ABSTRACT
Mu = (As · fyd − A′s · σ ′s) · [d − (a/2)] + A′s · σ ′s · (d − d ′) ± N · I/(A · y) (1)
where Mu = ultimate moment (kN · cm); As = area of the tensile rebar, A′s = area of the compressive rebar; fyd = yield stress of rebar; σ ′s = compressive stress of rebar; d = effective depth; d ′ = depth of the compressive rebar; a = equivalent depth of concrete compressive area; N = axial force (positive for compression); I = moment of inertia; A = area of concrete; y = distance to the tensile rebar from the center of gravity.
