This paper deals with the mean stress effect on the fatigue life of welded joints in FPSOs. Mean stresses in structural details of FPSOs are composed of residual stresses and mean stresses induced by external service loading conditions. Mean stresses, both the residual stresses and those induced by external load, affect on the fatigue life of structural details. Fatigue strength decreases as tensile mean stress increases. Under compressive mean stresses, fatigue lives are increased. Different fatigue analysis procedures to account for mean stress effect, i.e. JBP, JTP, DNV CN30.7 and IIW procedure, are used to compare the fatigue test data of different specimens representing different typical welded connections in ship-shaped structures from HHI in Korea. In this paper these procedures are compared and an improved procedure explicitly considering of the mean stress effect is also proposed. The fatigue strength of welded joints of FPSO is affected by the initial condition as well as possible redistribution (shake-down) of the residual stresses. The initial condition of welding residual stress and its re-distribution by static preload and cyclic load in the small scale specimens are evaluated with FE analyses and analytical equations, also compared with the test results obtained from measurement based on ordinary sectioning method.
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25th International Conference on Offshore Mechanics and Arctic Engineering
June 4–9, 2006
Hamburg, Germany
Conference Sponsors:
- Ocean, Offshore, and Arctic Engineering Division
ISBN:
0-7918-4748-9
PROCEEDINGS PAPER
Mean Stress Effect on Fatigue of Welded Joint in FPSOs
Bin Zhang,
Bin Zhang
Norwegian University of Science and Technology, Trondheim, Norway
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Torgeir Moan
Torgeir Moan
Norwegian University of Science and Technology, Trondheim, Norway
Search for other works by this author on:
Bin Zhang
Norwegian University of Science and Technology, Trondheim, Norway
Torgeir Moan
Norwegian University of Science and Technology, Trondheim, Norway
Paper No:
OMAE2006-92056, pp. 403-412; 10 pages
Published Online:
October 2, 2008
Citation
Zhang, B, & Moan, T. "Mean Stress Effect on Fatigue of Welded Joint in FPSOs." Proceedings of the 25th International Conference on Offshore Mechanics and Arctic Engineering. Volume 3: Safety and Reliability; Materials Technology; Douglas Faulkner Symposium on Reliability and Ultimate Strength of Marine Structures. Hamburg, Germany. June 4–9, 2006. pp. 403-412. ASME. https://doi.org/10.1115/OMAE2006-92056
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