Experimental Studies and Mechanical Properties Analysis of Three-Dimensional Oblique Rotating Friction Seismic Isolators

Abstract

Traditional isolation devices widely provide protection only against the horizontal components of earthquake motions. The vertical ground motions are transmitted through the isolation system unchanged or even magnified. Thus, in this paper, a mechanical model of a novel three-dimensional oblique rotating friction seismic isolator is proposed. The device with oblique-torsion coupling deformation is designed by combining three inclined rubber bearings. The test results show that the device have asymmetric behavior and a plump hysteretic loop in a vertical direction. After three times cyclic loading, the slope of the curve for the device hardly changes, and there is no damage in the loading process. The error of vertical post-yield stiffness of the device between the experimental result and theoretical prediction is within 10%, and it is in good agreement with the theoretical model prediction. In addition, the effects of different parameters are highlighted based on the theoretical mechanical model. The results show that the inclination angle, the friction coefficient, radius of PTFE, distance from the center of the inclined LRB to the center of the rotating block, and the performance of the inclined LRBs strongly influence the vertical behavior of the proposed device and should be worthy of attention in the design of devices.