Numerical study on surface distributed vortex-induced force on a flat-steel-box girder

To ensure the safety of bridges, the comfort of pedestrians and vehicles on bridges, the vortex-induced forces on flat-steel-box girders need to be investigated. The total vortex-induced forces integrated on the surfaces of girders have been studied extensively. This study will be mainly focused on the characteristics of surface distributed vortex-induced force, which can be beneficial to the vortex-induced vibration (VIV) reduction with local aerodynamic optimization. Computational Fluid Dynamics (CFD) method is employed for the simulation of the VIVof a flat-steel-box girder. The simulation results are verified through the comparison with the results of corresponding wind tunnel test. A self-adaptive nonlinear fitting method is proposed to determine the vortex-induced force model. A vortex-induced force contribution factor is defined to account the contribution of the components and the surface location. Based on the surface distributed vortex-induced force analysis, several conclusions are made. The vortex-induced force presents a fairly strong multiple-frequency characteristic, and the high-order terms should be carefully considered. Most energy of the VIV comes from the linear and third-order aerodynamic damping terms. In terms of location, the roof takes most of the aerodynamic damping and the total vortex-induced force. The flow separation around the underside upstream corner, the underside downstream corner and the middle downstream comer lead to large third-order aerodynamic damping term. The flow separation around the underside upstream corner has great contribution to the linear aerodynamic stiffness term.