Shake table test and numerical study on a capable and resilient lateral seismic isolation system for long-span cable-stayed bridges

Abstract

Seismic isolation of long-span cable-stayed bridges in the transverse direction requires both large restoring force and large deformation capacity for the girder–tower connections, especially in critical seismic conditions, which challenges a lot for the design of earthquake resisting system (ERS). A capable and resilient lateral isolation system (CRLIS) is proposed that comprises FRP cables and a parallel FVD for the girder–tower connections and can provide the desired large restoring force and large deformation capacity. Based on a practical long-span cable-stayed bridge, detailed design parameters of the CRLIS were presented through a parameter analysis, and then a 1/35-scale physical model of the long-span cable-stayed bridge was made and tested on a four-shake-table testing system in the Multi-functional Shaking Table Lab at Tongji University. Details of the physical model including the scale factor, configuration of the structural members, additional mass blocks, boundary conditions, and the essential pretest numerical validation were briefly introduced. The experimental results show that the CRLIS could significantly reduce the acceleration response of the girder and the shear force to the girder–tower connections, as well as a considerable reduction of the forces to the towers. Numerical simulation is also conducted and validated by the experimental data; specifically, the sensitivity of the numerical simulation result to the Rayleigh damping matrix is investigated and a definition of the Rayleigh damping matrix is suggested. Furthermore, the isolation effectiveness of the CRLIS is concisely analyzed.