FEM analysis for hysteretic behavior of thin-walled columns

An accurate finite-element-method-based analysis to predict the ultimate hysteretic behavior of thin-walled steel columns subjected to seismic loading is presented in this paper. For this purpose, we develop the three-surface cyclic metal plasticity model. The three-surface model includes less material parameters and internal variables for the ease of its implementation in the finite-element method analysis. This model is characterized by a discontinuous surface inserted between the yield surface and the bounding surface. The discontinuous surface is used to express the yield plateau and the change of hardening coefficient. Most material parameters in the three-surface model can be determined by the tensile coupon test. However, three parameters independent of material types are calibrated by the existing cyclic loading test results of thin-walled steel columns. This is to improve the accuracy of this analysis specifically in the simulation of the localized buckling behavior, which accompanies extremely large plastic strains.