Fatigue analysis of steel catenary risers based on a plasticity model

Abstract

The most critical issue in the steel catenary riser design is to evaluate the fatigue damage in the touchdown zone accurately. Appropriate modeling of the riser-soil resistance in the touchdown zone can lead to significant cost reduction by optimizing design. This paper presents a plasticity model that can be applied to numerically simulate riser-soil interaction and evaluate dynamic responses and the fatigue damage of a steel catenary riser in the touchdown zone. Utilizing the model, numerous riser-soil elements are attached to the steel catenary riser finite elements, in which each simulates local foundation restraint along the riser touchdown zone. The riser-soil interaction plasticity model accounts for the behavior within an allowable combined loading surface. The model will be represented in this paper, allowing simple numerical implementation. More importantly, it can be incorporated within the structural analysis of a steel catenary riser with the finite element method. The applicability of the model is interpreted theoretically and the results are shown through application to an offshore 8.625″ steel catenary riser example. The fatigue analysis results of the liner elastic riser-soil model are also shown. According to the comparison results of the two models, the fatigue life analysis results of the plasticity framework are reasonable and the horizontal effects of the riser-soil interaction can be included.

Keywords

steel catenary riser / fatigue analysis / riser-soil interaction / plasticity model / finite element method

References

[1] Aubeny CP, Biscontin G. Interaction model for steel compliant riser on soft seabed. Proceedings of 2008 Offshore Technology Conference, Houston, USA, OTC 19493, 2008

[2] Aubeny CP, Biscontin G. Seafloor-riser interaction model. International Journal of Geomechanics, 2009, 9(3): 133-141

[3] Bridge C, Laver K, Clukey E, Evans T. Steel catenary riser touchdown point vertical interaction models. Proceedings of 2004 Offshore Technology Conference, Houston, USA, OTC 16628, 2004

[4] Cassidy MJ, Martin CM, Houlsby GT. Development and application of force resultant models describing jacking-up foundation behavior. Marine Structures, 2004, 17(3–4): 165-193

[5] Cathie DN, Jaeck C, Ballard JC, Wintgens JF. Pipeline geotechnics-state-of-the-art. International Symposium on the Frontiers in Offshore Geotechnics: ISFOG 2005, London, 2005, 95-114

[6] Dong Y, Song R, Sun L. Deepwater steel catenary riser fatigue life estimate analysis. The Ocean Engineering, 2014, 32(2): 119-124

[7] Giertsen E, Richard V, Schrøder K. CARISIMA: A catenary riser/soil interaction model for global riser analysis. Proceedings of the 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, Canada, 2004, 633-640

[8] Hodder MS, Byrne BW. 3D experiments investigating the interaction of a model SCR with the seabed. Applied Ocean Research, 2010, 32(2): 146-157

[9] Hodder MS, White D, Cassidy M. Effect of remolding and reconsolidation on the touchdown stiffness of a steel catenary riser: observations from centrifuge modeling. Proceedings of 2009 Offshore Technology Conference, Houston, USA, OTC 19871, 2009

[10] Leira BJ, Passano E, Karunakaran D, Farnes KA, Giertsen E. Analysis guidelines and applications of a riser-soil interaction model including trench effects. Proceedings of the 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, Canada, 2004, 955-962

[11] Li T, Meissner H. Two-surface plasticity model for cyclic undrained behavior of clays. Journal of Geotechnical and Geoenvironmental Engineering, 2002, 128(7): 613-626

[12] Mekha B, Bhat S. Newer frontiers in the design of steel catenary risers for floating production systems. Proceedings of the 32nd International Conference on Ocean, Offshore and Arctic Engineering, Nantes, France, OMAE2013-11562, 2013

[13] Randolph M, Quiggin P. Non-linear hysteretic seabed model for catenary pipeline contact. Proceedings of the the 28th International Conference on Ocean, Offshore and Arctic Engineering, Honolulu, Hawaii, USA, 2009, 145-154

[14] Thethi R, Moros T. Soil interaction effects on simple catenary riser response. Proceedings of Deepwater Pipeline and Riser Technology Conference, Houston, USA, 2001, 1-25

[15] Tian Y, Cassidy MJ. Modeling of pipe-soil interaction and its application in numerical simulation. International Journal of Geomechanics, 2008, 8(4): 213-229

[16] Tian Y, Cassidy MJ, Gaudin C. Advancing pipe-soil interaction models in calcareous sand. Applied Ocean Research, 2010, 32(3): 284-297

[17] Wood MD. Geotechnical modeling., 2004, Oxfordshire, UK: Spon Press

[18] Xu J, Fang J, Else M. Wave loading fatigue performance of steel catenary risers (SCRs) in ultradeepwater applications. Proceedings of 2006 Offshore Technology Conference, Houston, USA, OTC 18180, 2006

[19] Zhang J. Geotechnical stability of offshore pipelines in calcareous sand., 2001, Perth, Australia: University of Western Australia

[20] Zhang J, Stewart DP, Randolph MF. Kinematic hardening model for pipeline-soil interaction under various loading conditions. The International Journal of Geomechanics, 2002, 2(4): 419-446

[21] Zhang J, Stewart DP, Randolph MF. Modeling of shallowly embedded offshore pipelines in calcareous sand. Journal of Geotechnical and Geoenviron Mental Engineering, 2002, 128(5): 363-371