Probabilistic evaluation of seismic performance of steel moment frames with and without infill panels on rigid and flexible soil

Evaluation of the damages caused by past earthquakes confirms that the infilled-frame buildings, which were built on soft soil, can be damaged more than expected values in design performance level. In-fact the lack of attention to the effects of infilled-frames on the behavior of the structure despite the recommendation of seismic regulations is a very important subject. However, according to the observed damages, the improvement of these regulations is undeniable. Therefore, in this study, to investigate the effect of the presence or absence of infill panels on the behavior of steel moment frames, by considering the effects of soil-structure interaction is examined. In this regard, incremental nonlinear dynamic analyzes were performed on two-dimensional frames with three, six, nine, twelve, fifteen and twenty floors. For this purpose, 21 far field ground motion accelerations were selected according to the FEMA-P695. Nonlinear time histoy analyses were performed in SeismoStruct software. Then, using statistical relationships, the seismic fragility curves of the studied models were extracted and compared for three performance levels, ie, IO, LS and CP. It should be noted that the seismic demand parameter was selected in the form of maximum relative displacement. The results show that with increasing the number of floors, the presence of infill reduces the vulnerability of the structure and vice versa, considering the effect of soil-structure interaction increases the vulnerability of the structure.