Research on Mechanism of Vortex-Induced Vibration Railing Effect of Double-Deck Large-Span Suspension Bridge

Large-span suspension bridges are susceptible to wind loads. Therefore, a more precise analysis of their wind-induced vibration response is necessary to ensure the structure's absolute safety. This investigation conducted wind tunnel tests for the construction and completion stages to reveal the vortex-induced vibration (VIV) phenomenon of a double-deck suspension bridge. The results showed that no VIV occurred during the construction stage. However, the inclusion of railings significantly deteriorated the aerodynamic performance of the suspension bridge, leading to significant VIV at +3 degrees and +5 degrees wind angles of attack. Additionally, reducing the railing ventilation rate can significantly suppress the VIV amplitude. A new analysis method based on computational fluid dynamics (CFD) simulation is proposed to investigate the VIV mechanism of the double-deck truss girder. Twenty-nine measurement points were used to explore the vortex that causes VIV. The numerical simulations found that the area above and aft of the upper deck dominated the vertical VIV, while the aft of the lower deck dominated the torsional VIV. Furthermore, the intensity of the vortex in these areas was significantly lower during the construction stage. Moreover, reducing the railing ventilation rate significantly suppresses the torsional VIV by reducing the intensity of the vortex in the region behind the lower deck.