Design of Arch Bridge with Variable Steel-Concrete Composite Section Based on Vertical Erection-Rotation Method

This paper presented an innovative use of a variable steel-concrete composite section for the main arch ribs to take combined advantages of steel and concrete strength. And vertical erection method that can significantly simplify and accelerate arch bridge construction with better structure integrity and higher stability during construction is developed. Since steel construction is superior to RC due to its advantages of high strength to weight ratio, offsite prefabrication and quick on-the-spot assembly, the use of steel box as the stiffening core of arch rib section becomes an ideal choice for the initial arch framing using the developed erection method. The prefabricated steel box can be erected vertically on temporarily restrained horizontal hinge device at the spring line with minimal hoisting equipments. The completed two half-leaf can then rotate down on its own weight to meet at the mid-span for closure in a few hours. The completed steel arch frame can serve as formwork and supporting system to provide a sufficient and safe platform for the placement of concrete that forms a variable composite rib section, and for erection of spandrel columns and deck system. This construction technique and structure optimization can significantly simplify and speed up arch bridge construction with increased work zone safety and better constructability, thus provides a viable solution for arch bridge construction with difficult site condition. Pilot project, a 75-meter highway bridge, was presented to demonstrate the basic concept, design features, general construction technology.