Effect of Longitudinal Carbon Fiber-Reinforced Polymer Plates on Shear Strength of Reinforced Concrete Beams

Shear strengthening of reinforced concrete (RC) beams has been done by bonding steel or carbon fiber-reinforced polymer (CFRP) plates or sheets on the beam sides. Beam sides may not always be accessible for strengthening. The objective of this study is to quantify the contribution of CFRP flexural reinforcement to the shear strength of RC beams. Three groups of three beams each were built without shear reinforcement. Each group had a different steel flexural reinforcement. One beam in each group was unstrengthened, while two beams were strengthened with CFRP plates on their soffit. The beams were tested under four-point loading and all failed in shear. The strengthened beams showed a 13 to 138% increase in shear capacity over the control beams. The shear capacity was calculated using ACI 318-11 and CSA 2004 shear design provisions, the modified University of Houston (UH) method, and Frosch method. The results indicated that the modified UH and CSA 2004 methods yielded the most accurate predictions. A finite element model was also developed to predict the response of the strengthened RC beams.