Mechanism and Aerodynamic Countermeasures of Vortex-Induced Vibration of a Cable-Stayed Bridge with Narrow Π-Shaped Girder Sections

Abstract

In this study, the investigations on the mechanism and aerodynamic countermeasures (ACs) of vortex-induced vibration (VIV) for a narrow Π-shaped girder (NG) section with the aspect ratio of B/D = 5 (B is the width and D is the height of the main deck) are conducted. First, the wind tunnel tests on VIV of the NG section with/without ACs are carried out. Furthermore, numerical simulations of VIV of the NG section with/without AC-VII, namely combined AC of modified fairings and inclined deflectors, for wind attack angle of +3° are conducted via fluid–structure interaction, respectively. Moreover, the mechanism of VIV of the NG section is analyzed from the characteristics of vorticity, pressure, and vortex-induced force (VIF) distributions, respectively. The research results show that the original NG section exhibits obvious vertical and torsional VIV for wind attack angles of +3° and +5°, respectively. Moreover, the ACs of low vertical stabilizers and horizontal separators, which are commonly applied to suppress the VIV responses of the wide Π-shaped girder section with aspect ratio B/D = 10–14, cannot effectively suppress the VIV responses of the NG section with B/D = 5. However, the AC-VII can effectively suppress the VIV responses. For the original NG section, the shear layer separation vortices that are generated on the windward side will extend to the leeward of the section and form the periodic shedding vortex, which is the mechanism of the VIV of the NG section. However, the AC-VII effectively suppresses the scale and vorticity intensity of the upper dominant vortex, avoiding the appearance of the vortex acceleration region at the leeward of the NG section. Therefore, the vorticity intensity of the upper and lower dominant vortexes is reduced during the shedding process, and the peak value of the fluctuating pressure in the VIV’s driving region is reduced by 86%.