# Damage Characteristics and Dynamic Response of RC Shells Subjected to Underwater Shock Wave
## 6 Conclusions  
This paper uses finite element numerical simulation to investigate the damage characteristics and dynamic response of bottom-sitting shell structures under underwater shock waves. The effects of the shock wave transmission medium, explosive equivalent, explosive distance, hydrostatic pressure, and reinforcement on the damage characteristics and dynamic response of semi-spherical and semi-cylindrical bottom-sitting RC shell structures were studied using validated numerical models. The main conclusions are as follows:  
1. The damage and vertical center deformation of semi-spherical and semi-cylindrical RC shells under underwater shock waves are significantly greater than those under air shock waves.
2. The damage to the semi-spherical RC shell is mainly concentrated in the lower part and the center of the semi-spherical RC shell, and gradually extends from the lower part to the center of the semi-spherical RC shell with an increase in explosive equivalent. The damage to the semi-cylindrical RC shell is mainly concentrated in the junction of the semi-cylindrical RC shell and side walls at both ends, the constraint position of the semi-cylindrical RC shell, and the center of the semi-cylindrical shell. The damaged area gradually extends from the junction between the semi-cylindrical RC shell and side walls at both ends, and the restraint on both sides of the semi-cylindrical shell to the center of the semi-cylindrical shell with an increase in explosive equivalent.
3. The damage and vertical center deformation of the semi-spherical and semi-cylindrical RC shells show a gradually increasing trend with an increase in explosive equivalent or decrease in explosive distance. Meanwhile, the damage to the inner surface of the semi-spherical RC shell is more severe than the outer surface.
4. The overall damage and vertical center deformation of the semi-spherical and semi-cylindrical RC shell can be reduced by the bottom reinforcement and an increase in the diameter of the steel bar within the diameter range of 10-16 mm. However, the effect of the diameter of the steel bar on the vertical center displacement of the semi-cylindrical RC shell is lower than for the semi-spherical RC shell.
5. The 'hoop effect' caused by hydrostatic pressure restrains the horizontal convex deformation and slightly decreases the macroscopic damage and vertical center deformation of the semi-spherical RC shell with an increase in hydrostatic pressure within the range of 0-2.0092 MPa. The hydrostatic pressure restrains the horizontal convex deformation of the semi-cylindrical RC shell. However, the inward concave deformation of the semi-cylindrical shell center is increased by hydrostatic pressure, inducing an increase in the damage and center vertical deformation of the semi-cylindrical RC shell.  
Conceptualization, F.L. and X.Z.; methodology, F.L. and L.X.; software, F.L. and J.Z.; validation, F.L., X.Z. and L.X.; formal analysis, F.L., J.Z. and Z.L.; investigation, F.L., Z.L. and L.T; resources, J.Z. and L.X.; data curation, F.L. and X.Z.; writing--original draft preparation, F.L., Z.L., J.W. and L.T.; writing--review and editing, F.L., Z.L. and J.W.; visualization, F.L. and L.T.; supervision, F.L.; project administration, F.L. and X.Z. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data used to support the findings of this study are available from the corresponding author upon request. The data are not publicly available due to privacy.  
**Acknowledgments:** We would like to express our sincerest gratitude to the anonymous unidentified reviewers for providing us with constructive and insightful comments and suggestions.  
**Conflicts of Interest:** The authors declare no conflicts of interest.