Sysmic analysis of base isolated irregular structures

Seismic base isolation, also known as base isolation system, nowadays is commonly applied worldwide to protect buildings prone to devastating earthquake events. The application was also stipulated by the Ministry of Health in 2012. The system is an effective solution for huge buildings like hospitals whose capacity is hundreds of beds that are required to reach the criterion of Immediate Occupancy (IO) in qualitative performance levels after earthquake events. Moreover, the application of the system is vital as the torsional response becomes more significant because of some irregularities related to architectural requirements. In this study, a hospital, namely Ali Osman Sönmez State Hospital, that is under construction in Acemler, Bursa city is investigated. As designed, there are some irregularities ambiguously rising the torsional performances. Aim at the effectiveness of the base isolation system applied to the building, its performances under various ground motions are compared with the counterparts of a reference structure that is modeled symmetrically. As a result, it is seen that in some cases, the base isolation systems increases the effects of torsional irregularity, and in some cases irregularity coefficients are obtained beyond the allowable limits in the structural system of the structure.