Recently, the G309 Heshui to Xifeng Highway Project achieved another milestone—the steel box girder installation for the pedestrian overpass along the route was successfully completed. The girder was precisely positioned onto its designated bearings, marking a significant phase in the construction of the project's ancillary works and laying a solid foundation for the full-line completion by year-end.
As a key project under Gansu Province's 14th Five-Year Plan for highway and waterway transportation development, the G309 Heshui to Xifeng section spans 53.143 kilometers. Constructed to Class-1 highway standards with a design speed of 80 kilometers per hour, the project carries a total investment of 7.73 billion yuan. The installed pedestrian overpass features a single-box, single-cell simply supported steel box girder. The main bridge spans 33 meters in length, with a girder height of 1.4 meters, a deck width of 4.0 meters, and a bottom plate width of 3.06 meters. The side flanges are plumb, and the deck cantilever width measures 0.5 meters. The main structure and stairway of the steel box girder utilize Q355D steel. Pot bearings are used for the bridge bearings, while slab bearings are employed for the ramp bearings.
At both ends of the steel box girder, the cross-section transitions to a rectangular box girder section with a width increased to 4.8 meters to facilitate the connection between the ramp and the box girder. The elevation at the connection point between the ramp and the box girder is adjusted through the thickness of the bridge deck pavement. The steel box girder employs orthotropic bridge deck panels, with the top, web, and bottom plates all featuring plate ribs. Longitudinal stiffeners on the top and bottom plates are spaced approximately 300mm apart; transverse stiffeners are installed at 2m intervals.
One ramp is provided on each side of the overpass. The full width of the ramps is 4.8 meters. The stair treads employ a three-span continuous steel beam structure, with the main steel beams positioned on both sides of the treads. Steps are installed at the abutments to connect seamlessly with the existing local road.
The steel box girders were prefabricated in a factory and installed on-site via crane. Each girder weighed approximately 57 tons. The construction team employed heavy-duty truck cranes to lift the main bridge structure as a single unit, continuously monitoring the girder's aerial positioning. They strictly controlled axial deviation within ±10mm and elevation deviation within ±15mm, ultimately achieving precise and stable placement of the steel box girders.
Pedestrian overpasses are critical infrastructure for ensuring pedestrian safety and separating pedestrian and vehicular traffic. The construction team strictly adhered to the principle of “safety first, quality paramount,” conducting comprehensive inspections of hoisting equipment operation and wire rope quality throughout the process. Simultaneously, they implemented welding quality control and anti-corrosion treatment measures to ensure the overpass structure is safe, stable, durable, and long-lasting. Upon completion, this overpass will completely eliminate the safety hazards associated with residents crossing the highway along the route and significantly enhance road traffic efficiency.