Design And Preliminary Experiments Of UHPC π-shaped Girder Bridge

In order to solve the problems of traditional simply-supported concrete girder bridge such as multi-joints, easily cracking and low durability, an innovative structure of Ultra High Performance Concrete(UHPC) π-shaped girder bridge was proposed. UHPC is characterized by high strength and excellent durability other than the traditional concrete. Therefore, the application of UHPC can significantly reduce structural geometry and simplify construction detail during the design stage, and achieve the rapid construction. In addition, the cast-in-situ UHPC seam construction method is of great convenient and can effectively improve the durability and integrality of the bridge panel, which has been widely applied in the precast concrete component interface connection.Base on the excellent property of UHPC, this thesis presents a study of the girder form of UHPC π-shaped girder bridge, which is characterized by fine, light, thin and smart. The width of the π-sharped girder web plate is relatively thin, and the thin plate with longitudinal and lateral ribs is also adopted in the bridge panel. The comparison between the UHPC π-shaped girder bridge and a traditional simply-supported concrete T-shaped girder bridge is also discussed, and the results show that the self-weight of this innovative structure intent to reduce 53 percent than the traditional one.This thesis presents a preliminary reinforcement design of π-shaped girder under the ultimate limit state and the serviceability limit state. Then, the experimental research of two 1:2 section scale models are given to study the flexure and shear behavior of UHPC π-shaped girder. The results prove that the cracking stress and the ultimate stress of UHPC π-shaped girder can satisfy the engineering requirement. The increase of the longitudinal reinforcement ratio can significantly improve the longitudinal cracking strain and limit the crack developing at the bottom of the girder. The theoretical calculation based on AFGC-SETRA UHPFRC Recommendations is relatively conservative, for the theoretical crack width is greater and the shear capacity is smaller than the experimental value.A bridge panel longitudinal seam structure with tongue-and-groove form joint and embedded steel bar is also designed in this thesis. For the study of π-sharped girder longitudinal seam strength, the joint full scale model experiment research is carried out. The results indicate that such joint can satisfy the stress requirement, for the seam cracking stress experimental value(12.2MPa) is larger than the maximum designed principal tensile stress(10.8MPa) of the bridge panel. The measuring strains near the seam are always at low level,while measuring strains crossing seams sussesivly go into nonlinearity. The strain growth appear inconsistent phenomenon shows that the joint interface is separated during the experiment.The finite element models of experimental beam are established by ABAQUS software and the nonlinear finite element analysis are carried out. The experimental values and the simulated values are in good agreement, which verifies accuracy and applicability of the material parameter in the concrete damaged plasticity(CDP) model. The parameter of Ultimate tensile stress in the CDP model has pronounced effect on the simulated results, such as the stiffness after cracking and the elastic limit. In addition, the finite element joint models have adopted the coulomb friction model, and the simulation results agree well with the experimental data. The calculated limit load using coulomb friction model is 18 percent smaller than that adopting the full-bond model, which illustrate that the seam strength still has some room for improvement in further research.