Performance evaluation of RC-MRFs with UHPSFRC and SMA rebars subjected to mainshock-aftershock sequences

Abstract

Although structures are generally subjected to mainshock-aftershock sequences, the current structural design process merely considers the main seismic event. This study aims to compare the performance of Reinforced Concrete Moment Resisting Frames (RC-MRFs) with Shape Memory Alloy (SMA) and Ultra-High-Performance Steel Fiber Reinforced Concrete (UHPSFRC) under the influences of mainshock and aftershock sequence. To achieve this aim, 3, 6, and 8-story five-span frames were simulated considering three different approaches: (i) RC frames; (ii) RC frames with SMA rebars in the plastic hinge length of the beams; (iii) RC frames with UHPSFRC and SMA in the plastic hinge length of the beams.Each frame was analyzed under two different scenarios, with and without considering seismic sequences to assess the post-earthquake performance of damaged RC frames. Time history analyses were conducted using seven real accelerograms. Maximum transient inter-story and roof drifts, as well as residual inter-story drifts, were determined and compared in undamaged and damaged structures to assess the effect of seismic sequence. As the performance evaluation of the damaged structures appears to be essential to make repair policy decisions and rescue operations, damage states were defined according to FEMA-356 based on maximum transient and residual drifts. Numerical results illustrate the salient effect of using SMA and UHPSFRC synergistically in reducing transient and residual drifts and enhancing the functionality of structures in both mainshock and aftershock.