Effect of column strength deterioration on the performance of steel moment-resisting frames subjected to multiple strong ground motions

Abstract This study evaluates the effect of column strength deterioration caused by local buckling on the seismic performance of steel moment-resisting frames (SMRFs) considering multiple strong ground motions. Various SMRF models considering two main design parameters, i.e., the column width-to-thickness ratio and the column-to-beam moment capacity ratio, are analyzed by conducting an inelastic earthquake response analysis that simulates the occurrence of multiple strong ground motions. A column hysteretic model that takes into account the strength deterioration caused by local bucking is employed in this analysis. The numerical analysis results show that column strength deterioration may cause the shift to a weak story mechanism and weak story collapse under the excitation of multiple strong ground motions. The number of excitations that can be withstood by the structure (before collapse) varies among the models. The collapse fragility under multiple excitations is investigated to find the combination of design parameters that can achieve a certain acceptable performance.