# Damage Characteristics and Dynamic Response of RC Shells Subjected to Underwater Shock Wave
## 1 Introduction
[12] discussed the dynamic response mode of ship sections under a lateral non-contact water explosion. [PERSON] et al. [13] researched the linear and nonlinear dynamic responses of unstiffened, internally stiffened, and externally stiffened cylindrical shell structures in underwater explosion conditions through water explosion tests and numerical simulation. [PERSON] et al. [14] simulated the damage to and calculated the dynamic response of shell structures under near-field water explosions using SPH and RKPM coupling methods. [PERSON] et al. [15] predicted the response of coated composite cylindrical shells under near-field water explosions by combining machine learning with high-flux multi-scale finite element (FE) simulation. [PERSON] et al. [16] conducted a study on the nonlinear dynamic response of water explosions in double-curved shallow shell of functionally graded material (Sandwich-FGM) sandwich plates based on the first-order shear deformation theory. Numerous studies have been conducted on the dynamic response of underwater non-bottom-sitting shell structures. However, there is a lack of research on the damage to and dynamic response of shells subjected to the coupling of underwater shock waves and hydrostatic pressure. Additionally, there is a scarcity of studies on the effects of reinforcement on the damage and dynamic response of RC shells. Therefore, it is imperative to conduct related research. Existing research indicates that various materials and shell structure forms are utilized to construct underwater immersed tube tunnels and pipelines. The pressure shell provides a normal working environment for internal equipment and electronic components under water, which requires adequate strength and dependable sealing performance [17]. The primary load-bearing structures of immersed tube tunnels and pipelines typically adopt prism or cylindrical shells [18], constructed predominantly from reinforced concrete or steel. The submarine pressure structures commonly adopt a stiffened cylindrical shell composed of a pressure shell and reinforcement [19]. In addition, the pressure spherical shells have been widely used in underwater vehicles and civil engineering fields [20; 21; 22]. Therefore, considering the complexity and cost of underwater construction, research on the dynamic response of semi-cylindrical and semi-spherical bottom-sitting RC shell structures subjected to underwater shock waves was conducted. As the core load of underwater explosions, the underwater shock wave is the research focus. Different from an explosion in air and rock mass, underwater explosion shock waves have high peak overpressure, slow attenuation, and widespread range, and their damage effect on adjacent underwater structures is more severe than on land structures [23; 24]. Underwater bottom-sitting shell structures are typically stationary. Besides being vulnerable to precision strikes, they are also susceptible to the effects of non-contact underwater shock waves generated when other targets are struck. Therefore, to further promote the development of the construction and related protection technologies of underwater bottom-sitting shell structures, the influences 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 subjected to underwater shock waves were studied using validated numerical models.