Performance improvement of base isolation systems by incorporating eddy current damping and magnetic spring under earthquakes

Abstract

An innovative subsystem with the incorporation of eddy current (EC) damping and magnetic negative stiffness spring (MNSS) is proposed to develop feasible strategies for performance improvement of existing base isolation techniques. The concept of integrating the eddy current damping mechanism and the nonlinear negative stiffness spring is firstly introduced for better energy transition behavior under earthquake excitations. The analytical expressions of the force characteristics of the EC and the MNSS components are presented accordingly, and a parametric study is conducted to evaluate the inherent properties of the integrated magnetic subsystem. To demonstrate the advantages of the EC–MNSS subsystem, an illustrative example of a two-DOF model simulating both the superstructure and the isolation layer is numerically investigated by adopting two representative isolators and the proposed subsystem. The EC–MNSS subsystem is illustrated to significantly and simultaneously improve the isolation performances in terms of base drift and structural acceleration. The energy exchange and dissipation behavior are further revealed by employing time history analysis and energy-displacement-velocity plots. Furthermore, the proposed EC–MNSS subsystem is implemented in a benchmark isolation problem adopting an eight-story frame structure subjected to bidirectional earthquake excitations. The simulation results indicate the superior and the comparable performances of the integrated isolation system as compared to those of the passive and the control-augmented isolations, respectively.