Performance of seismically isolated buildings with variable friction pendulum bearings under near-fault ground motions

Abstract

An advanced variable friction pendulum bearing (VFPB) seismic isolation system is investigated in this study to evaluate its performance for seismic mitigation under near-fault ground motions. Component tests on the modified-polyformaldehyde (M-POM) composite show that the friction coefficient of the M-POM–steel interfaces remains constant with changes in the sliding velocity. A numerical model for the VFPB comprising existing nonlinear elements in parallel is proposed, which is more implementable in currently available finite element software. The input parameters of the numerical model are modified to capture the observed behavior of the actual VFPB exactly. From the records of 120 near-fault ground motions, the influence of the characteristic parameters of near-fault ground motions on the seismic responses of seismically isolated buildings using VFPBs and traditional friction pendulum bearings (FPBs) is investigated through correlation analysis. It is observed that the velocity-related intensity indices have the greatest impact on the roof displacement and isolator deformation, while the roof acceleration is mostly influenced by acceleration-related intensity indices. Displacement-related intensity indices have the second-greatest impact on the roof displacement and isolator deformation. The numerical results demonstrate that when subjected to near-fault earthquakes, the VFPB can simultaneously reduce the isolator deformation by approximately 30% and the responses of the superstructure by approximately 5% compared with the conventional FPB.