Elastic-plastic Buckling of the Top End Closure of Cylindrical LNG Storage Tanks under Internal Pressure

In the top end closure of cylindrical storage tanks for refrigerated liquefied natural gases (LNG)subjected to internal pressure, one failure mode is bifurcation buckling. The top end closure is torispherical, and buckling may occur elastic-plastically. This paper describes the buckling characteristic and the buckling pressure of a top end closure of LNG tanks, which is designed according to the current design code, API Standard 620. The axisymmetric shell finite-element method considering both geometrical and material nonlinearity in the prebuckling state is carried out. Results show that the current design code estimates the buckling pressure fairly conservatively.