Elastic-plastic behavior of high-strength UOE linepipe. Strain-Based Design and associated issues

The present paper addresses issues of pipeline design associated with high-strength line pipe steel. After an introduction on engineering strategies towards complex loading conditions several failure mechanisms are addressed and explained. Various factors may interfere with the load bearing capacity, or, to be specific, strain capacity. On the one hand there is an-isotropy of the pipe mechanical properties, which are intrinsic to pre-material and the UOE process. On the other hand there is significant impact from the pipe coating process with heat input at temperatures between 170 °C and 220 °C. The latter one may change the trace of stress-strain curves from adequate to infavorable shapes. It then follows a concise description of the computational model that was developed, based upon classical concepts of plasticity theory. The paper concludes with pipeline engineering issues to which the model was applied. It follows that, despite its analytical set up, the model is capable of accurately capturing a large variety of relevant multi-axial loading paths.