## 1 Introduction  
The development of epoxy-coated reinforcement as a corrosion protection method was started in the early 1970s. Following successful demonstration projects in the mid-1970s, the adoption of epoxy-coated bars in highway bridges increased significantly, establishing it as the preferred corrosion protection technique. However, the first signs of inadequate field performance were noted in 1986 in Florida bridges, with additional examples reported in the United States and Canada during the 1990s, particularly in bridge barriers [1,2]. In environments subjected to de-icing, severe corrosion was observed on the outer side of the vertical bars on the traffic-facing side of the barrier wall, accompanied by section loss in the horizontal bars after 10 to 20 years of service. An investigation by the Ontario Ministry of Transportation (MTO) [3] indicated that the epoxy coating on steel bars deteriorates after a certain period, resulting in corrosion that leads to concrete cracking and spalling. Consequently, the MTO prohibited using epoxy-coated bars in bridge decks, while permitting the use of non-corrosive glass fiber-reinforced polymer (GFRP) bars to enhance bridge designs, thereby improving life expectancy and significantly lowering maintenance costs. Traditionally, GFRP bars are anchored to concrete through mechanisms such as friction, mechanical adhesion, and mechanical interlock provided by the profile of the bar's surface. The necessary embedment length of the bar within the concrete is determined by its bond strength with the surrounding concrete and the specific end condition [4,5], which may include straight ends, 90-degree bends, or 180-degree hooks. In contrast to steel bars, which can be manually bent, GFRP bar bends and hooks are produced in a factory setting and subsequently transported to the construction site for installation. Due to the significant reduction in pullout strength at the curved sections of the bar, attributed to the reorientation of fibers [6,7], GFRP manufacturers have introduced GFRP bars with cast anchorage. This type of headed anchor bar is anticipated to alleviate reinforcement congestion at cast joints. A limited number of researchers have examined the pullout capacity and bond strength of fiber-reinforced polymer (FRP) bars embedded in normal-strength concrete [8,9], as well as in high-strength concrete [4]. Additional research has focused on the pullout capacity of glass fiber-reinforced polymer (GFRP) bars within fiber-reinforced concrete [10,11], in geopolymer normal concrete [12,13], and in ultra-high-performance fiber-reinforced concrete (UHPFRC) [14, 15, 16, 17, 18]. Furthermore, [PERSON] et al. [19] conducted a study on the bond strength of carbon fiber-reinforced polymer (CFRP) bars in UHPFRC. Recently, some manufacturers specializing in glass fiber-reinforced polymer (GFRP) have launched GFRP bars that incorporate cast-headed ends, aimed at improving their anchorage with concrete. Several researchers have examined the pullout capacity and bond strength of these headed-end GFRP bars in various concrete types, including normal-strength concrete [6,20,21,22,23], high-strength concrete [4,5,24], and geopolymer normal concrete [13]. [PERSON] and [PERSON] [25] conducted experimental studies to assess the viability of employing double-headed GFRP bars as shear reinforcement in concrete beams. Additionally, [PERSON] and [PERSON] [26] and [PERSON] and [PERSON] [27] verified the use of GFRP bars with headed ends in TL-5 barrier design using vehicle crash tests, while verifying the design by loading the barrier-deck overhang to collapse [28, 29, 30]. Others verified the use of GFRP bar with 180\({}^{\circ}\) hook in Test-Level 5 (TL-5) barrier design using a crash test and static tests to collapse [31,32]. [PERSON] and [PERSON] [33] investigated the behavior of beam-column joints reinforced with GFRP-headed bars under seismic conditions, concluding that the headed bars demonstrated superior seismic performance compared to bent bars. [PERSON], [PERSON] et al.