Study On Stress Performance Of Prestressed Concrete Girders With HRBF500 Steel Bars For High-speed Railway Under Fatigue Load

As the new generation of steel materials,500 MPa level hot rolled bars of fine grains (HRBF500 steel bars) will be applied to highway, railway, bridges and high-speed railway because of its low-cost, high-strength and long life and many other advantages.So HRBF500 prestressed concrete beams need to be subjected to fatigue load.At present, study on fatigue performance of prestressed concrete structures with HRBF500 steel bars is still in the blank.Therefore, based on the Program (2008AA030704) supported by the National High Technology Research and Development Program of China (863 Program), four high-strength prestressed concrete T girders with HRBF500 steel bars for high-speed railway have been designed.Through the static tests and constant amplitude fatigue tests, the mechanical performance of four girders under fatigue load are researched.The main research contents are as the following:(1) According to the code for design on reinforced and prestressed concrete structure of railway bridge and culvert, four HRBF500 steel prestressed concrete T girders have been designed and manufactured.The monitoring and theoretical calculation of the losses of prestress have been compared and analyzed.(2) Firstly, through the static tests of four HRBF500 steel prestressed concrete T girders, the testing phenomenon,cracks,deflection,strains of prestressing tendons, strains of longitudinal reinforcement HRBF500 and strains of concrete in four girders with different degreeof prestressing and ratio of reinforcement have been compared and analyzed.(3) Secondly, through fatigue tests of four HRBF500 steel prestressed concrete T girders, influencing factors affected cracks, deflection, stresses in prestressing tendons, stresses in longitudinal reinforcement and strains of concrete have been analyzed.In addition, factors of influence on fatigue performance of girders, such as fatigue cyclic times N, degree of prestressing, ratio of reinforcement, initial fatigue load, ratio and amplitude of fatigue stresses, have also been comprehensive analyzed and researched. Based on the fatigue tests of four HRBF500 steel prestressed concrete T girders, the width of cracks, deflection and fatigue stresses in longitudinal tensile reinforcement under fatigue load have been further analyzed in theory. The theoretical basis for the design of HRBF500 steel prestressed concrete structures subjected by fatigue load is provided.