Influence of cable vibration on seismic response of cable-stayed bridges

Abstract

In cable-stayed bridges, modelling the cables is of particular significance for the seismic behaviour of the structure. The common practice of modelling a cable by a single truss element is inadequate for seismic response calculations because it essentially precludes the lateral cable vibration modes. The present paper studies the influence of cable vibrations on the seismic response of cable-stayed bridges. Three bridge examples with different spans and properties were used. Cable vibrations are accounted for through the use of multiple links for each cable. Cable vibration effects are found to be significant for seismic response calculations, particularly when the cable fundamental frequencies are overlapping with the first few frequencies of the bridge. Parametric studies are conducted with regard to the number of links per cable, the effect of the modulus of elasticity of the cables, and different earthquakes on the bridge response. Modelling the cables by two links per cable such that at least the fundamental modes of the cable vibrations are represented can significantly account for the effect of cable vibrations. It is also observed that the equivalent modulus method cannot in any way account for the cable vibration effects. Key words: cable vibration, dynamic analysis, equivalent modulus, multiple links, seismic response, cable-stayed bridge.