Effect of Windscreens on Vortex-Induced Vibrations of a Streamlined Closed-Box Girder

In this study, a comparative analysis of the impact of the attack angle and windscreen height on the vortex-induced vibration (VIV) in a streamlined closed-box girder was conducted using a 1:50 scaled model of a coastal cable-stayed bridge through wind tunnel tests and numerical simulations covering a range of attack angles and windscreen heights. The simulations were validated through experimental data, grid sensitivity analysis, and time-step independence. The results revealed that the VIV amplitude increased with increasing attack angle because of the interaction between vortices from the traffic lane and those in the wake region. Specifically, under a [Formula: see text] attack angle, pronounced VIV was observed in the section, with the maximum torsional VIV amplitude reaching up to 4.1[Formula: see text]times the code-specified limit. Spectral analysis revealed that within different wind speed lock-in ranges, the vibrations consistently corresponded to the torsional fundamental frequency mode. Further insight from proper orthogonal decomposition (POD) based on singular value decomposition (SVD) revealed that the large-amplitude torsional VIV of the section was caused by separated vortices over the traffic lane persistently transferring energy to the wake Kármán vortices, forming large-scale vortices that could lock in with the torsional mode of the main girder. Windscreens on both sides of the section effectively reduce the VIV amplitude through distinct mechanisms: the windward screen delays flow separation. Moreover, the leeward screen altered the path of the vortices toward the wake region. When the windscreen height reached 4.5[Formula: see text]m, the vortex movement path to the leeward side was completely blocked, fully suppressing the VIV. The effect of windscreen height on VIV was closely linked to lift, surface pressure, and their correlation. These findings provide valuable insights into wind-induced vehicular safety measures and VIV suppression strategies for sea-crossing bridges.