## 2 Literature Review
### EB-FRP for Shear Strenghtening of T-Beams  
Over the past three decades, numerous studies have investigated the use of EB-FRP laminates to shear-strengthen RC beams. Given the frequent lack of access to the top of beams with slabs (i.e., T-beams), the most typical FRP layout for shear-strengthening of T-beams consists of a three-sided jacket (also referred to as a \"U-wrap\" or \"U-jacket\") of unidirectional FRP laminate, with fibers oriented perpendicular to the beam's axis. For U-wrap applications, ACI 440.2R specifies an effective FRP strain that is inversely proportional to the number of FRP layers, with a maximum permissible design strain of 0.4%. Consequently, when multiple layers of FRP are applied, the strain in the FRP is reduced, thus decreasing the effectiveness of the FRP-strengthening scheme. EB-FRP shear reinforcement can take the form of a continuous sheet, completely covering the surface of the region to be strengthened, or equally spaced discrete strips. ACI 440.2R-08 [10] specifies a maximum center-to-center spacing for FRP strips of d/4, plus the width of the strip (with d being the effective depth of the concrete member). Continuous sheets provide more redundancy, but discrete strips allow for material optimization and cracking monitoring. Several experimental studies [11; 12; 13] indicated that CFRP U-strips achieved higher shear-strength contributions than continuous CFRP U-jackets.  
When shear cracks develop and intersect the FRP U-wrap, local debonding of the FRP occurs at the shear crack location, and the FRP material is engaged in tension, with increasing strain as the crack widens. For unanchored U-wraps, axial demands in the FRP are only resisted by the bonded portion of fabric extending past the crack. Given the limited available development and bond lengths in shear U-wrap applications on T-beams, it has been experimentally shown that FRP laminates alone tend to peel off early, resulting in little enhancement on the ultimate load or the displacement capacity of T-beams and, in some cases, trigger even more brittle failure modes [14]. Hence, it is imperative to provide mechanical anchorage at termination points of the FRP laminate to keep it in place, provide a load path for the tensile forces after its complete detachment, and allow the development of higher tensile strains. ACI 440.2R recognizes that mechanical anchorage can be used in shear-strengthening applications to achieve higher strains in the FRP laminates, but current shear capacity equations do not account for it. The latest version of the ACI 440.2R guideline (published in 2017) states that properly anchored U-wraps can be designed to fail by FRP rupture, but in no case does it allow the use of an effective strain higher than the lesser of 0.004 or 0.75\(\epsilon_{\text{fu}}\), where \(\epsilon_{\text{fu}}\) is the design rupture strain. The only EB-FRP design guidelines that incorporate the influence of mechanical anchorage in the shear design equations are those presented in NCHRP reports 655 [15] and 678 [16] by the Transportation Research Board (TRB), both of which are specific for concrete bridge members. ACI 440.2R and, similarly, all other EB-FRP design guidelines for strengthening concrete members only provide conceptual methods for mechanical anchorage but lack specific anchor design recommendations. Given the absence of an established anchorage design method, ACI 440.2R requires the performance of any anchorage system for FRP to be substantiated through testing.