## 2 Materials and Methods  
In order to check the ability of such equivalent closed hoop stirrup schemes to upgrade the shear capacity RC T-beam structural elements, specimens of prototype dimensions are constructed and tested in the laboratory. These specimens are deliberately designed to be deficient in shear from the beginning, as is shown by the reinforcing details in Figure 5a,b. Figure 5c depicts the way such a specimen is supported and loaded with a loading arrangement known as four-point flexure, whereby the load is gradually increased monotonically until each specimen reaches its limit state. As can be seen in Figure 5a-c, such a \"prototype RC T-beam\" specimen is provided with sufficient top and bottom longitudinal steel reinforcement (three reinforcing steel bars of 20 mm diameter each) to provide considerable flexural capacity. In terms of geometry, support conditions, loading and longitudinal, or transverse reinforcing this prototype T-beam is symmetric along a vertical axis going through its mid-span. Three distinct regions can be seen along the specimen's length with respect to its shear reinforcement. At the very far left and right ends, the transverse reinforcement consists of narrow spaced (every 15 mm) steel close hoop stirrups of 8 mm diameter. This is done in order to prohibit any shear failure at these regions hosting the supports as well as to provide sufficient confinement in order to enhance the bond strength of the longitudinal reinforcement in this region. Next, there is a 900 mm long central region where the steel close hoop stirrups of 8 mm diameter are spaced every 70 mm. This central region of the specimen is not required to resist any shear because of the employed loading; however, the used stirrups can enhance the flexural capacity by providing confinement to the compressive zone as well as prohibiting, up to a degree, of the buckling of the longitudinal reinforcement at the compressive tope zone because of the development of large bending moments at this region. Finally, there are two regions between the supports and the central region that are left without any internal shear reinforcement in terms of steel stirrups (east and west parts). These two regions develop under the employed loading large shear demands. Therefore, it is expected that because of this intentional shear deficiency the prototype RC T-beam in its virgin state will fail in shear in these regions. In this way, in the initial loading stage, this represents the initial control stage whereby the shear resistance is provided only by the concrete volume. Next, during three distinct loading stages corresponding to three distinct retrofitting schemes (see Section 2.2), these regions are provided with an externally applied specific shear reinforcing scheme. Each of these three distinct retrofitting schemes employs either open hoop or equivalent closed hoop FRP strips; the measured shear capacity during each of these three distinct retrofitting stages is compared to the corresponding capacity of the control virgin stage. In this way, the ability of each retrofit to upgrade the shear resistance is demonstrated. The results of the observed performance of this prototype RC T-beam, without or with a shear strength upgrade, are presented in Section 4. The prototype RC T-beam as well as the \"unit T-beams\", described in Section 2.1, were built with the same concrete (the concrete compressive strength is listed in Table 1), reinforcing bars (typical tensile test shown in Figure 6a), and carbon FRP strips (typical tensile test shown in Figure 6b). From a series of laboratory tests, the compressive strength of the concrete was found equal to f\({}_{\text{ck}}\) = 19.94 MPa, the yield and ultimate strength of the longitudinal reinforcing bars were found equal to 524.6 MPa and 683 MPa, whereas the ultimate strain of the CFRP material was found equal to 0.015 for [PERSON]'s modulus approximately equal to 260 GPa which is in agreement with the value given by the manufacturers. Figure 5: **(a)** Reinforcing details of RC T-beam specimen.