## 5 Discussion
### Criterion 3 for Prototype with an Intermediate Stiffener Web Height  
With respect to the specified criteria for the intermediate range of the ratio \(P_{1}/P_{cr\text{e}}\), spanning from 1.55 to 3.21, a distinct situation emerges warranting individual consideration. Within this intermediate range, prototypes are termed intermediate prototypes, and their corresponding perfectly similar models are referred to as intermediate reference models. To explore this range, reference models with web heights ranging from 47 mm to 57 mm are subjected to impact simulations under consistent conditions involving an impact mass of 0.4 t and an initial velocity of 3.0 m/s. The comprehensive details of the dimensions and numerical results for each reference model are illustrated in Table 17 and Figure 26. Furthermore, Figure 26 underscores the observation that the intermediate reference models, characterized by consistent web thicknesses, exhibit tendencies towards similar resistance behaviors, irrespective of the web depth and more obvious buckling behaviors as the web depth increases. Furthermore, an investigation of distorted models related to the intermediate reference model RP-T47 was undertaken. These distorted models adhere to the proposed criteria, and comprehensive details regarding their dimensions are presented in Table 18. Similarly, RP-T47-E maintained sectional area and static moment consistent with RP-T47, whereas RP-T47-T developed with a constant web thickness of 1.15 mm, preserving the same sectional area as RP-T47. To maintain consistency, the impact mass was adjusted using Equations (23) and (24). Consequently, numerical simulations were conducted, and the results are presented in Table 18. Furthermore, Figure 27 presents the acceleration and displacement history curves for the three simulation cases. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Item** & **Unit** & **RP-T47** & **RP-T50** & **RP-T55** & **RP-T57** \\ \hline Geometry dimensions & Attached plate & mm & 640 \(\times\) 340 & 640 \(\times\) 340 & 640 \(\times\) 340 & 640 \(\times\) 340 \\  & Attached plate thickness & mm & 1.3 & 1.3 & 1.3 & 1.3 \\  & Cross section dimension & mm & \(\pm\frac{47\times 1.15}{15\times 1.80}\) & \(\pm\frac{50\times 1.15}{15\times 1.80}\) & \(\pm\frac{55\times 1.15}{15\times 1.80}\) & \(\pm\frac{57\times 1.15}{15\times 1.80}\) \\  & Static moment & mm\({}^{3}\) & 2409.8 & 3747.2 & 4221.9 & 4725.1 \\ \hline Analytical comparison & \(P_{1}\) & N & 17,577.3 & 19,294.2 & 22,322.3 & 23,591.8 \\  & \(P_{cr\text{e}}\) in Timoshenko & N & 7670.7 & 7210.5 & 6555.0 & 6325.0 \\  & \(P_{cr\text{e}}\) (1.324P\({}_{cr}\)) & N & 10,156.1 & 9546.7 & 8678.8 & 8374.3 \\  & \(P_{1}/P_{cr\text{e}}\) & - & 1.73 & 2.02 & 2.57 & 2.82 \\ \hline Results & Plastic displacement & mm & 38.27 & 38.56 & 38.13 & 38.57 \\  & Peak acceleration & mm/s\({}^{2}\) & 191,251 & 192,594 & 191,688 & 194,377 \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Relevant geometrical parameters and results (intermediate reference models). Figure 26: Comparison between intermediate reference models. The reference model RP-T47 experienced a notable buckling phenomenon, causing a sudden reduction in acceleration just before the peak crest (displacement = 30.48 mm), whereas the distorted models did not exhibit this behavior, leading to significant deviations. Consequently, the substantial deviations between these distorted models and the reference model demonstrate that the two proposed criteria are not suitable for intermediate models represented by RP-T47. This section presents an empirical method to determine the appropriate value of \(P_{1}/P_{cr-e}\), which forms the basis for Criterion 3 to address intermediate prototypes. Importantly, owing to the different boundary conditions on the unloading side of the web plate, the suitable value of \(P_{1}/P_{cr-e}\) for the flat-bar stiffener, corresponding to the static moment-dominant and web thickness-dominant intervals, differed from that of the T-type stiffener.