Parametric optimization of a base-isolated structure based on system reliability

A simplified two-mass calculating model of a base-isolated structure was established in order to study the effect of crucial design parameters on the system reliability. A Bouc-Wen model was used to simulate the isolation layer and a Bouc-Wen model with stiffness degradation was used to simulate the upper structure. The motion equation of the base-isolated structure was established. The pseudo excitation method and reliability theories were used to analyze the random responses and dynamic reliability of the system under different period ratios, yield force ratios and damping ratios. The design parameters of the base-isolated structure were optimized with the system reliability as an objective. The above theories were used to analyze the stationary random earthquake responses of a base-isolated structure with a 8 degree seismic precautionary intensity. The story displacements and the system reliabilities of the isolation layer and the upper-structure were calculated. The results showed that properly selecting period ratio, yield force ratio and damping ratio can make the displacement responses minimum, so the system reliability of the base-isolated structure is high; validating the safety of base-isolated structures based on system reliability is a guide for structural performance design and state control of base-isolated structures.