خالد سنگين آبادي

Reinforced concrete (RC) structures may require external reinforcement due to earthquake damage, change of use, new guidelines, design and construction errors, and adverse environmental conditions. In recent years, in order to adapt to environmental changes, repair and strengthening of existing structures have been emphasized over destruction and reconstruction. Various methods are used to externally strengthen RC structures, with the use of fiber-reinforced polymer (FRP) composites being highly popular and practical due to their high strengthto-weight ratio, excellent resistance in aggressive environments, and minimal size change of the strengthened member. Several techniques are utilized to reinforce RC members with FRP composites. Externally bonded reinforcement (EBR) is one of the most common and straightforward strengthening methods. However, the use of EBR has always been linked to the undesirable phenomenon of premature debonding, which leads to the loss of expensive FRP materials. To delay debonding, a new method known as grooving method (GM) has been developed and invented. The EBR on groove (EBROG) and the EBR in groove (EBRIG) are two of the most frequently utilized GM techniques. The EBROG technique's ability to delay the debonding of FRP composites from the tensile side of flexural strengthened beams is of great significance. Therefore, experimental studies have been conducted on the application of the EBROG method to strengthen other structural members, such as columns, beams, and beam-column joints. Due to the superior performance of the EBROG method for strengthening structural members, extensive research has been carried out to comprehend the behavior of the EBROG bond through lap shear tests. The behavior of the EBROG bond has been the subject of very few analytical studies, despite a large number of experimental studies. Consequently, the primary goal of this study is to extract and present closed-form models for analyzing the behavior of the EBROG bond. To this end, all studies conducted on the use of the EBROG method to strengthen structural members and all studies conducted to understand the behavior of this bond were reviewed and discussed in comprehensive detail. Then, differential equations for the slip of the FRP composite in an EBROG bond were developed. Based on the relationship between shear stress and slip, these equations could be solved. Therefore, various models of the relationship between shear stress and slip, including two-linear and nonlinear shear stress-slip models, were employed. By solving these differential equations, analytical models containing slip, shear stress, and strain distributions along the bond were obtained to characterize the behavior of the EBROG bond. Then, various models were presented to evaluate the bond's strength and effective bond length, as well as the load-slip curve. On the basis of the use of fracture energy as a concept in fracture mechanics, the general form of the model for evaluating the bond's strength resembled wellknown fracture mechanics models for EBR bonds. Comparing analytical and laboratory results revealed that the presented models have acceptable accuracy and predictability for the behavior of the EBROG bond and parameters, including bond strength. Models that assumed a nonlinear shear stress-slip relationship had superior performance, efficiency, and precision than models that assumed a two-linear shear stress-slip relationship.