Overturning effects on seismic performance of the hybrid friction-based seismic isolation system

Abstract

The safety and reliability of the double-deck variable-depth composite truss bridge (DDVD-CTB) during earthquakes can be ensured by a hybrid friction-based seismic isolation system (HFBSIS). However, the overturning effects on seismic performance of HFBSIS is a significant concern, as it can induce vertical actions of isolation bearings. In this study, a single-degree-of-freedom (SDOF) system was first employed to describe the isolation system with the consideration of overturning effects. Following the nondimensionalization of motion equation, it indicated that the ratio of total axial load variations of spherical bearings to deadweight of the girder (γ) was a good indicator for the overturning effects on seismic performance. Then, the finite element (FE) model of SDOF system was developed and verified by the quasi-static cyclic test results. Finally, parametric sensitivity analyses were carried out to evaluate the degree of overturning effects on the seismic performance of the isolation system under different design parameters. Therefore, the maximum value γ of was less than 5 × 10−7 degree in the engineering practice. The nondimensionalization of motion equation considering overturning effects was approximately the same as that neglecting overturning effects, suggesting that overturning effects could be neglected when designing the HFBSIS in DDVD-CTB.