## 6 Pullout Strength of GFRP Bars
As shown in Figure 20a, the bar appeared to be fully bonded to the concrete surrounding after the test. Also, no fracture in the anchor head was observed. Moreover, no shear failure was visually observed at the bar-head interface. As for the headed-end bars with the unbonded straight portion, failure was primarily due to bar slippage from the end head as shown in Figure 20b at an average pullout force of 131.04 kN (about 66%). Comparing the results of Groups 2 and 3, one may observe that the bonded straight portion of the bar increased the pullout capacity by 10% beyond the pullout force of the headed end alone. As for the postinstalled GFRP bars, test results indicated that the straight bars, installed with an embedment length of 150 mm, predominantly failed due to slippage at the interface between the bar and adhesive. Additionally, the bars ruptured at the anchorage point outside the concrete specimen, as illustrated in Figure 21a,b. Visual evidence of bar slippage at the bar-adhesive interface was noted, while the adhesive appeared to be fully bonded to the surrounding concrete following the test. Furthermore, no slippage was observed between the adhesive and the concrete. An increase in embedment length to 195 mm \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline \multicolumn{1}{c}{**Type of Construction**} & \multicolumn{1}{c}{**Group**} & \multicolumn{1}{c}{**Embedment Length (mm)**} & \multicolumn{1}{c}{**No.**} & \multicolumn{1}{c}{**Failure Load**} & \multicolumn{1}{c}{**Average Failure Load**} & \multicolumn{1}{c}{**Type of Failure**} \\ \hline \multirow{6}{*}{Preinstalled bars} & (3): & & A & 137.38 & \multirow{6}{*}{\begin{tabular}{} \end{tabular} } & Bar slip from \\  & Headed-end & & & & & \\ \cline{3-5}  & GFRP bars & & B & 122.00 & 131.04 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar slip from \\  & with & & & STDEV = 7.65 & & \\ \cline{3-5}  & unbonded & & C & 137.38 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar slip from \\  & straight & & & C & 137.38 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar slip from \\  & portion & & & D & 127.40 & & \\ \hline \multirow{6}{*}{Postinstalled bars} & & & A & 158.70 & \multirow{6}{*}{\begin{tabular}{} \end{tabular} } & Bar crushing \\  & (1): GFRP bars & & A & 141.9 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar crushing \\  & with straight & & B & 146.83 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar crushing \\  & ends & & C & 158.97 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar slip \\ \cline{3-5}  & & & D & 103.10 & & Bar slip \\ \cline{3-5}  & & & A & 163.56 & \multirow{2}{*}{\begin{tabular}{} \end{tabular} } & Bar slip, \\  & (2): GFRP bars & & & 151.89 & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } & Bar crushing \\  & with straight & & B & 153.58 & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & Bar crushing \\  & ends & & C & 156.01 & & \\ \cline{3-5}  & & & D & 134.41 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._led to a rise in tensile force; however, the mode of failure remained largely consistent, as demonstrated in Figure 21a and summarized in Table 4.  
It can be inferred that the pullout strengths of postinstalled GFRP bars are comparable to those of GFRP-headed bars. A significant finding was that all test results indicated a pullout strength of no less than 100 kN, thereby ensuring the suitability of headed GFRP bars for use in bridge construction, per the guidelines set forth by the Ministry of Transportation of Ontario. The reported experimental pullout strength investigation complements the structural performance results of the full-scale barrier-deck tests. This enables direct comparison between measured pullout capacities and the tensile demand from transverse vehicle impact, as predicted by applied moment equations presented elsewhere [63; 64].