## 1 Introduction  
The liquefied natural gas cargo containment system (LNG CCS) can be exposed to harsh environments, such as cryogenic temperatures and, particularly, sloshing loads. Sloshing results from the relative motion of the free surface of the fluid in a cargo hold and ship motion, for example standing waves in partially filled cargo tanks on board an LNG carrier [1]. Severe and violent sloshing typically occurs when the vessel moves with motion periods similar to the highest sloshing resonance period of the liquid in the cargo tank. Violent sloshing may produce breaking waves and a high-velocity fluid surface. In such cases, the fluid can lead to impact loads on the containment system, and if an impact load exceeds the structural strength of the CCS, it can cause structural failure. There has been a real accident of primary barrier damage caused by a sloshing load [2; 3; 4]. The failure of an LNG CCS can lead to tremendous loss of human and material resources. Therefore, robust design and fabrication of LNG CCS is essential. The LNG wave inside the CCS is the form of crest, trough, and breaking wave, which interacts with the inner wall of the CCS and physically affects it, as shown in Figure 1. It takes three steps for a wave to load a wall: approaching, impact, and jet formation. The jet appears both upward and downward against the wall after impact [5]. As a result, the loading direction of the sloshing wave relative to the insulation panels is vertical or horizontal. When a violent sloshing acts on the insulation system with a vertical load, a sloshing load is applied to all components of the CCS, which can cause structural failure. Several studies have been conducted to evaluate the behavior and damage of materials and structures applied to CCS [6; 7; 8; 9; 10; 11]. In these studies, the material nonlinear behavior and failure/fracture features of the primary barrier (austenitic stainless steel), secondary barrier (multi-laminated adhesively bonded joints), and thermal insulation barrier (glass fiber-reinforced polyurethane foam) were experimentally estimated, and a computational analysis method as well as a numerical material model were proposed. Dynamic modeling has been proposed to precisely predict the impact behavior of structures [12; 13]. However, the LNG CCS structure is composed of various composite materials and the primary barrier has complex geometry, so it is very difficult to apply the dynamic modeling method. Moreover, a full-scale test, small-scale tank test, and a wet drop test were performed to analyze the fluid behavior due to the interaction of the wall and wave [5; 14; 15; 16; 17; 18; 19]. Due to the interaction of the LNG and the wall, the jet flow impact runs up along the wall of CCS [19; 20; 21] and the acceleration of the jet increases momentarily to 1500 times gravitational acceleration [22]. This impact load can affect the CCS (especially the primary barrier) much more than an ordinary LNG wave load. Thus, jet flow impact should be considered in the structural strength assessment. Several studies have been conducted to evaluate the effect of external loading on the behavior of corrugated membranes [9; 23; 24]. [PERSON] et al. (2011) performed a pressure test on the primary barrier for the Mark-III type CCS, and defined the critical pressure point at which buckling collapse occurred in the corrugation [9]. [PERSON] et al. (2014) conducted a cryogenic tensile test of primary barriers to simulate the hull bending moment environment, thus investigating the tensile behavior of the knot part [23]. They proposed a numerical model to simulate material nonlinear behavior. However, these studies have focused on the plastic behavior of the primary barrier under quasi-static loading or pressure. Figure 1: Schematic of sloshing impact applied to primary barrier in liquefied natural gas cargo containment system (LNG CCS). [PERSON] et al. (2008) performed a wet-drop test, which is the closest to actual conditions, by installing a real part of the primary barrier [24].