Effects of pipe steel heterogeneity on the tensile strain capacity of a flawed pipeline girth weld

• Pipe steel heterogeneity affects the tensile strain capacity of a girth weld.
• A theoretical framework predicts significant reductions of strain capacity.
• Finite element analysis of curved wide plate tests supports most predictions.
• Probabilistic analysis advises to take line pipe steel heterogeneity into account.
• Low Y/T, high uniform elongation and low steel production scatter are beneficial.

An accurate estimate of the tensile strain capacity of flawed girth welds is essential for the safe use of pipelines in harsh environments. Current strain-based flaw assessments neglect the unavoidable presence of strength heterogeneity between two connected pipes. This paper describes and quantifies the resulting effects on strain capacity. A theoretical framework predicts a remarkable sensitivity, which depends on the failure location (whether in the weld or base metal). A finite element study critically validates the predicted results. Probabilistic analysis reveals that pipe steel heterogeneity should be taken into account to allow for accurate evaluations of tensile strain capacity.