# Shear Behavior of Concrete Encased Steel Truss Composite Girders
## 2 Experimental Program  
### Test Specimens  
To identify the shear performance of EST composite girders, four full-scale specimens were fabricated to conduct a test. As shown in Table 1, the truss type (Pratt truss (P) and Warren truss (W)) and the presence of stirrups were set as main test variables. Reinforcing bars of 13 mm in diameter were used for the stirrups, and 25-mm-diameter rebars were used as tensile reinforcements. Figure 3 shows the details of the P-specimen series (specimen PV, specimen P) to which the Pratt truss was applied. In addition, PV and P represent the specimens with and without vertical stirrups, respectively. As shown in Figure 3a, the Pratt truss was composed of top and bottom chords as well as vertical and diagonal web members; furthermore, vertical shear reinforcements were placed at 300 mm intervals in the PV specimen, as shown in Figure 3b. In addition, six D25 tensile reinforcements were placed to prevent flexural failure and induce shear failure, and the thickness of the bottom chord was 20 mm. The bottom chord was considered as tensile reinforcement in the calculation of flexural strengths of the specimens. As shown in Figure 3c, the stirrup was not placed in the P specimen, and four D25 tensile reinforcements were placed on the tension side of the section. Except for the presence of stirrups and the tensile reinforcement placement, all the section details were the same for both specimens. The side cover thickness of the top chord, which corresponds to the resistance surface of concrete against horizontal shear, was 40 mm, whereas the top cover thickness was 65 mm. Meanwhile, the side cover thickness of the bottom chord was 72 mm, whereas the bottom cover thickness was 50 mm. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen** & **PV a** & **Pb b** & **WV c** & **W d** \\ \hline Truss type & Pratt & & & Warren \\ \hline Concrete compressive strength (MPa) & & & 29.7 & \\ \hline Width \(\times\) Height (mm) & 500 \(\times\) 600 & 500 \(\times\) 600 & 500 \(\times\) 600 & 500 \(\times\) 600 \\ \hline Thickness of bottom chord (mm) & 20 & 20 & 20 & 16 \\ \hline Longitudinal reinforcement & 6-D25 & 4-D25 & - & - \\ \hline Web members (Vertical) & PL–40 \(\times\) 6 @ 300 & PL–40 \(\times\) 6 @ 300 & - & - \\ \hline Web members (Diagonal) & PL–40 \(\times\) 6 @ 300 & PL–40 \(\times\) 6 @ 300 & PL–40 \(\times\) 6 @ 400 & PL–40 \(\times\) 6 @ 400 \\ \hline Stirrups & 2-D13@300 & & 2-D13@400 & \\ \hline \hline \end{tabular}  
* PV = Pratt truss with vertical stirrups; b P = Pratt truss without vertical stirrups. c WV = Warren truss with vertical stirrups; d W = Warren truss without vertical stirrups.  
\end{table} 
Table 1: Details of test specimens. Figure 2: Connection details at truss node. Figure 4 shows the details of the W specimen series (specimen WV, specimen W), to which the Warren truss is applied, and WV and W represent the specimens with and without vertical stirrups, respectively. The thickness of the bottom chord placed on the tension side of the section was 20 mm in the WV specimen and 16 mm in the W specimen. Except for the presence of stirrups and the thickness of the bottom chord, all the section details were the same for both specimens. In addition, the top, bottom, and side cover thicknesses were the same as those of the P specimen series. Figure 5 shows the dimensional details of the top and bottom chords. In the bottom chords, holes with a diameter of 30 mm were drilled at 300 mm intervals such that concrete could be secured tightly on the tension side of the section at the lower end of the bottom chord, preventing air voids. Note that the purpose of this experimental program was to evaluate the shear strength of EST composite girder. Therefore, all the specimens were designed to have sufficient flexural strengths for inducing shear failure. Detailed calculation process of the flexural strengths of test specimens is presented in the Appendix A.