Seismic Fragility Assessment of a Base-Isolated RC Frame Building Using Direct Displacement-Based Design and Force-Based Design

Base-isolated building structures prove highly effective in seismic events, particularly when designed using direct displacement-based methods. This design approach ensures that the structure’s behavior remains under control during such events. In the present study, 8-, 10-, and 12-story base-isolated RC frame structures were designed using the direct displacement-based design (DDBD) approach. The building was modeled using finite-element software and subjected to a set of ground motion records scaled to different intensity levels. The nonlinear behavior of the RC frame with lead rubber bearing (LRB) was evaluated using incremental dynamic analysis (IDA). The seismic fragility assessment of the base-isolated RC frames was conducted by generating fragility curves from the outcomes obtained through IDA. The probability of exceedance of various damage of base-isolated RC frames designed using the DDBD approach was then compared with the forced-based design (FBD) approach to compute the efficiency of the DDBD approach for base-isolated RC frames. The results indicate that the base-isolated RC frame designed using the DDBD method exhibits good seismic performance with 35.68% less response and a low probability of exceeding collapse.