## 3 Experimental Results and Analysis
### Crack Patterns  
Figure 9 presents photographs of the post-test crack patterns observed on the front faces of the test specimens. These photographs were captured immediately following the completion of the experiments. It is important to note that the crack diagrams within the figure were generated using image editing software (e.g., Photoshop (version 25.0)) to virtually flatten the curved surfaces of the specimens for clearer visualization of the crack paths. Overall, as the experiment progressed, a bending crack occurred near the centre of the experiment, and the specimen fractured in the form of a sinusoidal crack. Analysis of these crack diagrams reveal the presence of shear cracks in all specimens and furthermore supporting the conclusions drawn from the load-displacement curves regarding the dominant shear failure mode. Figure 8: The load–displacement curve on a hollow core ratio of 40%. Figure 7: The load–displacement curve on a hollow core ratio of 35%. The experimental results for maximum shear capacity were compared with the anticipated shear capacity predicted by the design code equation employed during specimen development (Section 2.1.1). The expected shear strength was calculated in accordance with the detailed formula provided in ACI 318-14 [39]. Table 4 summarizes the results, listing the specimen designation, expected shear capacity (calculated), and the ratio of these two values. Notably, all test specimens exhibited a maximum shear strength exceeding the expected shear strength by a minimum factor of 1.436. Figure 10 investigates the relationship between the hollow core ratio and shear capacity. Separate graphs are presented for specimens with and without dedicated shear reinforcement. Within each category, the graph is arranged with increasing hollow core ratios along the \(x\)-axis. As expected, the expected shear capacity (calculated based on ACI 318-14) exhibits a decreasing trend with an increasing hollow core ratio for the unreinforced specimens. This decrease can be attributed to the reduction in effective cross-sectional areas as the hollow core ratio increases. This observation highlights the potential vulnerability of the void slabs with higher hollow core ratios under shear loading conditions, particularly in the absence of dedicated shear reinforcement. Figure 11 explores the influence of dedicated shear reinforcement on the shear behaviour of the specimens. It presents a comparison of the expected and maximum shear capacities for specimens with and without a 45-degree shear reinforcement. As observed in the figure, both the expected shear strength (calculated based on ACI 318-14) and the measured maximum shear strength exhibit a decreasing trend with increasing hollow core ratio for specimens with a 45-degree shear reinforcement. This observation suggests that while shear reinforcement can enhance the overall shear capacity compared to unreinforced specimens (refer to Figure 6), its effectiveness diminishes as the hollow core ratio increases. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimen** & **Expected Shear Capacity** & **Experimental Shear Capacity** & **Experimental/Expected Shear Capacity** \\  & **(kN)** & **(kN)** & **Experimental/Expected Shear Capacity** \\ \hline HC-30 & 185.88 & 395.505 & 2.128 \\ HC-30-45 & 262.99 & 430.165 & 1.636 \\ HC-30-90 & 262.62 & 425.68 & 1.621 \\ HC-35 & 172.38 & 335.80 & 1.948 \\ HC-35-45 & 249.85 & 403.315 & 1.614 \\ HC-35-90 & 249.45 & 358.32 & 1.436 \\ HC-40 & 159.21 & 340.905 & 2.141 \\ HC-40-45 & 236.65 & 366.21 & 1.547 \\ HC-40-90 & 236.28 & 341.09 & 1.444 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Expected and experimental shear capacity. Figure 9: Post-test crack patterns at the end of the experiments. Finally, Figure 12 explores the influence of the shear reinforcement angle on the shear behaviour. It presents a comparison between the behaviour of specimens with a 45-degree and 90-degree shear reinforcement, both having the same void ratio.