## 5 Results and Discussion  
### Impact of the Central Opening and Side Contour Cutouts  
Figure 10 shows the von Mises stress distribution of the double-bottom floor in the presence of the different geometric discontinuities, for the case of 14.5 mm thickness and axial load. Figure 8: Difference between numerical and experimental regime. (**a**) Finite element analysis, (**b**) experimental test. \begin{table}
\begin{tabular}{c c c c c} \hline  & \(\sigma_{\text{VM}}\) (MPa) & Change (\%) & Elements & Nodes \\ \hline
1 & 80.84 & - & 362 & 2939 \\
2 & 104.98 & 25.9 & 10,981 & 19,757 \\
3 & 113.16 & 7.5 & 29,344 & 48,369 \\
4 & 118.83 & 4.8 & 74,110 & 116,065 \\ \hline \end{tabular}
\end{table} 
Table 3: Iteration procedure for mesh convergence. Figure 9: Comparison in maximum displacement (in mm). (**a**) FEM technique, (**b**) DIC technique. The double-bottom floor, under axial loading scenario and different geometrical conditions, shows a very significant variation of the stress distribution that represents the great influence of the openings present in the structural behavior of the same with respect to the initial condition of the solid plate, in terms of the increase of the maximum von Mises stress of 31.4%, 74.7%, and 77.7% with respect to the condition of the plate with central opening, plate with cutouts, and plate with central opening and cutouts, respectively. A great influence of the presence of the cutouts with respect to the central opening is observed, since there is a minimum difference of 3% of stress increase when all the geometrical discontinuities (central opening and cutouts) or only the cutouts are present (Figure 11). Figure 12 shows the stress distribution of the double-bottom floor in the presence of the different geometric discontinuities, for the case of 14.5 mm thickness and transverse loading. Figure 10: Von Mises stress distribution (Pa) with 14.5 mm thickness and axial load. (**a**) Solid plate, (**b**) plate with central opening, (**c**) plate with cutouts, (**d**) plate with central opening and cutouts. The double-bottom floor exhibits variations in stress distribution under transverse loading conditions and different geometric configurations, highlighting the impact of the openings on its structural behavior compared to the original solid plate. This results in increases in the maximum von Mises stress of 4.9%, 56.9%, and 60.4% for the plate with a central opening, the plate with cutouts, and the plate with both a central opening and cutouts, respectively. A notable rise in the maximum von Mises stress is evident when the loading scenario involves a transverse load as opposed to an axial load, with differences in maximum stress of 63.8%, 49.9%, 38.4%, and 35.78% observed for the solid plate, plate with a central opening, plate with cutouts, and plate with both features, respectively. Additionally, as the stress levels increase, the gap between the two loading conditions diminishes (Figure 13). A more unfavorable and at the same time more conservative load scenario is established for the transverse load case. A common pattern is observed in the structural behavior  
Figure 12: Von Mises stress distribution (Pa) with 14.5 mm thickness and transverse load. (**a**) Solid plate, (**b**) plate with central opening, (**c**) plate with cutouts, (**d**) plate with central opening and cutouts. Figure 13: Difference of maximum von Mises stress between axial load and transverse load at different geometrical discontinuities. regardless of the load scenario selected. A great influence of the presence of the cutouts with respect to the central opening is observed, since there is a minimum difference of 5.8% of stress increase when all the geometrical discontinuities (central opening and cutouts) or only the cutouts are present. Figure 14 shows the difference, in terms of von Mises stress distribution, between cutout no. 1 and no. 2 present in the double bottom, for the same SENT-type loading condition, with an improvement in von Mises maximum stress of 0.43% of cutout no. 2 over cutout no. 1.