Classical Versus Improved Thin Shell Theories: A Theoretical Argument or a Design Concern?

Differences in the response of thin nonshallow spherical shells resulting from the choice of the adopted shell theory (classical or improved) are addressed analytically and through a series of representative shell problems. The analytical approach utilized to study the variation between the two theoretical models is based on the response resulting from Singular loads. The differences are quantified in a set of problems that reflect on the assumptions used in formulating the analytical description of the two theories in question. The broad scope of this paper is to examine the impact of shear deformability, introduced by the improved theory on the stress field when amplified under specific loading and geometric conditions, when those are of primary concern to the engineers. Such cases associated with stress concentration around cutouts, interaction of shells with nozzles, stress field in the vicinity of concentrated surface loads, etc. The mathematical formulation is based on the derivation of appropriate Green functions and the computational scheme is formed upon a special type of boundary integral equation. Comparison solutions for stress concentration around circular cutouts of twisted and sheared shells, stress amplification in the junction of shell with nozzles, and local stress field induced by concentrated loads are presented for the two theories.