Seismic Behavior of RC Moment Resisting Structures with Concrete Shear Wall under Mainshock-aftershock Seismic Sequences

Abstract

A structure may subject to several aftershocks after a mainshock. In many seismic design provisions, the effect of the seismic sequences is not directly considered or underestimated. This paper studies the seismic behavior of RC moment-resisting structures with concrete shear wall under seismic sequences. Two three-dimensional structures of short and medium height were designed and analyzed. The former models were studied under a group of real mainshock-aftershock seismic sequences. The models were loaded and designed according to the fourth edition of the Iranian seismic code of standard no. 2800 and ACI-318 respectively. Furthermore, the non-linear dynamic time-history finite element analysis of models was performed via the explicit method. The parameters of maximum displacement, inter-story drift ratio, residual displacement, and finally the effect of the ratio of aftershock acceleration to mainshock acceleration were investigated and assessed. Due to the high lateral stiffness of shear walls, parallel with the complete elastic behavior, aftershocks cause no growth in inter-story drift ratio and relative displacement in the short structure model. In contrast, compared to the structure under the solely mainshock, the medium height structure model under seismic sequences showed significant growth in the amount of relative displacement (even more than 50% growth), inter-story drift ratio, plastic strain, and residual displacement (almost 30% growth). Furthermore, unlike the moment-resisting frame structures, models showed no significant growth in the drift ratio with the height. Assessments indicated that the ratio of aftershock to mainshock acceleration is a determinative parameter in structural behavior under seismic sequences.