The Seismic Resistant Analysis And Reinforcement Measures Of An Existing Water Pipe Bridge

Japan is one of the world most populous country of earthquake, and the seismic research of the bridge structure has been at the forefront of the world.Since the promulgation and execution of Japan's new seismic design code, the existing bridges require re-evaluating the seismic performance. According to the Japanese seismic design code revised in 2002,the paper evaluates the safety performance of a pipe bridge in Japan, in order to reinforce effectively.Pipe Bridges are special features bridges, which transport water using the superstructure in the form of box-section. It is one of the lifeblood of the town in life and in industry, so its seismic research is an important part of disaster prevention and mitigation. Different from ordinary bridges in the seismic research, the influence of hydrodynamic pressure on the water pipe bridge should be considered when researching water pipe bridges, in the form of added mass simulating that the hydrodynamic pressure effects on the dynamic characteristics and seismic responses of the water pipe bridge.Damping is a important parameter in the structural dynamic analysis. The appropriate model of the damping is discussed in the paper. First making modal analysis in the transverse direction and in the longitudinal direction respectively, by analyzing the modal characteristics and the damping distribution characteristics, in the transverse direction the paper uses the Rayleigh model and the damping matrix model assembled by Rayleigh damping matrices in the structural dynamic analysis, while using the Rayleigh model in the longitudinal direction. Evaluating the reasonableness of each damping model in linear dynamic analysis, the dynamic response in both directions is verified by comparing to the mode-superposition approach, then introducing the selected damping model in the elastoplastic seismic response analysis.For the seismic performance evaluation of water bridges, the paper calculates the water bridge building model modeling by the bar system of 3D beam element by using finite element analysis software TDAP. The reinforced concrete bridge piers use elastic-plastic beam element to simulate, and its constitutive curve uses Takeda model.The superstructure and steel members use elastic beam element to simulate, and the pile foundation uses node springs to simulate. The elastoplastic time-history analysisof the pipe bridge under rare earthquake motion is carried out in the transverse direction and the longitudinal direction of the bridge separately. From analytical results, it is found that the responsive displacement and force of piers in the transverse direction of the bridge is larger than that of the longitudinal direction.The main vertical members of steel truss piers entered the yield stage in the transverse direction.By the method of welding steel plate to the main vertical members of steel truss piers to improve the bearing capacity of the components, then evaluating the safety performance of the pipe bridge reinforced by rebuilding the finite element model, the results show that the bridge is in a safe condition.