Research Papers: Structures and Safety Reliability

Fatigue Design Recommendations for Conical Connections in Tubular Structures

[+] Author and Article Information
Inge Lotsberg

Veritasveien 1,
Høvik 1322, Norway
e-mail: Inge.Lotsberg@dnvgl.com

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received December 25, 2017; final manuscript received July 2, 2018; published online August 13, 2018. Assoc. Editor: Kazuhiro Iijima.

J. Offshore Mech. Arct. Eng 141(1), 011604 (Aug 13, 2018) (7 pages) Paper No: OMAE-17-1225; doi: 10.1115/1.4040800 History: Received December 25, 2017; Revised July 02, 2018

Conical connections are important structural members for the integrity of most types of welded tubular structures. They are for example used in traditional jacket structures for oil and gas production and in monopiles for support of wind turbines where an optimal design is aimed for. From contact with the industry, it is noted that there is uncertainty about the basis for the stress concentration factors (SCF) for conical connections in design standards for fatigue assessment. This is related to how fabrication tolerances are accounted for and how a transition in thickness from the cone to the tubular or the cylinder should be made to minimize stresses due to thickness transitions and fabrication tolerances. Analytical expressions for stress concentrations at conical transitions are outlined in this paper to get a better understanding of the effect of thickness of the cone and the cylinder. By a proper basis for fatigue design, it is possible to control additional stresses from thickness transitions and fabrication tolerances at these connections.

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Lotsberg, I. , 2016, Fatigue Design of Marine Structures, Cambridge University Press, New York.
Maddox, S. J. , 1985, Fitness for Purpose Assessment of Misalignment in Transverse Butt Welds Subjected to Fatigue Loading, International Institute of Welding, IIW Document XIII-1180-1985, London.
Maddox, S. J. , 1997, “Developments in Fatigue Design Codes and Fitness-for-Service Assessment Methods,” International Conference on Performance of Dynamically Loaded Welded Structures, S. J. Maddox and M. Prager, eds., San Francisco, CA, pp. 22–42.
DNV, 1977, Rules for the Construction and Inspection of Offshore Structures, Det Norske Veritas, Oslo, Norway.
BS, 1999, “Guidance on Methods for Assessing the Acceptability of Flaws in Metallic Structures,” BSI, London, Standard No. BS 7910.
EN, 2005, “Eurocode 3 Design of Steel Structures—Part 1-9: Fatigue,” European Committee for Standardization, Brussels, Belgium, Standard No. EN-1993-1-9. http://www.phd.eng.br/wp-content/uploads/2015/12/en.1993.1.9.2005-1.pdf
DNV GL, 2016, “Fatigue Design of Offshore Steel Structures,” DNV GL, Oslo, Norway, Standard No. DNVGL-RP-C203. https://rules.dnvgl.com/docs/pdf/DNV/codes/docs/2011-10/RP-C203.pdf
Lotsberg, I. , and Rove, H. , 2014, “Stress Concentration Factors for Butt Welds in Plated Structures,” ASME Paper No. OMAE2014-23316.
Connelly, L. M. , and Zettlemoyer, N. , 1993, “Stress Concentration at Girth Welds of Tubulars With Axial Wall Misalignment,” Proceedings of the Fifth International Symposium, M.G. Coutie and G. Davies, eds., E & FN Spon, Nottingham, UK.
Lotsberg, I. , 1998, “Stress Concentration Factors at Circumferential Welds in Tubulars,” J. Mar. Struct., 11(6), pp. 203–230. [CrossRef]
Flügge, W. , 1973, Stresses in Shells, 2nd ed., Springer Verlag, Berlin.
Timoshenko, S. P. , and Woinowsky-Krieger, S. , 1959, Theory of Plates and Shells, 2nd ed., McGraw-Hill Book Company, Tokyo, Japan.
Lotsberg, I. , 2009, “Stress Concentration Due to Misalignment at Butt Welds in Plated Structures and at Girth Welds in Tubulars,” Int. J. Fatigue, 31(8–9), pp. 1337–1345. [CrossRef]
Lotsberg, I. , 2008, “Stress Concentration Factors at Welds in Pipelines and Tanks Subjected to Internal Pressure,” J. Mar. Struct., 21(2–3), pp. 138–159. [CrossRef]
Lotsberg, I. , 2009, “Stress Concentrations at Butt Welds in Pipelines,” Mar. Struct., 22(2), pp. 335–337. [CrossRef]
Lotsberg, I. , and Holth, P. A. , 2007, “Stress Concentration Factors at Welds in Tubular Sections and Pipelines,” ASME Paper No. OMAE 2007-29571.
2000, “Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms—Working Stress Design,” 21st ed., American Petroleum Institute, Washington, DC, Standard No. API RP 2A-WSD. https://www.api.org/~/media/files/publications/whats%20new/2a-wsd_e22%20pa.pdf
ISO, 2007, “Fixed Steel Structures,” International Organization for Standardization, Geneva, Switzerland, Standard No. ISO 19902. http://www.jstra.jp/html/PDF/ISO_19902_2007.pdf


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Fig. 1

Conical connection

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Fig. 2

Circular cylindrical shell loaded symmetrically with respect to its axis

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Fig. 3

Geometry and forces at conical connection

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Fig. 4

Comparison of SCFs derived from classical shell theory and Eq. (1) for a cone at the larger diameter junction in a large diameter monopile

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Fig. 5

Moment distribution at the larger diameter junction in a large diameter monopile with thickness of the tubular equal 75 mm and the thickness of the cone equal 85 mm

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Fig. 6

Comparison of SCFs derived from classical theory and Eq. (1) for a large diameter junction at a cone in a typical jacket structure

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Fig. 7

Illustration of asymptotic behavior of SCF at the large diameter junction as function of cone thickness

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Fig. 8

Moment distribution at the larger diameter junction in a jacket with thickness of the tubular equal 30 mm and the thickness of the cone equal 40 mm, outer diameter 1430 mm and cone angle 8 deg

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Fig. 9

Stress concentrations at larger diameter cone junction in a jacket with thickness of the tubular equal 30 mm and the thickness of the cone equal 40 mm, outer diameter 1430 mm and cone angle 8 deg

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Fig. 10

Geometry with shift in neutral axis that results in local bending at the thickness transition due to axial force

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Fig. 11

Bending stress along the tubular section 1 in Fig. 3

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Fig. 12

Preferred thickness transition at the large diameter junction in conical connections



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