SEISMIC RESPONSE OF LRB BASE-ISOLATED STRUCTURES UNDER NEAR-FAULT PULSE-LIKE GROUND MOTIONS CONSIDERING POTENTIAL POUNDING

Under near-fault pulse-like ground motions, potential pounding may occur at the isolation level between the base-isolated building and its surrounding retaining walls. In this paper, the effect of pounding on the dynamic responses of base-isolated buildings is explored by using the modified Kelvin impact model and taking the inelasticity of the superstructure into account. It is shown from numerical results that floor accelerations at the time of pounding is substantially higher than those of the building without base-isolation, and the displacement time history of the drift at the ground floor takes the staircase-like form due to the presence of high spikes in the pounding force and the significant residual inter-story deformation. This indicates that higher ductility should be imposed on lower floors of the superstructure with base-isolation than the building without base-isolation, otherwise, the global collapse of the superstructure may be induced. Higher modes of vibration are excited during the pounding, which results in larger inter-story drifts.