The behaviour under earthquake loading of an LNG (liquefied natural gas)-tank with a diameter of 75 meters and a height of 32 meters has been studied analytically and numerically. Design rules for achieving a safe design, provided by Eurocode 8 'Design of structures for earthquake resistance - Part 4 : silos, tanks and pipelines' (ENV 1998.4) were evaluated. Special attention was paid to the failure mechanism of elephant's foot buckling. The results gave rise to a proposal for modification of some application rules in ENV 1998–4.
Tanks made of steel are widely used for the storage of water, oil, petrochemical fluids, etc. The behaviour of these tanks during seismic motion has been increasingly studied in the past years, motivated by the large damage caused to tanks during recent earthquakes. Tank damage involving buckling walls was observed during the San Fernando earthquake in 1971 (Peek and Jennings, 1988) and the Northridge earthquake in 1994 (Schiff, 1995,1997). An important failure mechanism of this type of tank is the elastoplastic buckling of the tank wall (elephant's foot buckling). Investigations on this topic have been conducted by various researchers. Research was carried out into the general behaviour of the tank-fluid system under seismic loading (Haroun and Housner, 1981). More specific investigations include the response to vertical ground motion and soil-structure interaction (Veletsos and Tang, 1986), effects of uplift of unanchored tanks (Malhotra 1997) and elastoplastic collapse of steel cylindrical tanks (Rotter, 1990). As a result of these studies, the EC 8 Design of structures for earthquake resistance - Part 4 :silos, tanks and pipelines (ENV 1998–4)' was published in 1998 as a European Prestandard, containing rules for the seismic design of tanks. This prestandard was published as a prospective standard for provisional application for an initial period of 3 years.
