Study on integrated aerodynamic measures for improving flutter and vortex-induced vibration performance of flat steel box girders
- P 485-494
Integrated aerodynamic measures for improving the flutter and vortex-induced vibration (VIV) performance of flat steel box girders (FBGs) were studied with a long-span suspension bridge. The critical flutter wind speed and VIV response of the FBG were first evaluated through 1 : 60 scale section model wind tunnel tests, including aerodynamic measures such as an upper central stabiliser, inner guide vanes at the maintenance vehicle tracks and horizontal stabilisers. Results indicated that adding an upper central stabiliser improved the flutter stability of the FBG but increased the VIV amplitude. Setting inner guide vanes at the maintenance vehicle tracks eliminated VIV under vertical and torsional damping ratios of 0.28% and 0.21% respectively, but significantly reduced the critical flutter wind speed. Horizontal stabilisers alone did not improve wind-induced stability. The combined use of the upper central stabiliser and guide vanes mitigated each other’s advantages: guide vanes reduced the flutter stability improvements of the upper central stabiliser, whereas the latter compromised the VIV suppression effectiveness of the guide vanes. However, a combined configuration of horizontal stabilisers, upper central stabilisers and guide vanes significantly enhanced flutter and VIV performance. The optimised section exhibited no VIV, with critical flutter wind speeds increasing by over 14.8% across all angles of attack compared to the original section. Computational fluid dynamics simulations revealed that large vortex shedding in the wake region induced periodic aerodynamic forces, which primarily triggered VIV. While the upper central and horizontal stabilisers enhanced vortex shedding on the upper surface of the girder, the resulting aerodynamic forces interfered with periodic forces from wake vortex shedding, effectively suppressing VIVs.