Geometrically nonlinearity analysis and performance evaluation of tuned inerter dampers for multidirectional seismic isolation

Abstract

Tuned inerter dampers (TIDs) have been widely studied for vibration control and seismic isolation. It is traditionally mounted in the direction of motion of the primary structures and mitigate only the vibration in the direction of mounted. In this study, a configuration of geometrically nonlinear TID (GNTID) is investigated for multidirectional seismic isolation of structures. The GNTID is set up in perpendicular to the motion of a primary structure, and generates a force which is nonlinear with respect to the motion of the structure. The dynamic response of a SDOF system with GNTID under harmonic excitation is obtained via the method of incremental harmonic balance, followed by a stability analysis to establish the unstable diagram of excitation amplitude and frequency. The optimal parameters of GNTID are derived by minimizing the absolute displacement transmissibility. By applying a sequence of curve fitting scheme, design formula for optimal tuning parameters of the GNTID are formulated which are expressed as functions of structural damping ratio, inertance-mass ratio for various excitation amplitude. Finally, two examples are given to demonstrate the vibration isolation performance of GNTID. The maximum transmissibility of the GNTID system is smaller compared with uncontrolled system, and it has wider vibration isolation frequency band. In addition, the application of GNTID in the base-isolated structure can significantly reduce the peak value of seismic response and realize multidirectional vibration isolation.