## 2 Materials and Methods
Instrumentation was provided to monitor the variation of the externally applied tensile axial load, as well as the relative slip displacement of the top end of the attached CFRP strip and the concrete surface of the web. Four strain gauges (s.g.1 to s.g.4, shown in Figure 9a-c) were bonded in place, two at each side of the CFRP strip. These strain gauges were placed at the vertical axis of symmetry of each CFRP strip/specimen at two heights along the bonded surface as shown in Figure 9a-c. The applied axial loading in this way reproduced the state of stress that develops after the formation of diagonal shear cracks at open hoop FRP strips in prototype T-beams (Figure 7a). Figure 8: (**a**) R/C T-beam without an FRP strip (**b**) R/C T-beam with an open hoop FRP strip simply attached. (**c**) Open hoop FRP strip anchored with a mechanical anchor. (**d**) Open hoop FRP strip anchored with a rope FRP anchor. Figure 7: (**a**) Force transfer mechanisms for externally bonded CFRP strips for shear retrofit and the concept of forming a “unit T-beam” specimen. (**b**) Three-dimensional drawing of a limited length unit “T-beam” specimen including a single CFRP strip external transverse shear reinforcement with a steel anchoring device together with the externally applied load. The following limit states were expected to occur during the \"unit T-beam\" loading. (a) Debonding of the CFRP strip of the concrete bond surface; (b) tensile rupture of the CFRP strip; (c) failure of the anchoring device. In all these \"unit T-beams\" shear strengthening schemes, shown in Figures 8a-d and 9a-c, open hoop CFRP strips were employed in an effort to avoid breaking the RC slab of the \"unit T-beam\", apart from drilling relatively small diameter holes. This technique is designed to be applied in the same way to the full-length prototype RC T-beams, providing in this way a construction retrofitting technique that has a significant practical advantage. In the first scheme, the open hoop CFRP strip was simply attached at the sides (webs) and bottom of the \"unit T-beam\", as shown in Figures 8b and 9a, leaving the R/C slab undisturbed ([PERSON] et al., 2005 [35], [PERSON] et al., 2010 [36], [PERSON] et al., 2013 [37]). Alternatively, in the second scheme, the open hoop CFRP strip was again attached at the sides of the \"unit T-beam\" employing this time side mechanical anchors devised by the authors [48], as shown in Figures 8c and 9b. Finally, in the last shear retrofitting scheme (Figure 8d), before attaching the open hoop CFRP strip at the sides and bottom of the R/C T-beam, as was carried out before, a CFRP anchor rope, which was specially provided by the FRP industrial suppliers [52], was inserted from the top of the slab through 16 mm diameter holes that were drilled for this purpose, as shown in Figures 8d and 9c. After this, CFRP anchor rope is placed in position through these holes and its fibers are spread out at the sides of the \"unit T-beam\" in such a way that this rope becomes flat and obtains a considerable width in order to be attached to the open hoop CFRP strip placed from the bottom of the T-beam. Epoxy resin is used to both fill the fibers of this CFRP anchor rope as well as to attach these spread rope fibers to the fibers of the open hoop CFRP strip. The same retrofitting process was also applied when upgrading in shear the prototype RC T-beam, as described in Section 2.2. Figure 9: Testing three different open hoop CFRP strips employing a “unit T-beam” loading arrangement. (**a**) R/C “unit T-beam” with an open hoop FRP strip simply attached. (**b**) R/C “unit T-beam” with an open hoop FRP strip anchored with a mechanical anchor. (**c**) R/C “unit T-beam” with an open hoop FRP strip anchored with a rope FRP anchor.