## 3 Results and Analysis of the Tests
### Load-Displacement Relations and Overall Behaviors  
Figures 7 and 8 show the load-displacement relationship and ultimate failure mode of each of the specimens, respectively. In Figure 7, the vertical axis indicates the load measured from the actuator, and the horizontal axis indicates the displacement measured from the central LVDT located underneath the PC slab (LVDT 6 in Figure 6). Figure 7 also shows the predicted flexural strength \(P_{m}\) (Equation (2) or Table 2 (2)), shear strength \(P_{\text{P-dpt}(c)}\) (Table 2 (7)), and service load at the construction stage, which accounts for the CIP topping concrete and working load. At the construction stage, PC slabs should be able to support the CIP topping concrete at approximately 15 cm and a working load (1.5 kN/m\({}^{2}\)) during the CIP topping concrete pouring. All the specimens were within the elastic range under the service load, as shown in Figure 7.  
In Specimens ZS-12.8 and CS-12.8, which had a high shear-to-span ratio of 12.8, a ductile flexural behavior with flexural cracks at the center of the PC slab was observed without any failure of the dapped ends (Figure 7a,b and Figure 8a,b). For CS-6.4, with the shear-to-span ratio reduced to 6.4 to induce a shear failure, the load carrying capacity rapidly decreased after the peak strength, and more flexural shear cracking occurred than in Specimens ZS-12.8 and CS-12.8. However, the flexural cracks occurred at the center of the PC slabs, and the specimen ultimately failed, with concrete crushing at the extreme compression fiber. Similar cracking patterns also occurred at the other outer surfaces of the specimens. In Specimens ZS-12.8 and CS-12.8 with Z-type and clip-type shear reinforcements, respectively, almost identical behavior was observed (Figure 7a,b). However, in Specim ZS-12.8 with Z-type shear reinforcement, cracks occurred at the dapped end approximately when the load was increased to 160 kN, whereas no damage was observed at the dapped \begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Yield Strength \(f_{y}\)** & **Tensile Strength \(f_{m}\)** \\ \hline D10 & 460.16 & 570.50 \\ D13 & 531.57 & 675.45 \\ D16 & 579.95 & 755.43 \\ Lattice bar & 589.97 & 661.23 \\ Strand \(\Phi\)15.2 (1860 MPa) & 1733.69 & 1884.39 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mechanical properties of the reinforcing bars (units in MPa). Figure 7: Load–deflection relationships of the specimens: (**a**) ZS-12.8, (**b**) CS-12.8, and (**c**) CS-6.4. end in Specim CS-12.8 with clip-type shear reinforcement until the end of the test. This disparity in the damage pattern at the dapped end will be analyzed in Section 4 in detail. As can be seen in Figure 8a, the insulation (EPS) attached to the lower part of the PC slab remained attached without any damage until the ultimate failure of the PC slab, which indicates that the adhesion between the EPS insulation and the PC slab was secure until the ultimate failure of the PC slab. Table 5 summarizes the test results of the specimens, including the yield load \(P_{y}\), measured maximum load \(P_{test}\), the load at failure or the load at the end of the test \(P_{u}\), the corresponding drift ratios \(\delta_{y}\) (yield drift ratio at \(P_{y}\)), \(\delta_{test}\) (the drift ratio at \(P_{test}\)), \(\delta_{u}\) (ultimate yield drift ratio at \(P_{u}\)), initial and yield secant stiffness (\(K_{i}\) and \(K_{y}\)), ductility ratio \(\delta_{u}/\delta_{y}\), and the mean value of the normalized strain in Z-type or clip-type shear reinforcements at each load level (i.e., \(P_{y}\), \(P_{test}\), and \(P_{u}\)). The yield drift \(\delta y\) was defined using the yield secant stiffness \(K_{y}\), corresponding to 75% of the maximum strength (i.e., at \(P_{y}\)). The ultimate drift \(\delta u\) was defined as the post-peak drift, corresponding to 75% of the maximum strength (i.e., at \(P_{u}\)) [37]. The drift ratios were obtained by dividing the displacement by the shear span lengths of specimens.