The ground effect on vortex induced vibration and coherence mode of a landscape Bridge in Π-shape

This study investigates the vortex-induced vibration (VIV) performance of a wide Π-shaped main girder bridge in coastal areas. The impact of the distance between the girder bottom and the ground termed the ground effect is explored. Sectional model wind tunnel tests indicate that the wind attack angle significantly affects the vertical bending vortex vibration of the main girder. VIV amplitude decreases as the distance between the girder bottom and the ground decreases. Ground effect is most pronounced at smaller distances, nearly suppressing VIV. The change in the wind attack angle has a weak effect on the main girder VIV when the ground effect is considered. Numerical simulations are applied to further verify that the ground effect has a significant contribution to suppressing the VIV. Meanwhile, the pressure and velocity fields of the fixed bridge are analyzed using Higher-order dynamic mode decomposition (HODMD), and the first mode (M1) is found to dominate the ground effect. The energy of each mode decreases further when the bridge is set to free vibration. Overall, the study provides comprehensive insights into the complex interplay of wind and ground effects on the VIV performance of wide Π-shaped main girders.