Experimental verification of polynomial friction pendulum isolators for near-fault seismic isolation

In order to improve the performance of seismic isolated structures in near-fault areas, a new type of sliding isolation bearings called Polynomial Friction Pendulum Isolator (PFPI) is proposed in this study. Different from a conventional friction pendulum system (FPS), the geometry of the sliding surface of a PFPI isolator is defined by a sixth-order polynomial function. As a result, the stiffness of the PFPI has a softening behavior followed by a hardening behavior, when the isolator displacement increases. The softening and hardening behaviors aim to reduce the structural acceleration and isolator drift, respectively. In order to verify the feasibility of the PFPI concept, an element test on prototype PFPI isolators and a shaking table test on a structure isolated by PFPI were all conducted. The result of the shaking table test demonstrates that when subjected to an earthquake with a long-period pulse component, the PFPI system is able to effectively suppress the maximum isolator drift, without causing the amplification of the structural acceleration.