## 5 Conclusions  
This study developed three numerical methods--a quasi-static structural method, a transient structural method, and a one-way FSI analysis method, based on convergence studies from FEM and FVM--for modelling a firefighting water tank. These methods were used to assess the structural integrity of the tank under seismic loads. The following conclusions can be drawn.  
1. There was no significant difference in the level of structural responses between the quasi-static (CASE I-3) and transient (CASE II) structural analysis. However, the one-way FSI (CASE III-1) analysis, which took fluid interactions into account, exhibited a significantly larger maximum total deformation and von Mises stress than the CASE I-3 and CASE II analyses. It was found that the amount of the total deformation and von Mises stress for the PDF panel at CASE III-1 increased by 85.8% and 87.2% against CASE I-3 and 85.1% and 84.3% against CASE II. This indicates that fluid interactions must be considered to obtain high-accuracy estimates of structural responses of water tanks under seismic loads.
2. The anti-wave plate affected both the free surface behaviour and the force generated by the sloshing in the tank wall, as demonstrated by the CASE III-1 and CASE III-2 analyses. However, the effect of the anti-wave plate height was not significantly appeared between CASE III-2 and CASE III-3. This demonstrates that the anti-wave plate is capable of mitigating both the free surface motions and the forces, but a higher anti-wave plate does not guarantee a more significant effect. Therefore, the optimal height of an anti-wave plate must be systematically assessed.
3. The anti-wave plate clearly decreased the structural responses in the PDF panel, as was shown by comparing the CASE III-1, III-2, and III-3 analyses. However, the maximum von Mises stress occurred near the connection between the bottom of the PDF panel and the anti-wave plate. Therefore, while the anti-wave plate effectively mitigated structural responses, a systematic design process should be employed when using an anti-wave plate, such that a significant increase in stress at the connection is prevented.  
We hope that the numerical modelling methods developed in this study will aid engineers and designers in the construction industries. We note that to improve the accuracy of the developed numerical modelling methods, a two-way FSI should be considered.  
Conceptualization, D.-M.L. and S.-E.L.; methodology, D.-M.L. and S.-E.L.; ANSYS Workbench (ver. 2020R2), S.-E.L.; formal analysis, S.-E.L.; investigation, D.-M.L. and S.-E.L.; resources, S.-E.L.; data curation, S.-E.L.; writing--original draft preparation, S.-E.L.; writing--review and editing, S.-E.L.; visualization, S.-E.L.; supervision, S.-E.L.; project administration, D.-M.L. and S.-E.L.; funding acquisition, S.-E.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2015R1A6A3A-01060166, NRF-2017R1A6A3A03003742).  
**Conflicts of Interest:** The authors declare no conflict of interest.