Shear Strengthening of Reinforced Concrete Beams Using CFRP Wraps

Abstract

The need to retrofit existing reinforced concrete (RC) structures have increased over the decades due to corrosion of steel reinforcement inside the concrete, neglect and overuse, and increased loading. Experimental and numerical studies in this research field showed that using fiber-reinforced Polymer (FRP) materials to strengthen RC members in shear, flexure, and column confinement applications is an effective method to retrofit RC structures. This strengthening technology has numerous advantages over conventional steel plating, such as providing high strength-to-weight ratio, versatility, durability, and ease of use to strengthen RC members. The purpose of this paper is to study the effect of strengthening shear deficient RC beams with externally bonded (EB) carbon fiber-reinforced polymer (CFRP) sheets with different wrapping configurations. Two shear strengthening wrapping schemes of CFRP sheets will be investigated; U-Wrapped and completely Wrapped. Although the completely wrapped scheme is more effective, however, due to its limitations, the U-Wrapped scheme became the most commonly used method in shear strengthening of RC structures. The drawback of this strengthening scheme is the premature failure caused by debonding of the CFRP laminates, without utilizing its full strength. The main aim of this study is to compare the performance of a U-Wrapped T-beam with two completely wrapped rectangular beams. The first strengthened rectangular specimen (WBR1) has a depth equivalent to the T-beam’s web height, while the second strengthened rectangular specimen (WBR2) has a depth equivalent to the T-beam’s total depth. In addition, a control T-beam and two rectangular beams were cast and tested as benchmark specimens. The experimental test results showed that the beam strengthened by U-Wrapped CFRP sheets increased the control beam’s shear strength by 114.82%, while the increase in shear capacity of the completely wrapped equivalent WBR1 and WBR2 beams over their control unstrengthened specimens was 69.28% and 201.63%, respectively. In addition, the completely wrapped scheme provided more ductility compared to that of the U-Wrapped T-beam specimen, that failed by CFRP sheets debonding in a brittle manner. Thus, it could be concluded that an ideal way to increase the shear capacity and ductility of RC beams is to completely wrap the beams using CFRP sheets. However, if the completely wrapping scheme is not possible due to geometrical obstructions, U-wrapping scheme could be effective in increasing the shear capacity of RC beams but will fail in a brittle mode by sheet debonding without utilizing its full strength. Anchoring the CFRP U-Wraps could be a viable solution to enhance the performance of strengthened RC beams that should be investigated in future research studies.