# Seismic Analysis of a Large LNG Tank Considering Different Site Conditions
## 1 Introduction  
LNG (liquefied natural gas) is a highly efficient energy source that has seen substantial market growth over the past few years due to an increasing shortage in oil resources. With a stronger demand for natural gas, LNG tanks have become a major component of urban infrastructure. In China alone, 69 large LNG tanks have been built, with an increase in capacity from 30,000 m\({}^{3}\) to 160,000 m\({}^{3}\). An additional 220,000 m\({}^{3}\) of large storage tanks are under construction. Due to largely varying geological conditions within the Chinese territory, the types of construction sites where these LNG storage tanks are located also vary. Site classification is an important parameter for large LNG tank construction, because LNG tanks exhibit different seismic characteristics at different sites. Previously, many people have studied the effect of site conditions on high-rise buildings and bridges, but no one has investigated the dynamic analysis of large LNG tanks under different site conditions. This paper studies the effect of ground motion on large LNG storage tanks under four site classes, which hasnot been presented in existing literature. Therefore, the research findings of this paper are of great significance for the dynamic analysis and seismic design of large LNG storage tanks. LNG storage tanks are especially vulnerable to damage during strong earthquakes due to their low redundancy, ductility, and energy-dissipating capacity compared to conventional structures [1]. In addition, the failure [2] of LNG tanks can result in secondary disasters such as fire and explosion that lead to casualties and property loss. Therefore, the seismic risks of LNG storage tanks are especially high compared to traditional buildings due to potential catastrophic consequences. For example, the 1964 Japan earthquake caused LNG tanks to explode and led to serious pollution. The bottom ring of a storage tank buckled during the 1976 Tangshan earthquake and caused liquid leakage [3]. As a result, reliability and accuracy is paramount to the design and analysis of large LNG tanks under earthquake loading. Compared to ordinary buildings and bridges, the analysis of LNG tanks is established on different dynamic theories that consider the effect of solid-liquid interaction. In recent years, the study of liquid-solid coupling is of great significance in many engineering fields, such as aerospace, shipping, petroleum, chemical engineering, and marine engineering. More specifically, LNG tanks are subject to both inertial earthquake loading and hydrodynamic pressure, which result in liquid sloshing problems. In 1969, [PERSON] [4] used a finite element method to perform preliminary numerical simulation on the seismic response of a tank-fluid coupling system. [PERSON] and [PERSON] [5,6] proposed a single-degree-of-freedom system that assumed a flexible tank wall, which vibrated under a given bending deformation mode. In 1981, [PERSON] and [PERSON] [7] developed a more realistic model that accounted for the coupled vibration effect. To address the dynamic interaction of liquid and the tank wall, this model divided the liquid into a convection component, a flexible impulsive component, and a rigid impulsive component. Subsequently, [PERSON] et al. [8] summarized the results of a comprehensive analytical investigation concerning the seismic analysis of ground supported, cylindrical liquid storage tanks subject to a horizontal component of earthquake ground motion. In 2000, [PERSON] et al. [9] proposed a simplified design method for cylindrical storage tanks on a rigid foundation considering the effect of impulsive and convective masses on flexible steel or concrete walls, and this method was adopted by European regulations. Based on fluid-solid interaction and other aforementioned dynamic theories, since the 1950s, many people have conducted research on the dynamic analysis of LNG storage tanks.