The Role and Optimization of Guide Vane Inclination in Suppressing Vortex-Induced Vibrations of Π-Shaped Girders

The Π-shaped composite girder is widely used in the construction of long span cable-stayed bridges, but its poor vortex-induced vibration (VIV) performance seriously affects its application prospects. The VIV performance and aerodynamic optimization measures of a Π-shaped composite girder are studied by using wind tunnel tests. The tests show that the VIV of the original Π-shaped section occurs at each wind attack angle, and the amplitude can be reduced by setting guide vanes and the lower central stabilizer at the bottom of the I-beam. The change of the inclination angle of guide vanes has a significant impact on the VIV suppression performance of the combined aerodynamic measures. The configuration with a 30° guide vane inclination angle exhibited optimal performance for VIV suppression, achieving the greatest reduction in amplitude. The VIV suppression mechanisms of the combined aerodynamic measure are studied by using computational fluid dynamics (CFD) numerical simulation. The calculation results show that the windward-side guide vane in the 30° inclination guide vane combination measure can significantly improve the flowing condition around the upstream section and cooperate with the lower central stabilizer to weaken the Kármán vortex of the Π-shaped section wake, thereby suppressing the girder’s VIV. Changing the inclination angle of the guide vane not only affects the generation of vortices near the guide vane itself but also affects the improvement of the lower central stabilizer on the vortex shedding state on the lower side of the section, thereby significantly improving the VIV suppression performance of the combined aerodynamic measure.