Rehabilitation of old three-hinged steel arch bridges - A case study of Ling Bridge

Ling Bridge, built by Siemens AG in 1936, is the only existing three-hinged steel arch bridge in China, and now declared a historic structure by the local government. Located on the busiest road that crosses the Ningbo city centre, the bridge has carried heavy traffic for more than 70 years. Concerned about the bridge's safety following frequent ship collisions in recent years and other damage, the bridge owners perform structural inspections every year. According to the latest inspection, Ling Bridge is suffering from a number of serious structural problems, including local deformation and deflection of the arch ribs, cracks in the deck and severe corrosion of the hangers. Therefore, at the end of 2014, the bridge management launched an overhaul of the bridge.

To maintain traffic flows and the cultural function of the bridge, the overhaul project is different from ordinary repair projects. The present overhaul mainly involves five parts of the structure: the hinges of the arch structure, the cantilever structure of the cross-beams, the deck system, the hangers and the arch ribs. This paper discusses the damage evolution of the diseases and pertinent strengthening measures taken to meet the requirements of structural safety and cultural protection.