Numerical and Experimental Investigation on Vortex-Induced Vibration Suppression of a Self-Anchored Suspension Bridge with a Central-Slotted Box Girder

In this study, the vortex-induced vibration (VIV) performance, mechanism, and control of a self-anchored suspension bridge with the central-slotted box girder (CSBG) under the operating wind velocity of the bridge were investigated via numerical simulations and experimental methods. First, the VIV responses and mechanism of the original CSBG at a wind angle of attack (AOA) of alpha = 0 degrees were investigated by fluid-structure interaction (FSI) calculations. Then, based on the VIV responses and mechanism, the corresponding aerodynamic countermeasures were proposed to suppress the VIV of the original CSBG. Finally, the small-scale (1:50) sectional model wind tunnel tests were conducted to verify the vibration suppression effect of the aerodynamic countermeasures. Moreover, the large-scale (1:30) sectional model wind tunnel tests were conducted to further verify the vibration suppression effect of the modified CSBG with the final aerodynamic countermeasure. The results showed that the vertical VIV occurs in the original CSBG at an AOA of alpha = 0 degrees, owing to the strong flow field connection between upstream and downstream box girders and vortices shedding off alternately at the tail of box girders. Moreover, for six types of closed grid plates with different BGP/BCS ratios (where BGP is the width of the closed grid plate and BCS is the width of the central slot), the flow field around the stationary CSBG showed that as BGP/BCS increases, less flow passes through the central slot, the tail vortex intensity weakens, and the fluctuating pressure coefficients become more stable. The 3.5-m-wide closed grid plate (BGP/BCS = 63.6%) at the central slot 0.5 m away from one side of the box girder was selected as the aerodynamic countermeasure, and the results of the FSI calculation showed that the vertical VIV of the original CSBG can be suppressed after taking the aerodynamic countermeasure. The results of the small-scale and large-scale sectional model wind tunnel tests verified the vibration suppression effect of the 3.5-m-wide closed grid plate. However, there were discrepancies in VIV responses between the small- and large-scale tests, especially for torsional VIV at an AOA of alpha = -5 degrees to +3 degrees. This study verified the potential of the computational fluid dynamics method to advance the VIV suppression of the bridge girder before conducting the wind tunnel tests.