Strengthening of Shear Deficient Beams with CFRP Laminates with Different Types of Anchorage Systems

Abstract

Retrofitting and repairing deteriorating structures have been achieved using several techniques. Strengthening of Reinforced Concrete (RC) members in shear with externally bonded fiber reinforced polymer (FRP) plates and sheets has been commonly accepted. FRP de-bonding from the concrete substrate is one of the most common types of failure in shear strengthening of RC beams. Many shear strengthening methods have used different anchorage systems to solve the problem of the de-bonding of FRP laminates. The most common types of anchorage in use include full wrapping, U-wrapping, FRP-spikes, in addition to other types of mechanical anchorages. This study explores the use of groove-epoxy and bore-epoxy anchorages. In this investigation, 15 shear deficient rectangular RC beams were strengthened with carbon (CFRP) sheets and plates bonded by groove-epoxy anchorages of different widths and bore-epoxy anchorages of different depths and spacing. The beams were tested under four-point bending. The aim of this study is to investigate the feasibility of using epoxy-anchorages, specifically groove-epoxy and bore-epoxy to reduce or eliminate FRP de-bonding failure and increase the FRP strength that will lead to an increase in shear strength of aging beams. Both methods have shown an increase in the shear capacity when compared with the control beams and with the externally bonded reinforcement (EBR) strengthening method without anchorage. In the groove-epoxy anchorage method, the two medium grooves of 10 mm width showed the best performance among the groove widths while in bore-epoxy anchorage method, the large bores of 30 mm diameter showed the best performance among the bore diameters. Groove-epoxy anchors have increased the shear capacity by 112 % over the control beam and 52 % over the EBR strengthened beam. Bore-epoxy anchors have increased the shear capacity up to 68 % over the control beam and 20 % over the EBR strengthened beam. The shear strength of three specimens were predicted using the relevant codes of practice (ACI-440.2R-08, CAN/CSA-S806-02, FIB 14 and TR55). The prediction showed that CAN/CSA-S806-02 is the most accurate when compared with the other codes.