Limit pressures for cylindrical shells with two adjacent circular cut outs

Cylindrical shells each with two equal circular openings were subjected to internal pressure until gross plastic deformation occurred. The opening diameter was kept constant throughout but the pitch was varied and two vessel sizes were used. In some specimens the two openings were disposed around the shell circumferentially and in some they were disposed along a cylinder generator. The experimental limit pressures so determined were compared with those calculated by using a lower bound analysis. Experimental limit pressures were also compared with those determined from tests on three specimens each having two adjacent openings with branch reinforcement.