Research on Mechanical Properties of Variable Stiffness Self-Centering Three-Dimensional Seismic Isolators

In order to improve the seismic performance of bridge structures, bridge isolation technology is increasingly innovating. However, current research is often limited by the contradiction between vertical bearing stiffness and seismic isolation performance: ensuring the daily operation of bridges requires high vertical stiffness load-bearing, while seismic isolation requires low dynamic stiffness. In response to this contradiction, this article proposes a Variable Stiffness Self centering Three dimensional Isolator (VSSC3DI), which consists of three parts: a vertical quasi zero stiffness isolation module and a lead core damper working together, and a combination system of friction pendulum and shape memory alloy (SMA) twisted wire in the horizontal direction. This article mainly studies the performance of vertical structures. By systematically explaining the working principle of the isolation device, constructing a static model and analyzing its force displacement relationship and the mechanism of quasi zero stiffness formation; Furthermore, the dynamic response of the system under external excitation was analyzed. Firstly, a corresponding nonlinear dynamic model was established, and the amplitude frequency response characteristics were solved using the averaging method. The excellent low-frequency isolation performance was confirmed through parameter analysis.