## 6 Pullout Strength of GFRP Bars  
To quantify the pullout capacity of the GFRP bars used in the experimental program, two cases were considered: preinstalled and postinstalled. In the case of preinstalled bars, a reinforced concrete slab of 1300 mm width, 7500 mm length, and 300 mm thickness, having an average concrete strength of 40 MPa, was prepared and cast. Steel bars of 15M in size and spacing of 300 mm center-to-center were used to reinforce the slab in both directions at the top and bottom. The cast concrete slab had three separate regions to allow for testing different bar configurations, namely: (i) preinstalled GFRP bars with straight ends, (ii) preinstalled GFRP bars with headed ends, and (iii) preinstalled GFRP bars with headed-end and unbonded straight portion. These regions are marked as Groups 1 through 3 in Figure 15a. Group 1 of bar pullout testing consisted of five straight GFRP bars, which are fully bonded to concrete with an embedment length of 195 mm; Group 2 incorporates the same type and number of headed fully bonded bars for the entire 247 mm embedment length. Group 3 consisted of five headed-end GFRP bars, which were not fully bonded to the concrete. The total embedment length of the bar was taken as 247 mm from the top of the slab; however, only the bottom 100 mm was fully bonded to the concrete. To achieve the unbonded condition, pipe insulation foam was used to wrap around the top 147 mm of the embedded length of the bar as depicted in Figure 15b. The reasoning behind using these conditions is to investigate the true pull-out strength contribution of the added anchor head. As for postinstalled bar pullout capacity testing, the same slab used for preinstalled bar testing was utilized. After testing the preinstalled GFRP bars, two bar groups were installed in the deck slab in locations marked with solid circles in Figure 16. Every group utilizes the same #5 bar, though with varying embedment lengths. Specifically, Groups 1 and 2 employed embedment lengths of 150 mm and 195 mm, respectively. Each group comprised 5 bars, resulting in a cumulative total of 15 bars, which includes an additional 5 bar specimens. In the process of installing the postinstalled GFRP bars, a hole was initially created using a concrete impact drill. A drill bit with a diameter of 27 mm was selected to accommodate the #5 bar size and ensure a proper bond between the epoxy, bar, and concrete components. A mark was placed on the drill bit to denote the necessary depth for each group of bars. Following the drilling, the hole was thoroughly cleaned; this involved using compressed air to remove all concrete debris, followed by scrubbing the entire hole with a brush and applying compressed air again. This cleaning procedure was conducted five times before the epoxy injection. After injecting epoxy to approximately three-quarters of the hole's depth, the GFRP bar was carefully positioned by applying pressure while simultaneously rotating the bar in a back-and-forth motion. Figure 17 illustrates the steps of installing the GFRP bars within the slab. Figure 16: Plan of concrete slab showing GFRP postinstalled bar locations. Figure 15: Layout and slab formwork with steel and GFRP reinforcement before casting for preinstalled GFRP bars: (**a**) Plan of the concrete slab showing preinstalled GFRP bar locations; (**b**) Headed bar with unbonded straight portion; (**c**) Group 1: GFRP bars with straight ends; (**d**) Group 2: Headed-end GFRP bars; (**e**) Group 3: Headed-end GFRP bars with unbonded straight portion. The pullout test follows the ASTM E488/E488M-15 test method [75], which describes all appropriate equipment and setup needed to experiment. The test setup consisted of a series of HSS sections resting on metal bearing plates that were spaced in a manner so that there was a minimum clearance radius of about two times the bar embedment length from the bar being tested to each support.