Probabilistic Seismic Assessment of RC Buildings Considering Soft and Extreme Soft Story Irregularities Subjected to Main Shock-Aftershock Sequences

Recent Iranian earthquake damages like the damages caused by the Kermanshah earthquake, revealed that RC buildings having soft story irregularities experienced more seismic vulnerability. Moreover, earthquake aftershocks increased the seismic failures in past earthquake events. But RC buildings having soft story irregularities and effects of earthquake aftershocks are not included in recent seismic design codes. In this article, for assessing the effects of soft story irregularities and also the effects of earthquake aftershocks, three, five, and eight story RC building models having intermediate sway moment frames are designed and then modeled in OPENSEES software platform and then IDA analysis are performed in order to producing the seismic fragility curves consistent with HAZUS definitions. The analytical results of seismic fragility curves revealed that the influence of soft story irregularities and also main earthquake shock-aftershock sequences on the vulnerability of considered RC building models. By increasing the height of the RC building structures, the effects of soft story irregularities and the earthquake aftershocks decreased in seismic vulnerability of the considered RC buildings.