Flexural Performance Of RC Continuous Beams Strengthened With CFRP Sheets

Bonding CFRP sheets has proved to be an effective and practical means of upgrading and strengthening RC beams. Recently, CFRP composite plates have bean used as an alternative to steel plates. CFRP composites have many advantages over steel plates, including a high strength-to-weight ratio, corrosion resistance, and ease of handling. However, CFRP composites are costly and have no ductility, which could lead to undesirable brittle failure of the strengthened elements.Although lot of research study have bean conducted on the strengthening and repair of simply supported reinforced concrete beams using external plates, there is little report work on the behavior of strengthened continuous beams. But in engineering, there are lots of bridges were built in continuous structure. Therefore, the systemic study of flexural performance of different damages RC continuous beams strengthened with CFRP sheets has important theories and realistic meaning. This paper, basing on the damage characteristics of current bridge, mainly conducted to investigate the effects of CFRP sheets reinforcement of flexural strength. CFRP sheets reinforcement parameters considered are: thickness and position of CFRP sheets and degree of damages;and on the base of characteristic of continuous structures, makes a relative system theory analysis for the flexure performance of CFRP-strengthened continuous beams. According to the order of chapter of the thesis, this paper contains such research result as following:1, Describe state-of-the-art of bridge in the world, discuss the application and outlook of reinforcement in bridge, site the varies of strengthened methods as well as show advantages and disadvantages among these methods. The state-of-the-art in strengthening technology with carbon fiber reinforced polymers (CFRP) in the world was summarized. Some problems of CFRP-strengthened on flexural performance in China are put forward. Then the research content is presented base on these problems.2, In order to improve the flexural capacity of strengthened beams, CFRP sheets are glued the bottom of the reinforced concrete beam, its construction form and material have changed. As a result, the traditional reinforced concrete theories are no longer suitable when it is apply to flexural strengthening design. On the foundation of analysis a quantity of internal and external experiments and theories, the paper give a calculation formula for load capacity of reinforced concrete beam strengthened with CFRP sheets. Thereafter, some debonding strength models of FRP-strengthened RCbeams are introduced.3, This paper introduces the purpose and meaning tested, design and make thebeams, strengthen scheme and strengthen performances, previous work, testing program, loading and measuring etc.4> Nine beams strengthened with CFRP sheets are tested. It is mainly conducted to investigate the effects of CFRP sheets reinforcement of flexural strength: crack propagation, deflection, strains of material, ultimate loads and failure modes. CFRP sheets reinforcement parameters considered in the analysis are: position and layers (one or two layers) of CFRP sheets and degree of damages. The results of the experimental indicate that significant strengthening on the ultimate load and rigidity of reinforced concrete beams can be realized by bonding CFRP sheets to the beams, press conditions of rebar are improved as well as restraining of the cracks. In conclusion, the maximum increase in ultimate loads for undamaged strengthening-beams varied between 10.8% to 36%. However, with the increase of damages loads, the load capacities of strengthened beams decrease correspondingly. The ratio of one layer strengthened damage beams varied between 12.9% to 22.1% and two layers between 23.7% to 36%.5, Due to the present research on CFRP-reinforced continuous concrete beam primarily fixing on description of experimental phenomena, this text, based on experimental results, discussed the flexural performance of CFRP-reinforced continuous concrete beams theoretically. On the analysis of the section rigid vary regular, the paper presents the calculation formula for section rigid. Moreover, the calculation formula of flexure and ductility are presented after analysis the function of CFRP-strengthened beams.The study on flexural performance of CFRP-strengthened continuous beams is a comprehensive and stronger synthesizing research field, involving more disciplines. And its engineering application prospect is extensive. And its social effect and economic effect are mass. The paper, based on test of continuous concrete beams strengthened with CFRP, systematically presented some research about reinforced with damage condition and obtained some data. It is contribute to technology of reinforcement. With the CFRP broaden used, the theoretical and experimental research will further relatively.