Crack Investigation Of RC Beams Strengthened With NSM FRP Reinforcement

Due to its light weight, high strength, good corrosion resistance and other obvious advantages, the application of Fiber Reinforced Polymers(FRP)is more and more widely in the field of civil engineering. Compared with the traditional strengthening materials, the use of FRP reinforcement has prominent advantages,because of its construction convenient,light weight and corrosion resistance.Especially Near-Surface mounted(NSM)strengthening technology,fully improve the efficiency of the utilization of FRP reinforcement. The NSM FRP strengthening technologyresearch mostly focus on the flexural ultimate load carrying capacity and bond slip behavior between FRP and concrete,The crack problem do not concrete theoretical analysis.The crack investigation is needed more research.Based on flexural testing of the four beams,the crack pattern of NSM strengthening beams were studied through the different groove numbers(single groove, double grooves),and the secondary stress(load to the 70% of yield load,then unload to zero).The effect of different parameters on the crack spacing and crack width is studied. The results showed that FRP reinforcement can limit crack.The crack spacing and crack width of the strengthening beams decreased compared the control beam.The double grooves method is superior to single groove method because the strength of FRP reinforcement in the double grooves can be utilized more efficiently than the single groove. The crack calculation model is presented based on the modification of the formulations in GB50010-2010. The calculation results agree well with the experimental results. The model of crack spacing and crack width is the base of design and application of FRP NSMstrengthening.