1.1
Scope
This Part specifies the minimum requirements of materials to be complied with in
buildings and works under the provisions of the Code.
For each of the building materials the applicable standard specifications and test methods
are listed. All materials shall conform to these Standards.
The list of standards given in this Part of the Code would be augmented from time to time
by amendments, revisions and additions of which the Authority shall take cognizance.
The latest version of a specification shall, as far as practicable, be applied in order to
fulfil the requirements of this Part.
In view of the limited number of Bangladesh Standards (BDS) for building materials
available at the present time, a number of standards of other countries have been
referenced in this Code as applicable standards. As more standards of BDS regarding
building materials become available and adopted by amendment of this Code, they shall
supplement and/or replace the relevant standards listed in this Part.
1.2
Terminology
This Section provides an alphabetical list of the terms used in and applicable to this Part
of the Code. In case of any conflict or contradiction between a definition given in this
Section and that in Part 1, the meaning provided in this Part shall govern for
interpretation of the provisions of this Part.
ACTUAL
DIMENSIONS
Measured dimensions of a designated item.
ADMIXTURE
Material other than water, aggregate, or hydraulic cement used
as an ingredient of concrete and added to concrete before or
during its mixing to modify its properties.
AGGREGATE
Granular material, such as sand, gravel, crushed stone, crushed
brick and iron blast-furnace slag, when used with a cementing
medium that forms hydraulic cement concrete or mortar.
AGGREGATE,
LIGHT WEIGHT
Aggregate with a dry, loose weight of 11.25 kN/m3 or less.
CONCRETE
A mixture of Portland cement or any other hydraulic cement,
fine aggregate, coarse aggregate and water, with or without
admixtures.
CONCRETE, PLAIN Concrete that does not conform to the definition of reinforced
concrete.
CONCRETE,
PRECAST
Plain or reinforced concrete element cast separately before they
are fixed in position.
CONCRETE,
PRESTRESSED
Reinforced concrete in which internal stresses have been
introduced to reduce potential tensile stresses in concrete
resulting from loads.
CONCRETE,
REINFORCED
Concrete containing adequate reinforcement, prestressed or
non-prestressed, and designed on the assumption that the two
materials act together in resisting forces.
FIBRE BOARD
A fibre-felted, homogenous panel made from lignocellulosic
fibres (usually wood or cane) and having a unit weight between
1.6 kN/m3 and 5 kN/m3.
HARD BOARD
A fibre-felted homogenous panel made of lignocellulosic fibres
consolidated under heat and pressure in a hot press to a density
of 4.9 kN/m3 or above.
MASONRY UNIT
Brick, tile, stone, glass-block or concrete-block used in
masonry constructions.
MASONRY UNIT,
GROUTED
HOLLOW
Form of grouted masonry construction in which certain
designated cells of hollow units are continuously filled with
grout.
MASONRY UNIT,
HOLLOW
A masonry unit whose net cross-sectional area in every plane
parallel to the bearing surface is less than 75 percent of the
gross cross-sectional area in the same plane.
MASONRY UNIT,
SOLID
A masonry unit whose net cross-sectional area in every plane
parallel to the bearing surface is 75 percent or more of the gross
cross-sectional area in the same plane.
NOMINAL
DIMENSIONS
Nominal dimensions of masonry units are equal to their
specified dimensions plus the thickness of the joint with which
the unit is laid.
PARTICLE BOARD
A manufactured panel product consisting of particles of wood
or combinations of wood particles and wood fibres cemented
together with synthetic resins or other suitable bonding system
by an appropriate bonding process.
PLYWOOD
A built-up panel of laminated veneers.
REINFORCED
MASONRY
Form of masonry construction in which reinforcement acting in
conjunction with the masonry is used to resist designed forces.
REINFORCEMENT
Reinforcing bars, plain or deformed, excluding prestressing
tendons, bar and rod mats, welded smooth wire fabric and
welded deformed wire fabric used in concrete.
REINFORCEMENT,
DEFORMED
Deformed reinforcing bars, bar and rod mats, deformed wire,
welded smooth wire fabric and welded deformed wire fabric.
REINFORCEMENT,
PLAIN
Reinforcement that does not conform to definition of deformed
reinforcement.
REINFORCEMENT,
SPIRAL
Continuously wound reinforcement in the form of a cylindrical
helix.
STIRRUP
Reinforcement used to resist shear and torsion stresses in
structural member; typically bars, wires, or welded wire fabric
(smooth or deformed) bent into L, U or rectangular shapes and
located perpendicular to or at an angle to longitudinal
reinforcement. (The term “Stirrup” is usually applied to lateral
reinforcement in flexural members and the term “ties” to those
in compression members).
STRUCTURAL
GLUED
LAMINATED
TIMBER
Any member comprising an assembly of laminations of lumber
in which the grain of all laminations is approximately parallel
longitudinally in which the laminations are bonded with
adhesives.
TENDON
Steel element such as wire, cable, bar, rod or strand, or a bundle
of such elements, used to impart prestress to concrete.
TIE
A loop of reinforcing bar or wire enclosing longitudinal
reinforcement.
YIELD STRENGTH
The stress at which plastic deformation takes place under
constant or reduced load.
Definitions and General Requirements
1.1
Introduction
1.1.1
Scope
The definitions providing meanings of different terms and general requirements for
the structural design of buildings, structures, and components thereof are specified in
this Chapter. These requirements shall apply to all buildings and structures or their
components regulated by this Code. All anticipated loads required for structural
design shall be determined in accordance with the provisions of Chapter 2. Design
parameters required for the structural design of foundation elements shall conform to
the provisions of Chapter 3. Design of structural members using various construction
materials shall comply with the relevant provisions of Chapters 4 to 13. The FPS
equivalents of the empirical expressions used throughout Part 6 are listed in
Appendix A.
This Code shall govern in all matters pertaining to design, construction, and material
properties wherever this Code is in conflict with requirements contained in other
standards referenced in this Code. However, in special cases where the design of a
structure or its components cannot be covered by the provisions of this Code, other
relevant internationally accepted codes referred in this Code may be used.
1.1.2
Definitions
The following definitions shall provide the meaning of certain terms used in this
Chapter.
BASE SHEAR
Total design lateral force or shear at the base of a
structure.
BASIC WIND
SPEED
Three-second gust speed at 10 m above the mean ground
level in terrain Exposure-B defined in Sec 2.4.6 and
associated with an annual probability of occurrence of
0.02.
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 which is provided to resist lateral forces.
BUILDING FRAME
SYSTEM
An essentially complete space frame which provides
support for loads.
CONCENTRIC
BRACED FRAME
(CBF)
A steel braced frame designed in conformance with Sec
10.20.13 or Sec 10.20.14.
COLLECTOR
A member or element used to transfer lateral forces from
a portion of a structure to the vertical elements of the
lateral force resisting elements.
DEAD LOAD
The load due to the weight of all permanent structural and
nonstructural components of a building or a structure,
such as walls, floors, roofs and fixed service equipment.
DIAPHRAGM
A horizontal or nearly horizontal system acting to transmit
lateral forces to the vertical resisting elements. The term
“diaphragm” includes horizontal bracing systems.
DUAL SYSTEM
A combination of Moment Resisting Frames and Shear
Walls or Braced Frames to resist lateral loads designed in
accordance with the criteria of Sec 1.3.2.4.
ECCENTRIC
BRACED FRAME
(EBF)
A steel braced frame designed in conformance with Sec
10.20.15.
HORIZONTAL
BRACING SYSTEM
A horizontal truss system that serves the same function as
a floor or roof diaphragm.
INTERMEDIATE
MOMENT FRAME
(IMF)
A concrete moment resisting frame designed in
accordance with Sec 8.3.10.
LIVE LOAD
The load superimposed by the use and occupancy of a
building.
MOMENT
RESISTING FRAME
A frame in which members and joints are capable of
resisting forces primarily by flexure.
ORDINARY
MOMENT FRAME
(OMF)
A moment resisting frame not meeting special detailing
requirements for ductile behaviour.
PRIMARY
FRAMING SYSTEM
That part of the structural system assigned to resist lateral
forces.
SHEAR WALL
A wall designed to resist lateral forces parallel to the
plane of the wall (sometimes referred to as a vertical
diaphragm or a structural wall).
SLENDER
BUILDINGS AND
STRUCTURES
Buildings and structures having a height exceeding five
times the least horizontal dimension, or having a
fundamental natural frequency less than 1 Hz. For those
cases where the horizontal dimensions vary with height,
the least horizontal dimension at mid height shall be used.
SOFT STOREY
A soft storey is one in which the lateral stiffness is less
than 70 percent of that in the storey above or less than 80
percent of the average 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 requirements of
Chapter 8 or 10 for concrete or steel frames respectively.
SPECIAL
STRUCTURAL
SYSTEM
A structural system not listed in Table 6.1.3 and specially
designed to carry the lateral loads. (See Sec 1.3.2.5).
STOREY
The space between any two floor levels including the roof
of a building. Storey-x is the storey below level x.
STOREY SHEAR, The summation of design lateral forces above the storey
under consideration.
STRENGTH
The usable capacity of an element or a member to resist
the load as prescribed in these provisions.
TERRAIN
The ground surface roughness condition when considering
the size and arrangement of obstructions to the wind.
THREE-SECOND
GUST SPEED
The highest average wind speed over a 3 second duration
at a height of 10 m. The three-second gust speed is
derived using Durst’s model in terms of the mean wind
speed and turbulence intensity.
TOWER
A tall, slim vertical structure.
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.
1.1.3
Symbols and Notation
The following symbols and notation shall apply to the provisions of this Chapter:
Dead load on a member including self-weight and weight of
components, materials and permanent equipment supported by the
member
Earthquake load
Lateral force applied at level
of a building
ℎ
Height of a building or a structure above ground level in metres
ℎ, ℎ
, ℎ
Height in metres above ground level to level
, - or -
respectively
level
=
ℎ level of a structure above the base; = 1 designates the first
level above the base
level
=
Upper most level of a structure
level
= ℎ level of a structure above the base; = 1 designates the first
level above the base.
Live load due to intended use or occupancy
Span of a member or component.
Overturning moment at level
Total design lateral force or shear at the base
Storey shear at storey level
Response modification or reduction coefficient for structural
system given in Table 6.2.19 for seismic design.
Fundamental period of vibration in seconds
Load due to wind pressure.
′
Weight of an element or component
Seismic zone coefficient given in Figure 6.2.24 or Table 6.2.14 or
Table 6.2.15
∆
Storey lateral drift.
1.2
Basic Considerations
1.2.1
General
All buildings and structures shall be designed and constructed in conformance with
the provisions of this Section. The buildings and portions thereof shall support all
loads including dead load specified in this Chapter and elsewhere in this Code.
Impact, fatigue and self-straining forces shall be considered where these forces
occur.
1.2.2
Buildings and Structures
A structure shall ordinarily be described as an assemblage of framing members and
components arranged to support both gravity and lateral forces. Structures may be
classified as building and non-building structures. Structures that enclose a space and
are used for various occupancies shall be called buildings or building structures.
Structures other than buildings, such as water tanks, bridges, communication towers,
chimneys etc., shall be called non-building structures. When used in conjunction with
the word building(s), the word structure(s) shall mean non-building structures, e.g.
‘buildings and structures’ or ‘buildings or structures’. Otherwise the word ‘structures’
shall include both buildings and non-building structures.
1.2.3
Building and Structure Occupancy Categories
Buildings and other structures shall be classified, based on the nature of occupancy,
according to Table 6.1.1 for the purposes of applying flood, surge, wind and
earthquake provisions. The occupancy categories range from I to IV, where
Occupancy Category I represents buildings and other structures with a low hazard to
human life in the event of failure and Occupancy Category IV represents essential
facilities. Each building or other structure shall be assigned to the highest applicable
occupancy category or categories. Assignment of the same structure to multiple
occupancy categories based on use and the type of load condition being evaluated
(e.g., wind or seismic) shall be permissible.
When buildings or other structures have multiple uses (occupancies), the relationship
between the uses of various parts of the building or other structure and the
independence of the structural systems for those various parts shall be examined. The
classification for each independent structural system of a multiple-use building or
other structure shall be that of the highest usage group in any part of the building or
other structure that is dependent on that basic structural system.
Table 6.1.1: Occupancy Category of Buildings and other Structures for Flood,
Surge, Wind and Earthquake Loads.
Nature of Occupancy
Occupancy
Category
Buildings and other structures that represent a low hazard to human life in
the event of failure, including, but not limited to:
•
Agricultural facilities
•
Certain temporary facilities
•
Minor storage facilities
I
All buildings and other structures except those listed in Occupancy
Categories I, III and IV
II
Buildings and other structures that represent a substantial hazard to human
life in the event of failure, including, but not limited to:
•
Buildings and other structures where more than 300 people
congregate in one area
•
Buildings and other structures with day care facilities with a
capacity greater than 150
•
Buildings and other structures with elementary school or
secondary school facilities with a capacity greater than 250
•
Buildings and other structures with a capacity greater than 500
for colleges or adult education facilities
•
Healthcare facilities with a capacity of 50 or more resident
patients, but not having surgery or emergency Treatment
facilities
•
Jails and detention facilities
Buildings and other structures, not included in Occupancy Category IV,
with potential to cause a substantial economic impact and/or mass
disruption of day-to-day civilian life in the event of failure, including, but
not limited to:
•
Power generating stationsa
•
Water treatment facilities
•
Sewage treatment facilities
•
Telecommunication centers
Buildings and other structures not included in Occupancy Category IV
(including, but not limited to, facilities that manufacture, process, handle,
store, use, or dispose of such substances as hazardous fuels, hazardous
chemicals, hazardous waste, or explosives) containing sufficient quantities
of toxic or explosive substances to be dangerous to the public if released.
III
Buildings and other structures designated as essential facilities, including,
but not limited to:
Hospitals and other healthcare facilities having surgery or
emergency treatment facilities
Fire, rescue, ambulance, and police stations and emergency
vehicle garages
Designated earthquake, hurricane, or other emergency shelters
Designated emergency preparedness, communication, and
operation centers and other facilities required for emergency
response
Power generating stations and other public utility facilities
required in an emergency
Ancillary
structures
(including,
but
not
limited
to,
communication towers, fuel storage tanks, cooling towers,
Electrical substation structures, fire water storage tanks or other
structures housing or supporting water, or other fire-suppression
material or equipment) required for operation of Occupancy
Category IV structures during an emergency
Aviation control towers, air traffic control centers, and
emergency aircraft hangars
Community water storage facilities and pump structures required
to maintain water pressure for fire suppression
Buildings and other structures having critical national defense
functions
Buildings and other structures (including, but not limited to, facilities that
manufacture, process, handle, store, use, or dispose of such substances as
hazardous fuels, hazardous chemicals, or hazardous waste) containing
highly toxic substances where the quantity of the material exceeds a
threshold quantity established by the authority having jurisdiction.
IV
a Cogeneration power plants that do not supply power on the national grid shall be
designated Occupancy Category II
1.2.4
Safety
Buildings, structures and components thereof, shall be designed and constructed to
support all loads, including dead loads, without exceeding the allowable stresses or
specified strengths (under applicable factored loads) for the materials of construction
in the structural members and connections.
1.2.5
Serviceability
Structural framing systems and components shall be designed with adequate stiffness
to have deflections, vibration, or any other deformations within the serviceability
limit of building or structure. The deflections of structural members shall not exceed
the more restrictive of the limitations provided in Chapters 2 through 13 or that
permitted by Table 6.1.2 or the notes that follow. For wind and earthquake loading,
story drift and sway shall be limited in accordance with the provisions of Sec 1.5.6.
In checking the serviceability, the load combinations and provisions of Sec 2.7.5
shall be followed.
Table 6.1.2: Deflection Limitsa, b, c, h (Except earthquake load)
Construction
-
Roof members:e
Supporting plaster ceiling
Supporting non-plaster ceiling
Not supporting ceiling
/360
/240
/180
/360
/240
/180
/240
/180
/120
Floor members
/360
/240
Exterior walls and interior partitions
With brittle finishes
With flexible finishes
/240
/120
Farm buildings
/180
Greenhouses
/120
Where, , , and stands for span of the member under consideration, live load,
wind load and dead load respectively.
Notes:
a.
For structural roofing and siding made of formed metal sheets, the total
load deflection shall not exceed /60. For secondary roof structural
members supporting formed metal roofing, the live load deflection shall
not exceed /150. For secondary wall members supporting formed metal
siding, the design wind load deflection shall not exceed /90. For roofs,
this exception only applies when the metal sheets have no roof covering.
b.
Interior partitions not exceeding 2 m in height and flexible, folding and
portable partitions are not governed by the provisions of this Section.
c.
For cantilever members, shall be taken as twice the length of the
cantilever.
d.
For wood structural members having a moisture content of less than 16%
at time of installation and used under dry conditions, the deflection
resulting from + 0.5 is permitted to be substituted for the deflection
resulting from + .
e.
The above deflections do not ensure against ponding. Roofs that do not
have sufficient slope or camber to assure adequate drainage shall be
investigated for ponding. See Sec 1.6.5 for rain and ponding requirements.
f.
ঞযব রিহফ ষড়ধফ রং ঢ়বৎসরঃঃবফ:ড় নব:ধশবহ ধং ০.৭:রসবং:যব ুপড়সঢ়ড়হবহঃ ধহফ
পষধফফরহমচ্ ষড়ধফং ভড়ৎ:যব ঢ়ঁৎঢ়ড়ংব ড়ভ ফবঃবৎসরহরহম ফবভষবপঃরড়হ ষরসরঃং যবৎবরহ.
g.
Deflection due to dead load shall include both instantaneous and long term
effects.
h.
For aluminum structural members or aluminum panels used in skylights
and sloped glazing framing, roofs or walls of sunroom additions or patio
covers, not supporting edge of glass or aluminum sandwich panels, the
total load deflection shall not exceed /60. For continuous aluminum
structural members supporting edge of glass, the total load deflection shall
not exceed /175 for each glass lite or /60 for the entire length of the
member, whichever is more stringent. For aluminum sandwich panels used
in roofs or walls of sunroom additions or patio covers, the total load
deflection shall not exceed /120.
1.2.6
Rationality
Structural systems and components thereof shall be analyzed, designed and
constructed based on rational methods which shall include, but not be limited to the
provisions of Sec 1.2.7.
1.2.7
Analysis
Analysis of the structural systems shall be made for determining the load effects on
the resisting elements and connections, based on well-established principles of
mechanics taking equilibrium, geometric compatibility and both short and long term
properties of the construction materials into account and incorporating the following:
1.2.7.1 Mathematical model
A mathematical model of the physical structure shall represent the spatial distribution
of stiffness and other properties of the structure which is adequate to provide a
complete load path capable of transferring all loads and forces from their points of
origin to the load-resisting elements for obtaining various load effects. For dynamic
analysis, mathematical model shall also incorporate the appropriately distributed
mass and damping properties of the structure adequate for the determination of the
significant features of its dynamic response. All buildings and structures shall be thus
analyzed preferably using a three dimensional computerized model incorporating
these features of mathematical model. It is essential to use three dimensional
computer model to represent a structure having irregular plan configuration as
mentioned in Sec 1.3.4.2 and having rigid or semirigid floor and roof diaphragms.
Requirements for two-dimensional model and three dimensional models for
earthquake analysis are described in Sections 2.5.11 to 2.5.14.
1.2.7.2 Loads and forces
All prescribed loads and forces to be supported by the structural systems shall be
determined in accordance with the applicable provisions of this Chapter and Chapter
2. Loads shall be applied on the mathematical model specified in Sec. 1.2.7.1 at
appropriate spatial locations and along desired directions.
1.2.7.3 Soil-structure interaction
Soil-structure interaction effects, where required, shall be included in the analysis by
appropriately including the properly substantiated properties of soil into the
mathematical model specified in Sec. 1.2.7.1 above.
1.2.8
Distribution of Horizontal Shear
The total lateral force shall be distributed to the various elements of the lateral force-
resisting system in proportion to their rigidities considering the rigidity of the
horizontal bracing systems or diaphragms.
1.2.9
Horizontal Torsional Moments
Structural systems and components shall be designed to sustain additional forces
resulting from torsion due to eccentricity between the centre of application of the
lateral forces and the centre of rigidity of the lateral force resisting system. Forces
shall not be decreased due to torsional effects. For accidental torsion effects on
seismic forces, requirements shall conform to Sec 2.5.7.6.
1.2.10 Stability Against Overturning and Sliding
Every building or structure shall be designed to resist the overturning and sliding
effects caused by the lateral forces specified in this Chapter.
1.2.11 Anchorage
Anchorage of the roof to wall and columns, and of walls and columns to foundations,
shall be provided to resist the uplift and sliding forces resulting from the application
of the prescribed loads. Additional requirements for masonry or concrete walls shall
be those given in Sec 1.7.3.6.
1.2.12 General Structural Integrity
Buildings and structural systems shall possess general structural integrity that is the
ability to sustain local damage caused due to misuse or accidental overloading, with
the structure as a whole remaining stable and not being damaged to an extent
disproportionate to the original local damage.
1.2.13 Proportioning of Structural Elements
Structural elements, components and connections shall be proportioned and detailed
based on the design methods provided in the subsequent Chapters for various
materials of construction, such as reinforced concrete, masonry, steel etc. to resist
various load effects obtained from a rational analysis of the structural system.
1.2.14 Walls and Framing
Walls and structural framing shall be erected true to plumb in accordance with the
design. Interior walls, permanent partitions and temporary partitions exceeding 1.8 m
of height shall be designed to resist all loads to which they are subjected. If not
otherwise specified elsewhere in this Code, walls shall be designed for a minimum
load of 0.25 kN/m2 applied perpendicular to the wall surfaces. The deflection of such
walls under a load of 0.25 kN/m2 shall not exceed
./0 of the span for walls with
brittle finishes and
-.0 of the span for walls with flexible finishes. However, flexible,
folding or portable partitions shall not be required to meet the above load and
deflection criteria, but shall be anchored to the supporting structure.
1.2.15 Additions to Existing Structures
When an existing building or structure is extended or otherwise altered, all portions
thereof affected by such cause shall be strengthened, if necessary, to comply with
the safety and serviceability requirements provided in Sections 1.2.4 and 1.2.5
respectively.
1.2.16 Phased Construction
When a building or structure is planned or anticipated to undergo phased
construction, structural members therein shall be investigated and designed for any
additional stresses arising due to such construction.
1.2.17 Load Combinations and Stress Increase
Every building, structure, foundation or components thereof shall be designed to
sustain, within the allowable stress or specified strength (under factored load), the
most unfavourable effects resulting from various combinations of loads specified in
Sec 2.7. Except otherwise permitted or restricted by any other Sections of this Code,
maximum increase in the allowable stress shall be 33% when allowable or working
stress method of design is followed. For soil stresses due to foundation loads, load
combinations and stress increase specified in Sec 2.7.2 for allowable stress design
method shall be used.
1.3
Structural Systems
1.3.1
General
Every structure shall have one of the basic structural systems specified in Sec 1.3.2
or a combination thereof. The structural configuration shall be as specified in Sec
1.3.4 with the limitations imposed in Sec 2.5.5.4.
1.3.2
Basic Structural Systems
Structural systems for buildings and other structures shall be designated as one of the
types A to G listed in Table 6.1.3. Each type is again classified as shown in the Table
by the types of vertical elements used to resist lateral forces. A brief description of
different structural systems are presented in following sub-sections.
1.3.2.1 Bearing wall system
A structural system having bearing walls/bracing systems without a complete vertical
load carrying frame to support gravity loads. Resistance to lateral loads is provided
by shear walls or braced frames.
1.3.2.2 Building frame system
A structural system with an essentially complete space frame providing support for
gravity loads. Resistance to lateral loads is provided by shear walls or braced frames
separately.
1.3.2.3 Moment resisting frame system
A structural system with an essentially complete space frame providing support for
gravity loads. Moment resisting frames also provide resistance to lateral load
primarily by flexural action of members, and may be classified as one of the
following types:
(a)
Special Moment Frames (SMF)
(b)
Intermediate Moment Frames (IMF)
(c)
Ordinary Moment Frames (OMF).
The framing system, IMF and SMF shall have special detailing to provide ductile
behaviour conforming to the provisions of Sections 8.3 and 10.20 of Part 6 for
concrete and steel structures respectively. OMF need not conform to these special
ductility requirements of Chapter 8 or 10.
Table 6.1.3: Basic Structural Systems
A. BEARING WALL SYSTEMS (no frame)
- Special reinforced concrete shear walls
- Ordinary reinforced concrete shear walls
- Ordinary reinforced masonry shear walls
- Ordinary plain masonry shear walls
B. BUILDING FRAME SYSTEMS (with bracing or shear wall)
- Steel eccentrically braced frames, moment resisting connections at columns away
from links
- Steel eccentrically braced frames, non-moment-resisting, connections at columns
away from links
- Special steel concentrically braced frames
- Ordinary steel concentrically braced frames
- Special reinforced concrete shear walls
- Ordinary reinforced concrete shear walls
- Ordinary reinforced masonry shear walls
- Ordinary plain masonry shear walls
C. MOMENT RESISTING FRAME SYSTEMS (no shear wall)
- Special steel moment frames
- Intermediate steel moment frames
- Ordinary steel moment frames
- Special reinforced concrete moment frames
- Intermediate reinforced concrete moment frames
- Ordinary reinforced concrete moment frames
D. DUAL SYSTEMS: SPECIAL MOMENT FRAMES CAPABLE OF RESISTING
AT LEAST 25% OF PRESCRIBED SEISMIC FORCES (with bracing or shear
wall)
- Steel eccentrically braced frames
- Special steel concentrically braced frames
- Special reinforced concrete shear walls
- Ordinary reinforced concrete shear walls
E. DUAL SYSTEMS: INTERMEDIATE MOMENT FRAMES CAPABLE OF
RESISTING AT LEAST 25% OF PRESCRIBED SEISMIC FORCES (with
bracing or shear wall)
- Special steel concentrically braced frames
- Special reinforced concrete shear walls
- Ordinary reinforced masonry shear walls
- Ordinary reinforced concrete shear walls
F. DUAL SHEAR WALL-FRAME SYSTEM: ORDINARY REINFORCED
CONCRETE
MOMENT
FRAMES
AND
ORDINARY
REINFORCED
CONCRETE SHEAR WALLS
G. STEEL SYSTEMS NOT SPECIFICALLY DETAILED FOR SEISMIC
RESISTANCE
1.3.2.4 Dual system
A structural system having a combination of the following framing systems:
(a)
Moment resisting frames (SMF, IMF or steel OMF), and
(b)
Shear walls or braced frames.
The two systems specified in (a) and (b) above shall be designed to resist the total
lateral force in proportion to their relative rigidities considering the interaction of the
dual system at all levels. However, the moment resisting frames shall be capable of
resisting at least 25% of the applicable total seismic lateral force, even when wind or
any other lateral force governs the design.
1.3.2.5 Special structural system
A structural system not defined above nor listed in Table 6.1.3 and specially
designed to carry the lateral loads, such as tube-in-tube, bundled tube, etc.
1.3.2.6 Non-building structural system
A structural system used for purposes other than in buildings and conforming to
Sections 1.5.4.8, 1.5.4.9, 2.4 and 2.5 of Part 6.
1.3.3
Combination of Structural Systems
When different structural systems of Sec 1.3.2 are combined for incorporation into
the same structure, design of the combined seismic force resisting system shall
conform to the provisions of Sec 2.5.5.5.
1.3.4
Structural Configurations
Based on the structural configuration, each structure shall be designated as a regular
or irregular structure as defined below:
1.3.4.1 Regular structures
Regular structures have no significant physical discontinuities or irregularities in plan
or vertical configuration or in their lateral force resisting systems. Typical features
causing irregularity are described in Sec 1.3.4.2.
1.3.4.2
Irregular structures
Irregular structures have either vertical irregularity or plan irregularity or both in
their structural configurations or lateral force resisting systems.
1.3.4.2.1
Vertical irregularity
Structures having one or more of the irregular features listed in Table 6.1.4 shall be
designated as having a vertical irregularity.
1.3.4.2.2
Plan irregularity
Structures having one or more of the irregular features listed in Table 6.1.5 shall be
designated as having a plan irregularity.
Table 6.1.4: Vertical Irregularities of Structures
Vertical
Irregularity
Type
Definition
Reference
Section
I
a. Stiffness Irregularity (Soft Storey):
Soft storey is one in which the lateral stiffness is less than 70
percent of that in the storey above or less than 80 percent of
the average stiffness of the three storeys above.
b. Stiffness Irregularity (Extreme Soft Storey):
Extreme soft storey irregularity is defined to exist where there
is a story in which the lateral stiffness is less than 60% of that
in the story above or less than 70% of the average stiffness of
the three stories above.
1.7.3.8,
2.5.5 to
2.5.14
and
2.5.17
II
Mass Irregularity:
Mass irregularity shall be considered to exist where the effective
mass of any storey is more than 150 percent of the effective
mass of an adjacent storey. A roof which is lighter than the floor
below need not be considered.
2.5.5 to
2.5.14
III
Vertical Geometric Irregularity:
Vertical geometric irregularity shall be considered to exist
where horizontal dimension of the lateral force-resisting system
in any storey is more than 130 percent of that in an adjacent
storey, one-storey penthouses need not be considered.
2.5.5 to
2.5.14
IV
In-Plane Discontinuity in Vertical Lateral Force-Resisting
Element:
An in-plane offset of the lateral load-resisting elements greater
than the length of those elements.
1.7.3.8,
2.5.5 to
2.5.14
Va
Discontinuity in Capacity (Weak Storey):
A weak storey is one in which the storey strength is less than 80
percent of that in the storey above. The storey strength is the
total strength of all seismic-resisting elements sharing the storey
shear for the direction under consideration.
2.5.5 to
2.5.14
and
2.5.17
Vb
Extreme Discontinuity in Capacity (Very Weak Storey):
A very weak storey is one in which the storey strength is less
than 65 percent of that in the storey above.
2.5.5 to
2.5.14
and
2.5.17
Table 6.1.5: Plan (Horizontal) Irregularities of Structures
Plan
Irregularity
Type
Definition
Reference
Section
I
Torsional Irregularity (to be considered when diaphragms
are not flexible):
a. Torsional irregularity shall be considered to exist when the
maximum storey drift, computed including accidental
torsion, at one end of the structure is more than 1.2 times
the average of the storey drifts at the two ends of the
structure.
b. Extreme Torsional Irregularity is defined to exist where the
maximum story drift, computed including accidental
torsion, at one end of the structure transverse to an axis is
more than 1.4 times the average of the story drifts at the
two ends of the structure. Extreme torsional irregularity
requirements in the reference sections apply only to
structures in which the diaphragms are rigid or semirigid.
1.7.3.8,
2.5.5 to
2.5.14
II
Reentrant Corners:
Plan configurations of a structure and its lateral force-resisting
system contain reentrant corners, where both projections of the
structure beyond a reentrant corner are greater than 15 percent
of the plan dimension of the structure in the given direction.
1.7.3.8,
2.5.5 to
2.5.14
III
Diaphragm Discontinuity:
Diaphragms with abrupt discontinuities or variations in
stiffness, including those having cutout or open areas greater
than 50 percent of the gross enclosed area of the diaphragm, or
changes in effective diaphragm stiffness of more than 50
percent from one storey to the next.
1.7.3.8,
2.5.5 to
2.5.14
IV
Out-of-plane Offsets:
Discontinuities in a lateral force path, such as out-of-plane
offsets of the vertical elements.
1.7.3.8,
2.5.5 to
2.5.14
V
Nonparallel Systems:
The vertical lateral load-resisting elements are not parallel to or
symmetric about the major orthogonal axes of the lateral force-
resisting system.
2.5.5 to
2.5.15
1.4
Design For Gravity Loads
1.4.1
General
Design of buildings and components thereof for gravity loads shall conform to the
requirements of this Section. Gravity loads, such as dead load and live loads applied
at the floors or roof of a building shall be determined in accordance with the
provisions of Chapter 2 of this Part.
1.4.2
Floor Design
Floor slabs and decks shall be designed for the full dead and live loads as specified in
Sections 2.2 and 2.3 respectively. Floor supporting elements such as beams, joists,
columns etc. shall be designed for the full dead load and the appropriately reduced
live loads set forth by the provisions of Sec 2.3.13. Design of floor elements shall
also conform to the following provisions:
(a)
Uniformly Distributed Loads: Where uniform floor loads are involved,
consideration may be limited to full dead load on all spans in combination
with full live load on adjacent spans and on alternate spans to determine
the most unfavourable effect of stresses in the member concerned.
(b)
Concentrated Loads: Provision shall be made in designing floors for a
concentrated load as set forth in Sec 2.3.5 applied at a location wherever
this load acting upon an otherwise unloaded floor would produce stresses
greater than those caused by the uniform load required therefore.
(c)
Partition Loads: Loads due to permanent partitions shall be treated as a
dead load applied over the floor as a uniform line load having intensity
equal to the weight per metre run of the partitions as specified in Sec
2.2.5. Loads for light movable partitions shall be determined in
accordance with the provisions of Sec 2.3.6.
(d)
Design of Members: Floor members, such as slabs or decks, beams, joists
etc. shall be designed to sustain the worst effect of the dead plus live
loads or any other load combinations as specified in Sec 2.7. Where floors
are used as diaphragms to transmit lateral loads between various resisting
elements, those loads shall be determined following the provisions of Sec
1.7.3.8. Detailed design of the floor elements shall be performed using the
procedures provided in Chapters 4 to 13 of Part 6 for various construction
materials.
(e)
Floors and associated structural members shall have adequate strength
and stiffness to prevent undesirable vibration due to human activity (e.g
walking, dancing, jumping, sporting activities etc.) or vibration caused by
machines which causes discomfort to the occupants and which is
detrimental to the safety, integrity and durability of the structure.
1.4.3
Roof Design
Roofs and their supporting elements shall be designed to sustain, within their
allowable stresses or specified strength limits, all dead loads and live loads as set out
by the provisions of Sections 2.2 and 2.3 respectively. Design of roof members shall
also conform to the following requirements:
(a)
Application of Loads: When uniformly distributed loads are considered
for the design of continuous structural members, load including full dead
loads on all spans in combination with full live loads on adjacent spans
and on alternate span, shall be investigated to determine the worst effects
of loading. Concentrated roof live loads and special roof live loads, where
applicable, shall also be considered in design.
(b)
Unbalanced Loading: Effects due to unbalanced loads shall be considered
in the design of roof members and connections where such loading will
result in more critical stresses. Trusses and arches shall be designed to
resist the stresses caused by uniform live loads on one half of the span if
such loading results in reverse stresses, or stresses greater in any portion
than the stresses produced by this unit live load when applied upon the
entire span.
(c)
Rain Loads: Roofs, where ponding of rain water is anticipated due to
blockage of roof drains, excessive deflection or insufficient slopes, shall
be designed to support such loads. Loads on roofs due to rain shall be
determined in accordance with the provisions of Sec 2.6.2. In addition to
the dead load of the roof, either the roof live load or the rain load,
whichever is of higher intensity, shall be considered in design.
1.4.4
Reduction of Live Loads
The design live loads specified in Sec 2.3, may be reduced to appropriate values as
permitted by the provisions of Sections 2.3.13 and 2.3.14.
1.4.5
Posting of Live Loads
In every building, of which the floors or parts thereof have a design live load of 3.5
kN/m2 or more, and which are used as library stack room, file room, parking garage,
machine or plant room, or used for industrial or storage purposes, the owner of the
building shall ensure that the live loads for which such space has been designed, are
posted on durable metal plates as shown in Figure 6.1.1, securely affixed in a
conspicuous place in each space to which they relate. If such plates are lost,
removed, or defaced, owner shall be responsible to have them replaced.
1.4.6
Restrictions on Loading
The building owner shall ensure that the live load for which a floor or roof is or has
been designed, will not be exceeded during its use.
Figure 6.1.1 Sample live load sign
1.4.7
Special Considerations
In the absence of actual dead and live load data, the minimum values of these loads
shall be those specified in Sections 2.2 and 2.3. In addition, special consideration
shall be given to the following aspects of loading and due allowances shall be made
in design if occurrence of such loading is anticipated after construction of a building:
(a)
Increase in Dead Load: Actual thickness of the concrete slabs or other
members may become larger than the designed thickness due to
movements or deflections of the formwork during construction.
(b)
Future Installations: Changes in the numbers, types and positions of
partitions and other installations may increase actual load on the floors of
a building.
(c)
Occupancy Changes: Increase in live loads due to changes of occupancy
involving loads heavier than that being designed for.
1.4.8
Deflection and Camber
Structural systems and members thereof shall be designed to have adequate stiffness
to limit deflections. The deflections of structural members shall not exceed the more
restrictive of the limitations of Chapters 2 to 13 of this Part or that permitted by
Table 6.1.2.or provisions of Sec 1.2.5 of this Chapter. In calculating deflections due
to gravity loads, long term effects (e.g. creep, shrinkage or stress relaxation) should
also be considered.
1.5
Design For Lateral Loads
1.5.1
General
Every building, structure or portions thereof shall be designed to resist the lateral
load effects, such as those due to wind or earthquake forces, in compliance with the
requirements prescribed in this Section.
1.5.2
Selection of Lateral Force for Design
Any of the lateral loads prescribed in Chapter 2, considered either alone or in
combination with other forces, whichever produces the most critical effect, shall
govern the design. However, the structural detailing requirements shall comply with
those prescribed in Sec 1.7 of this Chapter. When a dual structural system is used to
resist lateral loads, design shall also conform to Sec 1.3.2.4 of this Chapter.
1.5.3
Design for Wind Load
Design of buildings and their components to resist wind induced forces shall comply
with the following requirements:
1.5.3.1 Direction of wind
Structural design for wind forces shall be based on assumption that wind may blow
from any horizontal direction.
1.5.3.2 Design considerations
Design wind load on the primary framing systems and components of a building or
structure shall be determined on the basis of the procedures provided in Sec 2.4
Chapter 2 Part 6 considering the basic wind speed, shape and size of the building,
and the terrain exposure condition of the site. For slender buildings and structures,
dynamic response characteristics, such as fundamental natural frequency, shall be
determined to estimate gust response coefficient. Load effects, such as forces,
moments, and deflections etc. on various components of building due to wind shall
be determined from static analysis of the structure as specified in Sec 1.2.7.1 of this
Chapter.
1.5.3.3 Shielding effect
Reductions in wind pressure on buildings and structures due to apparent direct
shielding effects of the up wind obstructions, such as man-made constructions or
natural terrain features, shall not be permitted.
1.5.3.4 Dynamic effects
Dynamic wind forces such as that from along-wind vibrations caused by the dynamic
wind-structure interaction effects, as set forth by the provisions of Sec 2.4.8 Chapter
2 Part 6, shall be considered in the design of regular shaped slender buildings. For
other dynamic effects such as cross-wind or torsional responses as may be
experienced by buildings or structures having unusual geometrical shapes (i.e.
vertical or plan irregularities listed in Tables 6.1.4 and 6.1.5), response
characteristics, or site locations, structural design shall be made based on the
information obtained either from other reliable references or from wind-tunnel test
specified in Sec 1.5.3.5 below, complying with the other requirements of this
Section.
1.5.3.5 Wind tunnel test
Properly conducted wind-tunnel tests shall be required for those buildings or
structures having unusual geometric shapes, response characteristics, or site locations
for which cross-wind response such as vortex shedding, galloping etc. warrant
special consideration, and for which no reliable literature for the determination of
such effects is available. This test is also recommended for those buildings or
structures for which more accurate wind-loading information is desired than those
given in this Section and in Sec 2.4. Tests for the determination of mean and
fluctuating components of forces and pressures shall be considered to be properly
conducted only if the following requirements are satisfied:
(a)
The natural wind has been modelled to account for the variation of wind
speed with height,
(b)
The intensity of the longitudinal components of turbulence has been taken
into consideration in the model,
(c)
The geometric scale of the structural model is not more than three times
the geometric scale of the longitudinal component of turbulence,
(d)
The response characteristics of the wind tunnel instrumentation are
consistent with the measurements to be made, and
(e)
The Reynolds number is taken into consideration when determining
forces and pressures on the structural elements.
Tests for the purpose of determining the dynamic response of a structure shall be
considered to be properly conducted only if requirements (a) through (e) above are
fulfilled and, in addition, the structural model is scaled with due consideration to
length, distribution of mass, stiffness and damping of the structure.
1.5.3.6 Wind loads during construction
Buildings, structures and portions thereof under construction, and construction
structures such as formwork, staging etc. shall be provided with adequate temporary
bracings or other lateral supports to resist the wind load on them during the erection
and construction phase.
1.5.3.7 Masonry construction in high-wind regions
Design and construction of masonry structures in high-wind regions shall conform to
the requirements of relevant Sections of Chapter 7 Part 6.
1.5.3.8 Height limits
Unless otherwise specified elsewhere in this Code, no height limits shall be imposed,
in general, on the design and construction of buildings or structures to resist wind
induced forces.
1.5.4
Design for Earthquake Forces
Design of structures and components thereof to resist the effects of earthquake forces
shall comply with the requirements of this Section.
1.5.4.1 Basic design consideration
For the purpose of earthquake resistant design, each structure shall be placed in one
of the seismic zones as given in Sec 2.5.4.2 and assigned with a structure importance
category as set forth in Sec 2.5.5.1. The seismic forces on structures shall be
determined considering seismic zoning, site soil characteristics, structure importance,
structural systems and configurations, height and dynamic properties of the structure
as provided in Sec 2.5. The structural system and configuration types for a building
or a structure shall be determined in accordance with the provisions of Sec 2.5.5.4.
Other seismic design requirements shall be those specified in this Section.
1.5.4.2 Requirements for directional effects
The directions of application of seismic forces used in the design shall be those
which will produce the most critical load effects. Earthquake forces act in both
principal directions of the building simultaneously. Design provisions for considering
earthquake component in orthogonal directions have been provided in Sec 2.5.13.1.
1.5.4.3 Structural system and configuration requirements
Seismic design provisions impose the following limitations on the use of structural
systems and configurations:
(a)
The structural system used shall satisfy requirements of the Seismic
Design Category (defined in Sec. 2.5.5.2) and height limitations given in
Sec 2.5.5.4.
(b)
Structures assigned to Seismic Design Category D having vertical
irregularity Type Vb of Table 6.1.4 shall not be permitted. Structures with
such vertical irregularity may be permitted for Seismic Design Category
B or C but shall not be over two stories or 9 m in height.
(c)
Structures having irregular features described in Table 1.3.2 or Table
1.3.3 shall be designed in compliance with the additional requirements of
the Sections referenced in these Tables.
(d)
Special Structural Systems defined in Sec 1.3.2.5 may be permitted if it
can be demonstrated by analytical and test data to be equivalent, with
regard to dynamic characteristics, lateral force resistance and energy
absorption, to one of the structural systems listed in Table 6.2.19, for
obtaining an equivalent R and Cd value for seismic design.
1.5.4.4 Methods of analysis
Earthquake forces and their effects on various structural elements shall be
determined by using either a static analysis method or a dynamic analysis method
whichever is applicable based on the limitations set forth in Sections 2.5.5 to 2.5.12
and conforming to Sec 1.2.7.
1.5.4.5 Minimum design seismic force
The minimum design seismic forces shall be those determined in accordance with the
Sections 2.5.5 to 2.5.14 whichever is applicable.
1.5.4.6 Distribution of seismic forces
The total lateral seismic forces and moments shall be distributed among various
resisting elements at any level and along the vertical direction of a building or
structure in accordance with the provisions of Sections 2.5.5 to 2.5.12 as appropriate.
1.5.4.7 Vertical components of seismic forces
Design provisions for considering vertical component of earthquake ground motion
is given in Sec 2.5.13.2
1.5.4.8 Height limits
Height limitations for different structural systems are given in Table 6.2.19 of Sec
2.5.3.4 Chapter 2 Part 6 of this Code as a function of seismic design category.
1.5.4.9 Non-building structures
Seismic lateral force on non-building structures shall be determined in accordance
with the provisions of ASCE 7: Minimum Design Loads for Buildings and other
Structures. However, provisions of ASCE 7 may be simplified, consistent with the
provisions of Sec 2.5 Part 6 of this Code. Other design requirements shall be those
provided in this Chapter.
1.5.5
Overturning Requirements
Every structure shall be designed to resist the overturning effects caused by wind or
earthquake forces specified in Sections 2.4 and 2.5 respectively as well other lateral
forces like earth pressure, tidal surge etc. The overturning moment Mx at any storey
level-x of a building shall be determined as:
= ∑
3ℎ
ℎ4
5-
(6.1.1)
Where,
ℎ,ℎ, ℎ
= Height in metres at level- , -x or -n respectively.
= Lateral force applied at level- , = 1 to .
At any level, the increment of overturning moment shall be distributed to the various
resisting elements in the same manner as the distribution of horizontal shear
prescribed in Sec 2.5.7.5. Overturning effects on every element shall be carried down
to the foundation level.
1.5.6
Drift and Building Separation
1.5.6.1 Storey drift limitation
Storey drift is the horizontal displacement of one level of a building or structure
relative to the level above or below due to the design gravity (dead and live loads) or
lateral forces (e.g. wind and earthquake loads). Calculated storey drift shall include
both translational and torsional deflections and conform to the following
requirements:
(a)
Storey drift, ∆, for loads other than earthquake loads, shall be limited as
follows:
∆ ≤0.005ℎ for < 0.7 second
∆ ≤0.004ℎ for ≥0.7 second
∆ ≤0.0025ℎ for unreinforced masonry structures.
Where, ℎ = height of floor. The period used in this calculation shall be
the same as that used for determining the base shear in Sec 2.5.7.2.
(b)
The drift limits set out in (a) above may be exceeded where it can be
demonstrated that greater drift can be tolerated by both structural and
nonstructural elements without affecting life safety.
(c)
For earthquake loads, the story drift, ∆ shall be limited in accordance with
the limits set forth in Sec 2.5.14.1
1.5.6.2 Sway limitation
The overall sway (horizontal deflection) at the top level of the building or structure
due to wind loading shall not exceed
500 times the total height of the building above
ground, in accordance with Sec 2.7.5.
1.5.7
Building Separation
All components of a structure shall be designed and constructed to act as an integral
unit unless they are separated structurally by a distance sufficient to avoid contact
under the most unfavorable condition of deflections due to lateral loads. For seismic
loads, design guidelines are given in Sec 2.5.14.3.
1.5.8
P-Delta Effects
The resulting member forces and moments and the storey drifts induced by P-Delta
effects need not be considered when the stability coefficient (F) remains within 0.10.
This coefficient (described in Sec 2.5.7.9) may be evaluated for any storey as the
product of the total vertical dead and live loads above the storey and the lateral drift
in that storey divided by the product of the storey shear in that storey and the height
of that storey.
1.5.9
Uplift Effects
Uplift effects caused due to lateral loads shall be considered in design. When
allowable (working) stress method is used for design, dead loads used to reduce
uplift shall be multiplied by a factor of 0.85.
1.6
Design For Miscellaneous Loads
1.6.1
General
Buildings, structures and components thereof, when subject to loads other than dead,
live, wind and earthquake loads, shall be designed in accordance with the provisions
of this Section. Miscellaneous loads, such as those due to temperature, rain, flood
and surge etc. on buildings or structures, shall be determined in accordance with Sec
2.6. Structural members subject to miscellaneous loads, not specified in Sec 2.6 shall
be designed using well established methods given in any reliable references, and
complying with the other requirements of this Code.
1.6.2
Self-Straining Forces
Self-straining forces such as those arising due to assumed differential settlements of
foundations and from restrained dimensional changes due to temperature, moisture,
shrinkage, creep, and similar effects, shall be taken into consideration in the design
of structural members.
1.6.3
Stress Reversal and Fatigue
Structural members and joints shall be investigated and designed against possible
stress reversals caused due to various construction loads. Where required, allowance
shall be made in the design to account for the effects of fatigue. The allowable stress
may be appropriately reduced to account for such effects in the structural members.
1.6.4
Flood, Tidal/Storm Surge and Tsunami
Buildings, structures and components thereof shall be designed, constructed and
anchored to resist flotation, collapse or any permanent movement due to loads
including flood, tidal/Storm surge and tsunami, when applicable. Structural members
shall be designed to resist both hydrostatic and significant hydrodynamic loads and
effects of buoyancy resulting from flood or surge. Flood and surge loads on buildings
and structures shall be determined in accordance with Sec 2.6.3. Load combination
including flood and surge loads shall conform to Sec 2.7. Design of foundations to
sustain these load effects shall conform to the provisions of Sec 1.8.
Stability against overturning and sliding caused due to wind and flood or surge loads
simultaneously shall be investigated, and such effects shall be resisted with a
minimum factor of safety of 1.5, considering dead load only.
1.6.5
Rain Loads
Roofs of the buildings and structures as well as their other components which may
have the capability of retaining rainwater shall be designed for adequate gravity load
induced by ponding. Roofs and such other components shall be analysed and
designed for load due to ponding caused by accidental blockage of drainage system
complying with Sec. 2.6.2.
1.6.6
Other Loads
Buildings and structures and their components shall be analyzed and designed for
stresses caused by the following effects:
(a)
Temperature Effects (Sec 2.6.4).
(b)
Soil and Hydrostatic Pressure (Sec 2.6.5).
(c)
Impacts and Collisions
(d)
Explosions (Sec 2.6.6).
(e)
Fire
(f)
Vertical Forces on Air Raid Shelters (Sec 2.6.7).
(g)
Loads on Helicopter Landing Areas (Sec 2.6.8).
(h)
Erection and Construction Loads (Sec 2.6.9).
(i)
Moving Loads for Crane Movements
(j)
Creep and Shrinkage
(k)
Dynamic Loads due to Vibrations
(l)
Construction Loads
Design of buildings and structures shall include loading and stresses caused by the
above effects in accordance with the provisions set forth in Chapter 2.
1.7
Detailed Design Requirements
1.7.1
General
All structural framing systems shall comply with the requirements of this Section.
Only the elements of the designated lateral force resisting systems can be used to
resist design lateral forces specified in Chapter 2. The individual components shall be
designed to resist the prescribed forces acting on them. Design of components shall
also comply with the specific requirements for the materials contained in Chapters 4
to 13. In addition, such framing systems and components shall comply with the
design requirements provided in this Section.
1.7.2
Structural Framing Systems
The basic structural systems are defined in Sec 1.3.2 and shown in Table 6.1.3, and
each type is subdivided by the types of framing elements used to resist the lateral
forces. The structural system used shall satisfy requirements of seismic design
category and height limitations indicated in Table 6.2.19. Special framing
requirements are given in the following Sections in addition to those provided in
Chapters 4 to 13.
1.7.3
Detailing Requirements for Combinations of Structural Systems
For components common to different structural systems, a more restrictive detailing
shall be provided.
1.7.3.1 Connections to resist seismic forces
Connections which resist prescribed seismic forces shall be designed in accordance
with the seismic design requirements provided in Chapters 4 to 13. Detailed sketches
for these connections shall be given in the structural drawings.
1.7.3.2 Deformation compatibility
All framing elements not required by design to be part of the lateral force resisting
system, shall be investigated and shown to be adequate for vertical load carrying
capacity when subjected to lateral displacements resulting from the seismic lateral
forces. For designs using working stress methods, this capacity may be determined
using an allowable stress increase of 30 percent. Geometric non-linear (P-Delta)
effects on such elements shall be accounted for.
(a)
Adjoining Rigid Elements : Moment resisting frames may be enclosed or
adjoined by more rigid elements which would tend to prevent a space
frame from resisting lateral forces where it can be shown that the action
or failure of the more rigid elements will not impair the vertical and
lateral load resisting ability of the space frame.
(b)
Exterior Elements : Exterior nonbearing, non-shear wall panels or
elements which are attached to or enclose the exterior of a structure, shall
be designed to resist the forces according to Sec. 2.5.15 of Chapter 2, if
seismic forces are present, and shall accommodate movements of the
structure resulting from lateral forces or temperature changes. Such
elements shall be supported by structural members or by mechanical
connections and fasteners joining them to structural members in
accordance with the following provisions:
(i)
Connections and panel joints shall allow for a relative movement
between storeys of not less than two times the storey drift caused by
wind forces or design seismic forces, or 12 mm, whichever is
greater.
(ii) Connections to permit movement in the plane of the panel for storey
drift shall be either sliding connections using slotted or oversized
holes, connections which permit movement by bending of steel, or
other connections providing equivalent sliding and ductility
capacity.
(iii) Bodies of connections shall have sufficient ductility and rotation
capability to preclude any fracture of the anchoring elements or
brittle failures at or near welding.
(iv) Bodies of the connection shall be designed for 1.33 times the
seismic force determined by Sec. 2.5.15 of Chapter 2, or equivalent.
(v)
All fasteners in the connection system, such as bolts, inserts, welds,
dowels etc. shall be designed for 4 times the forces determined by
Sec. 2.5.15 of Chapter 2 or equivalent.
(vi) Fasteners embedded in concrete shall be attached to, or hooked
around reinforcing steel, or otherwise terminated so as to transfer
forces to the reinforcing steel effectively.
1.7.3.3 Ties and continuity
All parts of a structure shall be interconnected. These connections shall be capable of
transmitting the prescribed lateral force to the lateral force resisting system.
Individual members, including those not part of the seismic force–resisting system,
shall be provided with adequate strength to resist the shears, axial forces, and
moments determined in accordance with this Code. Connections shall develop the
strength of the connected members and shall be capable of transmitting the seismic
force (G) induced by the parts being connected.
1.7.3.4 Collector elements
Collector elements shall be provided which are capable of transferring the lateral
forces originating in other portions of the structure to the element providing the
resistance to those forces.
1.7.3.5 Concrete frames
When concrete frames are provided by design to be part of the lateral force resisting
system, they shall conform to the provisions of Chapter 8 of this Part.
1.7.3.6 Anchorage of concrete and masonry structural walls
The concrete and masonry structural walls shall be anchored to supporting
construction. The anchorage shall provide a positive direct connection between the
wall and floor or roof and shall be capable of resisting the horizontal forces specified
in Sections 2.4.11 and 2.5.15, or a minimum force of 4.09 kN/m of wall. Walls shall
be designed to resist bending between anchors where the anchor spacing exceeds 1.2
m. In masonry walls of hollow units or cavity walls, anchors shall be embedded in a
reinforced grouted structural element of the wall. Deformations of the floor and roof
diaphragms shall be considered in the design of the supported walls and the
anchorage forces in the diaphragms shall be determined in accordance with Sec
1.7.3.9 below.
1.7.3.7 Boundary members
Specially detailed boundary members shall be considered for shear walls and shear
wall elements whenever their design is governed by flexure.
1.7.3.8 Floor and roof diaphragms
Deflection in the plane of the diaphragm shall not exceed the permissible deflection
of the attached elements. Permissible deflection shall be that deflection which will
permit the attached element to maintain its structural integrity under the individual
loading and continue to support the prescribed loads. Design of diaphragms shall also
comply with the following requirements.
(a)
Diaphragm Forces: Diaphragms shall be designed to resist the seismic
forces given in Sec 2.5 or for similar non-seismic lateral forces,
whichever is greater.
(b)
Diaphragm Ties: Diaphragms supporting concrete or masonry walls shall
have continuous ties, or struts between the diaphragm chords to distribute
the anchorage forces specified in Sec 1.7.3.6 above. Added chords may
be provided to form sub-diaphragms to transmit the anchorage forces to
the main cross ties.
(c)
Wood Diaphragms: Where wood diaphragms are used to laterally support
concrete or masonry walls, the anchorage shall conform to Sec 1.7.3.6
above. In seismic Zones 2, 3 and 4 the following requirements shall also
apply:
(i)
Anchorage shall not be accomplished by use of toe nails or nails
subject to withdrawal, nor shall wood ledgers or framing be used in
cross-grain bending or cross-grain tension.
(ii) The continuous ties required by paragraph (b) above, shall be in
addition to the diaphragm sheathing.
(d)
Structures having irregularities
(i)
For structures assigned to Seismic Design Category D and having a
plan irregularity of Type I, 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 Sec 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 over
strength factor.
(ii) For structures having a plan irregularity of Type II in Table 6.1.5,
diaphragm chords and collectors shall be designed considering
independent movement of any projecting wings of the structure.
Each of these diaphragm elements shall be designed for the more
severe of the following cases:
Motion of the projecting wings in the same direction.
Motion of the projecting wings in opposing directions.
Exception:
This requirement may be deemed to be satisfied if the procedures of Sec 2.5.8 when
seismic forces are present, in conjunction with a three dimensional model, have been
used to determine the lateral seismic forces for design.
1.7.3.9 Framing below the base
When structural framings continue below the base, the following requirements shall
be satisfied.
(a)
Framing between the Base and the Foundation: The strength and
stiffness of the framing between the base and the foundation shall not be
less than that of the superstructure. The special detailing requirements of
Sec 8.3 or Sec 10.20, as appropriate for reinforced concrete or steel, shall
apply to columns supporting discontinuous lateral force resisting
elements and to SMF, IMF, and EBF system elements below the base that
are required to transmit forces resulting from lateral loads to foundation.
(b)
Foundations : The foundation shall be capable of transmitting the design
base shear and the overturning forces from the superstructure into the
supporting soil, but the short term dynamic nature of the loads may be
taken into account in establishing the soil properties. Sec 1.8 below
prescribes the additional requirements for specific types of foundation
construction.
1.8
Foundation Design Requirements
1.8.1
General
The design and construction of foundation, foundation components and connection
between the foundation and superstructure shall conform to the requirements of this
Section and applicable provisions of Chapter 3 and other portions of this Code.
1.8.2
Soil Capacities
The bearing capacity of the soil, or the capacity of the soil-foundation system
including footing, pile, pier or caisson and the soil, shall be sufficient to support the
structure with all prescribed loads, considering the settlement of the structure. For
piles, this refers to pile capacity as determined by pile-soil friction and bearing which
may be determined in accordance with the provisions of Chapter 3. For the load
combination including earthquake, the soil capacity shall be sufficient to resist loads
at acceptable strains considering both the short time loading and the dynamic
properties of the soil. The stress and settlement of soil under applied loads shall be
determined based on established methods of Soil Mechanics.
1.8.3
Superstructure-to-Foundation Connection
The connection of superstructure elements to the foundation shall be adequate to
transmit to the foundation the forces for which the elements are required to be
designed.
1.8.4
Foundation-Soil Interface
For regular buildings the base overturning moments for the entire structure or for any
one of its lateral force-resisting elements, shall not exceed two-thirds of the dead load
resisting moment. The weight of the earth superimposed over footings may be used
to calculate the dead load resisting moment.
1.8.5
Special Requirements for Footings, Piles and Caissons in Seismic Zones
2, 3 and 4
1.8.5.1 Piles and caissons
Piles and caissons shall be designed for flexure whenever the top of such members is
anticipated to be laterally displaced by earthquake motions. The criteria and detailing
requirements of Sec 8.3 for concrete and Sec 10.20 for steel shall apply for a length
of such members equal to 120 percent of the flexural length.
1.8.5.2 Footing interconnection
(a)
Footings and pile caps shall be completely interconnected by strut ties or
other equivalent means to restrain their lateral movements in any
orthogonal direction.
(b)
The strut ties or other equivalent means as specified in (a) above, shall be
capable of resisting in tension or compression a force not less than 10%
of the larger footing or column load unless it can be demonstrated that
equivalent restraint can be provided by frictional and passive soil
resistance or by other established means.
1.8.6
Retaining wall design
Retaining walls shall be designed to resist the lateral pressure of the retained material,
under drained or undrained conditions and including surcharge, in accordance with
established engineering practice. For such walls, the minimum factor of safety against
base overturning and sliding due to applied earth pressure shall be 1.5.
1.9
Design and Construction Review
Every building or structure designed shall have its design documents prepared in
accordance with the provisions of Sec 1.9.1. The minimum requirements for design
review and construction observation shall be those set forth under Sections 1.9.2 and
1.9.3 respectively.
1.9.1
Design Document
The design documents shall be prepared and signed by the Engineer responsible for
the structural design of any building or structure intended for construction. The
design documents shall include a design report, material specifications and a set of
structural drawings, which shall be prepared in compliance with Sections 1.9.2 and
1.9.3 below for submittal to the concerned authority. For the purpose of this
provision, the concerned authority shall be either persons from the government
approval agency for the construction, or the owner of the building or the structure, or
one of his representatives.
1.9.2
Design Report
The design report shall contain the description of the structural design with basic
design information as provided below, so that any other structural design engineer
will be able to independently verify the design parameters and the member sizes
using these basic information. The design report shall include, but not be limited to,
the following:
(a)
Mention of this Code including relevant Part, Chapter and Section.
(b)
Name of other referenced standards, and the specific portions, stating
chapter, section etc. of these Code and standards including any specialist
report used for the structural design.
(c)
Methods used for the calculation of all applied loads along with basic
load coefficients and other basic information including any assumption or
judgment made under special circumstances.
(d)
A drawing of the complete mathematical model prepared in accordance
with Sec 1.2.7.1 to represent the structure and showing on it the values,
locations and directions of all applied loads, and location of the lateral
load resisting systems such as shear walls, braced frames etc.
(e)
Methods of structural analysis, and results of the analysis such as shear,
moment, axial force etc., used for proportioning various structural
members and joints including foundation members.
(f)
Methods of structural design including types and strength of the materials
of construction used for proportioning the structural members.
(g)
Reference of the soil report or any other documents used in the design of
the structure, foundation or components thereof.
(h)
Statement supporting the validity of the above design documents with
date and signature of the engineer responsible for the structural design.
(i)
When computer programs are used, to any extent, to aid in the analysis or
design of the structure, the following items, in addition to items (a) to (g)
above, shall be required to be included in the design report:
(i)
A sketch of the mathematical model used to represent the structure
in the computer generated analysis.
(ii) The computer output containing the date of processing, program
identification, identification of structures being analysed, all input
data, units and final results. The computer input data shall be clearly
distinguished from those computed in the program.
(iii) A program description containing the information necessary to
verify the input data and interpret the results to determine the nature
and extent of the analysis and to check whether the computations
comply with the provisions of this Code.
(iv) The first sheet of each computer run shall be signed by the engineer
responsible for the structural design.
1.9.3
Structural Drawings and Material Specifications
The structural drawings shall include, but not be limited to, the following:
(a)
The first sheet shall contain :
(i)
Identification of the project to which the building or the structure, or
portion thereof belongs,
(ii) Reference to the design report specified in Sec 1.9.2 above,
(iii) Date of completion of design, and
(iv) Identification and signature with date of the engineer responsible for
the structural design.
(b)
The second sheet shall contain detail material specifications showing:
(i)
Specified compressive strength of concrete at stated ages or stages
of construction for which each part of structure is designed.
(ii) Specified strength or grade of reinforcement
(iii) Specified strength of prestressing tendons or wires
(iv) Specified strength or grade of steel
(v)
Specified strengths for bolts, welds etc.
(vi) Specified strength of masonry, timber, bamboo, ferrocement
(vii) Minimum concrete compressive strength at time of post-tensioning
(viii) Stressing sequence for post-tensioning tendons
(ix) General notes indicating clear cover, development lengths of
reinforcements, or any other design parameter relevant to the
member or connection details provided in drawings to be followed,
as applicable, and
(x)
Identification and signature with date of the Engineer responsible
for the structural design.
(c)
Drawing sheets, other than the first two, shall include structural details of
the elements of the structure clearly showing all sizes, cross-sections and
relative locations, connections, reinforcements, laps, stiffeners, welding
types, lengths and locations etc. whichever is applicable for a particular
construction. Floor levels, column centres and offset etc., shall be
dimensioned. Camber of trusses and beams, if required, shall be shown
on drawings. For bolt connected members, connection types such as slip,
critical, tension or bearing type, shall be indicated on the drawing.
(d)
Drawings shall be prepared to a scale large enough to show the
information clearly and the scales shall be marked on the drawing sheets.
If any variation from the design specifications provided in sheet two
occurs, the drawing sheet shall be provided additionally with the design
specifications including material types and strength, clear cover and
development lengths of reinforcements, or any other design parameter
relevant to the member or connection details provided in that drawing
sheet. Each drawing sheet shall also contain the signature with date of the
engineer responsible for the structural design.
1.9.4
Design Review
The design documents specified in Sec 1.9.1 shall be available for review when
required by the concerned authority. Review shall be accomplished by an
independent structural engineer qualified for this task and appointed by the
concerned authority. Design review shall be performed through independent
calculations, based on the information provided in the design documents prepared
and signed by the original structural design engineer, to verify the design parameters
including applied loads, methods of analysis and design, and final design dimensions
and other details of the structural elements. The reviewing engineer shall also check
the sufficiency and appropriateness of the supplied structural drawings for
construction.
1.9.5
Construction Observation
Construction observation shall be performed by a responsible person who will be a
competent professional appointed by the owner of the building or the structure.
Construction observation shall include, but not be limited to, the following:
(a)
Specification of an appropriate testing and inspection schedule prepared
and signed with date by the responsible person;
(b)
Review of testing and inspection reports; and
(c)
Regular site visit to verify the general compliance of the construction
work with the structural drawings and specifications provided in Sec
1.9.3 above.
Last modified on August 26, 2026
