A simplified method to evaluate the critical flutter speed for flexible bridge decks

Flutter instability of flexible bridge decks is investigated following the semi-empirical Scanlan’s approach based on flutter derivatives. In the present work, the equations of the stability eigenvalue-problem are manipulated and simplified on the basis of a large number of dynamic and aerodynamic data. A simple expression for the critical reduced wind speed and for the coupling frequency is then obtained. The major interest of this approximate method is the fact that the critical parameters depend on three flutter derivatives only. In addition, these aerodynamic functions are known to be the most reliable and the easiest to be identified through wind tunnel tests. The proposed formulas seem to work well in a wide range of cases, unless the frequencies susceptible to couple are not too close to unity.