Document Type : Research Paper


1 M.S. Student, Department of Offshore Engineering, Petroleum University of Technology, Abadan, Iran

2 Assistant Professor, Department of Offshore Engineering, Petroleum University of Technology, Abadan, Iran


A steel catenary riser (SCR) attached to a floating platform at its upper end encounters fluctuations in and near its touchdown zone (TDZ), which causes the interaction with the seabed. Subsea surveys and the analysis of SCR’s indicated that the greatest stress and highest damage occurred near the touchdown point (TDP), where the SCR first touches the seabed. Nowadays, the linear seabed spring is carried out, and it is assumed as a flat seabed. Improved nonlinear hysteretic seabed models have recently been proposed, which simulate the different stiffness in the seabed response in the TDZ. In this study, an advanced hysteretic nonlinear SCR-seabed soil interaction model has been implemented to simulate the exact behavior of the riser in the vicinity of the touchdown zone. This paper focusses on the seabed trench, which develops progressively under the SCR due to repeated contact. Also, different important parameters such as water depth and material of riser have been investigated based on the Caspian Sea environmental conditions. This paper highlights the impact of trenches of different depths on the fatigue performance of riser at TDZ.


Main Subjects

API RP 2RD, Recommended Practice for Design of Risers for Floating Production Systems, Washington, DC, USA: American Petroleum Institute, 2009.
Aubeny, C. P. and Biscontin, G., Seafloor-Riser Interaction Model, International Journal of Geomechanics, Vol. 9, p. 133–41, 2009.
Bai, X., Huang, W., and Augusto, M., Riser-soil Interaction Model Effects on the Dynamic Behavior of a Steel Catenary Riser, Marine Structures Vol. 41, p. 53–76, 2015.
Bridge, C. and Howells, H., Observations and Modeling of Steel Catenary Riser Trenches, In Proceedings of the Seventeenth International Offshore and Polar Engineering Conference, ISOPE, July 1-6, Lisbon, Portugal, p. 803–13, 2007.
Bridge, C., Laver, K., Clukey, Ed., and Evans, T., Steel Catenary Riser Touchdown Point Vertical Interaction Models, OTC, 2004.
DNV OS F201, Offshore Standard for Dynamic Risers, Norway, 2010.
Edwards, Jr., Roderick, Y., Zauli, R., Filho, M., and William, F., Load Monitoring at the Touchdown Point of the First Steel Catenary Riser Installed in a Deepwater Moored Semisubmersible Platform, In Prepared for presentation at the Offshore Technology Conference, OTC, 3–6 May, Houston, Texas, USA, 1999.
Elosta, H., Huang, Sh., and Incecik, A., Dynamic Response of Steel Catenary Riser Using a Seabed Interaction under Random Loads, Ocean Engineering Vol. 69, p. 34–43, 2013a.
Elosta, H., Huang, Sh., and Incecik, A., Wave Loading Fatigue Reliability and Uncertainty Analyses for Geotechnical Pipeline Models, Ships and Offshore Structures Vol. 9, No. 4, p. 450–63, 2013b.
McCormick, M. E., Ocean Engineering Mechanics, 1st Edit, Cambridge University Press, 2010.
Nakhaee, A. and Jun Zhang, J., Trenching Effects on Dynamic Behavior of a Steel Catenary Riser, Ocean Engineering, Vol. 37, No. 2–3, p.277–88, 2010.
Phifer, E. H., Kopp, F., and Swanson, R. C., Design and Installation of Auger Steel Catenary Risers, In Presented at the 26th Annual Offshore Technology Conference, OTC, 2-5 May, Houston, Texas, USA, 1994.
Randolph, M. and Quiggin, P., Nonlinear Hysteretic Seabed Model for Catenary Pipeline Contact, In Proceedings of the 28th International Conference on Ocean, Offshore and Arctic Engineering, OMAE, May 31-June 5, Honolulu, Hawaii, USA, 2009.
Serta, O. B. and Mourelle, M. M., Catenary Riser for the Marlim Field FPS P-XVIII. In Prepared for Presentation at the Offshore Technology Conference, OTC, 5-9 May, Houston, Texas, USA, 1997.
Shiri, H. and Randolph, M., The Influence of Seabed Response on Fatigue Performance of Steel Catenary Risers in Touchdown Zone, In 29th International Conference on Ocean, Offshore and Arctic Engineering, OMAE, Shaghai, China, 2010.
Sorensen, R. M., Basic Coastal Engineering, 3rd Edit, Springer, 2006.
Wang, K., Xue, H., Tang, W., and Guo, J., Fatigue Analysis of Steel Catenary Riser at the Touch-down Point Based on Linear Hysteretic Riser-Soil Interaction Model, Ocean Engineering Vol. 68, p. 102–111, 2013.