Flexural strengthening of reinforced concrete beams through externally bonded FRP sheets and near surface mounted FRP bars

•Detailed description of numerical modeling of strengthened RC beams with “ABAQUS 6.11” was presented.•A new strengthening method called combined externally bonded near-surface method was proposed.•A comparison was made on the flexural behavior of strengthened reinforced concrete beams via various strengthening techniques.•Effects of different geometrical and materials properties were investigated. Regarding the high interfacial shear stresses at end-plate, and end-plate cover separation in externally bonded methods, bar end-interfacial debonding and bar-end cover separation in near-surface mounted technique, a hybrid strengthening method called combined externally bonded near-surface method was proposed. In this method, the externally bonded and near-surface mounted techniques complement each other and mutually overcome their limitations. The purpose of this study is to numerically investigate the flexural strengthening efficiency of reinforced concrete beams with combined externally bonded FRP sheets and near-surface mounted FRP rods. The numerical analyses were conducted with finite element software ABAQUS 6.11, which can accurately simulate the experimental investigations on the flexural behavior of reinforced concrete beams strengthened with FRP composites. Validation of finite element simulation was confirmed first by making a comparison with the experimental study presented in the literature for both un-strengthened and strengthened beams with FRP materials. The verified model of the un-strengthened beam, which serves as a control beam, was used to simulate reinforced concrete beam strengthened with externally bonded FRP sheets and combined externally bonded near-surface mounted technique. The numerical results of mid-span bending moment deflection, ultimate bending moment, failure deflection, and ductility index were reported. Based on the results of this study, it is concluded that the developed finite element models for the externally bonded, near-surface mounted, and combined externally bonded near-surface techniques can be used by structural engineers as an alternative solution in design-oriented parametric studies of strengthened reinforced concrete elements. The performance of the combined externally bonded near-surface mounted technique was confirmed by making the comparison between the results of the intended method with other strengthening techniques.