| The rehabilitation and strengthening of insufficiently strong or damaged RC structures by means of extermally bonded Fiber Reinforced Plastics (FRP) sheets has received great attention in recent years in China. FRP presents several advantages, such as high strength-to-weight ratio, easy installation, and corrosion resistance. FRP has been used in civil engineering in U.S., Europe, Canada and Japan. Their application in China, however, has been very limited. In this dissertation, a comprehensive investigation of the behavior of reinforced concrete beams strengthened with externally bonded GFRP sheets and CFRP sheets has been conducted by author, who is participator for key item jVew Crafts and New Techniques of Strengthening and Requiring Existing Bridges of Liaoning Province Transportation Bureau of China. The objectives of this study were as follows:1. Nineteen RC beams with 150 X 250mm in cross section and 2700mm in length were tested experimentally to evaluate the strength enhancement provided by the GFRP sheets. Sixteen of the nineteen RC beams were externally with one, two or three layers of glass fiber-reinforced polymer composite. Six parameters are considered in test beams: compressive strength of the concrete, reinforcement ratio, the number of GFRP sheets, shear span ratio, anchorage system, and bonded length. The effects of those parameters on strength, ductility, and failure mechanisms were analyzed. It is shown that the application of GFRP sheets can considerably increase load resistance capacity and limit deflection in service. To eliminate debonding failure, it is suggested that the bond length should be enough.2. According to the results of experimental and analytical studies concerning the flexural strengthening of fourteen R.C. beams by the external bonding of FRP laminates, an ultimate section analysis procedure was developed and accurately predicts the ultimate loads. Also, this paper advances the maximal FRP area and minimum FRP area to avoid brittle failure of R.C. beams by the external bonding of FRP laminates. At the same time, the authors present the ratio of extreme depthxmto the depth hf and designed ultimate strain of GFRP. Finally, a parametricanalysis is conducted to investigate the effect on ultimate load capacity.3. Six initially loaded reinforced concrete (RC) beams with epoxy-bonded carbon fiberglass reinforced plastic (CFRP) sheets and two control RC beams were experimentally investigated. The results generally indicate that the flexural strength of the repaired beams is increased. In spite of the procedure of loading, the ultimate load capacity of the initially loaded reinforced concrete (RC) beams is basically same if the beams were preloaded with the same level loads. At the same time, an analytical method is performed to confirm the experimental results. The analytical results show a good agreement with the experimental results. Finally, adesigned method is proposed based on experimental data.4.Seven reinforced concrete (RC) beams with epoxy-bonded glass fiber reinforced plastic (GFRP) sheets and two control RC beams were experimentally investigated. The results generally indicate that the flexural strength of the repaired beams is increased, but the ultimate load of beams with tension delamination failure is reduced relatively. An experimental method of interfacial shear stress is proposed to analysis distribution of shear stress. At the same time, an analytical method is performed to confirm the experimental results. The analytical results show a good agreement with the experimental results. Finally, a simple method is proposed based on experimental data.5.Nine reinforced concrete (RC) beams with epoxy-bonded glass fiber reinforced plastic (GFRP) sheets and three control RC beams were experimentally investigated. An Experimental analysis method of ductility is proposed and a calculation method is performed to confirm the experimental results. A reduction factor is proposed based on experimental data. A new meth...
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