Development of a novel semiactive electromagnetic seismic isolation system

Abstract

Although conventional seismic isolation systems are effective, they have difficulty handling both near-fault ground motion with long-period velocity pulses and far-field motion because they have fixed damping. Seismic isolation systems with variable damping could solve this problem. This study developed a novel semiactive electromagnetic seismic isolation system (SA-EMSIS) with real-time damping ratio control. The SA-EMSIS consists of an electromagnetic seismic isolation system (EMSIS) and a module including a controllable resistor that affects the EMSIS’s damping ratio. A series of shaking table tests were performed to confirm the high performance of the device. In open-loop control experiments, the resistance of the module was controlled in real time, in turn affecting the SA-EMSIS damping ratio. Moreover, a closed-loop switching control experiment was conducted, successfully increasing the damping ratio of the SA-EMSIS under near-field ground motion, which simultaneously reduced the displacement and acceleration responses of the isolation system. In addition, the results of the developed mathematical model were consistent with the experimental results, verifying the accuracy of both the theoretical model and the experiment.