Shear strengthening of reinforced concrete T-beams using CFRP laminates anchored with bent CFRP splay anchors

Abstract Strengthening of reinforced concrete (RC) structures via external bonded fiber-reinforced polymer (EB-FRP) systems has been widely documented and used. This form of retrofitting has proven to be effective in enhancing flexural and shear capacity of RC beams. However, it is limited due to premature debonding of the FRP laminates prior to utilizing the laminates strength, and typically results in brittle member failure. To overcome this issue, studies have shown that proper anchorage systems mitigate debonding and enables the achievement of higher strengthening levels. Out of the many anchorage systems researched, FRP splay anchors have proven to be effective in enhancing member’s capacity by delaying the laminates debonding. However, the literature is lacking adequate information on the effect of splay anchors on the performance externally strengthened RC beams in shear. Accordingly, five shear deficient RC T-beams specimens were cast and strengthened with CFRP U-wrapped laminates and anchored with CFRP anchors. The parameter investigated in this study is the anchor dowel diameter. Three dowel diameters were tested: 12 mm, 14 mm, and 16 mm. The performance of the anchored U-wrapped specimens in terms of failure modes, load-deflection responses, shear strength, strain in CFRP laminates, and ductility is compared to that of unstrengthened and unanchored strengthened control specimens. Test results showed that CFRP anchors delayed debonding of the U-wraps, improved the shear strength of unanchored U-wraps, and significantly enhanced the ductility of the beam specimens. In addition, it was concluded that anchoring CFRP laminates with CFRP anchors highly utilized the strain attained in CFRP laminates. No clear trend was observed between anchor diameter and ultimate load-carrying capacity of the specimens. Based on the results of this study, anchor dowel diameter of 14 mm was found optimum for an anchor embedment depth of 85 mm.