FAILURE MODES FOR OFFSHORE PLATFORMS - FATIGUE

The Author extends the concepts of static overload due to extreme storm loads (which was discussed in an earlier paper), to the case of progressive fatigue failure. An example used here is a simple 8-pile platform subjected to a known load which is identical in magnitude and pattern to its storm design load. Estimates of the probability of failure are presented and from among the four initial members a moderate probability of localised yielding somewhere in the structure is evident, based on a nominal safety factor of 1.25. Consideration of the fully plastic ultimate strength of typical braces, leads, to substantially higher safety factors and a reduction of the indicated probability of initial failure by two orders of magnitude. In fail-safe redundant structures, however, the initial failure does not necessarily lead to immediate collapse. In the ductile-redundant model, braces are assumed to maintain their full capacity after reaching the ultimate limit, and an even further reduction in the indicated risk occurs.

• Supplemental Notes:
  • Presented at Boss '76, First International Conference on Behaviour of Off-shore Structures, August 2-5, 1976.
• Corporate Authors:

  Trondheim University, Norway

  Trondheim,   Norway 
• Authors:
  • Marshall, P W
• Publication Date: 1976

Media Info

• Features: References;
• Pagination: 15 p.

Subject/Index Terms

• TRT Terms: Failure; Offshore platforms; Static loads
• Old TRIS Terms: Failure mode; Static loading
• Subject Areas: Bridges and other structures; Marine Transportation; Materials;

Filing Info

• Accession Number: 00163432
• Record Type: Publication
• Source Agency: British Ship Research Association
• Report/Paper Numbers: Vol. II Proceeding
• Files: TRIS
• Created Date: Oct 29 1977 12:00AM