## 1 Introduction  
Owing to the International Maritime Organization's (IMO) environmental regulations, the demand for clean energy has increased significantly, particularly for decarbonization. Although hydrogen and ammonia-fueled vessels are still in the early stages of development, the demand for conventional liquified natural gas (LNG) as an energy resource is on the rise. The membrane-type LNG cargo tank is the most popular LNG containment system due to its cargo transportation efficiency. The most critical factor in the design of an LNG cargo containment system (CCS) is securing enough dynamic strength against the sloshing impact load [1]. To evaluate the strength of a CCS against the sloshing load, it is necessary to calculate the pressure from a hydrodynamic point of view and to evaluate the structural strength in various failure modes, i.e., crushing, shear, bending, and buckling, for the impact pressure. Experiments and numerical analyses are mainly performed to estimate the sloshing pressure. [PERSON] et al. [2] carried out a series of sloshing experiments to investigate fluid sloshing for different filling levels in a rectangular tank. [PERSON] et al. [3] studied the effectiveness of the four types of baffles in suppressing the pressure for a wide range of forcing frequencies. [PERSON] et al. [4] carried out a series of experiments on the hydrodynamics of an anti-sloshing technique using floating foams in a rectangular liquid tank, and an analytical potential flow solution was derived to explain the experimental observations. The effects of the various layers of floating foams on both the wave profiles and dynamic pressure histories in sloshing tanks were analyzed. [PERSON] et al. [5] developed sloshing load prediction using the artificial neural network method with an experimental database from the model scaled sloshing test. [PERSON] et al. [6] carried out a numerical investigation of sloshing flows inside the LNG fuel tank of a ship using the smoothed particle hydrodynamics model (SPH). [PERSON] et al. [7] performed computational fluid dynamics (CFD) calculations to study the sloshing wave interaction with the porous material layer. The improved model used to simulate the porous breakwater was validated against the available experimental data. [PERSON] et al. [8] focused on the sloshing simulation of an ice-breaking LNG carrier and proposed a numerical method using the circumferential crack method (CCM) and volume of fluid (VOF) with two key factors. [PERSON] et al. [9] compared the influence of different baffle factors, such as the number of baffles, liquid rate, and excitation frequency, through CFD simulations. Then, they compared the sloshing characteristics for those parameters by investigating the wave height, spectrum, hydrodynamic force, and velocity vector. However, owing to the randomness of the sloshing phenomenon, it is difficult to standardize the sloshing pressure applicable to the design stage. It is common practice to apply the impact pressure in a simplified form in the form of a triangle with a specific peak pressure and rise time [10; 11]. The peak pressure and rise time are normally determined based on the statistical data obtained through experiments and measurements. Although the simplified load history is applied, when it is applied to the structure, caution is still required due to the strong nonlinearity of the structure, the LNG box. This is because, in the case of the NO96-type CCS, a containment system consisting of complex parts, such as tongue, membrane, and weld joints (Figure 3 Schematic of the structural boundary nonlinearity in LNG CCS application(a)), is applied to prevent heat shrinkage/expansion/heat conduction at cryogenic temperatures. Therefore, as the complexity of the strength evaluation for sloshing is very high in terms of the hydrodynamic pressure and structural response, it is recommended that one considers the effects of all the possible factors in a complex way in the calculation, which is time consuming.