An alternative analytical approach to prediction of flutter stability limits of cable supported bridges

This paper presents a simplified analytical formulation, including closed-form algebraic expressions, for determining the critical flutter velocity of cable supported bridges. The formulae have been developed from the fundamental aeroelastic equations by introducing two assumptions: (1) Flutter derivatives may be approximated by expressions providing a frequency-independent description of self-excited forces. (2) The critical frequency is on the torsional branch of the solution and may be approximated by an uncoupled system of equations. The formulae have been tested for two typical cross sections, for a wide range of hypothetical structural configurations and the structural configurations of some well-known bridges. The numerical results produced by the formulae have been compared with results obtained by complex eigenvalue analysis, and it is concluded that the formulae give satisfactory results for all the cases considered. It is well known that multimodal effects may reduce the stability limits of an aeroelastic system. Hence, multimodal effects have been carefully studied to provide new insight into when a bimodal approach is sufficient, and when a more comprehensive multimodal approach is needed.