Vortex-Induced Vibration Response and Aerodynamic Optimization of Asymmetric Bluff-Body Steel Box Girders

To systematically investigate the vortex-induced vibration (VIV) characteristics of asymmetric bluff-body steel box girders and the suppression mechanism of guide plates, this study takes a curved pedestrian suspension bridge as the engineering background. A dynamic mesh-based computational fluid dynamics (CFD) method is employed to simulate the VIV responses of the original bridge section under different wind attack angles. The results indicate that when the wind flows from the anchorage side (A) at a wind attack angle of [Formula: see text], the main girder exhibits significant vertical VIV at a wind speed of 4.4[Formula: see text]m/s, with a peak amplitude of approximately 140[Formula: see text]mm. To address this vibration, three guide plate configurations (Cases 1–3) are proposed. Numerical simulations demonstrate that all schemes can effectively suppress torsional VIV, among which Case 3 shows the best performance in mitigating vertical vibration, reducing the peak amplitude by about 57%. Further analysis of the vorticity evolution, surface pressure distribution, and pressure coefficient under the critical condition reveals that the guide plate functions by disturbing vortex formation, weakening wake symmetry, and homogenizing surface pressure gradients. These mechanisms collectively intervene in the development of the Kármán vortex street, thereby suppressing coupled vertical and torsional VIV at the source. The findings provide theoretical support for aerodynamic optimization and vibration control of asymmetric bluff-body bridges.