Torsional Strength.

İnternational Design Codes

ACI 318-19 : Torsional Strength per ACI 318-19 with ideCAD (v12)

TSC 2018 : TSC Torsional Strength

Notation in ACI 318-19

A_o = gross area enclosed by torsional shear flow path, in.²
A_oh = area enclosed by centerline of the outermost closed transverse torsional reinforcement, in.²
A_cp = area enclosed by outside perimeter of concrete cross section, in.²
A_g = gross area of concrete section, in²
A_l = total area of longitudinal reinforcement to resist torsion, in.²
A_l,min = minimum area of longitudinal reinforcement to resist torsion, in.²
A_t = area of one leg of a closed stirrup, hoop, or tie resisting torsion within spacing s, in.²
b_w = web width or diameter of circular section, in.
f_c^' = specified compressive strength of concrete, psi
(f_c^')^0.5 = square root of specified compressive strength of concrete, psi
f_pc = compressive stress in concrete, after allowance for all prestress losses, at centroid of cross section resisting externally applied loads or at junction of web and flange where the centroid lies within the flange, psi.
f_yt = specified yield strength of transverse reinforcement, psi
N_u = factored axial force normal to cross section occurring simultaneously with V_u or T_u; to be taken as positive for compression and negative for tension, lb
p_cp = outside perimeter of concrete cross section, in.
p_h = perimeter of centerline of outermost closed transverse torsional reinforcement, in.
s = center-to-center spacing of items, such as longitudinal reinforcement, transverse reinforcement, tendons, or anchors, in.
T_cr = cracking torsional moment, in.-lb
T_th = threshold torsional moment, in.-lb
T_n = nominal torsional moment strength, in.-lb
T_u = factored torsional moment at section, in.-lb
V_u = factored shear force at section, lb
ϕ = strength reduction factor
λ = modification factor to reflect the reduced mechanical properties of lightweight concrete relative to normal weight concrete of the same compressive strength