Fatigue analysis of helix elements such as tensile armors and steel tubes are critical design issues for dynamic umbilicals and flexible pipes. The basis for assessment of fatigue damage of such elements is the long-term stress cycle distribution at critical locations on the helix elements caused by long-term environmental loading on the system. Establishment of the long-term stress cycle distribution will hence require global dynamic time domain analysis followed by cross-sectional analysis in a large number of irregular sea states. An overall computational consistent and efficient fatigue analysis scheme is outlined in this paper. A detailed description is given of cross-sectional analysis techniques required for fatigue stress calculation in helix elements exposed to bending, tensile and pressure loading. Special emphasis is placed on assessment of friction stresses caused by the stick/slip behaviour of helix elements in bending. Such effects are known to be of special importance for fatigue life assessments of deepwater applications of flexible pipes and umbilicals due to increased contact pressure between the individual elements in the cross-section. The described cross-sectional analysis techniques are based on an extensive literature survey and hence considered to represent industry consensus. The performance of the described calculation scheme is illustrated by case studies.
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ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering
June 6–11, 2010
Shanghai, China
Conference Sponsors:
- Ocean, Offshore and Arctic Engineering Division
ISBN:
978-0-7918-4913-2
PROCEEDINGS PAPER
Efficient Fatigue Analysis of Helix Elements in Umbilicals and Flexible Risers
Nils So̸dahl,
Nils So̸dahl
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
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Geir Skeie,
Geir Skeie
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
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Oddrun Steinkjer,
Oddrun Steinkjer
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
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Arve Johan Kalleklev
Arve Johan Kalleklev
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
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Nils So̸dahl
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
Geir Skeie
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
Oddrun Steinkjer
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
Arve Johan Kalleklev
Det Norske Veritas, AS, Ho̸vik, Oslo, Norway
Paper No:
OMAE2010-21012, pp. 1029-1037; 9 pages
Published Online:
December 22, 2010
Citation
So̸dahl, N, Skeie, G, Steinkjer, O, & Kalleklev, AJ. "Efficient Fatigue Analysis of Helix Elements in Umbilicals and Flexible Risers." Proceedings of the ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. 29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 5, Parts A and B. Shanghai, China. June 6–11, 2010. pp. 1029-1037. ASME. https://doi.org/10.1115/OMAE2010-21012
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