Dynamic Characteristics of Seismic Isolation with Quasi-Zero Stiffness, Rotational Inertia

Conventional seismic isolation reduces acceleration and structural damage. However, there is a trade-off between displacement and acceleration. Thus, seismically isolated layer may pound against moat walls when a large earthquake occurs. To address the above problem, we developed a displacement control system (DCS) in previous study. DCS is a seismically isolation system with quasi-zero stiffness (QZS) and rotational inertia. A QZS device is used to improve the control performance of seismically isolation system. However, if the dominant frequency of the input wave varies from low to high, a seismically isolation system with a QZS device causes nonlinear resonance and drastically degrades in control performance. Rotational inertia, however, elongates the natural period and prevents the nonlinear resonance caused by QZS. This study evaluated the steady-state response of our DCS subjected to harmonic excitation through analysis and shaking table tests. The response of DCS to seismic excitation was also investigated through shaking table tests. Comparing the analytical solutions and the test results showed that the analytical solutions agree well with the test results in terms of the frequency-amplitude relationship. The test results of seismic wave excitation indicate that our DCS suppresses the maximum response displacement within the seismic gap.