EnginSoft - Conference Abstracts

EnginSoft Users' Meeting 2006
Le Tecnologie CAE nell'Industria

Sloshing response of an LNG storage tank subjected to seismic loading

Dotoli Rosario - Consorzio CETMA
Perillo Marco - EnginSoft
Bardaro Danilo - Consorzio CETMA
Lisi Daniela - Consorzio CETMA
Manni Orazio - Consorzio CETMA

Abstract

The number of Liquefied Natural Gas tanks is continually increasing. These tanks are very large and their capacity is about 150,000 [m3]. According to safety standards these kinds of tanks consist of an inner steel shell, containing the LNG, and an outer reinforced concrete shell. Nevertheless, they represent a great risk if they fail during an earthquake. Several types of tank failures have been observed. Tanks may be damaged for different reasons. Large shell hoop tensile stresses, resulting from a combination of hydrostatic pressure and hydrodynamic pressure, due to horizontal and vertical ground motions, could fail the tank. A more common type of failure is known as “elephant’s foot buckling”. This is caused by the large overturning base moments, resulting from the impulsive and convective liquid loading on the tank wall during an earthquake. The high vertical compressive stresses, which develop in the tank wall, may cause the buckling of the structure.

The aim of this work is to simulate the seismic behaviour of an LNG tank during an earthquake. The analyses have been performed with LS-DYNA code using a Lagrangian approach.

The applied seismic loads have been registered during a Richter magnitude 7.1 earthquake (Magnitude Moment 6.9). Simulations have shown that fluid motion and fluid-structure interaction are responsible of a failure type known as “elephant’s foot”. 3-D results of the large model (76 [m] in diameter) have been visualized with the support of a multi-wall screen at CETMAVirtual Reality Centre (CVRC). This visualization system is based on a pc cluster, ORAD DVG 10, with tracking and stereo capabilities.

The FEM model consists of a flat anchored bottom and a cylindrical metallic wall in contact with the LNG:

• Diameter: 76[m]
• Wall high: 41[m]
• Liquid level: 38[m]
• The liquid volume is 172.000 [m3], with a mass of 68954[ton]