## 3 Results and Discussions
### Effect of Impact Energy  
The effect of the impact energy on a primary barrier was evaluated in terms of the reaction force profile and deformation. The drop object, together with the impactor, was released from 0.038 m, 0.071 m, 0.087 m, and 0.127 m onto the specimens with large and small corrugations. Figure 4 illustrates the reaction force profile under the first impact in relation to the impact energy. Figure 4 illustrates the reaction force profile under the first impact in relation to the impact energy. In the case of large corrugation specimen, the reaction force profile does not show similar shape in accordance with impact energy. This is because large corrugation has complex geometry such as four reinforcing ribs. Commonly, the peak reaction force tended to be generated later. However, in the case of small corrugation specimen, both duration and peak reaction forces increased as the impact energy increases. After reaching the peak point in the reaction force-time history, the rate of decrease in the reaction force for the large corrugation specimen increases with the increasing impact energy. However, all the small corrugation specimens show a steadily decreasing rate of the reaction force with the increasing impact energy. Figure 5 shows the increase in the impulse and maximum reaction force with increasing potential energy. As illustrated in Figure 5a, although the same drop object falls onto the specimens with the same impact energy, a somewhat larger impulse is measured for the large corrugation specimens than the small corrugation specimens. In addition, the impulse that is measured for both the specimen types is linearly proportional to the increase in the potential energy caused by the fall of the drop \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Duration (ms)**} & \multicolumn{2}{c}{**Rise Time (ms)**} & \multicolumn{2}{c}{**Rise Time/Duration**} \\ \cline{2-7}  & **Mean** & **STD** & **Mean** & **STD** & **Mean** & **STD** \\ \hline Exp. result & 37.7 & 108.2 & 19.4 & 75.9 & 0.510 & 0.021 \\ [PERSON] and [PERSON], 2008 & 27.4 & 41.0 & 11.4 & 17.6 & 0.480 & 0.200 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of experimental results and actual sloshing test in temporal pattern. Figure 4: Reaction force profile of (**a**) large and (**b**) small corrugation in accordance with impact energy. object. In fact, Figure 5b displays significant differences in the maximum reaction forces between the large and small corrugation specimens. The maximum reaction force is found to be larger for the large corrugation specimens than for the small corrugation specimens. The gap varies from 11.5% to 40.5%. Thus, the impulse measurements of both the specimens, represented by the integral of the reaction force-time history, are nearly similar, but the reduction in the duration has a decisive effect on the increase in the maximum reaction force. The effect of the impact energy of the impactor on the deformation of the primary barrier was investigated. Owing to the difficulty in measuring at a specific point, in the present study, the displacement of the upper and middle parts of a deformed corrugation was considered as representative. Figure 6 illustrates the method used to measure the displacements of the deformed specimens with large and small corrugations. Figure 7 presents the measured displacement between the large and small corrugations in accordance with the potential energy. Figure 5: (**a**) Impulse from reaction force and (**b**) maximum reaction force in accordance with impact energy. Figure 6: Displacement measurement method for primary barrier. Analysis of the displacement at the first impact as in accordance with the impact energy shows that a small corrugation is more deformed than a large corrugation; this is understood in terms of the displacement of the upper and middle parts of the corrugation.