Approximate expressions for the simulated response of slender longitudinal reinforcement in monotonic compression

Detailed non-linear three-dimensional (3D) finite-element analyses of the behaviour of reinforcing bars in compression were conducted for different slenderness ratios and for two different nominal strengths of steel. An equivalent engineering stress–strain response is determined for the bars, based on results obtained in natural coordinates. Approximate expressions to represent the equivalent engineering stress–strain response were fitted to the computed results. The approximate expressions are intended for use in moment–curvature analyses of reinforced concrete sections, where the contribution of the reinforcement is considered in the monotonic response of the cross-section, in cases where spalling of cover concrete allows the reinforcement to buckle. An example of moment–curvature analysis is carried out using the stress–strain relationship presented in this paper.