# Seismic Analysis of a Large LNG Tank Considering Different Site Conditions
## 1 Introduction
[PERSON] and [PERSON] [10] used mechanical models and finite element analysis to investigate the seismic response of a conventional and isolated cylindrical LNG tank. They obtained similar results from two numerical models and demonstrated that mechanical models could be applied to the preliminary analysis and design of such tanks. [PERSON] [11] presented a preliminary analysis of the potential effects of LNG tank insulation under earthquake conditions and assessed the potential for structural damage by comparing models with an insulation layer. [PERSON] et al. [12] established a system for selecting the optimum friction material to meet the seismic performance requirements of an LNG tank with a friction pendulum system. [PERSON] et al. [13] presented a theoretical solution for the von Mises stress on an LNG storage tank with elastic walls subject to seismic excitations. His solution was established based on the thin shell theory, and the precision of the theoretically simplified solution was proven with the simulation results. [PERSON] et al. [14] studied the effect of impact loading on the dynamic response of a 160,000 m\({}^{3}\) LNG prestressed concrete outer tank. Different types of impact damage were identified according to dynamic response results such as stress, energy, displacement, and critical impact velocity. [PERSON] et al. [15] investigated the effect of the multi-directional components of ground motion on an unanchored steel storage tank. They concluded that the vertical seismic component produced high compressive axial stress, which caused a significant increase in uplift and sliding at the tank bottom. [PERSON] et al. [15] applied an accurate and efficient Smoothed Particle Hydrodynamics-Finite Element Method (SPH-FEM) algorithm to evaluate the seismic response of a 160,000 m\({}^{3}\) LNG prestressed storage tank at different liquid levels. The maximum stress of the inner tank with 100% LNG liquid level exceeded 500 MPa under the selected seismic waves and raised concerns for its structural safety. Despite an abundance of studies on the seismic analysis for LNG tanks, the impact of site conditions has largely been ignored. Therefore, discussions in this paper regarding site influence is an important addition to the dynamic analysis and seismic design of large LNG storage tanks. In this study, the method of Smoothed Particle Hydrodynamics-Finite Element Method (SPH-FEM) is adopted to analyze the fluid-solid coupling problem in the seismic analysis of large LNG tanks. SPH-FEM methods inherent the advantages of SPH in modeling fluid behaviour while preserving the advantages of FEM in simulating FSI problems. [PERSON] et al. [16] first proposed the coupled SPH-FEM method using a master-slave algorithm to model the interaction between FE elements and SPH particles. [PERSON] and [PERSON] [17] used SPH-FEM to simulate the contact between a convergent-divergent nozzle and cavitating flow, and the resulted behaviour at liquid-vapour interface was confirmed by other numerical and experimental methods. [PERSON] and [PERSON] [18] applied the SPH-FEM method to a soil-structure interaction problem by conducting seismic analysis on a rectangular underground structure, and they were able to show that the magnitude of soil deformation and soil-structure contact status had an influence on the distribution and magnitude of seismic earth pressure. [PERSON] et al. [19] coupled FEM and SPH to analyze the effect of air in FSI problems, and he concluded that air had considerable effect on the behaviour of the structure after the initial fluid impact. In the case of an LNG tank that is too large to allow any direct physical experiments, SPH-FEM simulation provides an accurate and efficient method to predict its seismic response in this study.