Study on a rational evaluation method for load-carrying capacity of existing structures (Part 1: analytical study of steel bridge 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. Therefore, in this paper, as an example of load-carrying capacity evaluation of existing bridges, a method for calculating two factors used to evaluate load- carrying capacity is proposed. The factors in this paper focus on steel bridges. The first is a system factor that evaluates the excess capacity due to stress distribution and load sharing for members not considered in the design. The second is a condition factor that evaluates the reduction of load-carrying capacity due to damage. These factors were calculated from the results of a sophisticated analytical model using 3D FEM.