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.