Load that causes overall structural instability; the onset of gross plastic deformation. NOTE 1 Plastic collapse load is calculated with elastic-plastic material properties. NOTE 2 Plastic collapse is calculated using methods such as ASME BPVC, Section VIII, Division 2, Paragraph 5.2.4 or ASME BPVC, Section VIII, Division 3, Paragraph KD-230 using a true stress–strain material model.
Source: API TR 1PER15K-1, Protocol for Verification and Validation of High-pressure High-temperature Equipment, First Edition, March 2013. Global Standards