## 5 Discussion
### Prototype Stiffened Plates Considering a Relatively Large Web Height
When a stiffener has an extremely slender web, it is more likely to behave as a web girder than traditional stiffeners. The deformations of web girders subjected to in-plane concentrated loads have been extensively investigated. Various simplified analytical methods have been proposed to predict the resistance of web girders, with a particular focus on different formulations of the fold-height parameter \(H\)[3; 30]. [PERSON] et al. [30] studied the behavior of a web girder subjected to an in-plane concentrated load. According to the analytical solution [30] for web girders, the resistance responses are significantly influenced by the web thickness. In addition, in the large-deformation stage, the dynamic behavior is dominated by membrane behavior rather than bending action. Therefore, an expanded criterion, denoted as Criterion 2, was introduced to maintain the web thickness and sectional area as close to those of the reference model as possible, specifically for T-type stiffeners with very large web heights. To examine the effectiveness of the different design criteria, a series of distorted models obeying Criterion 1 and Criterion 2 were constructed based on RP-6, whose detailed dimensions and geometric properties are listed in Table 15. Through preserving a consistent sectional area and static moment, the web dimensions of RP6-E were determined. Based on this, a distorted model, RP6-T, was created with a web thickness of 1.15 mm to maintain a consistent sectional area. The impact mass was calculated using Equations (23) and (24). Subsequently, numerical simulations were performed, the results of which are presented in Table 15. Furthermore, Figure 23 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-6** & **RP6-E** & **RP6-T** \\ \hline Specim & Attached plate & mm & \(640\times 340\) & \(640\times 340\) & \(640\times 340\) \\  & Attached plate thickness & mm & 1.3 & 1.3 & 1.3 \\  & Stifener & mm & \(\frac{(6\times 1.15}{5\times 1.50})\) & \(75.12\times 1.218\) & \(79.57\times 1.15\) \\  & Sectional area & mm\({}^{2}\) & 195.5 & 195.5 & 195.5 \\  & Static moment & mm\({}^{3}\) & 3504.0 & 3503.7 & 3707.7 \\  & \((M_{S})_{m}\) & t & 0.00393 & 0.00393 & 0.00393 \\ \hline Load & \(R_{I}\) & mm & 80 & 80 & 80 \\  & \((M_{I})_{d2}/(M_{I})_{m}\) & & - & 1.0000 & 1.0000 \\  & \(M_{I}\) & t & 0.4000 & 0.4000 & 0.4000 \\  & \((v_{0})_{d2}\) & m/s & 3.0 & 3.0 & 3.0 \\ \hline Results & Plastic displacement & mm & 38.50 & 37.08 & 38.71 \\  & Difference & - & - & \(-3.70\%\) & 0.55\% \\  & Peak acceleration & mm/s\({}^{2}\) & 191,824 & 205,986 & 194,961 \\  & Difference & - & - & 7.38\% & 1.63\% \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Relevant geometrical parameters and results (RP-6). Figure 21: Results around first crest of center stiffener. (**a**) Before t1 (0.00075 s); (**b**) after t1 (0.001 s); (**c**) after t1 (0.0015 s). Figure 22: Results for second crest of center stiffener and adjacent stiffeners. (**a**) Before t2 (0.010 s); (**b**) after t2 (0.011 s); (**c**) after t2 (0.011875 s). During the initial phase, a pronounced similarity to the reference model was observed in the distorted model RP6-E, which was characterized by a static moment and was sectional. However, as the impact event transitioned into a large deformation stage, RP6-E continued to display observable variations, as shown in Figure 23. Conversely, the distorted model RP6-T shows a behavior that closely mirrors that of the reference model, exhibiting a noticeable reduction in deviation compared to the other distorted models. In summary, it is deduced that the resistance force during impact, particularly during the substantial deformation stages, is significantly influenced by the web plate thickness.