A modified strain-controlled reference stress approach for submarine pipelines under large-scale plastic strain

The reel-lay approach is widely applied in submarine pipelines. During the process of reeling and unreeling, pipelines are subjected to nominal strain of 1-4%. In this study, various pipeline geometries and crack dimensions were calculated using a finite element analysis and analytical solution under strain-controlled boundary conditions. A modified reference stress approach was applied under strain-controlled boundary conditions using a derived implicit analytical solution of the nominal stress. The limit load solution was modified through a γ factor based on the finite element analysis under strain-controlled boundary conditions. A regression analysis of γ was conducted and an empirical formula was determined. The modified strain-controlled reference approach is in contrast to other ECA methods and proved to be closer to the finite element analysis results.