Comparison of analysis methods for earthquake responses of LNG tank

Aseismic design of liquefied natural gas (LNG) tank is a key component of the LNG project. Major aseismic analysis techniques for LNG tank include recommended standard formula, fluid element method and additional mass method. All three methods have basically the same theoretical bases but different calculation modes and effects. Generally speaking, response spectrum for aseismic design specified in EN 1998-1-2004 is used for design of LNG tanks. EN 1998-1 standard formula is the simplified deviation of Haroun-Housner theory. By using fluid element in finite-element software to simulate actual earthquake responses of LNG tank, the fluid element method is used for sysmatic analysis of coupling fluid-storage-site soil system. Additional mass method involves superposition of mass related to fluid impact and the mass related to waving section on the corresponding equivalent height. It is the combination of fluid element method and standard formula. As far as calculation accuracy, safety margin and efficiency are concerned, additional mass method is recommended during engineering design of LNG projects to determine earthquake responses.