Experimental and numerical studies on suppression of vortex-induced vibrations of twin box girders by central grids

Abstract eng:
The control of vortex-induced vibrations (VIV) for a twin steel box girder suspension bridge with a main span of 1660m in the presence of central grids on the upper side of gap has been investigated by using dynamic wind tunnel tests and stationary numerical simulations. The obvious vertical bending VIV of the original girder as for service condition were observed with attack angle of 0,  ±3 and ±5 by the conventional dynamic section model tests with a geometric scale of L = 1:70 and a space ratio of L/B=2.29. Thereafter the aerodynamic countermeasures of central grids on the upper side with different ventilation rates were employed to mitigate the VIV. Based on the experimental results, the numerical simulations were carried out for the most unfavorable attack angle of -3 to further study the flow characteristics around the twin girder and investigate the mechanism of control of VIV by central grids. The results indicate that strong vortices form in the gap between the original two box girders, which impinge on the downstream box girder and cause periodical force. However, the vortices are obviously suppressed due to the presence of central grids on the upper side of gap. In addition, the most effective ventilation rate of central grids to reduce the amplitude of VIV is proposed.

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