The Main Bridge Design of Fenglai Daxi River Bridge on Wulong-Liangjiang Expressway

As a deck steel truss arch structure, the main bridge of the Fenglai Daxi River Bridge on the Wulong-Liangjiang Expressway has the world's largest span of 580 m. The bridge deck is about 310 m from the valley bottom, with large span, light structure, high design wind speed and relatively low foundation bearing capacity. The extreme crosswind in the bridge area causes a large proportion of internal forces in the main bridge structure, making the strength and stability issues acute. Crosswind load has become one of the dominant factors affecting the bridge design. Based on the study of wind field characteristics and reasonable structure, design innovation is made on the structural system, arch ring structure, and arch abutment structure of the Fenglai Daxi River Bridge to ensure that the bridge structure meets safety and economic requirements. The main arch rib adopts a steel truss structure with variable height and double parallel panel arrangement. Both top and bottom chords are arranged with continuous “K” shaped bracing, and the sway bracings is set by different spacing and types based on the force and torsional stiffness requirements of the arch ring. The columns on the arch adopt a steel bent structure, and the bridge deck beams are three steel-concrete continuous composite beams with variable span. Bearings with horizontal elastic deformation capacity are used between the column on the arch and the beam body to match the spatial stiffness of the arch, column and beam, so that all parts can bear forces together in both the vertical and horizontal directions.