LAUSR

Abstract Multiple cracks may be initiated in offshore pipelines due to imperfect manufacturing processes. Under complicated loading conditions, small closely cracks can grow and coalesce into a large one that may pose threats to the integrity and safety of the structures. One of the severe loading conditions is the large strain-controlled loading which exceeds the yield stress considerably. In this case, the existing codes such as the BS7910:2013 code will not be accurate in providing the failure assessment for re-characterized multiple cracks since they are derived based on the load-controlled method. Therefore, this study focuses on the nonlinear elastic-plastic fracture responses of a flawed pipeline with the interactions of a circumferential semi-elliptical surface crack and an elliptical embedded crack under the large plastic strains. It systematically explores the influence of the crack parameters and makes the comparison with the BS7910:2013 code. New strain-based CTOD estimation schemes are proposed with a user-friendly flowchart that could be helpful to easily perform the failure assessment of the 3-D multiple cracks in offshore pipelines.