A Master of Science thesis in Civil Engineering by Rayyan Bashar Saleh entitled, “Effect of Flexural NSM-FRP Bars on the Shear Strength of Reinforced Concrete Beams”, submitted in May 2019. Thesis advisor is Dr. Rami Haweeleh and thesis co-advisors are Dr. Jamal Abdalla and Dr. Elias Saqan. Soft and hard copy available.
Strengthening of reinforced concrete (RC) members in flexure and shear, using fiber-reinforced polymer (FRP) laminates and near surface mounted (NSM) bars has been developed over the last few decades. Conventionally, FRP composite laminates are attached to the vertical sides of RC beams to increase their shear strength. However, in some cases, the sides of the beam might be inaccessible or shallow. According to the ACI 318-14 guidelines and other codes of practice, longitudinal reinforcement contributes to the shear strength of RC beams. The objective of this study is to assess experimentally the effect of longitudinal NSM bars, which are mounted to the beam’s sides, on the shear strength of RC beams. The variables of the experimental program included the beam’s depth to evaluate the size effect, the concrete compressive strength, and the flexural FRP reinforcement ratio. A total of 18 shear deficient RC beams were built, strengthened with longitudinal NSM bars, and tested under three-point bending until failure. It was observed that the strengthened beam specimens exhibited an increase in shear capacity that ranged from 10 to 35% over the control beams. It was also observed that the increase in the concrete shear strength with longitudinal FRP bars for the high strength concrete specimens was not as effective as that with normal concrete strength specimens. The results have also revealed that the size effect phenomena has a significant effect on the test results, in which the increase in shear strength has decreased from around 35% to 10%, with the increase of beam’s height from 230 to 650 mm, respectively. It was concluded that equation 188.8.131.52 of the ACI 318-14 code, which gives a simplified expression for the concrete contribution to the shear strength of beams, is not conservative for beams with large depths. Thus, other published analytical shear strength models that account for size effect were utilized in this study to predict the strength of the tested specimens. This study utilized 10 different analytical models in predicting the shear strength of the tested RC beam specimens. The models that showed the closest agreement with the tested data were the University of Houston method and the model based on the second order simplified modified compression field theory. It can be concluded that flexural longitudinal NSM bars could be used as a viable solution to enhance the shear strength of RC beams.