Driving mechanism of vortex-induced vibration for the Humen Bridge and its mitigation

Vortex-induced vibration (VIV) of the Humen Bridge in 2020 raised a major concern about the application of shallow box girders in long-span bridges since their aerodynamic characteristics are highly sensitive to aerodynamic shape and deck attachments. In this study, large eddy simulation (LES) coupled with computational structural dynamics was first employed to reveal the VIV response of the Humen Bridge under different wind speeds and to investigate the flow structure and driving mechanism during the VIV process. Then, LES was further used to explore aerodynamic measures and their mechanisms to effectively mitigate the VIV of the Humen Bridge. Finally, sectional model wind tunnel tests were carried out to measure the wind pressure on the bridge deck and the wake flow with various deck attachments. The results indicate that, when VIV is observed on the original stiffening girder, pressure fluctuations on the bottom surface are intensified. The strong vortex shedding at the bottom of the stiffening girder is identified as the primary driver of the vertical bending VIV. This phenomenon can be effectively mitigated by moving the side maintenance rail (MR) inward or replacing it with invisible MRs. The upstream barrier and MR on the original stiffening girder obstruct the airflow, inducing strong flow separation. This results in an expansion of high negative pressure zones on both the top and bottom surfaces, generating significant mean and fluctuating aerodynamic forces.