanent lateral displacement, and other
structural damage due to the effects of flood loads in combination with
other loads as specified elsewhere in this Chapter.
2.6.3.4
Wave loads
Wave loads shall be determined by one of the following three methods: (1) by using
the analytical procedures outlined in this Section, (2) by more advanced numerical
modeling procedures, or (3) by laboratory test procedures (physical modeling).
Wave loads are those loads that result from water waves propagating over the water
surface and striking a building or other structure. Design and construction of
buildings and other structures subject to wave loads shall account for the following
loads: a) waves breaking on any portion of the building or structure; b) uplift forces
caused by shoaling waves beneath a building or structure, or portion thereof; c) wave
runup striking any portion of the building or structure; d) wave-induced drag and
inertia forces; and e) wave-induced scour at the base of a building or structure, or its
foundation. Nonbreaking and broken wave loads shall be calculated using the
procedures described in Sections 2.6.3.2.1 and 2.6.3.2.2 that show how to calculate
hydrostatic and hydrodynamic loads.
Breaking wave loads shall be calculated using the procedures described in Sections
###### 2.6.3.4.1 to 2.6.3.4.4. Breaking wave heights used in the procedures described in
these Sections shall be calculated for using Equations 6.2.73 and 6.2.74.
Hb = 0.78 ds
(6.2.73)
Where,
-4 5 breaking wave height in meter.
5 local still water depth in meter.
The local still water depth shall be calculated using Eq. 6.2.74 unless more advanced
procedures or laboratory tests permitted by this Section are used.
5 0.65-\
(6.2.74)
2.6.3.4.1
Breaking wave loads on vertical pilings and columns
The net force resulting from a breaking wave acting on a rigid vertical pile or column
shall be assumed to act at the still water elevation and shall be calculated by the
following:
&3 5 0.5ð> 3#-4
(6.2.75)
Where,
&3 = net wave force, in kN.
ð> = unit weight of water, in kN/m3 = 9.80 kN/m3 for fresh water and 10.05
kN/m3 or salt water.
3 = coefficient of drag for breaking waves, = 1.75 for round piles or columns,
and = 2.25 for square piles or columns.
# = pile or column diameter, in meter for circular sections, or for a square pile
or column, 1.4 times the width of the pile or column in meter.
-4 = breaking wave height, in meter.
2.6.3.4.2
Breaking wave loads on vertical walls
Maximum pressures and net forces resulting from a normally incident breaking wave
(depth-limited in size, with -4 5 0.78 acting on a rigid vertical wall shall be
calculated by the following:
;' 5 !ð> + 1.2ð>
(6.2.76)
&" 5 1.1 !ð> + 2.4ð>
(6.2.77)
Where,
;' = maximum combined dynamic Ô !ð> Õ and static (1.2ð> ) wave
pressures, also referred to as shock pressures in kN/m2.
&" =
net breaking wave force per unit length of structure, also referred to as
shock, impulse, or wave impact force in kN/m, acting near the still water
elevation.
! =
dynamic pressure coefficient. It shall be taken as 1.6, 2.8, 3.2 or 3.5 for
building occupancy categories I, II, III or IV respectively.
ð> =
unit weight of water, in kN/m3 = 9.80 kN/m3 for fresh water and 10.05
kN/m3 for salt water
=
still water depth in meter at base of building or other structure where the
wave breaks.
This procedure assumes the vertical wall causes a reflected or standing wave against
the water ward side of the wall with the crest of the wave at a height of 1.2 above
the still water level. Thus, the dynamic static and total pressure distributions against
the wall are as shown in Figure 6.2.31.
This procedure also assumes the space behind the vertical wall is dry, with no fluid
balancing the static component of the wave force on the outside of the wall. If free
water exists behind the wall, a portion of the hydrostatic component of the wave
pressure and force disappears (Figure 6.2.32) and the net force shall be computed by
Eq. 6.2.78 (the maximum combined wave pressure is still computed with Eq. 6.2.76).
&" 5 1.1 !ð> + 1.9ð>
(6.2.78)
Where,
&" = net breaking wave force per unit length of structure, also referred to as
shock, impulse, or wave impact force in kN/m, acting near the still water
elevation.
! = dynamic pressure coefficient. It shall be taken as 1.6, 2.8, 3.2 or 3.5 for
building occupancy categories I, II, III or IV respectively.
ð> = unit weight of water, in kN/m3 = 9.80 kN/m3 for fresh water and 10.05
kN/m3 for salt water
= still water depth in meter at base of building or other structure where the
wave breaks.
2.6.3.4.3
Breaking wave loads on nonvertical walls
Breaking wave forces given by Equations 6.2.77 and 6.2.78 shall be modified in
instances where the walls or surfaces upon which the breaking waves act are
nonvertical. The horizontal component of breaking wave force shall be given by
&)¼ 5 &"sina
(6.2.79)
Where,
&)¼ = horizontal component of breaking wave force in kN/m.
&" = net breaking wave force acting on a vertical surface in kN/m.
a = vertical angle between nonvertical surface and the horizontal.
2.6.3.4.4
Breaking Wave Loads from Obliquely Incident Waves.
Breaking wave forces given by Equations 6.2.77 and 6.2.78 shall be modified in
instances where waves are obliquely incident. Breaking wave forces from non-
normally incident waves shall be given by
& 5 &"sina
(6.2.80)
Where,
& = horizontal component of obliquely incident breaking wave force in kN/m.
&" = net breaking wave force (normally incident waves) acting on a vertical
surface in kN/m.
a =
horizontal angle between the direction of wave approach and the vertical
surface.
2.6.3.5
Impact loads
Impact loads are those that result from debris, ice, and any object transported by
floodwaters striking against buildings and structures, or parts thereof. Impact loads
shall be determined using a rational approach as concentrated loads acting
horizontally at the most critical location at or below -\ (Eq. 6.2.69). Eq. 6.2.81
provides a rational approach for calculating the magnitude of the impact load.
& 5
67T8+9+:+í+¿S
∆"
(6.2.81)
Where,
& = impact force in N
I = debris weight in N, to be taken equal to 4448 N unless more specific data is
available.
4 = velocity of the debris, m/s, assumed equal to the velocity of water V defined
in Sec. 2.6.3.2.2.
Q = acceleration due to gravity, 9.81 m/s2
∆± = duration of impact, which may be taken as 0.03 second
µ = importance co-efficient = 0.6, 1.0, 1.2 or 1.3 for building occupancy
categories I, II, III or IV respectively
; = orientation co-efficient = 0.8
3 = depth co-efficient, to be taken equal to 0.0 for water depth 0.3m or less
and equal to 1.0 for water depth 1.5m or more. Linear interpolation shall
be made for intermediate water depth values.
A= blockage co-efficient, to be taken equal to 0.0 for upstream flow channel
width 1.5m or less and equal to 1.0 for upstream flow channel width 9.1 m
or more. Linear interpolation shall be made for intermediate values of
upstream flow channel width. The upstream shall extend 30.0 m from the
building.
@' = maximum response ratio for impulsive load (half sine wave type) to be
obtained from Table 6.2.27.
2.6.4
Temperature Effects
Temperature effects, if significant, shall be considered in the design of structures or
components thereof in accordance with the provision of this Section. In determining
the temperature effects on a structure, the following provisions shall be considered:
(a)
The temperatures indicated, shall be the air temperature in the shade. The
range of the variation in temperature for a building site shall be taken into
consideration.
(b)
Effects of the variation of temperature within the material of a structural
element shall be accounted for by one of the following methods.
(i)
Relieve the stresses by providing adequate numbers of expansion or
contraction joints,
(ii) Design the structural element to sustain additional stresses due to
temperature effects.
(c)
when the method b(ii) above is considered to be applicable, the structural
analysis shall take into account the following :
(i)
The variation in temperature within the material of the structural
element, exposure condition of the element and the rate at which the
material absorb or radiate heat.
(ii) The warping or any other distortion caused due to temperature
changes and temperature gradient in the structural element.
(d)
When it can be demonstrated by established principle of mechanics or by
any other means that neglecting some or all of the effects of temperature,
does not affect the safety and serviceability of the structure, the
temperature effect can be considered insignificant and need not be
considered in design.
Figure 6.2.31 Normally incident breaking wave pressures against a vertical wall (space
behind vertical wall is dry)
| Col1 | Col2 | Col3 |
| ------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------- | -------------------------------------------------------------------- |
| **Figure 6.2.31 Normally incident breaking wave pressures against a vertical wall (space**
| \*\* Normally incident breaking wave pressures against a vertic\*\* | \*\* Normally incident breaking wave pressures against a vertic\*\* |
| **behind vertical wall is dry)** | **behind vertical wall is dry)** | **behind vertical wall is dry)** |
Figure 6.2.32 Normally incident breaking wave pressures against a vertical wall (still water
level equal on both sides of wall)
Table 6.2.27: Values of response ratio, 1ú\<, for impulsive loads
Ratio of impulse duration
(∆±) to natural period
(Sec. 2.5) of structure
@'
Ratio of impulse duration
(∆±) to natural period
(Sec. 2.5) of structure
@'
0.8
1.8
0.1
0.4
0.9
1.8
0.2
0.8
1.7
0.3
1.1
1.1
1.7
0.4
1.4
1.2
1.6
0.5
1.5
1.3
1.6
0.6
1.7
≥1.4
1.5
0.7
1.8
| Ratio of impulse duration @
'
(∆±) to natural period
(Sec. 2.5) of structure | Ratio of impulse duration @
'
(∆±) to natural period
(Sec. 2.5) of structure |
| ---------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| 0
0
0.1
0.4
0.2
0.8
0.3
1.1
0.4
1.4
0.5
1.5
0.6
1.7
0.7
1.8 | 0.8
1.8
0.9
1.8
1
1.7
1.1
1.7
1.2
1.6
1.3
1.6
≥1.4
1.5 |
2.6.5
Soil and Hydrostatic Pressure
For structures or portions thereof, lying below ground level, loads due to soil and
hydrostatic pressure shall be determined in accordance with the provisions of this
Section and applied in addition to all other applicable loads.
##### 2.6.5.1 Pressure on basement wall:
In the design of basement walls and similar vertical or nearly vertical structures
below grade, provision shall be made for the lateral pressure of adjacent soil.
Allowance shall be made for possible surcharge due to fixed or moving loads. When
a portion or the whole of the adjacent soil is below the surrounding water table,
computations shall be based on the submerged unit weight of soil, plus full
hydrostatic pressure.
##### 2.6.5.2 Uplift on floors:
In the design of basement floors and similar horizontal or nearly horizontal
construction below grade, the upward pressure of water, if any, shall be taken as the
full hydrostatic pressure applied over the entire area. The hydrostatic head shall be
measured from the underside of the construction.
2.6.6
Loads due to Explosions
Loads on buildings or portions thereof, shall be assessed in accordance with the
provisions of this Section.
##### 2.6.6.1 Explosion effects in closed rooms
(a)
Determination of Loads and Response: Internal overpressure developed
from an internal explosion such as that due to leaks in gas pipes,
evaporation of volatile liquids, internal dust explosion etc., in rooms of
sizes comparable to residential rooms and with ventilation areas
consisting of window glass breaking at a pressure of 4 kN/m2 (3-4 mm
machine made glass) may be calculated from the following method :
(i)
The overpressure, X; provided in Figure 6.2.33(a) shall be assumed
to depend on a factor ;/=, where, ; is the total window area in
m2 and = is the volume in m3 of the room considered,
(ii) The internal pressure shall be assumed to act simultaneously upon
all walls and floors in one closed room, and
(iii) The action X; obtained from Figure 6.2.33(a) may be taken as static
action.
When a time dependent response is required, an impulsive force function similar to
that shown in Figure 6.2.33(b) shall be used in a dynamic analysis, where t1 is the
time from the start of combustion until maximum pressure is reached and t2 is the
time from maximum pressure to the end of combustion. For t1 and t2 the most
unfavourable values shall be chosen in relation to the dynamic properties of the
structures. However, the values shall be chosen within the intervals as given in
Figure 6.2.33(b).
The pressure may be applied solely in one room or in more than one room at the
same time. In the latter case, all rooms are incorporated in the volume v. Only
windows or other similarly weak and light weight structural elements may be taken
as ventilation areas even though certain limited structural parts break at pressures less
than qo.
(b)
Limitations : Procedure for determining explosion loads given in (a)
above shall have the following limitations:
(i)
Values of qo given in Figure 6.2.33(a) are based on tests with gas
explosions in room corresponding to ordinary residential flats, and
may be applied to considerably different conditions with caution
after appropriate adjustment of the values based on more accurate
information.
(ii) Figures 6.2.33(a) and 6.2.33(b) shall be taken as guides only, and
probability of occurrence of an explosion shall be checked in each
case using appropriate values.
Figure 6.2.33 Magnitude and distribution of internal pressure in a building due to internal
gas explosion
##### 2.6.6.2 Minimum design pressure
Walls, floors and roofs and their supporting members separating a use from an
explosion exposure, shall be designed to sustain the anticipated maximum load
effects resulting from such use including any dynamic effects, but for a minimum
internal pressure or suction of 5 kN/m2, in addition to all other loads specified in this
Chapter.
2.6.6.3
Design pressure on relief vents
When pressure-relief vents are used, such vents shall be designed to relieve at a
maximum internal pressure of 1.0 kN/m2.
##### 2.6.6.4 Loads due to other explosions
Loads arising from other types of explosions, such as those from external gas cloud
explosions, external explosions due to high explosives (TNT) etc. shall be
determined, for specific cases, by rational analyses based on information from
reliable references or specialist advice shall be sought.
2.6.7
Vertical Forces on Air Raid Shelters
For the design of air raid shelters located in a building e.g. in the basement below
ground level, the characteristic vertical load shall be determined in accordance with
provisions of Sec 2.6.7.1 below.
##### 2.6.7.1 Characteristic vertical loads
Buildings in which the individual floors are acted upon by a total distributed live load
of up to 5.0 kN/m2, vertical forces on air raid shelters generally located below ground
level, such as a basement, shall be considered to have the characteristic values
provided in Table 6.2.27. In the case of buildings having floors that are acted upon
by a live load larger than 5.0 kN/m2, above values shall be increased by the
difference between the average live loads on all storeys above the one used as the
shelter and 5.0 kN/m2.
Table 6.2.28: Characteristic Vertical Loads for an Air Raid Shelter in a Building
No. of Storeys(1) above the Air Raid
Shelter
Vertical Load, kN/m2
\< 2
3 - 4
> 4
> Buildings of particularly stable construction
> irrespective of the number of storeys
28(2)
Notes:
(1) Storeys shall mean every usable storey above the shelter floor
(2) Buildings of particularly stable construction shall mean buildings having
bearing structural elements made from reinforced in-situ concrete.
2.6.8
Loads on Helicopter Landing Areas
In addition to all other applicable loads provided in this Chapter, including the dead
load, the minimum live load on helicopter landing or touch down areas shall be one
of the loads L1, L2 or L3 as given below producing the most unfavourable effect:
61 5 I1
(6.2.82a)
6 5 mI
(6.2.82b)
62 5 \[
(6.2.82c)
Where,
I1 = Actual weight of the helicopter in kN,
I = Fully loaded weight of the helicopter in kN,
\[ = A distributed load of 5.0 kN/m2,
m
\= 0.75 for helicopters equipped with hydraulic - type shock absorbers,
and
\= 1.5 for helicopters with rigid or skid-type landing gear.
The live load, 61 shall be applied over the actual areas of contact of landing. The
load, 6 shall be a single concentrated load including impact applied over a 300 mm
x 300 mm area. The loads 61 and 6 may be applied anywhere within the landing
area to produce the most unfavourable effects of load.
2.6.9
Erection and Construction Loads
All loads required to be sustained by a structure or any portion thereof due to placing
or storage of construction materials and erection equipment including those due to
operation of such equipment shall be considered as erection loads. Provisions shall
be made in design to account for all stresses due to such loads.
2.7
Combinations of Loads
2.7.1
General
Buildings, foundations and structural members shall be investigated for adequate
strength to resist the most unfavorable effect resulting from the various combinations
of loads provided in this Section. The combination of loads may be selected using the
provisions of either Sec 2.7.2 or Sec 2.7.3 whichever is applicable. However, once
Sec 2.7.2 or Sec 2.7.3 is selected for a particular construction material, it must be
used exclusively for proportioning elements of that material throughout the structure.
In addition to the load combinations given in Sections 2.7.2 and 2.7.3 any other
specific load combination provided elsewhere in this Code shall also be investigated
to determine the most unfavourable effect.
The most unfavourable effect of loads may also occur when one or more of the
contributing loads are absent, or act in the reverse direction. Loads such as F, H or S
shall be considered in design when their effects are significant. Floor live loads shall
not be considered where their inclusion results in lower stresses in the member under
consideration. The most unfavourable effects from both wind and earthquake loads
shall be considered where appropriate, but they need not be assumed to act
simultaneously.
2.7.2
Combinations of Load effects for Allowable Stress/Strength Design Method
##### 2.7.2.1 Basic combinations
Provisions of this Section shall apply to all construction materials permitting their
use in proportioning structural members by allowable stress/strength design method.
When this method is used in designing structural members, all loads listed herein
shall be considered to act in the following combinations. The combination that
produces the most unfavorable effect shall be used in design.
1. D + F
2. D + H + F + L + T
3. D + H + F + (Lr or R)
4. D + H + F + 0.75(L + T ) + (Lr or R)
5. D + H + F + (W or 0.7E)
6. D + H + F + 0.75(W or 0.7E) + 0.75L + 0.75(Lr or R)
7. 0.6D + W + H
8. 0.6D + 0.7E + H
When a structure is located in a flood zone or in tidal surge zone, the following load
combinations shall be considered:
9. In Coastal Zones vulnerable to tidal surges, 1.5Fa shall be added to other
loads in combinations (5), (6); E shall be set equal to zero in (5) and (6).
10. In non-coastal Zones, 0.75Fa shall be added to combinations (5), (6) and (7);
E shall be set equal to zero in (5) and (6).
##### 2.7.2.2 Stress increase
Unless permitted elsewhere in this Code, increases in allowable stress shall not be
used with the loads or load combinations given above in Sec 2.7.2.1.
2.7.3
Combinations of Load effects for Strength Design Method
When strength design method is used, structural members and foundations shall be
designed to have strength not less than that required to resist the most unfavorable
effect of the combinations of factored loads listed in the following Sections:
##### 2.7.3.1 Basic combinations
1.
1.4(D + F)
2.
1.2(D + F + T) + 1.6(L + H) + 0.5(Lr or R)
3.
1.2D + 1.6(Lr or R) + (L or 0.8W)
4.
1.2D + 1.6W + L + 0.5(Lr or R)
5.
1.2D + 1.0E + 1.0L
6.
0.9D + 1.6W + 1.6H
7.
0.9D + 1.0E + 1.6H
Each relevant strength limit state shall be investigated. Effects of one or more loads
not acting shall be investigated. The most unfavorable effect from both wind and
earthquake loads shall be investigated, where appropriate, but they need not be
considered to act simultaneously.
Exceptions:
1\.
The load factor on live load L in combinations (3), (4), and (5) is
permitted to be reduced to 0.5 for all occupancies in which minimum
specified uniformly distributed live load is less than or equal to 5.0
kN/m2, with the exception of garages or areas occupied as places of
public assembly.
2\.
The load factor on H shall be set equal to zero in combinations (6) and (7)
if the structural action due to H counteracts that due to W or E. Where
lateral earth pressure provides resistance to structural actions from other
forces, it shall not be included in H but shall be included in the design
resistance.
3\.
For structures designed in accordance with the provisions of Chapter 6,
Part 6 of this Code (reinforced concrete structures), where wind load W
has not been reduced by a directionality factor, it shall be permitted to use
1.3W in place of 1.6W in (4) and (6) above.
When a structure is located in a flood zone or in tidal surge zone, the following load
combinations shall be considered:
1. In Coastal Zones vulnerable to tidal surges, 1.6W shall be replaced by
1.6W+2.0Fa in combinations (4) and (6).
2. In Non-coastal Zones, 1.6W shall be replaced by 0.8W+1.0Fa in combinations
(4) and (6).
2.7.4
Load Combinations for Extraordinary Events
Where required by the applicable Code, standard, or the authority having jurisdiction,
strength and stability shall be checked to ensure that structures are capable of
withstanding the effects of extraordinary (i.e., low-probability) events, such as fires,
explosions, and vehicular impact.
2.7.5
Load Combination for Serviceability
Serviceability limit states of buildings and structures shall be checked for the load
combinations set forth in this Section as well as mentioned elsewhere in this Code.
For serviceability limit states involving visually objectionable deformations,
repairable cracking or other damage to interior finishes, and other short term effects,
the suggested load combinations for checking vertical deflection due to gravity load
is
1. D + L
For serviceability limit states involving creep, settlement, or similar long-term or
permanent effects, the suggested load combination is:
2. D + 0.5L
The dead load effect, D, used in applying combinations 1 and 2 above may be that
portion of dead load that occurs following attachment of nonstructural elements. In
applying combination 2 above to account for long term creep effect, the immediate
(e.g. elastic) deflection may be multiplied by a creep factor ranging from 1.5 to 2.0.
Serviceability against gravity loads (vertical deflections) shall be checked against the
limits set forth in Sec 1.2.5 Chapter 1 of this Part as well as mentioned elsewhere in
this Code.
For serviceability limit state against lateral deflection of buildings and structures due
to wind effect, the following combination shall be used:
3. D + 0.5L + 0.7W
Due to its transient nature, wind load need not be considered in analyzing the effects
of creep or other long-term actions. Serviceability against wind load using load
combination 3 above shall be checked in accordance with the limit set forth in Sec
##### 1.5.6.2 Chapter 1 of this Part.
2.8
List of Related Appendices
Appendix A
Equivalence of Nonhomogenous Equations in SI-Metric, MKS-
Metric, and U.S. Customary Units
Appendix B
Local Geology, Tectonic Features and Earthquake Occurrence in the
Region
Appendix C
Seismic Design Parameters for Alternative Method of Base Shear
Calculation