1.4Symbols

IS 800:2007, General Construction in Steel — Code of Practice

Last Updated 29 Oct 2026

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Symbols used in this standard shall have the following meanings with respect to the structure or member or condition, unless otherwise defined elsewhere in this Code.

A	— Area of cross-section
A_c	— Area at root of threads
A_e	— Effective cross-sectional area
A_cf	— Reduced effective flange area
A_f	— Total flange area
A_g	— Gross cross-sectional area
A_gf	— Gross cross-sectional area of flange
A_go	— Gross cross-sectional area of outstanding (not connected) leg of a member
A_n	— Net area of the total cross-section
A_nb	— Net tensile cross-sectional area of bolt
A_nc	— Net cross-sectional area of the connected leg of a member
A_nf	— Net cross-sectional area of each flange
A_no	— Net cross-sectional area of outstanding (not connected) leg of a member
A_pb	— Nominal bearing area of bolt on any plate
A_q	— Cross-sectional area of a bearing (load carrying) stiffener in contact with the flange
A_s	— Tensile stress area
A_sb	— Gross cross-sectional area of a bolt at the shank
A_tg	— Gross sectional area in tension from the centre of the hole to the toe of the angle section/channel section, etc (see 6.4) perpendicular to the line of force

A_tn	— Net sectional area in tension from the centre of the hole to the toe of the angle perpendicular to the line of force (see 6.4)
A_v	— Shear area
A_vg	— Gross cross-sectional area in shear along the line of transmitted force (see 6.4)
A_vn	— Net cross-sectional area in shear along the line of transmitted force (se: 6.4 )
a, b	— Larger and smaller projection of the slab base beyond the rectangle circumscribing the column, respectively (see 7.4)
a_o	— Peak acceleration
a₁	— Unsupported length of individual elements being laced between lacing points
B	— Length of side of cap or base plate of a column
b	— Outstand/width of the element
b₁	— Stiff bearing length, Stiffener bearing length
b_c	— Effective width of flange between pair of bolts
b_f	— Width of the flange
b_i	— Width of flange as an internal element
b_o	— Width of flange outstand
b_p	— Panel zone width between column flanges at beam-column junction
b_s	— Shear lag distance
b_t	— Width of tension field
b_w	— Width of outstanding leg
C	— Centre-to-centre longitudinal distance of battens
C_m	— Coefficient of thermal expansion
C_my, C_mz	— Moment amplification factor about respective axes
c	— Spacing of transverse stiffener
C_b	— Moment amplification factor for braced member
C_m	— Moment reduction factor for lateral torsional buckling strength calculation
C_s	— Moment amplification factor for sway frame
D	— Overall depth/diameter of the cross-section
d	— Depth of web, Nominal diameter
d₂	— Twice the clear distance from the

	compression flange angles, plates or tongue plates to the neutral axis
d_h	— Diameter of a bolt/ rivet hole
d_o	— Nominal diameter of the pipe column or the dimensions of the column in the depth direction of the base plate
d_p	— Panel zone depth in the beam-column junction
E	— Modulus of elasticity for steel
E (T)	— Modulus of elasticity of steel at T °C
E (20)	— Modulus of elasticity of steel at 20°C
E_p	— Modulus of elasticity of the panel material
F_cdw	— Buckling strength of un-stiffened beam web under concentrated load
F_d	— Factored design load
F_n	— Normal force
F_o	— Minimum proof pretension in high strength friction grip bolts.
F_psd	— Bearing capacity of load carrying stiffener
F_q	— Stiffener force
F_qd	— Stiffener buckling resistance
F_test	— Test load
F_{test, a}	— Load for acceptance test
F_{test, Min}	— Minimum test load from the test to failure
F_{test, R}	— Test load resistance
F_{test, S}	— Strength test load
F_w	— Design capacity of the web in bearing
F_x	— External load, force or reaction
F_xd	— Buckling resistance of load carrying web stiffener
f	— Actual normal stress range for the detail category
f₁	— Frequency for a simply supported one way system
f₂	— Frequency of floor supported on steel girder perpendicular to the joist
f_a	— Calculated stress due to axial force at service load
f_abc	— Permissible bending stress in compression at service load
f_ac	— Permissible compressive stress at service load
f_abt	— Permissible bending stress in tension at service load
f_apb	— Permissible bearing stress of the bolt at service load
f_asb	— Permissible stress of the bolt in shear at service load

f_at	— Permissible tensile stress at service load
f_atb	— Permissible tensile stress of the bolt at service load
f_aw	— Permissible stress of the weld at service load
f_b	— Actual bending stress at service load
f_bc	— Actual bending stress in compression at service load
f_bd	— Design bending compressive stress corresponding to lateral buckling
f_br	— Actual bearing stress due to bending at service load
f_bt	— Actual bending stress in tension at service load
f_bs	— Permissible bending stress in column base at service load
f_c	— Actual axial compressive stress at service load
f_cc	— Elastic buckling stress of a column, Euler buckling stress
f_cd	— Design compressive stress
f_cr,b	— Extreme fibre compressive stress corresponding elastic lateral buckling moment
f_e	— Equivalent stress at service load
f_f	— Fatigue stress range corresponding to 5 × 10⁶ cycles of loading
f_eq	— Equivalent constant amplitude stress
f_fd	— Design normal fatigue strength
f_{f, Max}	— Highest normal stress range
f_fn	— Normal fatigue stress range
f_nw	— Normal stress in weld at service load
f_o	— Proof stress
f_p	— Actual bearing stress at service load
f_pb	— Actual bearing stress in bending at service load
f_psd	— Bearing strength of the stiffeners
f_r	— Frequency
f_sb	— Actual shear stress in bolt at service load
f_t	— Actual tensile stress at service load
f_tb	— Actual tensile stress of the bolt at service load
f_u	— Characteristic ultimate tensile stress
f_ub	— Characteristic ultimate tensile stress of the bolt
f_um	— Average ultimate stress of the material as obtained from test
f_up	— Characteristic ultimate tensile stress of the connected plate

f_v	Applied shear stress in the panel designed utilizing tension field action
f_w	Actual stress of weld at service load
f_wd	Design stress of weld at service load
f_wn	Nominal strength of fillet weld
f_x	Maximum longitudinal stress under combined axial force and bending
f_y	Characteristic yield stress
f_y(T)	Yield stress of steel at T °C
f_y(20)	Yield stress of steel at 20°C
f_yb	Characteristic yield stress of bolt
f_yf	Characteristic yield stress of flange
f_ym	Average yield stress as obtained from test
f_yp	Characteristic yield stress of connected plate
f_yq	Characteristic yield stress of stiffener material
f_yw	Characteristic yield stress of the web material
G	Modulus of rigidity for steel
g	Gauge length between centre of the holes perpendicular to the load direction, acceleration due to gravity
h	Depth of the section
h_b	Total height from the base to the floor level concerned
h_c	Height of the column
h_e	Effective thickness
h_f	Centre-to-centre distance of flanges
h_i	Thickness of fire protection material
h_l	Height of the lip
h_s	Storey height
h_y	Distance between shear centre of the two flanges of a cross-section
I	Moment of inertia of the member about an axis perpendicular to the plane of the frame
I_fc	Moment of inertia of the compression flange of the beam about the axis parallel to the web
I_ft	Moment of inertia of the tension flange of the beam about minor axis
I_q	Moment of inertia of a pair of stiffener about the centre of the web, or a single stiffener about the face of the web
I_s	Second moment of inertia
I_so	Second moment of inertia of the stiffener about the face of the element perpendicular to the web

I_T —	Transformed moment of inertia of the one way system (in terms of equivalent steel, assuming the concrete flange of width equal to the spacing of the beam to be effective)
I_t —	St. Venant’s torsion constant
I_w —	Warping constant
I_y —	Moment of inertia about the minor axis of the cross-section
I_z —	Moment of inertia about the major axis of the cross-section
K_h —	Effective stiffness of the beam and column
K_h —	Reduction factor to account for the high strength friction grip connection bolts in over sized and slotted holes
KL —	Effective length of the member
KL/r —	Appropriate effective slenderness ratio of the section
KL/r_y —	Effective slenderness ratio of the section about the minor axis of the section
KL/r_z —	Effective slenderness ratio of the section about the major axis of the section
(KL/r)_o —	Actual maximum effective slenderness ratio of the laced column
(KL/r)_e —	Effective slenderness ratio of the laced column accounting for shear deformation
K_v —	Shear buckling co-efficient
K_w —	Warping restraint factor
k —	Regression coefficient
k_sm —	Exposed surface area to mass ratio
L —	Actual length, unsupported length, Length centre-to-centre distance of the intersecting members, Cantilever length
L_e —	Length of end connection in bolted and welded members, taken as the distance between outermost fasteners in the end connection, or the length of the end weld, measured along the length of the member
L_LT —	Effective length for lateral torsional buckling
L_m —	Maximum distance from the restraint to the compression flange at the plastic hinge to an adjacent restraint (limiting distance)
L_o —	Length between points of zero moment (inflection) in the span

l	— Centre-to-centre length of the supporting member
l_e	— Distance between prying force and bolt centre line
l_g	— Grip length of bolts in a connection
l_j	— Length of the joint
l_s	— Length between points of lateral support to the compression flange in a beam
l_v	— Distance from bolt centre line to the toe of fillet weld or to half the root radius for a rolled section
l_w	— Length of weld
M	— Bending moment
M_a	— Applied bending moment
M_cr	— Elastic critical moment corresponding to lateral torsional buckling of the beam
M_d	— Design flexural strength
M_dv	— Moment capacity of the section under high shear
M_dy	— Design bending strength about the minor axis of the cross-section
M_dz	— Design bending strength about the major axis of the cross-section
M_eff	— Reduced effective moment
M_fr	— Reduced plastic moment capacity of the flange plate
M_fd	— Design plastic resistance of the flange alone
M_nd	— Design bending strength under combined axial force and uniaxial moment
M_ndy, M_ndz	— Design bending strength under combined axial force and the respective uniaxial moment acting alone
M_p	— Plastic moment capacity of the section
M_pb	— Moment in the beam at the intersection of the beam and column centre lines
M_pc	— Moments in the column above and below the beam surfaces
M_pd	— Plastic design strength
M_pdf	— Plastic design strength of flanges only
M_q	— Applied moment on the stiffener
M_s	— Moment at service (working) load
M_tf	— Moment resistance of tension flange
M_y	— Factored applied moment about the minor axis of the cross-section

M_yq	— Moment capacity of the stiffener based on its elastic modulus
M_z	— Factored applied moment about the major axis of the cross-section
N	— Number of parallel planes of battens
N_d	— Design strength in tension or in compression
N_f	— Axial force in the flange
N_SC	— Number of stress cycles
n	— Number of bolts in the bolt group/critical section
n_e	— Number of effective interfaces offering frictional resistance to slip
n_h	— Number of shear planes with the threads intercepting the shear plane in the bolted connection
n_s	— Number of shear planes without threads intercepting the shear plane in the bolted connection
P	— Factored applied axial force
P_cc	— Elastic buckling load
P_d	— Design axial compressive strength
P_dy, P_dz	— Design compression strength as governed by flexural buckling about the respective axis
P_e	— Elastic Euler buckling load
P_Min	— Minimum required strength for each flange splice
P_r	— Required compressive strength
P_v	— Actual compression at service load
P_y	— Yield strength of the cross-section under axial compression
p	— Pitch length between centres of holes parallel to the direction of the load
p_s	— Staggered pitch length along the direction of the load between lines of the bolt holes (see Fig. 5)
Q	— Prying force
Q_a	— Accidental load (Action)
Q_c	— Characteristic loads (Action)
Q_d	— Design load (Action)
Q_p	— Permanent loads (Action)
Q_v	— Variable loads (Action)
q	— Shear stress at service load
R	— Ratio of the mean compressive stress in the web (equal to stress at mid depth) to yield stress of the web; reaction of the beam at support
R_d	— Design strength of the member at room temperature

$\begin{aligned} R_{\mathrm{i}} \\ R_{\mathrm{r}} \\ R_{\mathrm{tf}} \\ R_{\mathrm{u}} \\ r \\ r_{\mathrm{l}} \\ r_{\mathrm{f}} \\ r_{\mathrm{vv}} \\ r_{\mathrm{y}} \\ r_{\mathrm{z}} \\ S \\ S_{\mathrm{c}} \\ S_{\mathrm{d}} \\ S_{\mathrm{o}} \\ S_{\mathrm{p}} \\ S_{\mathrm{u}} \\ s_{\mathrm{c}} \\ s_{\mathrm{t}} \\ s_{\mathrm{a}} \\ T \\ T_{\mathrm{b}} \\ T_{\mathrm{cf}} \\ T_{\mathrm{d}} \\ T_{\mathrm{dg}} \\ T_{\mathrm{dn}} \\ T_{\mathrm{db}} \\ T_{\mathrm{e}} \\ T_{\mathrm{f}} \\ T_{\mathrm{l}}\end{aligned}$

R_i	— Net shear in bolt group at bolt “i”
R_r	— Response reduction factor
R_f	— Flange shear resistance
R_u	— Ultimate strength of the member at room temperature
r	— Appropriate radius of gyration
r_l	— Minimum radius of gyration of the individual element being laced together
r_f	— Ratio of the design action on the member under fire to the design capacity
r_vv	— Radius of gyration about the minor axis (v-v) of angle section.
r_y	— Radius of gyration about the minor axis
r_z	— Radius of gyration about the major axis
S	— Minimum transverse distance between the centroid of the rivet or bolt group or weld group
S_c	— Constant stress range
S_d	— Design strength
S_o	— Original cross-sectional area of the test specimen
S_p	— Spring stiffness
S_u	— Ultimate strength
S_c	— Anchorage length of tension field along the compression flange
S_t	— Anchorage length of tension field along the tension flange
S_a	— Actual stiffener spacing
T	— Temperature in degree Celsius; Factored tension
T_b	— Applied tension in bolt
T_cf	— Thickness of compression flange
T_d	— Design strength under axial tension
T_dg	— Yielding strength of gross section under axial tension
T_dn	— Rupture strength of net section under axial tension
T_db	— Design strength of bolt under axial tension; Block shear strength at end connection
T_e	— Externally applied tension
T_f	— Factored tension force of friction type bolt
T_l	— Limiting temperature of the steel
T_nb	— Nominal strength of bolt under axial tension
T_nd	— Design tension capacity

T_ndf	— Design tension capacity of friction type bolt
T_nf	— Nominal tensile strength of friction type bolt
T_s	— Actual tension under service load
t	— Thickness of element/angle, time in minutes
t_f	— Thickness of flange
t_p	— Thickness of plate
t_pk	— Thickness of packing
t_q	— Thickness of stiffener
t_s	— Thickness of base slab
t_e	— Effective throat thickness of welds
t_w	— Thickness of web,
V	— Factored applied shear force
V_b	— Shear in batten plate
V_hf	— Factored frictional shear force in friction type connection
V_cr	— Critical shear strength corresponding to web buckling
V_d	— Design shear strength
V_db	— Block shear strength
V_nb	— Nominal shear strength of bolt
V_nbf	— Bearing capacity of bolt for friction type connection
V_p	— Plastic shear resistance under pure shear
V_n	— Nominal shear strength
V_npb	— Nominal bearing strength of bolt
V_nsb	— Nominal shear capacity of a bolt
V_nsf	— Nominal shear capacity of bolt as governed by slip in friction type connection
V_s	— Transverse shear at service load
V_sh	— Factored shear force in the bolt
V_sd	— Design shear capacity
V_sdf	— Design shear strength in friction type bolt
V_sf	— Factored design shear force of friction bolts
V_t	— Applied transverse shear
V_tf	— Shear resistance in tension field
W	— Total load
w	— Uniform pressure from below on the slab base due to axial compression under the factored load
w_tf	— Width of tension field
X_t	— Torsional index
Z_e	— Elastic section modulus
Z_ec	— Elastic section modulus of the

	member with respect to extreme compression fibre
Z_et	— Elastic section modulus of the member with respect to extreme tension fibre
Z_p	— Plastic section modulus
Z_v	— Contribution to the plastic section modulus of the total shear area of the cross-section
y_g	— Distance between point of application of the load and shear centre of the cross-section
y_s	— Co-ordinate of the shear centre in respect to centroid
α	— Imperfection factor for buckling strength in columns and beams
α_t	— Coefficient of thermal expansion
β_M	— Ratio of smaller to the larger bending moment at the ends of a beam column
β_My, β_Mz	— Equivalent uniform moment factor for flexural buckling for y-y and z-z axes respectively
β_MLT	— Equivalent uniform moment factor for lateral torsional buckling
χ	— Strength reduction factor to account for buckling under compression
χ_m	— Strength reduction factor, χ, at f_ym
χ_LT	— Strength reduction factor to account for lateral torsional buckling of beams
δ	— Storey deflection
δ_L	— Horizontal deflection of the bottom of storey due to combined gravity and notional load
δ_p	— Load amplification factor
δ_U	— Horizontal deflection of the top of storey due to combined gravity and notional load
φ	— Inclination of the tension field stress in web
γ	— Unit weight of steel
γ_f	— Partial safety factor for load
γ_m	— Partial safety factor for material
γ_m0	— Partial safety factor against yield stress and buckling
γ_m1	— Partial safety factor against ultimate stress
γ_mb	— Partial safety factor for bolted connection with bearing type bolts
γ_mf	— Partial safety factor for bolted connection with High Strength Friction Grip bolts

$\gamma_{\mathrm{ft}}$ — Partial safety factor for fatigue load

γ_fft	— Partial safety factor for fatigue load
γ_mft	— Partial safety factor for fatigue strength
γ_mv	— Partial safety factor against shear failure
γ_mw	— Partial safety factor for strength of weld
ε	— Yield stress ratio (250 / f_y)^1/2
λ	— Non-dimensional slenderness ratio = √f_y (KL/r)² / π² E = √f_y/f_cc = √P_y / P_cc
λ_cr	— Elastic buckling load factor
λ_e	— Equivalent slenderness ratio
λ_LT	— Non-dimensional slenderness ratio in lateral bending
λ_scr	— Elastic buckling load factor of each storey
μ	— Poisson’s ratio
μ_c	— Correction factor
μ_f	— Coefficient of friction (slip factor)
μ_r	— Capacity reduction factor
θ	— Ratio of the rotation at the hinge point to the relative elastic rotation of the far end of the beam segment containing plastic hinge
ρ	— Unit mass of steel
τ	— Actual shear stress range for the detail category
τ_b	— Buckling shear stress
τ_ab	— Permissible shear stress at the service load
τ_cr,e	— Elastic critical shear stress
τ_f	— Fatigue shear stress range
τ_f,Max	— Highest shear stress range
τ_fd	— Design shear fatigue strength
τ_fn	— Fatigue shear stress range at N_SC cycle for the detail category
τ_v	— Actual shear stress at service load
ψ	— Ratio of the moments at the ends of the laterally unsupported length of a beam
Γ	— Frame buckling load factor
NOTE	— The subscripts y, z denote the y-y and z-z axes of the section, respectively. For symmetrical sections, y-y denotes the minor principal axis whilst z-z denotes the major principal axis

The subscripts $y, z$ denote the $y$ -y and $z$ -z axes of the section, respectively. For symmetrical sections, $y$ -y denotes the minor principal axis whilst $z$ -z denotes the major principal axis (see 1.8).