PLASTICITY MODEL WITH CONSIDERATION OF HARDENING AND EXPANTION OF PLASTIC REGIONS FOR STEEL BEAM-COLUMNS SUBJECTED TO REPEATED AXIAL FORCE AND BIAXIAL BENDING

Abstract

This paper describes the plasticity model which can take account for gradual plastification and hardening for steel beam-columns subjected to axial force and biaxial bending moment. The beam model composed of fibers, in which plastic regions expand in one direction, is developed. It is clarified how the basic equations (the yield function, the plastic flow rule and the hardening rule) should be formulated in bilinear stress-strain relation using an additive decomposition technique of the total displacement for the beam model. Finally, numerical examples are shown to examine the performance of the model with the return mapping algorithm and a convenient evaluation method of the plastic regions.