Effect of Cable Vibrations on Cable-Stayed Bridges during Large Earthquakes

Abstract

Support movements cause nonlinear vibrations in cables, but it is unclear how exactly the cables in cable-stayed bridges respond to the complicated support movements induced by earthquakes. In this study, we employed a displacement approach that separated the cable vibrations into pseudostatic and relative dynamic responses. The former depicted the cable response under static loadings, the latter were caused by the dynamic components of the pseudostatic components. A three-dimensional finite-element model of a cable-stayed bridge was established, with the exact pseudostatic response of the cables included. The cable vibrations were determined following seismic displacements at the cable–deck and cable–tower connections. It was revealed that the cable vibrations were significant both during and after the shaking from the earthquake, and that the maximum response was reached after the shaking in most cases. The longitudinal and vertical seismic inputs mainly cause parametric and in-plane resonant vibrations, whereas the transverse inputs triggered out-of-plane resonant vibrations in the cables. The cable vibrations were more significant when high spectral accelerations of the ground motions occurred in the vibration periods of the cables. It was concluded that the nonlinear cable vibrations should be taken into consideration under larger earthquake conditions.