Research on the vortex-induced vibration and aerodynamic mitigation measures of parallel H-shaped composite girders under aerodynamic interference effects

This study investigated the vortex-induced vibration (VIV) characteristics and triggering mechanism of the parallel H-shaped composite girders by wind tunnel test and Computational Fluid Dynamics (CFD) simulations. The effects and suppression mechanisms of aerodynamic mitigation measures, such as vertical stabilizer plates, horizontal plates, and fairings, on VIV were investigated. The results showed that vertical VIVs occurred in the parallel bridge at an investigated angle of attack (AOA) of 0 degrees,-3 degrees, and 3 degrees. The characteristics of the VIV responses of the upstream deck are similar to those of the single bridge. However, the VIV amplitude of the downstream deck is magnified and far surpasses the allowable value under the effects of the wake vortex of the upstream deck, particularly at a positive AOA. The vertical stabilizing plate can only suppress the VIV of the upstream deck because it mitigates the vortex formation on the lower of the upstream deck. Nevertheless, the fairing has the ability to simultaneously suppress the vortices on the upper and lower of the upstream deck and minimize the influence of its wake vortices on the downstream deck. It effectively prevents the merging and distortion of vortices on the upper of the downstream deck, thereby suppressing the VIV of parallel H-shaped composite girders. In addition, the lengthening and bilateral arrangement of the fairing can augment its ability to suppress VIV. Particularly at a-3 degrees AOA, it successfully creates a highly stable shear layer of the upstream deck and makes the vortices on the surface of the downstream deck significantly suppressed.