Multimode coupled flutter and buffeting analysis of long span bridges

In this paper, the equations of structural motion are expressed in time-invariant state-space equations by expressing the frequency dependent self-excited forces in terms of rational functions. Accordingly, the multimode coupled flutter analysis is reduced to evaluate the eigenvalues of a constant matrix at each prescribed wind velocity. This formulation is computationally efficient in comparison with the conventional iterative approach. The complex mode approach is utilized for analyzing efficiently the coupled buffeting response. This approach is computationally more efficient than the conventional scheme in which a matrix inversion is required to evaluate the system transfer function at each frequency. A long span cable-stayed bridge and a suspension bridge are used to investigate the coupled flutter. The effect of the aerodynamic coupling among modes on the buffeting response is ascertained and compared to conventional mode-by-mode approach.