Research On Flexural Behavior Of Externally Prestressed Concrete Beams With CFRP Tendons

With increasing of China's economy and society, old bridge reinforcement and maintenance problems also increase. External prestressing technology has the advantages of construction speed, security, economy, so it has been widely used in the old bridge reinforcement, and has made great economic and social effects. In the traditional technique of external prestressing, steel bar commonly was used as external prestressed tendon, but the exposed steel bars were easy to be corroded. In order to fundamentally solve this problem, alternative materials were urgently needed. Since the material advantages are light-weight, high-strength, noncorrosive and fatigue resistance, Carbon Fiber-Reinforced Polymer (CFRP) tendons get more focus. Based on the static experiment of 15 concrete beams, this study attempts to analyze the flexural behavior of concrete beam strengthened by external CFRP tendon, discuss the anchor design of external CFRP tendon and the algorithm of friction loss.(1) Research on the performance of anchor deviceBased on the characteristic of CFRP tendon, friction-bonded anchor device and deviator of external CFRP tendon were designed in this paper. Through the slip resistance coefficient test, discusses the connection properties of different plates groove depth, breadth, different concrete surface mesh, dosage of corundum, different surface coating adhesive, and different bolt pre-tightening force of steel and concrete surface resistance coefficient of sliding resistance, and gives the suggested value of slip resistance coefficient. In addition, through the experiment of 2 strengthened concrete beams, study the properties of anchor device in tension phase. Analysis the strain distribution rule of high strength bolts and deformation features of anchor device, check the reliability of friction-binding anchor device.(2) Prestressing loss of external CFRP tendonsBased on the existing prestressing loss calculation method, compare the tension test results of external prestressing CFRP tendons, discuss the friction loss algorithm and the reasonable value of friction coefficient.(3) Experimental research on flexural behavior of externally prestressed concrete beams with CFPR tendonBased on the static experiment of 13 concrete beams strengthened by external CFRP tendons, this study attempts to analyze the flexural behavior of strengthened beams, including deformation, crack, damage model, bearing resistance capacity and so on. Research the effect of the distribution of CFRP tendons, strengthen class of concrete, reinforcement ratio of steel and the load levels on the bearing resistance capacity of externally prestressed concrete beams with CFRP tendons. Discuss the simplified algorithm of the ultimate stress of external CFRP tendons and the bearing resistance capacity of concrete beams strengthened by external CFRP tendons. Compare the calculation values with the test values.The research results of this paper provided a new reference for anchor design of external prestressing CFRP tendons, improved the reinforcement technology of external CFRP tendons. At the same time, It had some great significance to practical application of reinforcement technology of external CFRP tendons.