In this paper, enhancement in the shear capacity of reinforced concrete (RC) members strengthened with carbon fiber –reinforced polymer (CFRP), using grooving method (GM) through externally bonded reinforcement in groove (EBRIG), was first investigated by laboratory tests. To achieve it, Eight RC rectangular beams were constructed, and interaction between externally applied CFRP sheets and internal steel stirrups was investigated. The specimens, with dimensions of 200 300 2000 mm (width height length), were tested under four-point bending and their failure mechanisms were briefly compared. The specimens were then further examined by a numerical tool for validating against experimental results. Outcomes inferred that vertical utilization of EBRIG technique enhanced shear capacity of the beams with and without stirrups by an average of 37% and 71%, respectively. Diagonal utilization of EBRIG method angled at 45° increased the shear capacity about 60% and 95% in the strengthened beams with and without stirrups, respectively. Results indicated that by increasing stirrup spacing, the effective strain of CFRP fibers increased. Results also showed that ductility of strengthened beams without stirrups decreased compared to control specimens, while ductility of strengthened beams with stirrups increased. Furthermore, modeling the cohesive layer for the CFRP-concrete interface revealed a good estimation of load-deflection behavior compared with the experimental results. Numerical results also demonstrated that bonding stresses of the interface layer reached higher values in strengthened specimens with stirrups compared to specimens without stirrups.

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