Flexural Performance Of Different Damages Reinforced Concrete Beams Strengthened With CFRP Sheets

With the improvement of loading grade, increase of traffic and extension of service years, many bridges can not satisfy to the requirement of modern communications due to serious diseases and inadequate safety. Therefore, in order to improve the function of the bridge and extend the service life of the bridge, the study and engineering application of maintenance, reinforcement and repairing in bridge structure have been a wild concern in the world. This is a research task with important theories and realistic meaning.With its good physics and mechanics function, the carbon fiber reinforced polymer (CFRP) has been applied to the bridge reinforcement more and more. However, the study of concrete structure strengthened with CFRP sheets primarily focus on the research of flexural performance of strengthened beams, which by changing thickness of CFRP sheets, ratio of rebar and strength of concrete. The study of flexural performance of concrete strengthened beams, which is based on the different damaged conditions, has hardly been seen, let alone the comparison analysis with numerical simulation. Therefore, the systemic study of flexural performance of different damages RC beams strengthened with CFRP sheets, which integrate numerical simulation, has important theories and realistic meaning. This paper, on the base of analysis of reinforcement methods and the damage characteristics of current bridge, mainly conducted to investigate the effects of CFRP sheets reinforcement of flexural strength. CFRP sheets reinforcement parameters considered in the analysis are: thickness of CFRP sheets and degree of damages. In order to compare with the results of experiment, some suitable models of damaged beams strengthened with CFRP sheets have been made with finite element soft. 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 strengthening technology in China are put forward. And this paper point out the main emphases of CFRP in the aspects of bridge reinforcement in the future.2 In order to improve the flexural capacity of strengthened beams, CFRP sheetsare 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.3 Eight simple supported 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: layers of CFRP sheets (one or two layers) 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. However, with the increase of damages loads, the load capacities of strengthened beams decrease correspondingly. In conclusion, the maximum increase in ultimate loads and rigidity for beams strengthened with one layer CFRP sheets varied between 45% to 85% and 8% to 42% respectively, with two layers CFRP sheets varied between 88% to 108% and 20% to50%.4, On the ground of suitable numerical model and numerous calculations, some nonlinear finite element models on strengthened beams were made with elem...