scope:

Complete expressions are derived for the lower bound loads which cause yielding of general plate and shell elements subjected to membrane, bending and shear loads. The analyses are based on the Tresca yield criterion, and statically admissible stress distributions are used to obtain lower bound yield loads. These generalized yield surfaces are not restricted to shells of revolution subjected to axisymmetric loads. Stress limits based on these yield surface equations are proposed herein to evaluate elastically-calculated primary stresses obtained using finite element or other methods. The proposed evaluation method provides a consistent and nearly uniform margin of safety against gross plastic yielding.