Limit Design of Perforated Cylindrical Shells per ASME Code

Limit pressures are evaluated for cylindrical perforated shells containing circular holes arranged in the various penetration patterns typically found in practice. Statically admissible discontinuous fields of stress are used to obtain rigorous lower-bound limit pressures. These solutions are shown to be quite close to the actual limit pressures based on the efficiency of the discontinuous fields of stress and a comparison with upper-bound solutions. The optimal spacing parameters are obtained over the interesting range of ligament efficiencies for both the diamond (romboidal) and rectangular penetration patterns. The results of this work show that for most penetration configurations, the present ASME standards require substantially thicker shells than would be needed to maintain the same safety factors that are used for unperforated shells. On the other hand, the British and German standards allow the use of thinner shells than would be needed to maintain the safety factors for unperforated shells. Revised design curves which provide the same margin of safety for all configurations are derived and are proposed for use in design standards.