Response analysis of base isolated structure with nonlinear damper considering higher harmonic components

The seismic isolation system utilizing steel laminated rubber bearing at the base of the structure is attracting attention. The application of the system to the containment building of the fast breeder reactor has been investigated. According to the resonance phenomena with ground motion containing long period components, the displacement responses of base-isolated structure is expected to become quite large. Therefore, the base isolation system needs to install various types of devices to dissipate vibration energy. In this paper, to suppress such the large displacement response of the base-isolated structure, the dynamic characteristics of four types of nonlinear dampers are studied. These nonlinear dampers operate weakly in the range of small displacement and strongly against the large displacement. Especially, the simplified equations for calculating the maximum responses are proposed by the approximated function consisting of the fundamental and third harmonic components in the Fourier series expansion of damping force. Furthermore, the magnitude of spike in acceleration response is calculated based on the proposed equations. Finally, the effect of third higher harmonic component on the acceleration response of base-isolated structure is compared among four types of nonlinear dampers