Behavior of Various Anchorage Systems Used for Shear Strengthening of Concrete Structures with Externally Bonded FRP Sheets

Efforts to prevent the debonding failure mode of externally bonded fiber-reinforced polymer (FRP) strengthening systems have led to the investigation of many different kinds of anchorage systems. An effective anchorage system allows externally bonded FRP reinforcements to continue carrying load, even after debonding occurs. In this study, an experimental program was performed on six full-scale RC T-beams strengthened in shear using externally bonded carbon FRP sheets with three different anchorage systems, the so-called (1) discontinuous mechanical anchorage (DMA) system, (2) sandwich discontinuous mechanical anchorage (SDMA) system, and (3) additional horizontal strips (HS) system. The experimental results showed that the SDMA system performed best, followed by the DMA and HS systems. The RC T-beams strengthened with the SDMA system showed a 59–91% increase in shear strength, altering the failure mode from FRP debonding to FRP rupture. In addition, the shear contribution of internal transverse steel reinforcement (stirrups) changes, depending on the types of anchorage system.