Vortex-Induced Vibration Performance and Suppression Mechanism for a Long Suspension Bridge with Wide Twin-Box Girder

This study investigates the vortex-induced vibration (VIV) behavior of a twin-box girder bridge by means of aerodynamic sectional wind tunnel test and particle image velocimetry (PIV) measurements. The effect of grid plates on suppressing the VIV of twin-box girder model is examined and the influence of four design parameters of grid plates [porosity, flat plate width (FPW) ratio, composition type, and installation position] is studied. The primary causes of VIV and the suppression mechanism of grid plates are discussed in detail. It is found that torsional VIV is more vulnerable to the change in wind attack angle than is vertical VIV. The installation of grid plates noticeably suppresses the VIV of test model and its effect depends on the variation of different design parameters. For the porosity and FPW ratio, there is an optimal range in which the improvement of VIV suppression is more significant; the optimal value of porosity is about 42%–67%, and the optimal value of FPW ratio is about 0.042–0.167. Moreover, the uniform distribution of grid plates is more preferable in terms of suppressing VIV than is nonuniform distribution, whereas the installation of grid plates on the upper side leads to better performance of VIV suppression than does installation on the lower side. The primary cause of VIV of the twin-box girder is closely related to the formation of large-scale vortex shedding at the tail of the upstream box girder. The generation of large-scale vortex can be eliminated by appropriate selection of the design parameters of grid plates.