Empirical formulas of the flutter critical wind speed for cable-suspended bridges under various wind angles of attack

This study aims to develop empirical formulas to estimate the flutter critical wind speed (FCWS) of cable-suspended bridges considering the effect of wind angle of attack (AoA). On the basis of simplified closed-form solution derived by Xinzhong Chen, the effects of wind AoAs and structural parameters on FCWS are introduced by modifying the flutter indexes. The simplified closed-form solution was transformed into a flutter index form, which facilitated a visual comparison of the impact of flutter derivatives and structural parameters on flutter performance. Based on this reformulated solution, an analysis was conducted to investigate the effects of wind AoAs and structural parameters on flutter indexes. This analysis revealed that, as the wind AoA increases, the critical flutter index transitioned from being a constant to a parameter dependent on structural parameters. When specifically targeting cable-suspended bridges, the critical flutter index could be expressed as a function of wind AoAs and frequency ratios. Following these findings, the empirical formulas were obtained using the nonlinear least squares method. Finally, the accuracy and applicability range of the proposed formulas were confirmed through numerical validation. The empirical formulas of FCWS of cable-suspended bridges are accurate when the AoA is less than 7°.