Elastoplastic analysis of steel members and frames subjected to cyclic loading

The present paper addresses the cyclic elastoplastic large displacement analysis of steel columns and portal frames. In the analysis, a modified two-surface plasticity model developed at Nagoya University is employed to model material nonlinearity. The developed finite element formulation takes into account the important cyclic characteristics of structural steel, even within the yield plateau, such as the decrease and disappearance of the yield plateau, reduction of the elastic range and cyclic strain hardening, as well as the spread of plasticity across the section. Comparisons between the analytical and experimental results show that the modified two-surface model can be used to predict the inelastic cyclic behavior of steel structures with good accuracy. Based on the results of parametric studies, empirical formulas are proposed to predict the strength and ductility capacity of pipe-section steel bridge piers.