## 1 Introduction  
Fiber-reinforced polymer (FRP) materials have been used for many years for repairing and strengthening reinforced concrete (RC) and prestressed structural elements exposed to bending and/or shear. Many design codes, such as those in [1, 2, 3], treat problems related to the application of FRPs in RC structures and give basic guidelines for their use. This being the case, two basic methods are applied: the externally bonded (EB-FRP) method and the near-surface mounting (NSM FRP) method. The EB-FRP method appeared earlier and has wider applications because of its practical values [4]. On the other hand, the NSM FRP method has significant advantages, which have been shown in many studies [5, 6, 7, 8, 9]. The basic advantage of the NSM FRP technique of strengthening compared to that of EB-FRP is based on its better adhesiveness, which mostly affects the ultimate strengths of strengthened structures [10, 11, 12]. One of the recent investigations regarding the EB and NSM FRP techniques, which is mainly concerned with the bond effect, is international research [13] in which 11 laboratories and seven manufacturers took part. In the mentioned paper, experimental results have been discussed and compared in order to examine the following: (1) the bonding of NSM strips and bars, (2) the influence of alternative single-bond or double-bond shear pulling setups that were adopted by the participating laboratories, and (3) the influence of different concrete mixture qualities coming from different countries on concrete strength. It has been concluded that the greatest influences on the bond strength are the axial stiffness and surface treatments of FRP NSM systems. Nevertheless, there are other factors that influence the bond effect, such as the groove dimensions, epoxy type, FRP type, and concrete quality [14; 15; 16]. In addition to the above, the application of the NSM FRP technique for strengthening RC structures significantly improves the protection of FRP strengthening with regard to high temperatures and vandalism [17; 18]. In addition to the NSM FRP strengthening technique, the time-dependent variation in the corrosion resistance of basalt fiber-reinforced polymer (BFRP) bars reinforced geopolymer concrete in a seawater environment has also been investigated. It has been concluded that geopolymer concrete possesses better corrosion resistance compared to Portland cement concrete, while the reduction in BFRP bars' ultimate strength in seawater is directly proportional to the bar diameter [19]. The problem of the splicing of the cut-off of FRP bars is present in cases of long structural elements and in cases of bar diameters greater than \(\mathcal{O}\)10 mm, considering the limited transport length (10-12 m) and the impossibility of winding into coils [20]. To the best knowledge of the authors, the problem of the splicing of the cut-off of FRP reinforcement has not been treated sufficiently in the literature when it comes to the NSM method. It has been limited primarily to the investigation of anchoring length; that is, the bond effect [21; 22]. This, among other things, is also concerned with numerical testing [23; 24; 25; 26]. Recommendations for required anchoring lengths in cases of the classical way of cut-off splicing via longitudinal overlapping (as for steel reinforcement) relate to manufacturer's data for specific materials, shapes, and surface treatments of the additional FRP reinforcement [20], and relate to limited classic lap splice research recommendations [27; 28; 29]. The aim of this research was the prediction of the behavior of beams strengthened via NSM FRP reinforcement with the splicing of an NSM FRP reinforcement cut-off in the bending zone. For the splicing of an NSM FRP reinforcement cut-off, the authors proposed a new method, called double-strap joint NSM FRP. This method implies the widening of the groove in the FRP bar cut-off zone and setting two FRP supplement bars symmetrically. The connection of the supplement and main FRP bars, as well as with concrete, is provided using epoxy.