Steel and Composite Structures

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Reserve capacity of fatigue damaged internally ring stiffened tubular joints

  • Thandavamoorthy, T.S. (Shock and Vibration Laboratory, Structural Engineering Research Centre, CSIR Campus)
  • Received : 2003.08.05
  • Accepted : 2004.04.07
  • Published : 2004.04.25
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Abstract

Offshore platforms have to serve in harsh environments and hence are likely to be damaged due to wave induced fatigue and environmental corrosion. Welded tubular joints in offshore platforms are most vulnerable to fatigue damage. Such damages endanger the integrity of the structure. Therefore it is all the more essential to assess the capacity of damaged structure from the point of view of its safety. Eight internally ring stiffened fatigue damaged tubular joints with nominal chord and brace diameter of 324 mm and 219 mm respectively and thickness 12 mm and 8 mm respectively were tested under axial brace compression loading to evaluate the reserve capacity of the joints. These joints had earlier been tested under fatigue loading under corrosive environments of synthetic sea water and hence they have been cracked. The extent of the damage varied from 35 to 50 per cent. One stiffened joint was also tested under axial brace tension loading. The residual strength of fatigue damaged stiffened joint tested under tension loading was observed to be less than one fourth of that tested under compression loading. It was observed in this experimental investigation that in the damaged condition, the joints possessed an in-built load-transfer mechanism. A bi-linear stress-strain model was developed in this investigation to predict the reserve capacity of the joint. This model considered the strain hardening effect. Close agreement was observed between the experimental and predicted results. The paper presents in detail the experimental investigation and the development of the analytical model to predict the reserve capacity of internally ring stiffened joints.

Keywords

References

  1. API RP 2A-LRFD (1993), "Recommended practice for planning, designing, and constructing fixed offshore platforms-load and resistance factor design", American Petroleum Institute, Washington D.C. First Ed., July.
  2. ASTM D 1141-1975 (1980), "Specification for substitute ocean water", American Society for Testing and Materials, Philadelphia, Re-approved.
  3. Bian, L.C. and Lim J.K. (2003), "Fatigue strength and stress concentration factors of CHS-to-RHS T-joints", J. Constr. Steel Res., 59(5), May, 627-640. https://doi.org/10.1016/S0143-974X(02)00048-2
  4. Bozhen, C. (1990), "Stress analysis of ring stiffened tubular joints for offshore structures - review of studies in China", China Ocean Engineering, 4(1), 1-12.
  5. Calderon, A.S. (2003), "World energy outlook to the year 2020", Oil Asia Journal, 24(1), Jan.-Mar., 8-9.
  6. Cheaitani, M.J. and Burdekin, F.M. (1994), Tubular Structures VI, P. Grundy, A. Holgate and B. Wong, (Eds.), A.A. Balkemaa Publisher, Rotterdam, 607-616.
  7. Chen, Y. and Wang, W. (2003), "Flexural behavior and resistance of uni-planar KK and X tubular joints", Steel and Composite Structures, An Int. J., 3(2), April, 123-140. https://doi.org/10.12989/scs.2003.3.2.123
  8. Choo, Y.S., Qian, X.D., Liew, J.Y.R. and Wrdenier, J. (2003), "Static strength of thick walled CHS X-joints. Part I. New Approach in Strength Definition", J. Constr. Steel Res., 59(10), October, 1201-1228. https://doi.org/10.1016/S0143-974X(03)00054-3
  9. Dexter, E.M. and Lee, M.M.K. (2001), "A general strength prediction formulation for axially loaded planar and multiplanar tubular joints", Tubular Structures IX, R. Puthli and S. Herion, Eds., A.A. Balkema Publisher, Lisser, 185-194.
  10. Gowda, S.S. (1991), "Fatigue of steel structures: state of the art", Proc Fourth Indian Conference on Ocean Engineering, INCOE-91, N10, Goa, India, 267-274.
  11. IS: 226 (1975), "Indian standard specification for structural steel (standard quality)", Indian Standards Institution, New Delhi, Fifth Revision, April.
  12. Lie, S.T., Chiew, S.P., Lee, C.K. and Huang, Z.W. (2001), "Modelling through thickness and surface cracks in tubular joints", Tubular Structures IX, P. Puthli and S. Herion, (eds.), Swets and Zeitlinger, Lisse, 285-290.
  13. Pinna, R., Ronalds, B.F. and Andrich, M.A. (2003), "Cost effective design criteria for Australian monopad platforms", J. Offshore Mechanics and Arctic Engineering, ASME, 125(2), May, 132-138. https://doi.org/10.1115/1.1555115
  14. Saad, S.B., Leen, S.B, and Hyde, T.H. (2001), "Finite element study on the static strength of a cracked tubular T-joint", Tubular Structures IX, R. Puthli, and S. Herion, Eds., A.A. Balkuma Publishers, Lisse, 247-255.
  15. Thandavamoorthy, T.S., Madhava Rao, A.G. and Santhakumar, A.R. (1995a), "Assessment and rehabilitation of damaged offshore structures", Proc Nordic Steel Construction Conference '95, Malmo, Sweden Vol. II, 741-747.
  16. Thandavamoorthy, T.S., Madhava Rao, A.G. and Santhakumar, A.R. (1995b), "Damage assessment of offshore structures", Structural Steel, Vol. I Steel Structures, N.E. Shanmugam and V.S. Choo, Eds., Pergamon, Oxford, 551-556.
  17. Thandavamoorthy, T.S., Madhava Rao, A.G. and Santhakumar, A.R. (1998), "Appraisal and repair of damaged steel offshore structures", J. the Institution of Engineers (India), 78, February, 147-153.
  18. Thandavamoorthy, T.S. (1998), "Assessment and rehabilitation of damaged offshore structures", Ph.D. Thesis, Anna University, Chennai, April.
  19. Thandavamoorthy, T.S. (2000), "Investigations on internally ring-stiffened joints of offshore platforms", J. Offshore Mechanics and Arctic Engineering, ASME, 122(4), November, 233-242. https://doi.org/10.1115/1.1290401
  20. Thandavamoorthy, T.S. (2002a), "Behaviour of unstiffened tubular joints of offshore platforms", J. the Institution of Engineers (India), 82, February, 224-228.
  21. Thandavamoorthy, T.S. (2002b), "Finite element modelling of the behaviour of internally ring stiffened T-joint of offshore platforms," J. the Institution of Engineers (India), 83, November, 139-145.
  22. Thandavamoorthy, T.S. (2003), "Comparative behaviour of stiffened and unstiffened welded tubular joints of offshore platforms", Steel and Composite Structures, An Int. J., 3(5), October, 321-333. https://doi.org/10.12989/scs.2003.3.5.321
  23. UEG (1985a), Design of Tubular Joints for Offshore Structures, Publication UR 33, Vol. 1, Underwater Engineering Group, London.
  24. UEG (1985b), Design of Tubular Joints for Offshore Structures, Publication UR 33, Vol. 2, Underwater Engineering Group, London.
  25. UEG (1985c), Design of Tubular Joints for Offshore Structures, Publication UR 33, Vol. 3, Underwater Engineering Group, London.
  26. Valdes V. and Ramirez, R.O. (2000), "Issues and challenges in the requalification of offshore platforms in Mexico", J. Offshore Mechanics and Arctic Engineering, ASME, 122(3), August, 153-156. https://doi.org/10.1115/1.1287344
  27. Van Wingerde, A.M., Packer, J.A. and Wardenier, J. (1996), "New guidelines for fatigue design of HSS connections", J, Struct, Eng., ASCE, 122(2), 125-132. https://doi.org/10.1061/(ASCE)0733-9445(1996)122:2(125)

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