Aerodynamic interference effects on a new bridge from adjacent parallel existing bridge

In order to improve the traffic capacity, the method of building a new bridge near the existing one is usually adopted. This method inevitably suffers from the aerodynamic interference effect because of the spacing between the existing and new bridges. In this paper, wind tunnel test and computational fluid dynamics technique (CFD) are used to investigate the static and dynamic interference phenomenon between the existing bridge and the new bridge. Through wind tunnel force tests, static aerodynamic force of new bridge is studied by varying horizontal spacing ratio. The wind tunnel vibration tests are used to study the influence of the existing bridge on the Vortex-induced vibration (VIV) characteristics of the new bridge under different horizontal spacing ratios, vertical spacing ratios, and different wind attack angles, Finally, by integrating experimental surface pressure data and CFD results, the vertical and torsional VIV of the new bridge alongside the aerodynamic interference mechanisms under different conditions are explained. The results show that the drag coefficients of downstream new girder display a shielding effect due to the upstream existing girder. What's more, the lift and torque coefficients are more affected by the wind attack angle. The horizontal spacing ratio change has a more pronounced effect on vertical VIV. The interference effect remains significant at X/B = 8. The change of the vertical height leads to the reduction of the pressure difference between the top and bottom of the plate, and thus significantly reducing the torsional VIV of upstream new girder.