Development of the BS 7910 Failure Assessment Diagram for Strain Based Design With Application to Pipelines

Engineering Critical Assessment (ECA) uses J estimation schemes to derive the crack tip loading of complex structures to determine their tolerance to crack-like flaws. The methods currently being used were derived in the 1980s for structures with primary stresses below the material yield strength. These are now being extensively used for loads beyond this level for what has been called Strain Based Design (SBD). Some papers have shown the standards BS7910:2005 and R6 Revision 4 can be unconservative when used for SBD. A possible reason has been identified and a suitable modification proposed. The proposed modification is briefly reviewed in the present paper together with a comparison of the method with suitable crack driving force data.