Comparison of the effects of aftershocks on the performance of a concentrically braced frame equipped with a shape memory alloy damper and a steel moment resisting frame

Using shape memory alloys as a novel tool due to their self-centering property to reduce damage and control seismic behavior of structures can be effective. Considering that the occurrence of aftershocks can always cause cumulative damage in structures, it is important to investigate the performance of the above systems under aftershocks. The present study evaluates a four-story steel frame in the state without braces and with convergent braces equipped with shape memory alloy dampers. To investigate the effect of aftershocks on the behavior of the two frames and perform incremental dynamic analysis, the OpenSees software was used. For this purpose, 29 records related to the main earthquake and the actual recorded aftershock were used. To investigate the response of the structures, first, the main earthquake was scaled to bring the structure to the collapse level, and then the aftershock was applied to the frames considering three levels of drift structure (0.01, 0.025, and 0.04) under the main earthquake. The results show that the braced structure equipped with a damper, compared to the structure without braces, experiences 13% more acceleration, 30% less residual drift, and 21% less relative drift after experiencing 0.04 drift caused by the main earthquake. Additionally, in both structures, more destructive effects are observed when they are under aftershock