Multi-mode Coupled Buffeting Analysis of Cable-stayed Bridges

A procedure for the spectral analysis of buffeting response of long span bridges under unsteady wind loads is developed, with emphasis placed on inclusion of the multi-mode vibrations. The effect of mean wind velocity is considered through the aerodynamic stiffness and damping matrices using the flutter derivatives, while the effect of buffeting through the auto- and cross-power spectral densities. Compared with the conventional approach, the present approach is featured by the fact that no selection has to be made concerning the dominant modes. It can be reasonably used in analyzing cable-stayed bridges of complex geometry or of asymmetric shape, such as the Kao-Ping-Hsi Bridge, where the conventional approach has its limitations. The numerical studies indicate that using the conventional approach, by which the coupling effect is ignored, may significantly overestimate the critical wind velocity, while underestimating the buffeting responses of cable-stayed bridges.