Experimental Verification of the Eddy-current Inerter System with Cable Bracing for Seismic Mitigation

Abstract

In this study, a novel vibration mitigation device which uses a displacement amplification mechanism is proposed. It is called cable-bracing inerter system (CBIS) and provides the additional damping force through inerter element, friction element and eddy current damping element. Eddy current damping is a non-contacting damping mechanism, and the damping ratio can be easily adjusted by varying the air gap between the permanent magnets and the conductor in this device. In the traditional tuned mass dampers, large additional mass is often required for its seismic control which is a limitation of a tuned mass damper. This device overcomes this kind of limitation and its effective masses can be several times than the actual mass. In this paper, we present a comprehensive study that involves experimental, analytical, and computational approaches. First, we described the principle of the CBIS which includes eddy current damping mechanism and an apparent mass amplifier using inerter. CBIS utilizes two cables which are easy to install to transmit control forces and deformation between the main structure and CBIS. Second, the theoretical model was given and to simplify the theoretical model of CBIS, the flexibility of the cable was neglected and the motion governing equation was also given. A series of free vibration tests and shaking table tests were conducted on a single degree of freedom (SDOF) steel-frame model with/without a CBIS to evaluate the effectiveness and performance of the CBIS in suppressing the vibration of the model. In the free vibration tests, the extend Kalman filter is used to identify the parameters of structure and CBIS. The results show that by using a properly designed inerter system, a lightly damped primary system can achieve a considerable reduction in its response with a small weight penalty. The experimental results show that the CBIS can effectively reduce the displacement and acceleration responses under different earthquake excitations.