Life-cycle evolution of the ultimate load carrying capacity of RC cable-stayed bridges

The approach for analyzing the evolution of the failure pattern and the corresponding ultimate load carrying capacity (ULC) of reinforced concrete cable-stayed bridges based on inspection and monitoring was proposed. First, a finite element model of the structure was established using periodic inspection and monitoring data. The ultimate bearing capacity of components was calculated with consideration of durability. Then, the vehicle load was applied to the model to obtain the internal force of the girder components. Finally, the location that the load effects exceed the resistance capacity is set as plastic hinge and a variant model was obtained, furthermore, an increased vehicle load was applied to the variant model of the bridge, the load effects are re-calculate and another variant model was obtained. This procedure was continued until the vehicle load reaches the maximum value, which was just the ultimate load carrying capacity, and the corresponding variant model was defined as the failure pattern of the girder. A cable-stayed bridge was employed in the case study. Four representative states of the bridge were selected to demonstrate the evolution of failure pattern and ultimate load carrying capability based on the data of inspection and structural health monitoring using the proposed approach. Evolution of the failure pattern and ultimate load carrying capacity of the bridge during its service period were investigated. The results verified the feasibility of the proposed approach in analyzing the failure pattern and ultimate load carrying capability of the cable-stayed bridge under vehicle loads. The crack of girder, corrosion of steel bar, and change of boundary conditions may result in damage of the bridge and variation in structural analytical model, which have dramatic impact on the failure pattern and ultimate load carrying capacity of the structure.