| The rehabilitation and strengthening of insufficiently strong or damaged RC structures by means of externally bonded carbon fiber reinforced plastic (CFRP) sheets has received a great attention in the past decade in China. The results corresponding have been drawn a good many, however, most researches were concentrated on the normal RC members. Studies on high-strength RC members have been very limited. Combining with the research program of National natural science foundation of china and Liaoning province transportation bureau, a comprehensive investigation of the behavior of high-strength RC beams strengthened with externally bonded CFRP has been conducted. The objectives of this study were listed as follows:1. Twelve RC beams with 2700mm in length were tested experimentally to evaluate their flexural behavior. Four parameters in this program which included the reinforcement ratio, the reinforcement quantity of CFRP sheets, different strengthening methods and bonding length were taken into account. The effects of those parameters on failure mechanisms, strength enhancement, and section stiffness were analyzed. It is shown that the application of CFRP can considerably increase the ultimate flexural capacity.2. According to the results of the twelve test beams, theoretical analyses were carried out. Calculation expressions in different ultimate states were presented based on variant failure models, together with the introduction of the maximal and minimum CFRP area in order to avoid the brittle failure. Simultaneously, the propositional expression of allowable ultimate strain of CFRP was given based on the author's and the existing experiments.3. Five high-strength reinforced concrete beams strengthened with externally bonded CFRP which includes three precracked beams and two reference beams were tested. The influence of damaged degree were studied and analyzed, It is shown that deferent damaged degree shows similar limit loads, but deferent section stiffness.4. A practical formula for calculating the short-term stiffness of reinforced concrete beams strengthened with carbon fiber plastic sheets had been established on the basis of analyzing the rule of changes in the sectional stiffness of these beams. The calculation results agreed well with the test results, which could work as references for strengthening design. |
