The original scope of work for this effort entailed the following six tasks:
1. GOM Structures Overview: Utilize information from previous TAP studies to categorize existing platforms according to their condition with regards to remaining fatigue life.
2. Platform Vintage and Condition: Assessing the conditions of the primary structural joints and numbers of a platform will be specified and applied to the main types of GOM platforms.
3. Current Fatigue Design Methods: A critical review of existing fatigue design methods will be carried out in this task.
4. High Stress Low Cycle Fatigue: Develop a procedure for the evaluation of cyclic high stress on fatigue of critical connection on GOM OCS structures.
5. Fatigue of Deformed/Corroded Welds: Corroded/deformed connections will be evaluated and methodologies for their quantification will be developed.
6. Validation: Actual fatigue tests performed at the DNV laboratory, or fatigue performance from existing platform connections will be employed to compare with calculated results.
However, during execution of the work, it was recognized that the development of new fatigue calculation method for corroded/deformed tubular joint welds would require extensive testing in order to establish the relevant S-N curves. The scope of such an effort would substantially exceed the available resources for this project. Review of limited number of inspection reports for platforms in the GOM indicates that fatigue of corroded/deformed joints may not be a major damage scenario. However with the aging structures in the GOM fatigue could prove to be important. Therefore, it was decided that the scope of work be revised to allow the application of existing fracture mechanics and fatigue calculation methods to evaluate the viability of tubular joints with existing defects either due to initial fabrication or due to in-service fatigue. Therefore Tasks 5 and 6 were replaced by: 5. Fatigue of existing cracks in welds in tubular joints: connections will be evaluated and procedures for calculation of remaining fatigue life will be proposed. 6. Case studies: proposed joint fatigue strength calculation procedures will be applied to a jacket structure and the results verified against existing experience/technology
This project has been completed. The final meeting was held at BSEE's offices in New Orleans January 5, 2012.