There is currently little specific guidance on the application of Finite Element Based Limit Load Analysis to determine the primary load capacity of structures in the current ASME BPVC Section III. Consequently, a draft Code Case is currently under development to provide a structured framework within which such assessments may be made.
In this paper, the proposed Code Case methodology has been applied to demonstrate the process by which the primary load capacity of two geometrically complex structures may be calculated. The first structure is a curved pipe elbow into which a nozzle entry is placed, the second structure a large pressure vessel incorporating bolted joints.
The proposed Code Case step-by-step methodology is followed, including investigations into the propensity of the structures to exhibit geometric weakening or strengthening. The initial limit loads are calculated, and by selective application of elastic material, subsequent failure loads are calculated allowing design factors beyond initial failure to be determined.
Additional studies are also presented, investigating the effect of element types and secondary pre-stress effects on the failure modes.
