Effects of additional static wind angle of attack on discrepancies between 2D and 3D flutter of suspension bridges

Abstract

The disparity in critical flutter wind speed ($U_{\mathrm{cr}}$) between two-dimensional (2D) section models and three-dimensional (3D) full aeroelastic bridge models is crucial for determining the wind-induced safety of long-span suspension bridges. However, it remains unclear whether this disparity is due to the effects of additional static wind angle of attack (ASWAOA), multi-modal coupled effects, or both. In present study, the mechanisms underlying the difference between 2D and 3D $U_{\mathrm{cr}}$ of suspension bridges are investigated using analytical methods with focusing on the ASWAOA effects. Firstly, suspension bridges are simplified to simply-supported bridges to eliminate multi-modal coupled effects, enabling a thorough investigation into the ASWAOA effects on 2D and 3D $U_{\mathrm{cr}}$. The concept and calculation method for evaluating the equivalent ASWAOA of 3D models are also proposed. Secondly, the ASWAOA effects on 2D and 3D flutter performances of suspension bridges with simple and continuous span-layout types are further discussed. The results show that the ASWAOA effects substantially reduce the 2D and 3D $U_{\mathrm{cr}}$ as positive initial wind angle of attack increases. However, the discrepancy between 2D and 3D equivalent ASWAOA is minimal, and the suspension bridges experiencing multi-modal coupled flutter indicates that the discrepancies between 2D and 3D $U_{\mathrm{cr}}$ arise primarily from the multi-modal coupled effects rather than the ASWAOA effects.