scope:

The design of a class MC containment vessel against buckling shall be based on the requirements of Subsection NE of the Code. NE-3133 provides specific design rules for unstiffened or ring stiffened cylindrical shells, spherical shells and formed heads under external pressure and unstiffened cylinders under axial compression. NE-3222.1(a) and (c) provide general guidelines for other shell geometries and loading conditions. The purpose of this Case is to provide stability criteria for determining the structural adequacy against buckling of containment shells with more complex shell geometries and loading conditions than those covered by NE-3133. Such effects as symmetrical or unsymmetrical dynamic loading conditions, circumferential and/or meridional stiffening for heads as well as cylindrical shells, combined stress fields, discontinuity stresses and secondary stresses are considered in the stability evaluation.

Acceptable stress analysis procedures and methods for determining stress components to be used in the stability evaluation are given. The buckling capacity of the shell is based on linear bifurcation (classical) analyses reduced by capacity reduction factors which account for the effects of imperfections and nonlinearity in geometry and boundary conditions and by plasticity reduction factors which account for nonlinearity in material properties.