Experimental Evaluation of Failure Strain and Bond Strength of FRP Sheet-Concrete Joint in the Grooving Methods Reza Zamani Ghaleh Reza.zamani@cv.iut.ac.ir September, 20, 2020 Department of Civil Engineering Isfahan University of TechNology, Isfahan 84156-83111, Iran Degree: M. Sc Language: Farsi Supervisor: Dr. Davood Mostofinejad, Prof. Email Address: dmostofi@cc.iut.ac.ir Nowadays, a large number of RC structures need to be strengthened or retrofitted for various reasons. Among the different strengthening techniques, using FRP composites has become the most common method in the strengthening of RC structures. Externally bonded reinforcement (EBR) is the most common method for the installation of FRP sheets on the concrete surface. In contrast to the ease of implementation, this method also has some disadvantages; one of the most important of them is the premature debonding of the sheet from the concrete surface, which is the most common and undesirable failure mode. In recent years, the grooving method (GM) has been developed at Isfahan University of Technology (IUT) to eliminate or delay the debonding phenomenon. Grooving methods consist of externally bonded reinforcement on groove (EBROG) and externally bonded reinforcement in groove (EBRIG). Generally, in order to control the debonding of FRP sheets from the concrete surface, the failure strain of the sheets is limited to the value of their debonding strain. Until today, different relations have been presented to calculate the debonding strain of bonded FRP sheets by the EBR method, but No relation has been presented to calculate the failure strain of bonded FRP sheets by the EBROG method. In this study, however, some relations will be presented by using the results of lap shear tests carried out. On the other hand, the bonding capacity of FRP sheet-to-concrete joints by the EBRIG method has Not been assessed so far in comparison with the EBR and EBROG methods. Here, 31 concrete prisms with dimensions of 150×150×350 mm are made in 3 categories of low, medium, and high strength concrete. 29 specimens are strengthened by the EBROG method with CFRP sheets in different widths in the range of 13 to 69 mm and a constant bond length of 200 mm. Moreover, two specimens are strengthened by 50 mm wide and 200 mm long CFRP sheets and are subjected to lap shear test. Displacement and strain fields are evaluated by sequential imaging and analysis of the images using the particle image velocimetry (PIV) method. The presentation of appropriate relations to calculate the failure strain of EBROG FRP sheet-to-concrete joints is the most important outcome of this study. The results indicated the acceptable accuracy of the relations in estimating the bond capacity of EBROG joints. These relations were also validated by using the results of a set of specimens of past research, where it also showed good accuracy of the presented relations in predicting the bond capacity of the joints. Keywords: FRP Composites, FRP Debonding, EBR method, Grooving methods (GM), EBROG method, EBRIG method, Failure strain, Particle Image Velocimetry (PIV).