| Vortex-induced vibration is one of wind-induced vibrations which are often observed at low speed wind for long-span bridges. There have been many bridge girder which have taken vortex-induced vibration at home and abroad place, seriously affected the driving comfort and safety.Although certain aerodynamic measures for vortex-induced vibration reduced have been found,it’s still uncertain for a specific bridge girder. The reason is that the mechanism of wind-induced vibrations is still under development.Aiming at the flat box girder often used in long-span bridges, pressure-measured tests have been conducted in stationary and vibrational state, and the mechanism of wind-induced vibrations was studied in aerodynamic characteristics of cross-section and the spanwise correlation of aerodynamic forces(1) Mechanism analysis for vortex-induced vibration of flat box girder based on aerodynamic characteristics of cross-section. Compared with means, standard deviations of fluctuated pressure and power spectra of fluctuated pressure as well as coherence function monitoring node pressure and aerodynamic forces in different condition, the vortex mechanism were discovered. It revealed that severe fluctuation of pressure in the middle and downstream regions at the upper face constructs the fundamental momentum for vortex resonance and the high correlation between measuring point and total aerodynamic forces, the fluctuated pressure keep the same frequencies.(2) Mechanism analysis for vortex-induced vibration of flat box girder based on the spanwise correlation of aerodynamic forces. Comparing the spanwise correlation of monitoring node pressure and aerodynamic forces in vibration and static, the vortex mechanism were discovered. It revealed that the spanwise correlation of local and total aerodynamic forces became higher obviously, specially the upstream and downstream regions at upper face and leeward side webplate as well as windward web plate. |
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