Seismic Fragility Curves of a Friction Pendulum Base Isolated Structure Under Near-Fault Ground Motion Data

Base isolation is widely recognized as one of the most effective seismic protection strategies for buildings, particularly in earthquake-prone areas. In this study, a ten-story seismically-isolated structure with curved surface friction isolators (friction pendulum bearings) is analyzed, considering two primary engineering demand parameters: maximum inter-story drift ratio and maximum isolator displacement. A set of near-fault ground motion records containing long-period velocity pulses and higher amplitudes was selected and scaled. For the seismic performance assessment of the structure, Incremental dynamic analysis is performed for each ground motion dataset. The structural response is evaluated based on predefined performance limit states. The results indicate that the maximum inter-story drift ratio remains within acceptable limits without exceeding the thresholds for extensive or collapse damage states. However, the isolator displacement demand reaches all damage state thresholds under near-fault excitations. These findings emphasize the critical role of the isolator displacement capacity in the seismic risk assessment of seismically isolated structures.