This study evaluates the seismic performance of steel moment-resisting frames (SMRFs) under multiple strong ground motions. The cumulative damage of beam members is used as the main damage index. A cumulative damage formula is generated based on the experimental results of the steel beam-to-column connection test considering the ductile fracture. Local buckling of members is not considered in this study. Six SMRF models with two parameters (the number of stories and the strength of the column base) are analyzed by conducting an inelastic response analysis. Three different ground motion intensities (peak ground velocity = 0.5 m/s (design level), 0.75 m/s, and 1.0 m/s), each with five repeated excitations are used in the inelastic response analysis to simulate the occurrence of multiple strong ground motions. Stable behavior with a linear increment in cumulative damage is found in most cases, especially when the ground motion intensity is equal to the design level. However, when the intensity is greater than the design level, both ductile fracture and weak story collapse are observed in several cases.

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