Aerodynamic interference mechanism of vertical vortex-induced vibration of a ]T-shaped girder paralleled with a truss girder

In this study, the aerodynamic interference characteristics and mechanism of vertical vortex-induced vibration (VIV) of a ]T-shaped steel-concrete composite girder of a highway cable-stayed bridge and a steel truss girder of a railway cable-stayed bridge are investigated via experimental and numerical simulation methods, respectively. To this end, firstly, wind tunnel tests are conducted on section models with a geometry scale of 1:60, consisting of the ]T-shaped girder paralleled with truss girders to investigate their aerodynamic interference behaviors. Moreover, the fluid-structure interaction (FSI) approach based on dynamic mesh and user defined functions (UDF) is applied to study the wind-induced vibrations (WIV) of the single ]T-shaped girder and two parallel main decks for wind attack angle of 0 degrees, respectively. Furthermore, the characteristics of vorticity, surface pressure, and vortex-induced force (VIF) distributions of the ]T-shaped girder and the truss girder are analyzed to investigate the aerodynamic interference mechanism. The results reveal that, the significant vertical vortex-induced vibrations (VIV) of the single ]T-shaped girder are observed, however, no obvious vertical VIV occurs for the single truss girder. Moreover, when the truss girder locates in the windward of the ]T-shaped girder, no obvious vertical VIV responses are observed. However, the ]T-shaped girder and the truss girder both exhibit significant vertical VIV responses for wind from the ]T-shaped girder side, and the maximum vertical VIV amplitude of the ]T-shaped girder is amplified by 32% compared with the single ]T-shaped girder. The vortices shed from the truss girder section disrupt the regular vortex shedding of the ]T-shaped girder section, thus suppressing the VIV of the ]T-shaped girder section. The WIV of the truss girder section is due to the forced vibration caused by the vortex impact of the dominant vortices shed from the ]T-shaped girder section. As the downstream flow field is blocked by the truss girder section, the scale and intensity of the dominant vortices is increased, leading to an amplification of the VIF and the VIV amplitude of the ]T-shaped girder section.