Influence of Near-Fault Ground Motions on the Response of Base-Isolated Reinforced Concrete Buildings considering Seismic Pounding

Performance of base-isolated buildings subjected to near-fault ground motions containing long-period pulses is of increasing concern, because these ground motions have the potential to impose large seismic demands on structures. A review of previous studies on the performance evaluation of base-isolated reinforced concrete (RC) buildings under near-fault ground motions shows that these studies lack in the consideration of seismic pounding and the use of lower bound and upper bound values of isolator properties according to the current state of practice. Accordingly, in this study the performance of a typical four-story base-isolated RC building is evaluated using a three-dimensional nonlinear finite element model, considering bounding values of isolator properties, to investigate the influences of (i) pulse-like nature of near-fault ground motions and (ii) seismic pounding with retaining walls at the base. Two sets of ground motions containing 14 far-fault non-pulse-like ground motions and 14 near-fault pulse-like ground motions, representing the risk-targeted maximum considered earthquake (MCER), are used. It is found that the response indicators of the building under near-fault motions are significantly larger than those under far-fault motions. Analysis results reveal that the building response indicators are significantly increased due to seismic pounding. Nonetheless, if a bounding analysis is conducted, consideration of seismic pounding in the analysis does not have appreciable consequences on the prediction of damage to structural elements and drift-sensitive nonstructural components, while dramatic increase in floor accelerations due to pounding is critical for acceleration-sensitive nonstructural components.