Aerodynamic interference between two boxes in parallel arrangement and flow field characteristics around the girder

Aerodynamic characteristics of long-span bridges with box girders have been investigated widely, and this paper presents a study on a cable-stayed bridge with two box girders in parallel arrangement. Computational fluid dynamics (CFD) numerical simulations were adopted to analyze the aerodynamic interference between the upper and the lower box girders. After checking the reliability of the numerical model, different angles of attack and different distances between the two girders were considered, and the variations of the aerodynamic characteristics were discussed, including the aerodynamic coefficients and the static pressure distributions. Then, the wind environment around the two box girders was focused, and the effect on the aerodynamic coefficients of a vehicle was also studied. The results show that the aerodynamic interference between the two box girders is strong, so the aerodynamic characteristics of the two boxes are different from those of a single box. The flow field between the boxes have higher wind velocities, which makes the aerodynamic force on the upper box and the lower box become upward and downward, respectively. Meanwhile, the aerodynamic forces on vehicles above the lower deck surface are larger due to the accelerated flow between the two boxes.