Abstract

Vortex-induced vibration (VIV) poses a significant serviceability concern for wide streamlined box girders of long-span suspension bridges. This study investigates the VIV performance and aerodynamic mitigation of a wide streamlined box girder with a width-to-depth ratio (B/D) of approximately 10 through sectional model wind tunnel testing. The original cross-section was found to exhibit pronounced heaving and torsional VIV at positive wind angles of attack, with amplitudes considerably exceeding the prescribed serviceability limits. A systematic experimental investigation was conducted to evaluate the influence of three geometric parameters, i.e., wind fairing inclination angle, inspection rail position, and pedestrian railing porosity and panel arrangement, on VIV performance. Experimental results demonstrate that reducing the wind fairing inclination angle from 65° to 45° is the most effective mitigation measure. An appropriate porosity of the pedestrian railing is shown to substantially improve VIV performance. Furthermore, under equivalent overall porosity, a uniformly distributed alternation of solid and ventilated panels yields markedly superior VIV suppression compared with continuously sealed arrangements. Subsequent flutter and aerostatic wind tunnel tests confirm that the recommended cross-section preserves the favorable flutter stability and aerostatic performance of the original design. Strouhal number analysis reveals that the VIV lock-in is governed by St ≈ 0.12. Notably, the St number obtained from the pitching moment coefficient is nearly twice that obtained from the lift coefficient.

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