## 4 Performance Evaluation of Void Slab with Shear Reinforcement
### Shear Capacity Evaluation Based on Standard Formulae in Different Codes
#### 4.1.3 Ceb-Fip 1990  
The expected shear strengths for all test specimens were calculated following the CEB-FIP Model Code 1990 design procedures, established by the International Federation for Structural Concrete (fib). Table 7 summarises the results, categorised by the type of shear reinforcement (unreinforced, 45-degree, and 90-degree) and the hollow core ratio.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**No Reinforcement**} & \multicolumn{3}{c}{**45\({}^{\circ}\) Reinforcement**} & \multicolumn{3}{c}{**90\({}^{\circ}\) Reinforcement**} \\ \hline
**Name** & **HC-30** & **HC-35** & **H-C40** & **HC-30-45** & **HC-35-45** & **HC-40-45** & **H-C30-90** & **HC-35-90** & **HC-40-90** \\ \hline V\({}_{\text{test}}\) (kN) & 395.5 & 335.8 & 340.9 & 430.2 & 403.3 & 366.2 & 425.7 & 358.3 & 341.1 \\ V\({}_{\text{UBC}}\) & 183.5 & 170.5 & 157.5 & 260.9 & 247.9 & 234.9 & 260.6 & 247.6 & 234.5 \\ V\({}_{\text{test}}\)/V\({}_{\text{UBC}}\) & 2.16 & 1.97 & 2.16 & 1.65 & 1.63 & 1.56 & 1.63 & 1.45 & 1.45 \\ \hline AVG. & 2.1 & & & 1.61 & & & 1.51 & & \\ Var. & 0.012 & & & 0.002 & & & 0.011 & & \\ S.D. & 0.11 & & & 0.047 & & & 0.104 & & \\ \hline \hline \end{tabular} Note: AVG. is average, Var. is Variance, and S.D. is Standard Deviation.  
\end{table}
Table 6: Ratios between experimental shear capacity and expected shear capacity with different reinforcement from UBC 2.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**No Reinforcement**} & \multicolumn{3}{c}{**45\({}^{\circ}\) Reinforcement**} & \multicolumn{3}{c}{**90\({}^{\circ}\) Reinforcement**} \\ \hline
**Name** & **HC-30** & **HC-35** & **H-C40** & **HC-30-45** & **HC-35-45** & **HC-40-45** & **H-C30-90** & **HC-35-90** & **HC-40-90** \\ \hline V\({}_{\text{test}}\) (kN) & 395.5 & 335.8 & 340.9 & 430.2 & 403.3 & 366.2 & 426.7 & 358.3 & 341.1 \\ V\({}_{\text{CEB}}\) & 182.9 & 173.4 & 163.7 & 287.9 & 278.4 & 268.6 & 261.3 & 251.8 & 242.0 \\ V\({}_{\text{test}}\)/V\({}_{\text{CEB}}\) & 2.16 & 1.94 & 163.7 & 1.49 & 1.45 & 1.36 & 1.63 & 1.42 & 1.41 \\ \hline AVG. & & 2.06 & & & 1.43 & & & 1.49 & \\ Var. & & 0.012 & & & 0.004 & & & 0.015 & \\ S.D. & & 0.111 & & & 0.067 & & & 0.124 & \\ \hline \hline \end{tabular} Note: AVG. is average, Var. is Variance, and S.D. is Standard Deviation.  
\end{table}
Table 7: Ratios between experimental shear capacity and expected shear capacity with different reinforcement from CEB-FIP 1990.  
Unreinforced specimens displayed a variation in their expected shear strengths. The minimum value observed was 1.94 for HC-35 (the hollow core ratio of 35%), while the maximum value reached 2.16 for HC-30 (the hollow core ratio of 30%). The average expected shear strength for this group was 2.06. Additionally, the variance and standard deviation were 0.012 and 0.111, respectively.  
In contrast to the unreinforced specimens, those with a 45-degree shear reinforcement exhibited a significantly narrower range of expected shear strengths. This range spanned from a minimum of 1.36 to a maximum of 1.49. Furthermore, the average value for this group was 1.43. Notably, the variance (0.004) and standard deviation (0.067) were both lower compared to the unreinforced group. These reduced values suggest a more consistent performance in terms of expected shear strength for specimens with a 45-degree shear reinforcement:  
* The results for 90-degree reinforced specimens presented an interesting observation. While they exhibited a wider range of expected shear strengths (1.41 to 1.63) compared to the 45-degree specimens, this range remained lower than that observed in the unreinforced group.
* The average expected shear strength for the 90-degree specimens was 1.49, with a variance of 0.015 and a standard deviation of 0.124. These findings suggest that while a 90-degree reinforcement may not offer the same level of consistency as a 45-degree reinforcement, it still provides some improvement compared to unreinforced specimens.