Study on the Calculation Method of Bearing Capacity of Old Steel Arch Bridge

Due to the long-term action of load, the material properties and structural shape of bridge structure will gradually change during service, resulting in the change of bearing capacity. In this paper, a calculation method of maximum bearing capacity is proposed for old steel arch bridges. The calculation method considers the material nonlinearity and geometric nonlinearity, as well as the residual deformation of the structure of the old bridge caused by the overload vehicle, collision of the vehicle and ship, resulting in the difference between the actual structure and the design drawing. Taking an 85 year old steel arch bridge in Ningbo as an example, the current material properties and the current configuration of the structure are actually tested, and the bearing capacity is calculated. The results show that: (1) The steel used in the bridge is well protected, and the properties of steel still meet the requirements; (2) For steel arch bridges, the deformation of arch ribs, especially the deformation out of plane, may greatly weaken the bearing capacity of the bridge; (3) It is necessary to consider the material nonlinearity and geometric nonlinearity for the calculation of the maximum bearing capacity of the old bridge.