A leverage-type semi-active isolation system for seismic structures in near-fault regions

Although a conventional passive isolation system may effectively mitigate the dynamic response of a seismic structure in an usual earthquake, it may also encounter a low-frequency resonance problem when subjected to a near-fault earthquake that usually possesses a long-period pulse-like waveform. This long-period wave component may result in an excessive of the isolator displacement and decrease isolation efficiency. To overcome this problem, a semi-active sliding isolation system called Leverage-type Stiffness Controllable Isolation System (LSCIS) is proposed in this study. By varying the ratio of the leverage arm of the LSCIS, the isolation stiffness of the LSCIS system can be controlled by a proposed semi-active control method. So, the system is more controllable than a passive isolation system. The result of numerical simulation has shown that the proposed system is able to effectively mitigate the resonance problem induced by a near-fault earthquake. As a result, that the base displacement and superstructure acceleration of the isolated structure can be reduced simultaneously, as compared to a conventional isolation system.