The application of fiber-reinforced polymer (FRP) composites in strengthening reinforced concrete structures has increased over past decades. Their superior properties, such as being light-weight, high-strength, corrosion-resistant and easy to apply, pave the road for their usage. However, premature debonding of FRP from concrete substrate is a drawback, as it reduces the strengthening efficiency. Strain values that are below the ultimate FRP strain are reached until debonding happens. Therefore, full capacity of the material is not utilized. To overcome this issue, prestressing FRP was proposed and put into practice. Higher strain values are developed in the composite, which implicates better efficiency of the FRP high-tensile strength. In addition to the higher yield and ultimate strength of the member, the prestressed FRP application enhances the serviceability state by increasing the cracking load and decreasing the deflection of the strengthened beam. A major concern regarding the prestressed FRP is to secure the anchoring of the strip so that the prestressing force can transfer from FRP to the concrete. The externally bonded reinforcement on groove (EBROG) method was introduced as a substitute for the EBR method to improve the structural behavior of FRP-strengthened members in different applications. This method was first developed at Isfahan University of Technology (IUT). Considering the advantages of prestressed FRP on one hand and the EBROG method on the other hand, in this thesis, bond behavior of prestressed FRP-to-concrete attached via the EBROG method was investigated for the first time. Moreover, flexural behavior of RC beams strengthened with unstressed and prestressed CFRP strips is investigated through four-point bending tests. Since out-of-plane deformations dominate the behavior of the prestressed FRP, a full-field three-dimensional digital image correlation (3D DIC) system was utilized to measure the displacements. Experimental results showed that significant increase in the bond strength of the EBROG joint was observed compared to EBR. By using two longitudinal grooves of 10 mm width, and 5, 10 or 20 mm depth, bond strengths were increased with a factor of 2.1, 2.4 or 3.0, respectively, compared to the EBR method. While releasing the force, out-of-plane tensile stresses were engendered in the adhesive/concrete layer due to the eccentricity of the released force. These peeling stresses produced large out-of-plane deformations leading to mode I failure in fracture mechanics. The grooving method stiffened the concrete substrate and provided another path for crack propagation under the prestressed FRP; so that the cracks could not develop near the surface layer, but penetrated deep inside the concrete. Moreover, the cracks propagated extensively in the concrete width. These reasons led to a high bond strength of prestressed EBROG joints. Bond strengths of prestressed joints were determined through two different methods, namely fracture energy and fracture plane. Furthermore, to anchor the prestressed CFRP strips to the concrete beams, newly developed U-anchors were utilized in combination with the EBROG method. This novel full non-metallic system was proposed to strengthen beams and slabs with prestressed CFRP strips. Four-point bending tests demonstrated that in case of non-prestressed CFRP, the EBROG method was able to delay CFRP debonding and made it capable to resist tensile strains in the reinforcement up to 50% higher than that of the EBR method. In addition, while the CFRP was prestressed up to approximately 4600 micro strain, during the loading, a strain value up to 12400 micro strain was developed in the strip prior to the CFRP debonding. It means that 70% of tensile rupture strain of CFRP could be developed by sung the new introduced method. Keywords : Prestressed CFRP strip, prestress force-release test, externally bonded reinforcement on grooves, EBROG, 3D DIC, flexural RC beam, four-point bending, CFRP U-anchor.