INFLUENCE OF CABLE VIBRATION ON SEISMIC RESPONSE OF CABLE-STAYED BRIDGES

In cable-stayed bridges, modelling the cables is of particular signifi cance for the seismic behaviour of the structure. The common practice of modelling a cable by a single truss element is inadequate for seism ic response calculations because it essentially precludes the lateral cable vibration modes. The present paper studies the influence of cabl e vibrations on the seismic response of cable-stayed bridges. Three br idge examples with different spans and properties were used. Cable vib rations are accounted for through the use of multiple links for each c able. Cable vibration effects are found to be significant for seismic response calculations, particularly when the cable fundamental frequen cies are overlapping with the first few frequencies of the bridge. Par ametric studies are conducted with regard to the number of links per c able, the effect of the modulus of elasticity of the cables, and diffe rent earthquakes on the bridge response. Modelling the cables by two l inks per cable such that at least the fundamental modes of the cable v ibrations are represented can significantly account for the effect of cable vibrations. It is also observed that the equivalent modulus meth od cannot in any way account for the cable vibration effects.