# Evaluation of Horizontal Shear Performance of Composite Girders Using Separable Shear Connectors
## 4 Verification of Flexural Tests on Composite Girders
### Flexural Test and Result Analysis  
Flexural tests on the composite girders were conducted at Myongji University Hybrid Structure Testing Center (Republic of Korea) by using a line load applied at the center of a span of 9.0 m. The test was performed in the displacement control mode, specifically monitoring the central vertical deflection with a continuous, monotonically increasing control speed of 1.4 mm/s (5000 kN, UTM). Figure 13 illustrates the specimen and sensor arrangement. Displacement meters were positioned at L/4, L/2, and 3L/4 along the span to measure the vertical deflection and relative slip at the girder-deck interface, with additional meters at both ends to exclusively monitor the relative slip at the interface. Figure 13 depicts the test setup for the DY_F specimen secured with only stud bolts. Figure 14 details that flexural cracks propagated to the deck, which resulted in the crushing of the top of the concrete deck. Although DY_F and DY_H exhibited consistent overall flexural behavior, diagonal cracks developed from the interface at the ends, where the shear connectors were installed, and extended toward the girder. This phenomenon was attributed to the higher horizontal shear stress on the end shear connectors, resulting in fewer shear connectors and wider spacing than those in other specimens. As illustrated in Figure 14, DY_H, which had only 42% of the required shear connectors, exhibited numerous transverse cracks at the girder top surface, indicating simultaneous shear failure because of an insufficient number of shear connectors. Figure 13: Bending-test setup and linear variable differential transformer (LVDT) installations. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{PSC Cintler} & \multicolumn{2}{c}{PC Stab} & \multicolumn{2}{c}{**Slarer Connector**} & \multicolumn{2}{c}{**Flexural Strength**} & \multicolumn{2}{c}{**Helemental**} & \multicolumn{2}{c}{**Sheser Strength**} & \multicolumn{2}{c}{**Design**} \\ \cline{2-13} \multirow{-2}{*}{**Spacening**} & \multirow{-2}{*}{ \begin{tabular}{c} **Companion** \\ **Strength** \\ **(MPa)** \\ \end{tabular}  } & \multirow{-2}{*}{ \begin{tabular}{c} **Modules of** \\ **Strength** \\ **(MPa)** \\ \end{tabular}  } & \multirow{-2}{*}{ \begin{tabular}{c} **Companion** \\ **Strength** \\ **(MPa)** \\ \end{tabular}  } & \multirow{-2}{*}{\ \begin{tabular}{c} **Modules of** \\ **Strength** \\ **(MPa)** \\ \end{tabular}  } & \multirow{-2}{*}{ \begin{tabular}{c} **Consons-** \\ **Strength** \\ **(MPa)** \\ \end{tabular}  } &  
Table 6 summarizes the maximum load, vertical deflection, and relative horizontal slip measurements at the interface for each specimen. The relative slip was quantified as the absolute value of the deformation between the top surface of the girder and the bottom surface of the deck at the same cross-section. All specimens exhibited more than 30% of the design flexural strength and 16-94% more horizontal shear strength than expected. Specifically, the horizontal shear strength of DY_F, which used the same number of shear connectors, increased by approximately 4% over the Rebar_F specimen. Specimen DY_H was designed with approximately 42% fewer shear connectors than those for DY_F, which resulted in simultaneous flexural and horizontal shear failures. Despite considerable reduction in the number of shear connectors, the ultimate load resistance remained comparable. The DY_F specimen exhibited 32.7% less relative slip than the Rebar_F specimen did, whereas the DY_H specimen, which had fewer shear connectors, exhibited a considerably larger slip of up to 15.03 mm, indicating greater horizontal shear deformation at the interface. Figure 15 reveals that the shear and flexural strengths of all the specimens surpass their corresponding designed values. The Rebar_F (Figure 15a) and DY_F (Figure 15b) specimens exhibited similar maximum loads and maximum deformation, whereas the DY_H (Figure 15c) specimen exhibited a large deflection because of shear deformation.