Chapter 10: Steel Structures

10.1 General Provisions for Structural Steel Buildings and Structures

This Section states the scope of the Specification, summarizes referenced Specification, code, and standard documents, and provide requirements for materials and contract documents.

10.1.1 Scope

The specification contained in Chapter 10 Part 6 of this Code sets forth criteria for the design, fabrication, and erection of structural steel buildings and other structures, where other steel-structures are defined as those structures designed, fabricated, and erected in a manner similar to steel-buildings, with building-like vertical and lateral load resisting elements. Where conditions are not covered by this specification, designs are permitted to be based on tests or analysis, subject to the approval of the authority having jurisdiction. Alternate methods of analysis and design shall be permitted, provided such alternate methods or criteria are acceptable to the authority having jurisdiction.

10.1.1.1 Low-seismic applications

When the seismic response modification coefficient, R (as specified in Chapter 2 Part 6) is taken equal to or less than 3, the design, fabrication, and erection of structural-steel-framed buildings and other steel-structures shall comply with this specification except that such structures need not to comply with the specifications set forth in Sec 10.20 Seismic Provisions.

10.1.1.2 High-seismic applications

When the seismic response modification coefficient, R (as specified in Chapter 2 Part 6) is taken greater than 3, the design, fabrication and erection of structural-steel-framed buildings and other structures shall comply with the requirements in the Sec 10.20 Seismic Provisions, in addition to the provisions of other sections (whichever applicable) this specification.

10.1.2 Symbols, Glossary and Referenced Specifications, Codes and Standards

10.1.2.1 Symbols

The Section or Table number in the right-hand column refers to where the symbol is first used.

Symbol	Meaning	Section
A	Column cross-sectional area, mm²	10.10.10.6
A	Total cross-sectional area of member, mm²	10.5.7.2
ABM	Cross-sectional area of the base metal, mm²	10.10.2.4
$A_b$	Nominal unthreaded body area of bolt or threaded part, mm²	10.10.3.6
$A_b$	Cross-sectional area of a horizontal boundary element (HBE), mm²	10.20.17.2.1
$A_{bi}$	Cross-sectional area of the overlapping branch, mm²	10.11.2.3
$A_{bj}$	Cross-sectional area of the overlapped branch, mm²	10.11.2.3
$A_c$	Cross-sectional area of a vertical boundary element (VBE),mm²	10.20.17.2.1
$A_D$	Area of an upset rod based on the major thread diameter, mm²	Table 6.10.10
$A_e$	Effective net area, mm²	10.4.2
$A_{eff}$	Summation of the effective areas of the cross section based on the reduced effective width, $b_e$ , mm²	10.5.7.2
$A_f$	Flange area, mm²	10.20.8
$A_{fc}$	Area of compression flange	10.7.3.1
$A_{fg}$	Gross tension flange area, mm²	10.6.13.1
$A_{fn}$	Net tension flange area, mm²	10.6.13.1
$A_{ft}$	Area of tension flange, mm²	10.7.3.1
$A_g$	Gross area of member, mm²	10.2.3.13
$A_g$	Gross area of section based on design wall thickness, mm²	10.7.6
$A_g$	Chord gross area, mm²	10.11.2.2
$A_g$	Gross area, mm²	10.20.9
$A_{gv}$	Gross area subject to shear, mm²	10.10.4.3
$A_n$	Net area of member, mm²	10.2.3.13
$A_{nt}$	Net area subject to tension, mm²	10.10.4.3
$A_{nv}$	Net area subject to shear, mm²	10.10.4.2
$A_{pb}$	Projected bearing area, mm²	10.10.7
$A_{sc}$	Area of the yielding segment of steel core, mm²	10.20.16
$A_{sf}$	Shear area on the failure path, mm²	10.4.5.1
$A_{st}$	Stiffener area, mm²	10.7.3.3
$A_{st}$	Area of link stiffener, mm²	10.20.15
$A_t$	Net tensile area, mm²	10.17.4
$A_w$	Web area, the overall depth times the web thickness,, mm²	10.7.2.1
$A_w$	Effective area of the weld, mm²	10.10.2.4
$A_w$	Link web area, mm²	10.20.15
$A_{wi}$	Effective area of weld throat of any^thweld element, mm²	10.10.2.4
$A_1$	Area of steel concentrically bearing on a concrete support, mm²	10.10.8
$A_2$	Maximum area of the portion of the supporting surface that is geometrically similar to and concentric with the loaded area, mm².	10.10.8
$B$	Factor for lateral-torsional buckling in tees and double angles	10.6.9.2
$B$	Overall width of rectangular HSS member, measured 90^oto the plane of connection, mm.	10.11.1.1, Table 6.10.2
$B$	Overall width of rectangular HSS main member, measured 90^o to the plane of the connection,mm.	10.11.2.1, 10.11.3.1
$B_b$	Overall width of rectangular HSS branch member, measured 90^oto the plane of the connection, mm.	10.11.2.1, 10.11.3.1
$B_{bi}$	Overall branch width of the overlapping branch	10.11.2.3
$B_{bj}$	Overall branch width of the overlapped branch	10.11.2.3
$B_p$	Width of plate, measure 90^oto the plane of the connection, mm.	10.11.1.1
$B_p$	Width of plate, transverse to the axis of the main member,mm.	10.11.2.3
,	Factors used in determiningfor combined bending and axial forces when first-order analysis is employed	10.3.2.1
$C$	HSS torsional constant	10.8.3.1
$C_a$	Ratio of required strength to available strength	Table 6.10.8
$C_b$	Lateral-torsional buckling modification factor for nonuniform moment diagrams when both ends of the unsupported segment are braced	10.6.1
$C_d$	Coefficient relating relative brace stiffness and curvature	10.19.3.1, 10.20.9
$C_d$	Deflection amplification factor	P.2
$C_f$	Constant based on stress category, given in Table 6.10.14	10.17.3
$C_m$	Coefficient assuming no lateral translation of the frame	10.3.2.1
$C_p$	Ponding flexibility coefficient for primary member in a flat roof	10.16.1
$C_r$	Coefficient for web sidesway buckling	10.10.10.4
$C_r$	Parameter used for determining the approximate fundamental period	P.2
$C_s$	Ponding flexibility coefficient for secondary member in a flat roof	10.16.1
$C_v$	Web shear coefficient	10.7.2.1
$C_w$	Warping constant, mm⁶	10.5.4
$D$	Nominal dead load	10.16.2
$D$	Dead load due to the weight of the structural elements and permanent features on the building, N.	10.20.9
$D$	Outside diameter of round HSS, mm.	Table 6.10.8
$D$	Outside diameter of round HSS member, mm.	Table 6.10.1
$D$	Outside diameter of round HSS member, mm.	10.11.1.1
$D$	Outside diameter of round HSS main member, mm.	10.11.2.1
$D$	Outside diameter of round HSS main member, mm.	10.11.3.1
$D$	Outside diameter, mm.	10.5.7.2
$D$	Chord diameter, mm.	10.11.2.2
$D_b$	Outside diameter of round HSS branch member,mm.	10.11.2.1
$D_b$	Outside diameter of round HSS branch member,mm.	10.11.3.1
$D_s$	Factor used in Eq. 6.10.144, dependent on the type of transverse stiffeners used in a plate girder	10.7.3.3
$D_u$	In slip-critical connections, a multiplier that reflects the ratio of the mean installed bolt pretension to the specified minimum bolt pretension	10.10.3.8
E	Earthquake load	10.20.4
E	Effect of horizontal and vertical earthquake-induced loads	10.20.9
E	Modulus of elasticity of steel, $E$ = 200,000 MPa	10.20.8
$E$	Eccentricity in a truss connection, positive being away from the branches, mm.	10.11.2.1
$E$	Modulus of elasticity of steel = 200000 MPa	Table 6.10.1
$E_c$	Modulus of elasticity of concrete, MPa.	10.18.2.3
$E_{cm}$	Modulus of elasticity of concrete at elevated temperature, MPa
EI	Flexural elastic stiffness of the chord members of special segment, (N-mm²)	10.20.12
$E_m$	Modulus of elasticity of steel at elevated temperature, MPa.	10.18.2.3
$F_a$	Available axial stress at the point of consideration, MPa.	10.8.2
$F_{BM}$	Nominal strength of the base metal per unit area, MPa.	10.10.2.4
$F_{BW}$	Available flexural stress at the point of consideration about the major axis, MPa.	10.8.2
$F_{bz}$	Available flexural stress at the point of consideration about the minor axis, MPa.	10.8.2
$F_c$	Available stress, MPa.	10.11.2.2
$F_{cr}$	Critical stress, MPa.	10.5.3
$F_{cr}$	Buckling stress for the section as determined by analysis, MPa.	10.6.12.2
$F_{cry}$	Critical stress about the minor axis, MPa.	10.5.4
$F_{crz}$	Critical torsional buckling stress, MPa.	10.5.4
$F_e$	Elastic critical buckling stress, MPa.	10.3.1.3
$F_{ex}$	Elastic flexural buckling stress about the major axis, MPa.	10.5.4
$F_{EXX}$	Electrode classification number, MPa.	10.10.2.4
$F_{ey}$	Elastic flexural buckling stress about the minor axis, MPa.	10.5.4
$F_{ez}$	Elastic torsional buckling stress, MPa.	10.5.4
$F_L$	A calculated stress used in the calculation of nominal flexural strength, MPa.	Table 6.10.1
$F_n$	Nominal torsional strength	10.8.3.3
$F_n$	Nominal tensile stress $F_{nt}$ , or shear stress, $F_{nv}$ , from Table 6.10.10, MPa.	10.10.3.6
$F_{nt}$	Nominal tensile stress from Table 6.10.10, MPa.	10.10.3.7
$F_{nt}'$	Nominal tensile stress modified to include the effects of shearing stress, MPa.	10.10.3.7
$F_{nv}$	Nominal shear stress from Table 6.10.10, MPa.	10.10.3.7
$F_{SR}$	Design stress range, MPa.	10.17.3
$F_{TH}$	Threshold fatigue stress range, maximum stress range for indefinite design life from Table 6.10.14, MPa.	10.17.1
$F_u$	Specified minimum tensile strength of the type of steel being used, MPa.	10.4.2
$F_u$	Specified minimum tensile strength of the connected material, MPa.	10.10.3.10
$F_u$	Specified minimum tensile strength of HSS material, MPa.	10.11.1.1
$F_u$	Specified minimum tensile strength of HSS material, MPa.	10.11.2.1
$F_u$	Ultimate strength of HSS member, MPa.	10.11.3.1
$F_u$	Specified minimum tensile strength, MPa.	10.20.6
$F_{um}$	Specified minimum tensile strength of the type of steel being used at elevated temperature, MPa.	10.18.2
$F_w$	Nominal strength of the weld metal per unit area, MPa.	10.10.2.4
$F_{wi}$	Nominal stress in any $i^{th}$ weld element, MPa.	10.10.2.4
$F_{wix}$	x component of stress $F_{wi}$ , MPa.	10.10.2.4
$F_{wiy}$	y component of stress $F_{wi}$ , MPa.	10.10.2.4
$F_y$	Specified minimum yield stress of the type of steel being used, MPa. As used in this Specification, “yield stress”	10.20.6, Table 6.10.1
$F_y$	denotes either the specified minimum yield point (for those steels that have a yield point) or specified yield strength (for those steels that do not have a yield point
$F_y$	Specified minimum yield stress of the compression flange, MPa.	10.15.3
$F_y$	Specified minimum yield stress of the column web, MPa.	10.10.10.6
$F_y$	Specified minimum yield stress of HSS member material, MPa.	10.11.1.1
$F_y$	Specified minimum yield stress of HSS main member material, MPa.	10.11.2.1
$F_y$	Specified minimum yield stress of HSS main member, MPa.	10.11.3.1
$F_{yb}$	Specified minimum yield stress of HSS branch member material, MPa.	10.11.2.1
$F_{yb}$	Specified minimum yield stress of HSS branch member, MPa.	10.11.3.1
$F_{yb}$	$F_y$ of a beam, MPa.	10.20.9
$F_{yc}$	$F_y$ of a column, MPa.	10.20.9
$F_{ybi}$	Specified minimum yield stress of the overlapping branch material, MPa.	10.11.2.3
$F_{yf}$	Specified minimum yield stress of the flange, MPa.	10.10.10.1
$F_{ym}$	Specified minimum yield stress of the type of steel used at elevated temperature, MPa.	10.18.2
$F_{yp}$	Specified minimum yield stress of plate, MPa.	10.11.1.1
$F_{ysc}$	Specified minimum yield stress of the steel core, or actual yield stress of the steel core as determined from a coupon test, MPa.	10.20.16
$F_{yst}$	Specified minimum yield stress of the stiffener material, MPa.	10.7.3.3
$F_{yw}$	Specified minimum yield stress of the web, MPa.	10.10.10.2
$G$	Shear modulus of elasticity of steel = 77 200 MPa.	10.5.4
$G$	Gap between toes of branch members in a gapped K- connection, neglecting welds, mm.	10.11.2.1
$H$	Flexural constant	10.5.4
$H$	Overall height of rectangular HSS member, measured in the plane of connection, mm.	10.11.1.1
$H$	Overall height of rectangular HSS main member, measured in plane of connection, mm.	10.11.2.1
$H$	Overall height of rectangular HSS main member, measured in plane of connection, mm.	10.11.3.1
$H$	Overall height of rectangular HSS member, measured in the plane of connection, mm.	Table 6.10.2
$H$	The load length parameter, applicable only to rectangular	10.11.2.1
$H$	HSS; the ratio of the length of contact of the branch with the chord in the plane of the connection to the chord width = $N/B$ , where, $N = H_b/\sin\theta$
$H$	Height of story, which may be taken as the distance between	10.20.8
$H$	the centerline of floor framing at each of the levels above and below, or the distance between the top of floor slabs at each of the levels above and below, mm
$H_b$	Overall height of rectangular HSS branch member, measured in the plane of the connection, mm.	10.11.3.1
$H_b$	Overall height of rectangular HSS branch member, measured in the plane of the connection, mm.	10.11.2.1
$H_{bi}$	Overall depth of the overlapping branch	10.11.2.3
$\Sigma H$	Story shear produced by the lateral forces used to compute $\Delta_H$ , N.	10.3.2.1
$I$	Moment of inertia in the place of bending, mm⁴.	10.3.2.1
$I$	Moment of inertia about the axis of bending, mm⁴.	10.14.3
$I$	Moment of inertia, mm⁴	10.20.12
$I_c$	Moment of inertia of a vertical boundary element (VBE) taken perpendicular to the direction of the web plate line, mm⁴	10.20.17
$I_d$	Moment of inertia of the steel deck supported on secondary members, mm⁴	10.16.1
$I_p$	Moment of inertia of primary members, mm⁴	10.16.1
$I_s$	Moment of inertia of secondary members, mm⁴	10.16.1
$I_x, I_y$	Moment of inertia about the principal axes, mm⁴	10.5.4
$I_y$	Out-of-plane moment of inertia, mm⁴	10.19.2
$I_z$	Minor principal axis moment of inertia, mm⁴	10.6.10.2
$I_{yc}$	Moment of inertia about y-axis referred to the compression	10.6.1
$I_{yc}$	flange, or if reverse curvature bending referred to smaller flange, mm⁴
$J$	Torsional constant, mm⁴	10.5.4
$K$	Effective length factor determined in accordance with Sec 10.3	10.3.1.2
$K$	Effective length factor for prismatic member	10.20.13
$K_z$	Effective length factor for torsional buckling	10.5.4
$K_1$	Effective length factor in plane of bending, calculated based on the assumption of no lateral translation set equal to 1.0 unless analysis indicates a smaller value to be used.	10.3.2.1
$K_2$	Effective length factor in the plane of bending, calculated based on a sidesway buckling analysis	10.3.2.1
$L$	Story height, mm.	10.3.2.1
$L$	Laterally unbraced length of a member, mm.	10.5.2
$L$	Length of member between work points at truss chord centerlines,mm.	10.5.5
$L$	Length of the member, mm.	10.8.3
$L$	Actual length of end-loaded weld, mm.	10.10.2.2
$L$	Nominal occupancy live load	10.18.1.4
$L$	Span length, mm.	10.19.2
$L$	Span length of the truss, mm.	10.20.12
$L$	Distance between VBE centerlines, mm	10.20.17
$L_b$	Distance between braces, mm.	10.19.2
$L_b$	Length between points that are either braced against lateral	10.6.2,
$L_b$	displacement of compression flange or braced against twist of the cross section, mm.	10.20.13
$L_c$	Distance between plastic hinge locations, mm	10.20.9
$L_c$	Clear distance, in the direction of the force, between the edge	10.10.3.10
$L_c$	of the hole and the edge of the adjacent hole or edge of the material,mm.
$L_c$	Link length, mm	10.20.15
$L_{cf}$	Clear distance between VBE flanges, mm	10.20.17
$L_e$	Total effective weld length of groove and fillet welds to rectangular HSS,mm.	10.11.2.3
$L_p$	Limiting laterally unbraced length for the limit state of yielding, mm.	10.6.2.2
$L_p$	Column spacing in direction of girder, m	10.16
$L_p$	Limiting laterally unbraced length for full plastic flexural strength, uniform moment case,mm.	10.20.12
$L_{pd}$	Limiting laterally unbraced length for plastic analysis, mm.	10.15.7
$L_{pd}$	Limiting laterally unbraced length for plastic analysis, mm	10.20.13
$L_q$	Maximum unbraced length for $M_r$ (the required flexural strength),mm.	10.19.2
$L_r$	Limiting laterally unbraced length for limit state of inelastic lateral-torsional buckling, mm.	10.6.2.2
$L_s$	Column spacing perpendicular to direction of girder, m	10.16.1
$L_s$	Length of the special segment, mm	10.20.12
$L_v$	Distance from maximum to zero shear force,mm.	10.7.6
$M_A$	Absolute value of moment at quarter point of the unbraced segment, N-mm.	10.6.1
$M_a$	Required flexural strength in chord, using ASD load combinations, N-mm.	10.11.2.2
$M_a$	Required flexural strength, using ASD load combinations, N-mm.	10.20.9
$M_{av}$	Additional moment due to shear amplification from the location of plastic hinge to the column centerline based on ASD load combinations, N-mm.	10.20.9
$M_B$	Absolute value of moment at centerline of the unbraced segment, N-mm.	10.6.1
$M_{br}$	Required bracing moment,N-mm.	10.19.2
$M_C$	Absolute value of moment at three-quarter point of unbraced segment, N-mm.	10.6.1
$M_{C(x,y)}$	^{Available flexural strength determined in accordance with Sec} 10.6,N-mm.	10.8.1.1
$M_{Cx}$	Available flexural-torsional strength for strong axis flexure determined in accordance with Sec 10.6,N-mm.	10.8.1.3
$M_e$	Elastic lateral-torsional buckling moment, N-mm.	10.6.10.2
$M_{lt}$	First-order moment under LRFD or ASD load combinations caused by lateral translation of the frame only, N-mm.	10.3.2.1
$M_{max}$	Absolute value of maximum moment in the unbraced segment,N-mm.	10.6.1
$M_n$	Nominal flexural strength, N-mm.	10.6.1
$M_n$	Nominal flexural strength, N-mm.	10.20.11
$M_{nc}$	Nominal flexural strength of the chord member of special segment, N-mm.	10.20.12
$M_{nt}$	First-order moment using LRFD or ASD load combinations assuming there is no lateral translation of the frame, N-mm.	10.3.2.1
$M_p$	Plastic bending moment,N-mm.	Table 6.10.1
$M_p$	Nominal plastic flexural strength, N-mm.	Table 6.10.8
$M_{pa}$	Nominal plastic flexural strength modified by axial load, N- mm.	10.20.15
$M_{pb}$	Nominal plastic flexural strength of the beam, N-mm.	10.20.9
$M_{pc}$	Nominal plastic flexural strength of the column, N-mm.	10.20.8
$M_{p,exp}$	Expected plastic moment, N-mm.	10.20.9
$M_r$	Required second-order flexural strength under LRFD or ASD load combinations, N-mm.	10.3.2.1
$M_r$	Required flexural strength using LRFD or ASD load combinations,N-mm.	10.8.1
$M_r$	Required flexural strength in chord, N-mm.	10.11.2.2
$M_r$	Expected flexural strength, N-mm.	10.20.9
$M_{r-ip}$	Required in-plane flexural strength in branch,N-mm.	10.11.3.2
$M_{r-op}$	Required out-of-plane flexural strength in branch,N-mm.	10.11.3.2
$M_u$	Required flexural strength, using LRFD load combinations, N- mm.	10.20.9
$M_u$	Required flexural strength in chord, using LRFD load combinations,N-mm.	10.11.2.2
$M_{uv}$	Additional moment due to shear amplification from the location of plastic hinge to the column centerline based on LRFD load combinations, N-mm.	10.20.9
$M_{u,exp}$	Expected required flexural strength, N-mm.	10.20.15
$M_y$	Yield moment about the axis of bending, N-mm.	Table 6.10.1
$M_1$	Smaller moment, calculated from a first-order analysis, at the ends of that portion of the member unbraced in the plane of bending under consideration, N-mm.	10.3.2.1
$M_2$	Larger moment, calculated from a first-order analysis, at the ends of that portion of the member unbraced in the plane of bending under consideration, N-mm.	10.3.2.1
$N$	Length of bearing (not less than_k_for end beam reactions),mm.	10.10.10.2
$N$	Bearing length of the load, measured parallel to the axis of the	10.11.1.1
$N$	HSS member, (or measured across the width of the HSS in the case of the loaded cap plates), mm.
$N$	Number of stress range fluctuations in design life	10.17.3
$N_b$	Number of bolts carrying the Applied tension	10.10.3.9
$N_i$	Additional lateral load	10.3.2.2
$N_i$	Notional lateral load Applied at level $i$ , N.	10.14.3
$N_s$	Number of slip planes	10.10.3.8
$O_v$	Overlap connection coefficient	10.11.2.2
$P$	Pitch, mm per thread	10.17.4
$P_a$	Required axial strength of a column using ASD load combinations, N.	10.20.8
$P_{ac}$	Required compressive strength using ASD load combinations, N.	10.20.9
$P_b$	Required strength of lateral brace at ends of the link, N.	10.20.15
$P_{br}$	Required brace strength, N.	10.19.2
$P_c$	Available axial compressive strength, N.	10.8.1.1
$P_c$	Available tensile strength, N.	10.8.1.2
$P_c$	Available axial strength of a column, N.	10.20.9
$P_{co}$	Available compressive strength out of the plane of bending, N.	10.8.1.3
$P_{e1},P_{e2}$	Elastic critical buckling load for braced and unbraced frame, respectively, N.	10.3.2.1
$P_{eL}$	Euler buckling load, evaluated in the plane of bending, N.	10.14.3
$P_{l(t,c)}$	First-order axial force using LRFD or ASD load combinations as a result of lateral translation of the frame only (tension or compression, N.	10.3.2.1
$P_{n(t,c)}$	First-order axial force using LRFD or ASD load combinations,	10.3.2.1
$P_{n(t,c)}$	assuming there is no lateral translation of the frame (tension or compression, N.
$P_n$	Nominal axial strength, N.	10.4.2
$P_n$	Nominal axial strength of a column, N.	10.20.8
$P_{nc}$	Nominal axial compressive strength of diagonal members of the special segment, N.	10.20.12
$P_{nt}$	Nominal axial tensile strength of diagonal members of special segment, N.	10.20.12
$P_{rc}$	Required compressive strength using ASD or LRFD load combinations, N.	10.20.9
$P_r$	Required second-order axial strength using LRFD or ASD load combinations, N.	10.3.2.1
$P_r$	Required axial compressive strength using LRFD or ASD load combinations, N.	10.3.2.2
$P_r$	Required tensile strength using LRFD or ASD load combinations, N.	10.8.1.2
$P_r$	Required strength, N.	10.10.10.6
$P_r$	Required axial strength in chord, N.	10.11.2.2
$P_r$	Required axial strength in branch, N.	10.11.3.2
$P_r$	Required compressive strength, N.	10.20.15
$P_u$	Required axial strength in compression, N.	10.15.4
$P_u$	Required axial strength of a column or a link in LRFD load combinations, N.	10.20.8
$P_{uc}$	Required compressive strength using LRFD load combinations, N.	10.20.9
$P_y$	Member yield strength, N.	10.3.2.2
$P_y$	Nominal axial yield strength of a member, equal to $F_yA_g$ , N.	Table 6.10.8
$P_{ysc}$	Axial yield strength of steel core, N.	10.20.16
$Q$	Full reduction factor for slender compression elements	10.5.7
$Q_a$	Reduction factor for slender stiffened compression elements	10.5.7.2
$Q_b$	Maximum unbalanced vertical load effect applied to a beam by the braces, N.	10.20.13
$Q_1$	Axial forces and moments generated by at least 1.25 times the expected nominal shear strength of the link	10.20.15
$Q_f$	Chord-stress interaction parameter	10.11.2.2
$Q_s$	Reduction factor for slender unstiffened compression elements	10.5.7.1
R	Seismic response modification coefficient	10.20.1
$R$	Seismic response modification coefficient	10.1.1.1
$R$	Nominal load due to rainwater or snow, exclusive of the ponding contribution, MPa.	10.16.2
$R_a$	Required strength (ASD)	10.2.3.4
$R_{FIL}$	Reduction factor for joints using a pair of transverse fillet welds only	10.17.3
$R_m$	Factor in Eq. 6.10.8 dependent on type of system	10.3.2.1
$R_m$	Cross-section monosymmetry parameter	10.6.1
$R_n$	Nominal strength, N.	10.2.3.3
$R_n$	Nominal strength, N.	10.20.6
$R_n$	Nominal slip resistance, N.	10.10.3.8
$R_{pc}$	Web plastification factor	10.6.4.1
$R_{PJP}$	Reduction factor for reinforced or unreinforced transverse partial-joint-penetration (PJP) groove welds	10.17.3
$R_{pt}$	Web plastification factor corresponding to the tension flange yielding limit state	10.6.4.4
$R_t$	Ratio of the expected tensile strength to the specified minimum	10.20.6
$R_t$	tensile strength $F_u$ , as related to overstrength in material yield stress $R_y$
$R_u$	Required strength (LRFD)	10.2.3.3
$R_u$	Required strength	10.20.9
$R_v$	Panel zone nominal shear strength	10.20.9
$R_{wl}$	Total nominal strength of longitudinally loaded fillet welds, as determined in accordance with Table 6.10.8	10.10.2.4
$R_{wt}$	Total nominal strength of transversely loaded fillet welds, as	10.10.2.4
$R_{wt}$	determined in accordance with Table 6.10.8 without the alternate in Sec 10.10.2.4 (a)
$R_y$	Ratio of the expected yield stress to the specified minimum yield stress, %	10.20.6
$S$	Elastic section modulus of round HSS, mm³	10.6.8.2
$S$	Lowest elastic section modulus relative to the axis of bending, mm³	10.6.12
$S$	Chord elastic section modulus, mm³	10.11.2.2
$S$	Spacing of secondary members, m	10.16.1
$S_c$	Elastic section modulus to toe in compression relative to axis of bending, mm^3.	10.6.10.3
$S_{eff}$	Effective section modulus about major axis, mm³	10.6.7.2
$S_{xt}, S_{xc}$	Elastic section modulus referred tension and compression flanges, respectively, mm³	Table 6.10.1
$S_x, S_y$	Elastic section modulus taken about the principal axes, mm³	10.6.2.2, F6
$S_y$	For channels, taken as the minimum section modulus	10.6.6
$T$	Nominal forces and deformations due to design-basis fire defined in Sec 4.2.1	10.18.1.4
$T_a$	Tension force due to ASD load combinations, kN.	10.10.3.9
$T_b$	Minimum fastener tension given in Table 6.10.9, kN.	10.10.3.8
$T_c$	Available torsional strength, N-mm.	10.8.3.2
$T_n$	Nominal torsional strength, N-mm.	10.8.3.1
$T_r$	Required torsional strength, N-mm.	10.8.3.2
$T_u$	Tension force due to LRFD load combinations, kN.	10.10.3.9
$U$	Shear lag factor	10.4.3.3
$U$	Utilization ratio	10.11.2.2
$U_{bs}$	Reduction coefficient, used in calculating block shear rupture strength	10.10.4.3
$U_p$	Stress index	10.16.2
$U_s$	Stress index	10.16.2
$V_a$	Required shear strength using ASD load combinations, N.	10.20.9
$V_c$	Available shear strength, N.	10.7.3.3
$V_n$	Nominal shear strength, N.	10.7.1
$V_n$	Nominal shear strength of a member, N.	10.20.15
$V_p$	Nominal shear strength of an active link, N.	Table 6.10.8
$V_{pa}$	Nominal shear strength of an active link modified by axial load magnitude, N.	10.20.15
$V_{ne}$	Expected vertical shear strength of the special segment, N.	10.20.12
$V_r$	Required shear strength at the location of the stiffener, N.	10.7.3.3
$V_r$	Required shear strength using LRFD or ASD load combinations, N.	10.8.3.2
$V_u$	Required shear strength using LRFD load combinations, N.	10.20.10
$Y_i$	Gravity load from the LRFD load combination or 1.6 times the ASD load combination Applied at level $i$ , N.	10.3.2.2
$Y_t$	Hole reduction coefficient, N.	10.6.13.1
$Z$	Plastic section modulus about the axis of bending, mm³	10.6.7.1
Z	Plastic section modulus of a member, mm³.	10.20.9
$Z_b$	Branch plastic section modulus about the correct axis of bending, mm³	10.11.3.3
$Z_b$	Plastic section modulus of the beam, mm³.	10.20.9
$Z_c$	Plastic section modulus of the column, mm³.	10.20.9
$Z_x$	Plastic section modulus $x$ -axis, mm³.	10.20.8
$Z_{RBS}$	Minimum plastic section modulus at the reduced beam section, mm³.	10.20.9
$Z_{x,y}$	Plastic section modulus about the principal axes, mm³	10.6.2, F6.1
$a$	Shortest distance from edge of pin hole to edge of member measured parallel to direction of force, mm.	10.4.5.1
$a$	Distance between connectors in a built-up member, mm.	10.5.6.1
$a$	Clear distance between transverse stiffeners,mm.	10.6.13.2
$a$	Half the length of the non-welded root face in the direction of the thickness of the tension-loaded plate, mm.	10.17.3
a	Angle that diagonal members make with the horizontal	10.20.12
$a_w$	Ratio of two times the web area in compression due to Application of major axis bending moment alone to the area of the compression flange components	10.6.4.2
$b$	Width of unstiffened compression element; for flanges of I-shaped members and tees, the width $b$ is half the full-flange width, $b_f$ ; for legs of angles and flanges of channels and zees, the width $b$ is the full nominal dimension; for plates, the width $b$ is the distance from free edge to the first row of fasteners or line of welds, or the distance between adjacent lines of fasteners or lines of welds; for rectangular HSS, width $b$ is the clear distance between the webs less the inside corner radius on each side, mm.	10.2.4.1, 10.2.4.2
$b$	Full width of longest angle leg, mm.	10.5.7.1
$b$	Outside width of leg in compression, mm.	10.6.10.3
$b$	Width of the angle leg resisting the shear force, mm.	10.7.4
b	Width of compression element as defined in Specification Sec 10.2.4.1, mm.	Table 6.10.8
$b_{cf}$	Width of column flange, mm.	10.10.10.6
$b_{cf}$	Width of column flange, mm.	10.20.9
$b_e$	Reduced effective width,mm.	10.5.7.2
$b_{eff}$	Effective edge distance; the distance from the edge of the hole to the edge of the part measured in the direction normal to the applied force, mm.	10.4.5.1
$b_{eoi}$	Effective width of the branch face welded to the chord	10.11.2.3
$b_{eov}$	Effective width of the branch face welded to the overlapped brace.	10.11.2.3
$b_f$	Flange width, mm.	10.2.4.1
$b_f$	Flange width, mm.	10.20.9
$b_{fc}$	Compression flange width, mm.	10.6.4.2
$b_{ft}$	Width of tension flange, mm.	10.7.3.1
$b_l$	Longer leg of angle, mm.	10.5.5
$b_s$	Shorter leg of angle, mm.	10.5.5
$b_s$	Stiffener width for one-sided stiffeners, mm.	10.19.2
$d$	Full nominal depth of section, mm.	10.2.4.1
$d$	Pin diameter,mm.	10.4.5.1
$d$	Full nominal depth of tee, mm.	10.5.7.1
$d$	Depth of rectangular bar, mm.	10.6.11.2
$d$	Nominal fastener diameter, mm.	10.10.3.3
$d$	Diameter, mm.	10.10.7
$d$	Roller diameter,mm.	10.10.7
d	Nominal fastener diameter, mm.	10.20.7
d	Overall beam depth, mm.	10.20.15
$d_b$	Beam depth,mm.	10.10.10.6
$d_b$	Nominal diameter (body or shank diameter), mm.	10.17.4
$d_c$	Column depth, mm.	10.10.10.6
$d_c$	Overall column depth, mm.	10.20.9
$d_z$	Overall panel zone depth between continuity plates, mm.	10.20.9
$e$	Eccentricity in a truss connection, positive being away from the branches, mm.	10.11.2.1
e	EBF link length, mm.	10.20.15
$f_a$	Required axial stress at point of consideration of LRFD or ASD load combinations, MPa.	10.8.2
$f_{b(w,z)}$	Required flexural stress at the point of consideration (major axis, minor axis) using LRFD or ASD load combinations, MPa.	10.8.2
$f_{cm}'$	Specified minimum compressive strength of concrete at elevated temperatures, MPa.	10.18.2
$f_o$	Stress due to D + R (the nominal dead load + the nominal load	10.16.2
$f_o$	due to rainwater or snow exclusive of the ponding contribution, MPa.
$f_v$	Required shear strength per unit area, MPa.	10.10.3.7
$g$	Transverse center-to-center spacing (gage) between fastener gage lines, mm.	10.2.3.13
$g$	Gap between toes of branch members in a gapped K- connection, neglecting welds, mm.	10.11.2.1
$h$	Clear distance between flanges less the fillet or corner radius for rolled shapes; for built-up sections, the distance between adjacent lines of fasteners or the clear distance between flanges when welds are used; for tees, the overall depth; for rectangular HSS, the clear distance between the flanges less the inside corner radius on each side, mm.	10.2.4.2, Table 6.10.8
$h$	Distance between centroids of individual components perpendicular to the member axis of buckling,mm.	10.5.6.1
h	Distance between horizontal boundary element centerlines, mm.	10.20.17
$h_c$	Twice the distance from the centroid to the following: the inside face of the compression flange less the fillet or corner radius, for rolled shapes; the nearest line of fasteners at the compression flange or the inside faces of the compression flange when welds are used, for built-up sections, mm.	10.2.4.2
$h_o$	Distance between flange centroids, mm.	10.6.2.2
$h_o$	Distance between flange centroids, mm	10.20.9
$h_p$	Twice the distance from plastic neutral axis to the nearest line	10.2.4.2
$h_p$	of fasteners at the compression flange or inside face of compression flange when welds are used, mm
$h_{sc}$	Hole factor	10.10.3.8
$j$	Factor defined by Eq. 6.10.141 for minimum moment of inertia for a transverse stiffener	10.7.2.2
$k$	Distance from outer face of flange to the web toe of fillet, mm.	10.10.10.2
$k$	Outside corner radius of HSS, which is permitted to be taken as 1.5 $t$ if unknown, mm.	10.11.1.3
$k_c$	Coefficient for slender unstiffened elements, mm.	Table 6.10.1
$k_s$	Slip-critical combined tension and shear coefficient	10.10.3.9
$k_v$	Web plate buckling coefficient	10.7.2.1
$l$	Largest laterally unbraced length along either flange at the point of load, mm.	10.10.10.4
$l$	Length of bearing,mm.	10.10.7
$l$	Length of connection in the direction of loading,mm.	Table 6.10.2
l	Unbraced length between stitches of built-up bracing members,mm.	10.20.13
l	Unbraced length of compression or bracing member, mm.	10.20.13
$n$	Number of nodal braced points within the span	10.19.2
$n$	Threads per mm.	10.17.4
$p$	Ratio of element $i$ deformation to its deformation at maximum stress	10.10.2.4
$p$	Projected length of the overlapping branch on the chord	10.11.2.2
$q$	Overlap length measured along the connecting face of the chord beneath the two branches	10.11.2.2
$r$	Governing radius of gyration, mm.	10.5.2
r	Governing radius of gyration, mm.	10.20.13
$r_{crit}$	Distance from instantaneous center of rotation to weld element with minimum $\Delta_u/r_i$ ratio, mm.	10.10.2.4
$r_i$	Minimum radius of gyration of individual component in a built- up member, mm.	10.5.6.1
$r_{ib}$	Radius of gyration of individual component relative to its centroidal axis parallel to member axis of buckling, mm.	10.5.6.1
$\bar{r}_o$	Polar radius of gyration about the shear center,mm.	10.5.4
$r_t$	Radius of gyration of the flange components in flexural compression plus one-third of the web area in compression due to application of major axis bending moment alone	10.6.4.2
$r_{ts}$	Effective radius of gyration used in the determination of $L_r$ for	10.6.2.2
$r_{ts}$	the lateral-torsional buckling limit state for major axis bending of doubly symmetric compact I-shaped members and channels
$r_x$	Radius of gyration about geometric axis parallel to connected leg, mm.	10.5.5
$r_y$	Radius of gyration about y-axis, mm.	10.5.4
$r_y$	Radius of gyration about $y$ -axis, mm.	10.20.9
$r_z$	Radius of gyration for the minor principal axis, mm.	10.5.5
$s$	Longitudinal center-to-center spacing (pitch) of any two consecutive holes, mm.	10.2.3.13
$t$	Thickness of element, mm.	10.2.4.2
t	Thickness of element, mm.	Table 6.10.8
$t$	Wall thickness, mm.	10.5.7.2
$t$	Angle leg thickness, mm.	10.6.10.2
$t$	Width of rectangular bar parallel to axis of bending, mm.	10.6.11.2
$t$	Thickness of connected material, mm.	10.10.3.10
$t$	Thickness of plate, mm.	10.4.5.1
$t$	Design wall thickness for HSS equal to 0.93 times the nominal wall thickness for ERW HSS and equal to the nominal wall thickness for SAW HSS, mm.	10.2.3.12
$t$	Total thickness of fillers, mm.	10.10.5
t	Thickness of connected part, mm.	10.20.7
t	Thickness of column web or doubler plate, mm.	10.20.9
$t$	Design wall thickness of HSS main member, mm.	10.11.3.1
$t$	Design wall thickness of HSS main member, mm.	10.11.2.1
$t$	Design wall thickness of HSS member, mm.	10.11.1.1
$t_b$	Design wall thickness of HSS branch member, mm.	10.11.2.1
$t_b$	Design wall thickness of HSS branch member, mm.	10.11.3.1
$t_{bf}$	Thickness of beam flange, mm.	10.20.9
$t_{bj}$	Thickness of the overlapped branch,mm.	10.11.2.3
$t_{cf}$	Thickness of the column flange,mm.	10.10.10.6
$t_{cf}$	Thickness of column flange, mm.	10.20.9
$t_f$	Thickness of the loaded flange, mm.	10.10.10.1
$t_f$	Thickness of flange, mm.	10.20.17
$t_{fc}$	Compression flange thickness, mm.	10.6.4.2
$t_p$	Thickness of plate, mm.	10.11.1.1
$t_p$	Thickness of the attached transverse plate, mm.	10.11.2.3
$t_p$	Thickness of tension loaded plate, mm.	10.17.3
$t_p$	Thickness of panel zone including doubler plates, mm.	10.20.9
$t_s$	Web stiffener thickness, mm.	10.19.2
$t_w$	Web thickness, mm.	Table 6.10.1
$t_w$	Thickness of web, mm.	Table6.10.8
$t_w$	Thickness of element, mm.	10.5.7.1
$t_w$	Column web thickness, mm.	10.10.10.6
$t_w$	Beam web thickness, mm.	10.19.3
$w$	Width of cover plate, mm.	10.6.13.3
$w$	Weld leg size, mm.	10.10.2.2
$w$	Plate width, mm.	Table 6.10.2
$w$	Leg size of the reinforcing or contouring fillet, if any, in the direction of the thickness of the tension-loaded plate, mm.	10.17.3
$w_z$	Width of panel zone between column flanges, mm.	10.20.9
x	Parameter used for determining the approximate fundamental period	Appendix P.2
$x_o,y_o$	Coordinates of the shear center with respect to the centroid, mm.	10.5.4
$\bar{x}$	Connection eccentricity,mm.	Table 6.10.2
$y$	Subscript relating symbol to weak axis
$z$	Subscript relating symbol to minor principal axis bending
$Z_b$	Minimum plastic section modulus at the reduced beam section, mm³	10.20.9
$\alpha$	Factor used in Eq. 6.10.2.2	10.3.2.1
$\alpha$	Separation ratio for built-up compression members $=h/(2r_{ib})$	10.5.6.1
$\alpha$	Angle of diagonal members with the horizontal	10.20.12
$\alpha$	Angle of web yielding in radians, as measured relative to the vertical	10.20.17
$\beta$	Reduction factor given by Eq. 6.10.159	10.10.2.2
$\beta$	The width ratio; the ratio of branch diameter to chord diameter	10.11.2.1,
$\beta$	$= D_b/D$ for round HSS; the ratio of overall branch width to chord width $= B_b/B$ for rectangular HSS	10.11.3.1
$\beta$	Compression strength adjustment factor	10.20.16
$\beta_T$	Brace stiffness requirement excluding web distortion, N-mm/radian.	10.19.2
$\beta_{br}$	Required brace stiffness	10.19.2
$\beta_{eff}$	Effective width ratio; the sum of the perimeters of the two branch members in a K-connection divided by eight times the chord width	10.11.2.1
$\beta_{eop}$	Effective outside punching parameter	10.11.2.3
$\beta_{sec}$	Web distortional stiffness, including the effect of web transverse stiffeners, if any, N-mm/radian.	10.19.2
$\beta_w$	Section property for unequal leg angles, positive for short legs in compression and negative for long legs in compression	10.6.10.2
$\Delta$	First-order interstory drift due to the design loads,mm.	10.3.2.2
$\Delta$	Design story drift	10.20.15
$\Delta_b$	Deformation quantity used to control loading of test specimen (total brace end rotation for the sub-assemblage test specimen; total brace axial deformation for the brace test specimen)	Appendix R.2
$\Delta_{bm}$	Value of deformation quantity, $\Delta_b$ , corresponding to the design story drift	Appendix R.6
$\Delta_{by}$	Value of deformation quantity, $\Delta_b$ , at first significant yield of test specimen	Appendix R.6
$\Delta_h$	First-order interstory drift due to lateral forces,mm.	10.3.2.1
$\Delta_i$	Deformation of weld elements at intermediate stress levels, linearly proportioned to the critical deformation based on distance from instantaneous center of rotation, $r_i$ , mm.	10.10.2.4
$\Delta_m$	Deformation of weld element at maximum stress,mm.	10.10.2.4
$\Delta_u$	Deformation of weld element at ultimate stress (fracture), usually in element furthest from instantaneous center of rotation, mm.	10.10.2.4
$\delta$	Deformation quantity used to control loading of test specimen	Appendix Q.6
$\delta_y$	Value of deformation quantity $\delta$ at first significant yield of test specimen	Appendix Q.6
$\rho'$	Ratio of required axial force $P_u$ to required shear strength $V_u$ of a link	10.20.15
$\gamma$	The chord slenderness ratio; the ratio of one-half the diameter to the wall thickness $=D/(2t)$ for round HSS; the ratio of one- half the width to wall thickness $=B/(2t)$ for rectangular HSS	10.11.2.1, 10.11.3.1
$\xi$	The gap ratio; the ratio of the gap between the branches of a gapped K-connection to the width of the chord = g/ B for rectangular HSS	10.11.2.1
$\eta$	The load length parameter, applicable only to rectangular HSS; the ratio of the length of contact of the branch with the chord in the plane of the connection to the chord width $=N/B$ , where $N = H_b/\sin\theta$	10.11.2.1, 10.11.3.1
$\lambda$	Slenderness parameter	10.6.3
$\lambda_p$	Limiting slenderness parameter for compact element	10.2.4
$\lambda_{pf}$	Limiting slenderness parameter for compact flange	10.6.3
$\lambda_{pw}$	Limiting slenderness parameter for compact web	10.6.4
$\lambda_r$	Limiting slenderness parameter for noncompact element	10.2.4
$\lambda_{rf}$	Limiting slenderness parameter for noncompact flange	10.6.3
$\lambda_{rw}$	Limiting slenderness parameter for noncompact web	10.6.4
$\lambda_p,\lambda_{ps}$	Limiting slenderness parameter for compact element	10.20.8
$\mu$	Mean slip coefficient for class A or B surfaces, as Applicable, or as established by tests	10.10.3.8
$\phi$	Resistance factor	10.2.3.3
$\phi$	Resistance factor	10.20.6
$\phi_b$	Resistance factor for flexure	10.6.1
$\phi_b$	Resistance factor for flexure	10.20.8
$\phi_c$	Resistance factor for compression	10.5.1
$\phi_c$	Resistance factor for compression	10.20.8
$\phi_{sf}$	Resistance factor for shear on the failure path	10.4.5.1
$\phi_T$	Resistance factor for torsion	10.8.3.1
$\phi_t$	Resistance factor for tension	10.4.2
$\phi_v$	Resistance factor for shear	10.7.1
$\phi_v$	Resistance factor for shear strength of panel zone of beam- to-column connections	10.20.9
$\phi_v$	Resistance factor for shear	10.20.15
$\phi_{total}$	Link rotation angle	Appendix Q.2
$\Omega$	Safety factor	10.2.3.4
$\Omega$	Safety factor	10.20.6
$\Omega_b$	Safety factor for flexure	10.6.1
$\Omega_b$	Safety factor for flexure = 1.67	10.20.8
$\Omega_c$	Safety factor for compression	10.5.1
$\Omega_c$	Safety factor for compression = 1.67	10.20.8
$\Omega_{sf}$	Safety factor for shear on the failure path	10.4.5.1
$\Omega_T$	Safety factor for torsion	10.8.3.1
$\Omega_t$	Safety factor for tension	10.4.2
$\Omega_v$	Safety factor for shear	10.7.1
$\Omega_v$	Safety factor for shear strength of panel zone of beam-to- column connections	10.20.9
$\Omega_o$	Horizontal seismic overstrength factor	10.20.4
$\theta$	Angle of loading measured from the weld longitudinal axis, degrees	10.10.2.4
$\theta$	Acute angle between the branch and chord, degrees	10.11.2.1
$\theta$	Acute angle between the branch and chord, degrees	10.11.3.1
$\theta$	Interstory drift angle, radians	Appendix Q.3
$\omega$	Strain hardening adjustment factor	10.20.16
$\varepsilon_{cu}$	Strain corresponding to compressive strength of concrete, $f_c'$	10.18.2
$\tau_b$	Parameter for reduced flexural stiffness using the direct analysis method	10.14.3
Σ^∗	Moment at beam and column centerline determined by projecting the sum of the nominal column plastic moment strength, reduced by the axial stressH/, from the top and bottom of the beam moment connection	10.20.9
Σ^∗	Moment at the intersection of the beam and column centerlines determined by projecting the beam maximum developed moments from the column face. Maximum developed moments shall be determined from test results	10.20.9

10.1.2.2 Definitions

ACTIVE FIRE PROTECTION	Building materials and systems that are activated by a fire to mitigate adverse effects or to notify people to take some action to mitigate adverse effects.
ADJUSTED BRACE STRENGTH	Strength of a brace in a buckling-restrained braced frame at deformations corresponding to 2.0 times the design story drift.
ALLOWABLE STRENGTH*	Nominal strength divided by the safety factor, J/Ω.
ALLOWABLE STRESS	Allowable strength divided by the appropriate section property, such as section modulus or cross- section area.
AMPLIFICATION FACTOR	Multiplier of the results of first-order analysis to reflect second-order effects.
AMPLIFIED SEISMIC LOAD	Horizontal component of earthquake load multiplied byΩF, whereand the horizontal component ofare specified in the Code.
APPLICABLE BUILDING CODE	Building Code under which the structure is designed.
ASD(ALLOWABLE STRENGTH DESIGN)	Method of proportioning structural components such that the allowable strength equals or exceeds the required strength of the component under the action of the ASD load combinations.
ASD LOAD COMBINATION	Load combination in the Code intended for allowable strength design (allowable stress design).
AUTHORITY HAVING JURISDICTION	Organization, political subdivision, office or individual charged with the responsibility of administering and enforcing the provisions of the Code.
AVAILABLE STRENGTH*	Design strength or allowable strength, as appropriate.
AVAILABLE STRESS^*	Design stress or allowable stress, as appropriate.
AVERAGE RIB WIDTH	Average width of the rib of a corrugation in a formed steel deck.
AUTHORITY HAVING JURISDICTION (AHJ)	Organization, political subdivision, office or individual charged with the responsibility of administering and enforcing the provisions of this Code.
BATTEN PLATE	Plate rigidly connected to two parallel components of a built-up column or beam designed to transmit shear between the components.
BEAM	Structural member that has the primary function of resisting bending moments. Beam-column. Structural member that resists both axial force and bending moment. Bearing. In a bolted connection, limit state of shear forces transmitted by the bolt to the connection elements.
BEARING (LOCAL COMPRESSIVE YIELDING)	Limit state of local compressive yielding due to the action of a member bearing against another member or surface.
BEARING-TYPE CONNECTION	Bolted connection where shear forces are transmitted by the bolt bearing against the connection elements.
BLOCK SHEAR RUPTURE	In a connection, limit state of tension fracture along one path and shear yielding or shear fracture along another path.
BRACED FRAME	An essentially vertical truss system that provides resistance to lateral forces and provides stability for the structural system.
BRANCH FACE	Wall of HSS branch member.
BRANCH MEMBER	For HSS connections, member that terminates at a chord member or main member.
BUCKLING	Limit state of sudden change in the geometry of a structure or any of its elements under a critical loading condition.
BUCKLING STRENGTH	Nominal strength for buckling or instability limit states.
BUCKLING-RESTRAINED BRACED FRAME (BRBF)	Diagonally braced frame safisfying the requirements of Section16 in which all members of the bracing system are subjected primarily to axial forces and in which the limit state of compression buckling of braces is precluded at forces and deformations corresponding to 2.0 times the design story drift.
BUCKLING-RESTRAINING SYSTEM	System of restraints that limits buckling of the steel core in BRBF. This system includes the casing on the steel core and structural elements adjoining its connections. The buckling-restraining system is intended to permit the transverse expansion and longitudinal contraction of the steel core for deformations corresponding to 2.0 times the design story drift.
BUILT-UP MEMBER, CROSS- SECTION, SECTION, SHAPE	Member, cross-section, section or shape fabricated from structural steel elements that are welded or bolted together.
CAMBER	Curvature fabricated into a beam or truss so as to compensate for deflection induced by loads.
CASING	Element that resists forces transverse to the axis of the brace there by restraining buckling of the core. The casing requires a means of delivering this force to the remainder of the buckling-restraining system. The casing resists little or no force in the axis of the brace.
CHARPY V-NOTCH IMPACT TEST	Standard dynamic test measuring notch toughness of a specimen.
CHORD MEMBER	For HSS, primary member that extends through a truss connection.
CLADDING	Exterior covering of structure.
COLD-FORMED STEEL STRUCTURAL MEMBER	Shape manufactured by press-braking blanks sheared from sheets, cut lengths of coils or plates, or by roll forming cold-or hot-rolled coils or sheets; both forming operations being performed at ambient room temperature, that is, without manifest addition of heat such as would be required for hot forming.
COLUMN	Structural member that has the primary function of resisting axial force.
COLUMN BASE	Assemblage of plates, connectors, bolts, and rods at the base of a column used to transmit forces
	between the steel superstructure and the foundation.
COMBINED SYSTEM	Structure comprised of two or more lateral load- resisting systems of different type.
COMPACT SECTION	Section capable of developing a fully plastic stress distribution and possessing a rotation capacity of approximately three before the onset of local buckling.
COMPARTMENTATION	The enclosure of a building space with elements that have a specific fire endurance.
COMPLETE-JOINT- PENETRATION GROOVE WELD (CJP)	Groove weld in which weld metal extends through the joint thickness, except as permitted for HSS connections.
COMPOSITE	Condition in which steel and concrete elements and members work as a unit in the distribution of internal forces.
CONCRETE CRUSHING	Limit state of compressive failure in concrete having reached the ultimate strain.
CONCRETE HAUNCH	Section of solid concrete that results from stopping the deck on each side of the girder in a composite floor system constructed using a formed steel deck.
CONCRETE-ENCASED BEAM	Beam totally encased in concrete cast integrally with the slab.
CONNECTION	Combination of structural elements and joints used to transmit forces between two or more members.
CONVECTIVE HEAT	The transfer of thermal energy from a point of
TRANSFER	higher temperature to a point of lower temperature through the motion of an intervening medium.
CONTINUITY PLATES	Column stiffeners at the top and bottom of the panel zone; also known as transverse stiffeners.
CONTRACTOR	Fabricator or erector, as applicable.
COPE	Cutout made in a structural member to remove a flange and conform to the shape of an intersecting member.
COVER PLATE	Plate welded or bolted to the flange of a member to increase cross-sectional area, section modulus or moment of inertia.
CROSS CONNECTION	HSS connection in which forces in branch members or connecting elements transverse to the main member are primarily equilibrated by forces in other branch members or connecting elements on the opposite side of the main member.
DEMANDCRITICAL WELD	Weld so designated by these Provisions.
DESIGNEARTHQUAKE	The earthquake represented by the design response spectrum as specified in the Code.
DESIGNSTORYDRIFT	Amplified story drift (drift under the design earthquake, including the effects of inelastic action), determined as specified in the Code.
DESIGN-BASIS FIRE	A set of conditions that define the development of a fire and the spread of combustion products throughout a building or portion thereof.
DESIGN LOAD^*	Applied load determined in accordance with either LRFD load combinations or ASD load combinations, whichever is applicable.
DESIGN STRENGTH*	Resistance factor multiplied by the nominal strength,{J.
DESIGN STRESS RANGE	Magnitude of change in stress due to the repeated application and removal of service live loads. For locations subject to stress reversal it is the algebraic difference of the peak stresses.
DESIGN STRESS^*	Design strength divided by the appropriate section property, such as section modulus or cross section area.
DESIGN WALL THICKNESS	HSS wall thickness assumed in the determination of section properties.
DIAGONAL BRACING	Inclined structural member carrying primarily axial force in a braced frame.
DIAGONAL STIFFENER	Web stiffener at column panel zone oriented diagonally to the flanges, on one or both sides of the web.
DIAPHRAGM PLATE	Plate possessing in-plane shear stiffness and strength, used to transfer forces to the supporting elements.
DIAPHRAGM	Roof, floor or other membrane or bracing system that transfers in-plane forces to the lateral force resisting system.
DIRECT ANALYSIS METHOD	Design method for stability that captures the effects of residual stresses and initial out-of-plumbness of frames by reducing stiffness and applying notional loads in a second-order analysis.
DIRECT BOND INTERACTION	Mechanism by which force is transferred between steel and concrete in a composite section by bond stress.
DISTORTIONAL FAILURE	Limit state of an HSS truss connection based on distortion of a rectangular HSS chord member into a rhomboidal shape.
DISTORTIONAL STIFFNESS	Out-of-plane flexural stiffness of web.
DOUBLE CURVATURE	Deformed shape of a beam with one or more inflection points within the span.
DOUBLE-CONCENTRATED FORCES	Two equal and opposite forces that form a couple on the same side of the loaded member.
DOUBLER	Plate added to, and parallel with, a beam or column web to increase resistance to concentrated forces.
DRIFT	Lateral deflection of structure.
DUAL SYSTEM	Structural system with the following features (1) an essentially complete space frame that provides support for gravity loads; (2) resistance to lateral load provided by moment frames (SMF, IMF or OMF) that are capable of resisting atleast 25 percent of the base shear, and concrete or steel shearwalls, or steel braced frames (EBF,S CBF or OCBF); and (3) each system designed to resist the total lateral load in proportion to its relative rigidity.
DUCTILE LIMIT STATE	Ductile limit states include member and connection yielding, bearing deformation at bolt holes, as well as buckling of members that conform to the width- thickness limitations of Table 6.10.18. Fracture of a member or of a connection, or buckling of a connection element, is not a ductile limit state.
ECCENTRICALLY BRACED FRAME (EBF)	Diagonally braced frame meeting there quirements of Section 15 that has at least one end of each bracing member connected to a beam a short distance from another beam-to-brace connection or a beam-to-column connection.
EFFECTIVE LENGTH FACTOR, K	Ratio between the effective length and the unbraced length of the member.
EFFECTIVE LENGTH	Length of an otherwise identical column with the same strength when analyzed with pinned end conditions.
EFFECTIVE NET AREA	Net area modified to account for the effect of shear lag.
EFFECTIVE SECTION MODULUS	Section modulus reduced to account for buckling of slender compression elements.
EFFECTIVE WIDTH	Reduced width of a plate or slab with an assumed uniform stress distribution which produces the same effect on the behavior of a structural member as the actual plate or slab width with its nonuniform stress distribution.
ELASTIC ANALYSIS	Structural analysis based on the assumption that the structure returns to its original geometry on removal of the load.
ELEVATED TEMPERATURES	Heating conditions experienced by building elements or structures as a result of fire, which are in excess of the anticipated ambient conditions.
ENCASED COMPOSITE COLUMN	Composite column consisting of a structural concrete column and one or more embedded steel shapes.
END PANEL	Web panel with an adjacent panel on one side only.
ENGINEER OF RECORD	Engineer having authority or license from government approved Authority to sign and seal engineering and contract documents.
END RETURN	Length of fillet weld that continues around a corner in the same plane. Engineer of record. Licensed professional responsible for sealing the contract documents. Expansion rocker. Support with curved surface on which a member bears that can tilt to accommodate expansion.
EXPANSION ROLLER	Round steel bar on which a member bears that can roll to accommodate expansion.
EXEMPTED COLUMN	Column not meeting the requirements of Eq. 6.10.300 for SMF.
EXPECTED TENSILE	Tensile strength of a member, equal to the specified
STRENGTH *	minimum tensile strength, , multiplied byJ.
EXPECTED YIELD STRENGTH	Yield strength in tension of a member, equal to the expected yield stress multiplied by.
EXPECTED YIELD STRESS	Yield stress of the material, equal to the specified minimum yield stress, %,multiplied byJ%.
EYEBAR	Pin-connected tension member of uniform thickness, with forged or thermally cut head of greater width than the body, proportioned to provide approximately equal strength in the head and body.
FACTORED LOAD	Product of a load factor and the nominal load. Fastener. Generic term for bolts, rivets, or other connecting devices.
FATIGUE	Limit state of crack initiation and growth resulting from repeated application of live loads.
FAYING SURFACE	Contact surface of connection elements transmitting a shear force.
FILLED COMPOSITE COLUMN	Composite column consisting of a shell of HSS or pipe filled with structural concrete.
FILLER METAL	Metal or alloy to be added in making a welded joint. Filler. Plate used to build up the thickness of one component. Fillet weld reinforcement. Fillet welds added to groove welds.
FILLET WELD	Weld of generally triangular cross section made between intersecting surfaces of elements.
FIRE	Destructive burning, as manifested by any or all of the following: light, flame, heat, or smoke.
FIRE BARRIER	Element of construction formed of fire-resisting materials and tested in accordance with ASTM Standard E119, or other approved standard fire resistance test, to demonstrate compliance with the Building Code.
FIRE ENDURANCE	A measure of the elapsed time during which a material or assembly continues to exhibit fire resistance.
FIRE RESISTANCE	That property of assemblies that prevents or retards the pas- sage of excessive heat, hot gases or flames under conditions of use and enables them to continue to perform a stipulated function.
FIRE RESISTANCE RATING	The period of time a building element, component or assembly maintains the ability to contain a fire, continues to perform a given structural function, or both, as determined by test or methods based on tests.
FIRST-ORDER ANALYSIS	Structural analysis in which equilibrium conditions are formulated on the undeformed structure; second-order effects are neglected.
FITTED BEARING STIFFENER	Stiffener used at a support or concentrated load that fits tightly against one or both flanges of a beam so as to transmit load through bearing.
FLASHOVER	The rapid transition to a state of total surface involvement in a fire of combustible materials within an enclosure.
FLARE BEVEL GROOVE WELD	Weld in a groove formed by a member with a curved surface in contact with a planar member.
FLARE V-GROOVE WELD	Weld in a groove formed by two members with curved surfaces.
FLAT WIDTH	Nominal width of rectangular HSS minus twice the outside corner radius. In absence of knowledge of the corner radius, the flat width may be taken as the total section width minus three times the thickness.
FLEXURAL BUCKLING	Buckling mode in which a compression member deflects laterally without twist or change in cross- sectional shape.
FLEXURAL-TORSIONAL BUCKLING	Buckling mode in which a compression member bends and twists simultaneously without change in cross-sectional shape.
FORCE	Resultant of distribution of stress over a prescribed area.
FORMED SECTION	See cold-formed steel structural member.
FORMED STEEL DECK	In composite construction, steel cold formed into a decking profile used as a permanent concrete form.
FULLY RESTRAINED MOMENT CONNECTION	Connection capable of transferring moment with negligible rotation between connected members.
GAGE	Transverse center-to-center spacing of fasteners.
GAP CONNECTION	HSS truss connection with a gap or space on the chord face between intersecting branch members.
GENERAL COLLAPSE	Limit state of chord plastification of opposing sides
	of a round HSSchord member at a cross- connection.
GEOMETRIC AXIS	Axis parallel to web, flange or angle leg.
GIRDER FILLER	Narrow piece of sheet steel used as a fill between edge of a deck sheet and flange of a girder in a composite floor system constructed using a formed steel deck.
GIRDER	See Beam.
GIRT	Horizontal structural member that supports wall panels and is primarily subjected to bending under horizontal loads, such as wind load.
GOUGE	Relatively smooth surface groove or cavity resulting from plastic deformation or removal of material.
GRAVITY AXIS	Axis through the center of gravity of a member along its length.
GRAVITY FRAME	Portion of the framing system not included in the lateral load resisting system.
GRAVITY LOAD	Load, such as that produced by dead and live loads, acting in the downward direction.
GRIP (OF BOLT)	Thickness of material through which a bolt passes.
GROOVE WELD	Weld in a groove between connection elements. See also AWS D1.1.
GUSSET PLATE	Plate element connecting truss members or a strut or brace to a beam or column.
HEAT FLUX	Radiant energy per unit surface area.
HEAT RELEASE RATE	The rate at which thermal energy is generated by a burning material.
HORIZONTAL SHEAR	Force at the interface between steel and concrete surfaces in a composite beam.
HSS	Square, rectangular or round hollow structural steel section produced in accordance with a pipe or tubing product specification.
INELASTIC ANALYSIS	Structural analysis that takes into account inelastic material behavior, including plastic analysis.
IN-PLANE INSTABILITY	Limit state of a beam-column bent about its major axis while lateral buckling or lateral-torsional buckling is prevented by lateral bracing.
INSTABILITY	Limit state reached in the loading of a structural component, frame or structure in which a slight disturbance in the loads or geometry produces large displacements.
INTERMEDIATE MOMENT FRAME (IMF)	Moment frame system that meets the requirements of Sec 10.20.10.
INTERSTORY DRIFT ANGLE	Interstory displacement divided by story height, radians.
INVERTED-V-BRACED FRAME	See V-braced frame.
JOINT ECCENTRICITY	For HSS truss connection, perpendicular distance from chord member center of gravity to intersection of branch member work points.
JOINT	Area where two or more ends, surfaces, or edges are attached. Categorized by type of fastener or weld used and method of force transfer.
K-AREA	The_k-area_is the region of the web that extends from the tangent point of the web and the flange- web fillet (AISC “k” dimension) a distance of 38 mm in to the web beyond the “k” dimension.
K-BRACED FRAME	A bracing configuration in which braces connect to a column at a location with no diaphragm or other out-of-plane support.
K-CONNECTION	HSS connection in which forces in branch members or connecting elements transverse to the main member are primarily equilibrated by forces in other branch members or connecting elements on the same side of the main member.
KSI	Kip per square inch, a US customary unit of stress.
LOWEST ANTICIPATED SERVICE TEMPERATURE (LAST)	The lowest1-hour average temperature with a 100-year mean recurrence interval.
LRFD (LOAD AND RESISTANCE FACTOR DESIGN)	Method of proportioning structural components such that the design strength equals or exceeds the required strength of the component under the action of the LRFD load combinations.
LRFD LOAD COMBINATION	Load combination in the Code intended for strength design (load and resistance factor design).
LACING	Plate, angle or other steel shape, in a lattice configuration, that connects two steel shapes together.
LAP JOINT	Joint between two overlapping connection elements in parallel planes.
LATERAL BRACING	Diagonal bracing, shear walls or equivalent means for providing in-plane lateral stability.
LATERAL BRACING MEMBER	Member that is designed to inhibit lateral buckling or lateral- torsional buckling of primary framing members.
LATERAL LOAD RESISTING SYSTEM	Structural system designed to resist lateral loads and provide stability for the structure as a whole.
LATERAL LOAD	Load that produced by wind or earthquake effects, acting in a lateral direction.
LATERAL-TORSIONAL BUCKLING	Buckling mode of a flexural member involving deflection normal to the plane of bending occurring simultaneously with twist about shear center of the cross-section.
LEANING COLUMN	Column designed to carry gravity loads only, with connections that are not intended to provide resistance to lateral loads.
LENGTH EFFECTS	Consideration of the reduction in strength of a member based on its unbraced length.
LIMIT STATE	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 have reached its ultimate load-carrying capacity (strength limit state).
LINK	In EBF, the segment of a beam that is located between the ends of two diagonal braces or between the end of a diagonal brace and a column. The length of the link is defined as the clear distance between the end soft wodiagonal braces or between the diagonal brace and the column face.
LINK INTERMEDIATE WEB STIFFENERS	Vertical web stiffeners placed within the link in EBF.
LINK ROTATION ANGLE	Inelastic angle between the link and the beam outside of the link when the total story drift is equal to the design story drift.
LINK SHEAR DESIGN STRENGTH	Lesser of the available shear strength of the link developed from the moment or shear strength of the link.
LOAD	Force or other action that results from the weight of building materials, occupants and their possessions, environmental effects, differential movement, or restrained dimensional changes.
LOAD EFFECT	Forces, stresses and deformations produced in a structural component by the applied loads.
LOAD FACTOR	Factor that accounts for deviations of the nominal load from the actual load, for uncertainties in the analysis that transforms the load into a load effect and for the probability that more than one extreme load will occur simultaneously.
LOCAL BENDING^**	Limit state of large deformation of a flange under a concentrated tensile force.
LOCAL BUCKLING^**	Limit state of buckling of a compression element within a cross section.
LOCAL CRIPPLING^**	Limit state of local failure of web plate in the immediate vicinity of a concentrated load or reaction.
LOCAL YIELDING^**	Yielding that occurs in a local area of an element.
LRFD (LOAD AND RESISTANCE FACTOR DESIGN)	Method of proportioning structural components such that the design strength equals or exceeds the required strength of the component under the action of the LRFD load combinations.
LRFD LOAD COMBINATION	Load combination in the Code intended for strength design (load and resistance factor design.
MAIN MEMBER	For HSS connections, chord member, column or other HSS member to which branch members or other connecting elements are attached.
MEASURED FLEXURAL RESISTANCE	Bending moment measured in a beam at the face of the column, for a beam-to-column test specimen tested in accordance with Appendix S.
MECHANISM	Structural system that includes a sufficient number of real hinges, plastic hinges or both, so as to be able to articulate in one or more rigid body modes.

Overview

BNBC 2020

Part I - Administration

Part II - Development Control

Part III - General Building Requirements

Part IV - Fire Protection

Part V - Building Materials

Part VI - Structural Design

10.1 General Provisions for Structural Steel Buildings and Structures

10.1.1 Scope

10.1.1.1 Low-seismic applications

10.1.1.2 High-seismic applications

10.1.2 Symbols, Glossary and Referenced Specifications, Codes and Standards

10.1.2.1 Symbols

10.1.2.2 Definitions

​10.1 General Provisions for Structural Steel Buildings and Structures

​10.1.1 Scope

​10.1.1.1 Low-seismic applications

​10.1.1.2 High-seismic applications

​10.1.2 Symbols, Glossary and Referenced Specifications, Codes and Standards

​10.1.2.1 Symbols

​10.1.2.2 Definitions

10.1 General Provisions for Structural Steel Buildings and Structures

10.1.1 Scope

10.1.1.1 Low-seismic applications

10.1.1.2 High-seismic applications

10.1.2 Symbols, Glossary and Referenced Specifications, Codes and Standards

10.1.2.1 Symbols

10.1.2.2 Definitions