## 2 Literature Review
### FRP Anchors  
Considering their corrosion resistance, compatibility with FRP fabric, and documented superior performance in shear-strengthening applications [14; 17], FRP anchors (also referred to in the literature as \"spike anchors\") were selected over steel anchors for the retrofit designs of the shear-deficient RC-MRF beams in the building. FRP anchors consist of a bundle of fibers saturated with epoxy, with one end (referred to as \"dowel\") inserted into a predrilled hole filled with epoxy; the other end is splayed out in a fan shape and bonded to the FRP fabric, creating a load path to transfer tensile forces from the FRP laminate to the concrete member. The fan portion of FRP anchors (also referred to as \"splay\") must cover the whole width of FRP fabric and overlap with adjacent anchor fans to ensure correct force transfer [18; 19]. The load transfer mechanism in the dowel portion of the FRP anchor assimilates that of metallic adhesive anchors. For design purposes, anchors should not limit the strength of the EB-FRP system; therefore, all failure modes in the FRP anchors should be avoided. In this regard, FRP anchors can be designed for rupture of the FRP laminates, i.e., ultimate strain of the FRP fabric, or for the actual maximum expected load demand in the FRP fabric, i.e., design strain, which is limited to 0.004 by ACI 440.2R, as previously discussed. Obviously, the first approach produces considerably larger anchors. FRP anchors are widely used by practicing engineers despite the absence of specific design guidance. At the time the FRP-strengthening schemes for the building were iterated (i.e., 2014-2015), FRP anchors were still a relatively new technique, and only limited experimental validation was available. FRP anchors were first studied in Japan [18]. Initial efforts to identify the failure modes of FRP anchors and the primary parameters affecting their tensile capacity focused on pullout tests of isolated straight-embedded FRP anchors [20; 21; 22]. However, early studies used handmade FRP anchors constructed using rolled FRP fabric, a very different configuration from the manufactured FRP anchors being used in real-life applications. [PERSON] [20] reported that larger-diameter dowels resulted in stronger FRP anchors and identified an effective embedment length of 10 cm (4 in), beyond which the capacity of the straight FRP anchors did not increase. [PERSON] and [PERSON] [21] identified three failure modes, namely, concrete cone failure, combined cone-bond failure, and anchor rupture. They also reported that the average bond strength between anchors and concrete decreases with both increasing anchor diameter and increasing embedment length but is not significantly affected by the strength of concrete. [PERSON] et al. [23] provided limited design recommendations for 90\({}^{\circ}\)-bent CFRP anchors based on test results of flexurally-strengthened beams using anchored CFRP laminates. Those included a minimum-dowel embedment depth of 13-15 cm (5-6 in), with at least 5 cm (2 in) into the core concrete and a cross-sectional area for FRP anchors designed to reach fracture of the FRP laminate of at least twice the area of the FRP laminate to be developed. The recommendation on the area of the FRP anchors was intended to overcome the loss of strength due to stress concentrations at the anchor bend, which can cause the anchor to rupture prematurely. It was also reported that the use of a larger number of smaller anchors with reduced spacing is more effective in developing the capacity of the FRP laminate than a few large anchors [23]. The first design model for FRP anchors, and the only available approach for this retrofit project, was developed by [PERSON] and [PERSON] [24] based on the failure modes and strength equations for adhesive metallic anchors and test data for straight CFRP anchors made from rolled carbon fiber sheets [20; 21; 22]. This model is only valid for straight anchors, and it does not consider the influence of the anchor size, the fan angle, or the fan-to-sheet failure mode.