Engineering Critical Assessments of Marine Pipelines with 3D Surface Cracks Considering Weld Mismatch

Offshore pipelines are usually constructed by the use of girth welds, while welds may naturally contain flaws. Currently, fracture assessment procedures such as BS 7910 are based on the stress-based methods and their responses for situations with large plastic strain is suspicious. DNVOS- F101 with limited modifications proposes a strain-based procedure for such plastic loads. In this paper 3D nonlinear elastic-plastic finite element analyses using the ABAQUS software are performed in order to compare existing stress- and strain-based procedures beside newly strainbased method which is called CRES approach in order to improve the criteria used in current guidelines particularly at large plastic strains. It is concluded that although BS 7910 values are closer to finite element results than other methods in elastic region, but it is still conservative. In the area of large plastic strain, CRES method is very less conservative in both case of with and without internal pressure in comparison to others. The comparison of numerical simulation results with those available experimental data reveals a good agreement.