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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.

This study develops a variable friction bearing (VFPB) that introduces a variable friction mechanism into a traditional friction pendulum bearing (FPB), in which a new friction composite is applied. The device is developed using simple processing technology. A method for determining which sliding band is active based on the friction coefficient of each sliding band is proposed, and the operating principle of the VFPB is illustrated. The force–displacement relationships and relevant parameters of interest are subsequently derived based on the principles of operation of the VFPB. Parametric studies are conducted to investigate the effects of the friction coefficient and number of sliding bands on the behavior of this novel VFPB. To investigate the mechanical behavior of the VFPB under various vertical loads and sliding velocities, characterization tests for a full-scale VFPB are carried out. An analysis model consisting of existing nonlinear elements is proposed for time-history analysis because it can be immediately implemented in currently available analysis software. The error of the analysis model is controlled within 10%.

Herein, analytical and experimental investigations are conducted to characterize the performance of a novel variable friction pendulum bearing (VFPB) capable of progressively exhibiting different hysteretic properties for different displacement amplitudes. An analytic scheme comprising existing nonlinear elements is proposed, which can be easily implemented using currently available analysis software. The analytic-scheme accuracy is verified through comparison with experimental data. Thereafter, a design method is developed for seismically isolated buildings employing VFPB. Elastic-plastic time-history analyses are performed to study the seismic performance of the base-isolated building using VFPB, by comparing its performance with that of a friction pendulum bearing (FPB). Both the buildings isolated employing VFPB and FPB exhibit excellent aseismic performance. The VFPB is more effective than FPB in reducing the response of superstructure without increasing isolator displacement for the rare earthquake scenario, especially for very rare earthquake scenario. The stiffness and damping of VFPB change to predictable values at calculable and controllable displacement. Therefore, it can be designed to achieve multiple performance objectives corresponding to different levels of ground shaking.