| The relationship of fiber reinforced polymer (FRP)-to-concrete bond-slip is the fundament to analyze the behavior of FRP-strengthened RC structures. The maximal bond stressτf as well as its corresponding slipδf, and the maximal slipδu are three main parameters of a bond-slip model. The direct-pull test is the most popular way to measure the bond-slip relationship. Researchers, however, haven't obtain a reliable measured bond-slip relationship. This is because the existed specimens are prone to fail under a small load level, leading to no chance to measure the maximal slipδu. In order to overcome the above shortage, a new kind of specimen was designed in this thesis. The new kind of specimen was validated to be feasible for measuring the maximal slipδu through an experiment study. Another experiment study was also carried out and the range of theδu was measured to be 0.31～0.52mm.Fourteen beams were produced and strengthened by using CFRP, GFRP and hybrid fiber reinforced polymer(HFRP) respectively. All beams were loaded in four-point bending to investigate the characteristics of crack spacing and crack width. The measured values were compared with the existing formula on crack spacing and crack width, and it is shown that the predicted values were agree roughly with the test results. Besides, the ultimate capacity and deformability of the beams strengthened by different kinds of FRP are analyzed.
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