Dynamic analysis method of offshore jack-up platforms in regular and random waves

Abstract

A jack-up platform, with its particular structure, showed obvious dynamic characteristics under complex environmental loads in extreme conditions. In this paper, taking a simplified 3-D finite element dynamic model in extreme storm conditions as research object, a transient dynamic analysis method was proposed, which was under both regular and irregular wave loads. The steps of dynamic analysis under extreme conditions were illustrated with an applied case, and the dynamic amplification factor (DAF) was calculated for each response parameter of base shear, overturning moment and hull sway. Finally, the structural response results of dynamic and static were compared and analyzed. The results indicated that the static strength analysis of the Jack-up Platforms was not enough under the dynamic loads including wave and current, further dynamic response analysis considering both computational efficiency and accuracy was necessary.

Keywords

jack-up platforms / wave loads / dynamic analysis / dynamic amplification factor

References

[1] ABS Dynamic analysis procedure for self-elevating drilling units, 2004, Houston: American Bureau of Shipping, 5-20

[2] ABS ABS rules for building and classing mobile offshore drilling units 2001, part 3-hull construction and equipment, 2005, Houston: American Bureauof Shipping., 31-44

[3] Bienen B., Cassidy M.J. Advances in the three-dimensional fluid-structure-soil interaction analysis of offshore jack-up structures. Marine Structures, 2006, 19(2–3): 110-140

[4] Cassidy M.J., Taylor P.H., Taylor R.E. Evaluation of long-term extreme response statistics of jack-up platforms. Ocean Engineering, 2002, 29(13): 1603-1631

[5] Feng G., Li X., Yu H. Strength assessment of 300ft jack-up platform in survival conditions. Ship and Ocean Engineering, 2011, 40(5): 160-163

[6] Huang Z., Tang W., Wang Y. Analysis and suppression on the dynamic amplification factor of self-elevating offshore platform. Journal of Shanghai Jiao Tong University, 2010, 44(6): 816-819

[7] Hunt R.J., Marsh P.D. Opportunities to improve the operational and technical management of jack-up deployments. Marine Structure, 2004, 17(3–4): 261-73

[8] Li H., Wu W., Gan J. Research on multi-purpose offshore jack-up platform based on ANASYS. Journal of Huazhong University of Science and Technology (Urban Science Edition), 2010, 27(3): 86-90

[9] Runpei L., Zhinong W. Structural analysis of offshore platform, 1992, Shanghai: Shanghai Jiao Tong University Press, 24-54

[10] Lu H. The dynamic response of offshore Jack-up Platform, 2005, Wuhan: Wuhan University of Technology, 34-65

[11] Lu Y, Chen Y, Tan P, Bai Y (2001). Prediction of jack-up dynamic response. Proceedings of the 20th International Conference on Offshore Mechanics and Artic Engineering (OMAE), Rio de Janeiro, Brazil.

[12] Martin C.M. Physical and numerical modeling of offshore foundations under combined loads, 1994, Oxford: University of Oxford, 22-29

[13] Qiu D. Wave theory and its engineering application, 1985, Beijing: Higher Education Press, 18-19

[14] Spidsoe N., Karunakaran D. Nonlinear dynamic behaviour of jack-up platforms. Marine Structures, 1996, 9(1): 71-100

[15] Wheeler JD (1969). Method for calculating forces produced by irregular waves. Proc. of the Offshore Technical Conference, Houston, 71–82.

[16] Williams M.S., Thompson R.S.G., Houlsby G.T. Non-linear dynamic analysis of offshore jack-up units. Computers and Structures, 1998, 69(2): 171-180

[17] Williams M.S., Thompson R.S.G., Houlsb G.T. A parametric study of the non-linear dynamic behaviour of an offshore jack-up unit. Engineering Structures, 1999, 21(5): 383-394

[18] Xu C., Chen G., Xie J. A general review of research works on the structure response analysis and reliability assessment for jack-up platform. China Offshore Platform, 2003, 18(4): 6-11

[19] Xu C., Chen G., Xie J. Non-linear dynamic analysis model for jack-ups under extreme storm condition. Journal of the University of Petroleum, 2003, 27(4): 80-87

[20] Zhao J. The static and dynamic analysis of the jack-up platform’s legs in survival condition, 2007, Tianjin: Tianjin University, 36-41

[21] Zheng X.Y., Liaw C.Y. Non-linear frequency domain analysis of jack-up platforms. International Journal of Non-linear Mechanics, 2004, 39(2): 1519-1534