Collapse loads for circumferentially through-wall cracked pipes subjected to combined torsion and bending moments

• Crack evaluation procedure for pipe under combined applied loads does not exist.
• Collapse moment for circumferential through wall cracked pipe was analyzed.
• Collapse bending moments for pipes under torsion moments were obtained.
• It is found that pure bending moments can be used in lieu of combined moments.

Pressurized piping items in power plants may experience combined torsion and bending moments during operation. Currently, there is a lack of guidance in flaw evaluation procedures for combined loading modes of pressure, torsion and bending loads. Recently, collapse bending moments for pipes under torsion moments were analyzed by finite element modelling. Equivalent moments defined as the root of the sum of the squares of the torsion and bending moments are shown to be equal to pure bending moments for various diameter pipes containing circumferentially part through cracks. This paper focuses on behaviour of plastic collapse moments for pipes with circumferential through-wall cracks using finite element analysis, and describes the behaviour of the equivalent bending moments for flaw evaluation procedures, referring the results of part through cracked pipes.