Study on a rational evaluation method for load-carrying capacity of existing structures (Part 3: analytical study of substructure by 3D FEM)

The Specifications for highway bridges, revised in 2017, transitioned from the allowable stress method to the partial factor design method. Furthermore, the application of partial factor design methods and limit state design methods is now beginning to be considered for repair and reinforcement work during the maintenance phase. However, because the partial factors are determined using a simple structural analysis method, the bridge components that affect the bridge response (hereafter referred to as the bridge system) are not systematically considered. In addition, because the Specifications for highway bridges are standards for evaluating the load-carrying capacity of newly constructed bridges, they do not stipulate any load-carrying capacity evaluation that considers damage to existing bridges. This study was conducted to consider the application of partial factor design and limit state design methods for repair and reinforcement design at the maintenance stage, focusing on the substructure. First, the effect of rebar corrosion on the load-bearing performance of bridge piers was calculated as a factor. It was confirmed that when the corrosion of the rebar progresses by 20%, it affects the load-bearing capacity of the bridge pier. Second, the effect of variations in concrete strength on the load-bearing performance of bridge piers was factored. The concrete strength of structures approximately 50 years after completion varies greatly compared to when they were first constructed. It was confirmed that load-bearing performance needs to be evaluated in accordance with strength variations.