Responses of CableStayed Bridge Transversely Isolated with ElastoPlastic Cable Pairs and Fluid Viscous Damper Subjected to Near Fault Ground Motions

Abstract:

The response feature of cablestayed bridge with elastoplastic cable pairs and viscous damper adopted in lateral pylon seismic isolation design under near fault ground motions was investigated. Real near fault ground motions were simulated using the equivalent near fault pulse model, and the three sets of synthetic seismic waves with various pulse periods corresponding to II site condition are synthesized. Based on Yongning Yellow River Bridge, nonlinear time history analysis was performed under the synthetic near fault ground motions, and the effects of variation of design parameters of isolation device on the seismic response of the bridge in terms of relative girderpylon displacement were studied. The results show that the responses under synthetic ground motions are comparable to those records with the same pulse characteristics, which can satisfy the need of engineering practice. Near fault ground motions are likely to cause large displacement response. Therefore, it is strongly recommended that the natural period of the structure should be set apart from the pulse period by properly determining the design parameter of the elastoplastic cables. Allowing certain inelastic behavior of cables does not lead to the increase, sometimes even a decrease, of relative girderpylon displacement response when compared with a hypothetic case where the cables behave elastically all along.