Shear Fatigue Performance Of Reinforced Concrete Beams Strengthened With CFRP Sheets

Bridge, crane beam, sleeper, ocean structure, pressure institution and nuclear reactor safety shell are often endured stress from many circle times and biggish repetition loading, and fatigue collapse is very easy accrued because of long and repeating loading. Fatigue damage once invalidated railway bridge, fatigue crack ever resulted in collapse of artesian well desk in ocean. Thereby, in order to avoid occurring the accident and extortionate reconstructed expense, it is necessary for us to research repairing and reinforcement of fatigue damage in RC structure.With its good physics and mechanics function, the carbon fiber reinforced plastics have been applied to the bridge reinforcement more and more. Presently, researching in concrete structure strengthened with CFRP-sheet made a great achievement, in addition, researching in anti-bending fatigue performance of concrete structure strengthened with CFRP-sheet attracted pursuers, and they obtained a part achievement. However, the study of shear fatigue performance of the concrete structure strengthened with CFRP-sheet has not been seen. Thereby, to study the shear fatigue performance of concrete beam strengthened with CFRP-sheet has the important theories and realistic meaning. To aim at this problem, in term to the feature of fatigue loading of bridge, this paper, on the base of analysis of current bridge reinforcement, makes a relative system experiment research and theory analysis for the shear fatigue performance of CFRP strengthened concrete beam, and offers the experimental basis for the fact that the long-term fatigue performance of strengthening the concrete structure of CFRP is studied.Six RC beams were made in the trial and experiments on inclined section shear fatigue were made. Experiments include nakedness girder, the anti-transformation of the reinforced beams and the transformation of the reinforced beams, studying shear fatigue performances on concrete beam strengthened with plastering different quantity of CFRP. One beam was used in the constant trial, the rest of beams were used in the fatigue loading trial, two of them were damaged firstly, then fatigue tested used for simulating the facts.The main content of the thesis successively included the following several respect according to the chapter:(1) This paper explains the structure damages and strengthens the current situation studied, has introduced the advantage that some existing reinforcement technology and CFRP strengthen, the fatigue destruction and studying the current situation of and the concrete structure, the survey domestic and international CFRP is used for improving the research current situation of the fatigue performance of beam of concrete.(2) The form and material of RC beams with CFRP strengthened both change. While shear design calculating, the traditional reinforced concrete theory is obviously no longer suitable. On the basis of many experimental study and theory are analyzed, this paper provide the shearing calculation formula of RC beams with CFRP strengthened. Then introduced some fatigue theories.(3) This paper introduces the purpose and meaning tested, design and make the beams, strengthen scheme and strengthen performances, previous work, testing program, loading and measuring etc.(4) This paper is experimentally investigated that under the fatigue loading, the change of stresses of stirrup and CFRP corresponding to the fatigue loads, the reinforcement effect for shearing shear with different amount of CFRP sheets and the diagonal crack propagation etc for the undamaged beams and damaged beams. The experimental results indicated that the stresses of stirrup is decreased by 20%~50%, the width of diagonal crack is decreased by 35 %~ 45%, and the larger amount of CFRP sheets, the more significant this effect, the strengthening effect of the undamaged beams is superior to that of the damaged beams. Accordingly, externally bonded CFRP sheets of U-wraps can improve the shear fatigue performance and increase the fatigue life of reinforced concrete beam significantly.(5) It...