Fracture assessment procedures for steel pipelines using a modified reference stress solution

An accurate defect assessment procedure is needed to ensure integrity of girth welded steel pipelines while avoiding unnecessary repairs. An integral part of such a procedure is an estimation scheme for the crack driving force. In this work, a modified reference stress solution was developed for the assessment of elastic-plastic pipes with surface breaking defects. For the particular case of interest (reeled offshore pipelines), the loading is phrased in terms of applied strain. The stress-based approach has therefore been extended to the case of strain/displacement control. The results obtained using the modified reference stress solution have been compared with a three-dimensional finite-element analysis. Very good agreement has been obtained. The predictions are also significantly better than those obtained from existing approaches. A comparison between the proposed method and full scale testing will be presented in a separate paper.