Characteristic Validation and Performance Evaluation of Vertical Seismic Isolator with Link-crank Mechanism

Abstract

Seismic isolation is an effective way to reduce damage caused by earthquakes. One of the mainstream seismic isolation systems is seismic isolation rubber. This system isolates horizontal vibration but doesn’t isolate vertical vibration. In recent years, earthquakes with large vertical vibrations have been reported. Therefore, we need the seismic isolation device that can be isolated in the vertical direction. A vertical seismic isolation device of the previous study had the problems that it was soft in the vertical direction and bad response to disturbance. Also, the horizontal vibration affects the vertical seismic isolation performance. In this study, we propose a seismic isolation device that solves the problems of the previous research and verify its characteristics and evaluate its performance. To verify its characteristics, we model the device using SimulationX. In the new seismic isolation device, the rigidity of the device can be changed by the motor drive. Also, to decrease horizontal vibration of the device, three link mechanisms are concentrically arranged at equal intervals. This device can set the natural frequency low by the negative rigidity mechanism. We performed three tests to verify its characteristics and evaluate its performance. In the damping free vibration test, we found that the amplitude difference between the experiment and the simulation is different in the upper and lower sides when we considered the equilibrium height as a reference. In the vibration test, we confirmed sufficient seismic isolation effect in multiple seismic waves. In the resonance avoidance test, we confirmed that the device avoids the resonance by the motor drive.