Buckling Strength of a Non-Spherical Tank in the Partially Filled Condition

-Estimation of the reduction factor due to initial shape imperfection-

Abstract

Buckling strength of a non-spherical tank in the partially filled condition, which is one of the severest loading conditions in terms of the buckling design of Moss-type LNG tanks, is investigated both experimentally and theoretically. As the first part of the study, an axisymmetric loading condition for an upright tank position is considered. The buckling collapse test of scaled models is performed under the loading condition similar to the partially filled condition. The non-linear FE analyses of the test models are carried out and the results are compared with the test results to verify the accuracy of the imperfection sensitivity obtained by the FE analysis. A method to estimate the reduction factor of the elastic buckling strength due to initial shape imperfection is proposed by introducing a concept of an equivalent toroidal shell analogy and applying the Hutchinson’s solution to the toroidal shell under combined circumferential compression and meridional tension based on the Koiter’s initial post-buckling theory. A simplified method to estimate the elastoplastic buckling strength is also proposed by applying the Mises’s type plastic correction to the estimated elastic buckling strength. The reasonable accuracy of the estimated elastic and elastoplastic buckling strengths is demonstrated through a comparison with the results of scaled model tests and FE analyses.