Special aspects of the dynamic behavior of spherical containment shells

Abstract

Theoretical investigations of the containment response due to dynamic earthquake loading are common practice in the licensing procedure. Two different aspects are considered; first, the stresses must essentially remain below the yield point; and second, the compressive membrane stresses must not cause buckling near the containment clamping. The computations are usually based on simplified models; deviations from the ideal spherical geometry caused by nozzles with reinforced sections or due to inevitable manufacturing tolerances are usually not considered. However, it is known from experiments with thin cylindrical shells that little deviations from the ideal geometry may have a significant influence on the dynamic response. Similar phenomena might also occur in thin spherical shells. Therefore, theoretical and experimental investigations are carried out in which the influence of imperfections on the dynamic response of spherical containment shells will be determined. Both theoretical and experimental results show that point masses attached to the shell will have a strong, but only local effect on the dynamic containment response. Consequently, simplified decoupled models are adequate for the analysis. A first static buckling experiment shows that two types of buckling modes have to be considered; one mode caused by meridional, and the other modes caused by circumferential compressive stresses. The deformations are concentrated in the clamping region of the shell.