Experiment and Numerical Investigations on a Vertical Isolation System with Quasi-Zero Stiffness Property

Abstract

Isolation devices with quasi-zero stiffness (QZS) are characterized for their better performance under low-frequency excitations, and they have attracted increasing research interest in recent years. This paper presents a QZS vertical isolation system with disc spring and helical spring connected in parallel. The disc spring can provide variable stiffness and even negative stiffness when it is loaded at the flat position. The static force-displacement relation is first introduced, and the equation of motion is established and simplified. Two simulation approaches are studied to numerically calculate the dynamic response of the QZS system, including using the Simulink and an open-source calculation platform - OpenSees. To verify the theories and simulations, static and shake table tests are designed and performed. The main test results include the static force-displacement relation, transmissibility curves, damping levels, and time history response under harmonic and impact excitations. The tests and simulation results indicate that the QZS vertical isolation system has a satisfactory isolation performance and the proposed numerical calculation methods can accurately predict the dynamic response of the system.