# Evaluation of Horizontal Shear Performance of Composite Girders Using Separable Shear Connectors
## 3 Evaluation of Horizontal Shear Performance
### Analysis of Horizontal Shear Test Results  
Figure 8 depicts the load-slip displacement graphs for each specimen. Figure 8a,c detail load-displacement graphs for the rebar type and S-DY type, respectively, demonstrating ductile behavior even after maximum failure load, whereas Figure 8b of the M-DY model exhibits brittle behavior as the shear connector experiences shear failure at maximum load. Table 3 summarizes the failure loads, slip displacements, and failure modes of each specimen. Failure load was defined as the maximum load observed on the load-slip displacement curve, with the maximum slip displacement being the slip at the load corresponding to 90% of this maximum. The initial slip displacement was recorded over 25 repeated loading cycles, and the total slip displacement was defined as the difference between the maximum and initial slip displacements.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & \multirow{2}{*}{\
\begin{tabular}{c} **Ultimate** \\ **Force (kN)** \\ \end{tabular} } & \multicolumn{3}{c}{**Slip (mm)**} & \multicolumn{3}{c}{**Averaged Value**} & \multirow{2}{*}{
\begin{tabular}{c} **Difference Ratio (DY/Rebar)** \\ \end{tabular} } \\ \cline{3-3} \cline{5-10}  & & & & & **Utimate Force** & & **Total Slip** & **Ultimate Force** & **Total Slip** \\  & & & & **(kN)** & **(mm)** & **(kN)** & **(mm)** \\ \hline \multirow{3}{*}{Rebar} & s1 & 351.7 & & 17.28 & & 391.4 & 20.71 & 1.00 & 1.00 \\  & s2 & 432.2 & 0.39 & 21.10 & 20.71 & (36.40) & (-) & 1.00 & 1.00 \\  & s3 & 399.3 & & 32.52 & & & & \\  & s1 & 345.4 & 0.61 & 12.48 & 11.87 & & 394.1 & 11.40 & \\ M-DY & s2 & 374.3 & 0.81 & 11.74 & 10.93 & (61.00) & (0.66) & 1.01 & 0.55 \\  & s3 & 462.5 & & 10.51 & & & & \\  & s1 & 373.5 & 1.26 & 16.27 & 15.01 & & & \\ S-DY & s2 & 342.6 & 1.35 & 15.53 & 14.18 & 353.9 & 14.59 & & \\  & s3 & 345.7 & & 16.98 & & (17.02) & (0.59) & 0.90 & 0.70 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Test results for horizontal shear tests.  
Figure 8: Load–slip displacement curves. (**a**) Rebar; (**b**) M-DY; (**c**) S-DY.  
Based on the average values for specimens of each model listed in Table 3, the ultimate strength of the M-DY model is 394.1 kN, which is very close to the 391.4 kN for the rebar model. By contrast, the S-DY model exhibited a value of approximately 10% lower, at 353.9 kN. The model experienced a considerable increase in relative slip because of the pull-out failure of rebar shear connectors. The M-DY model exhibited an average slip of 11.4 mm because of the failure of only the shear connectors without damage to the deck concrete. Figure 9 depicts the failure photographs of each model. The behaviors of all six specimens within each model group were consistent, both rebar and M-DY. However, the S-DY model demonstrated cracking in the girder concrete and pull-out of the embedded nut part, likely because of insufficient confinement and a short embedding depth, resulting in inadequate anchorage strength. The degrees of slip in the DY-type specimens were generally lower than those in the rebar-type specimens. Nevertheless, all the values exceeded the relative slip of 6 mm required for studs under the ductile design criteria of Eurocode 4. The failure modes indicated that failure occurred in the girder concrete because of the inadequate confinement of the embedded shear connectors, resulting in the pull-out of either the embedded rebar shear connectors or the nuts of the separable shear connectors. This problem is addressed in the flexural tests of the composite girders.