This paper investigates the change in seismic demands of a reinforced concrete (RC) building retrofitted by seismic isolation technique, due to change in superstructure characteristics. First, an RC building that possesses the general characteristics of fixed-base building stock in Türkiye is identified. Then, it is retrofitted by means of Lead Rubber Bearings (LRBs) and subjected to bidirectional ground motion excitations through nonlinear response history analyses (NRHA). Concrete compressive strength, dimensions of both beams and columns, and first story height are the parameters considered in the analyses. Two different numerical models are established by considering both linear and nonlinear element definitions for the superstructure. In either case, LRBs are represented by deteriorating hysteretic force-displacement relations that consider the effect of heating in the lead core during cyclic motion. Results indicate that increasing the beam dimensions is the most effective approach in retrofitting of the analyzed structural model to reduce inter-story drift ratios (ISDRs). An increase in beam dimensions led to an approximately 30% reduction in ISDRs, while enhancements in concrete compressive strength and dimensions of columns yielded reductions of nearly 20%. The elastic superstructure model may lead to underestimated ISDRs by more than 1.5 folds compared to its nonlinear counterpart.
Kayı et al. (Tue,) studied this question.