Experiment study on vortex-induced vibration of a twin-box girder with large cantilever plates

Due to their good aerodynamic stability performance, twin-box girders are frequently adopted in long-span cable-supported bridges. However, they are also susceptible to vortex-induced vibration (VIV) since the central slot changes the flow patterns around a bridge girder. In this paper, the VIV performance of a twin-box girder with large cantilever plates was investigated through wind tunnel tests of sectional models with 1:75 and 1:30 scale ratios. Furthermore, the effects of increasing the damping ratio and installing various conventional aerodynamic countermeasures such as guide vanes, grid plates, and central stabilizers on VIV suppression of the twin-box girder were investigated. A new type of aerodynamic countermeasure named the L-shaped windshield was proposed to suppress the VIV response of the twin-box girder to an acceptable level. The results indicated that significant vertical VIV occurred for the twin-box girder, and increasing the damping ratio and installing conventional aerodynamic countermeasures could not suppress the VIV response of the twin-box girder effectively. The attachments obviously worsened the vertical VIV performance of the twin-box girder, and the attachments on the upper surface showed a more significant effect. It was further demonstrated that the L-shaped windshield is an effective countermeasure that can completely suppress the vertical VIV of the twin-box girder by greatly reducing the motion-induced vortexes in the central slot with the help of low turbulence in the turbulent flow field.