Ground Effects on the Vortex-induced Vibration of Bridge Decks

Abstract

The present study investigated the ground effects on the VIV of a closed box girder based on wind tunnel tests and numerical methods. First, we presented a vibration measurement system for wind-tunnel test to simulate ground effects on the bridge girder. Second, we investigated the Strouhal number (St), the VIV lock-in phenomena over a range of wind velocities, and the maximum VIV amplitudes and their change laws in correlation with the height from the ground in two different ground conditions. The outcomes showed the following: that a low height from the ground can lead to high St numbers; that ground effects did not change the width of VIV lock-in range, but did impel VIVs to occur earlier in the uniform flow field; and that the maximum VIV amplitudes was reduced and the VIV lock-in range narrowed in the turbulent flow field. Finally, we conducted the numerical simulation method to study the ground effect mechanism on VIVs. The numerical results showed that the periodic vortex shedding will generate periodic forces on the structure, which leads to the occurrence of VIVs. Ground effects can speed up vortex shifting, whereas aerodynamic forces on the deck are weakened.