Abstract

A study is conducted of the response of a jack-up rig to random wave loading. Steady current and wind load effects are also included. The effects of varying the relative motion assumption (in the Morison equation) and of varying the bottom fixity assumptions are investigated. One “fixity” model employs nonlinear soil springs. Time domain simulations are performed using linearized as well as fully nonlinear models for the jack-up rig. Comparisons of response statistics are made for two seastates. Hydrodynamic damping causes the rms response to be lower in the relative Morison case. The absence of this source of damping in the absolute Morison force model gives rise to larger resonance/dynamic effects—this tends to “Gaussianize” the response. Hence, the relative Morison model leads to stronger non-Gaussian behavior than the absolute Morison model. This is reflected in moments as well as extremes. The different support conditions studied are seen to significantly influence extreme response estimates. In general, stiffer models predict smaller rms response estimates, but also exhibit stronger non-Gaussian behavior. The choice of the Morison force modeling assumption (i.e., the relative versus the absolute motion formulation) is seen to have at least a secondary role in influencing response moments and extremes.

Issue Section:
Research Papers
Topics:
Jack-up drilling rigs, Modeling, Waves, Damping, Engineering simulation, Morison equation, Resonance, Simulation, Soil, Springs, Statistics, Stress, Wind
1.
Arnesen, K., Dahlberg, R., Kjeo̸y, H., and Carlsen, C. A., 1988, “Soil Structure Interaction Aspects,” Proceedings of the International Conference on Behaviour of Offshore Structures, Trondheim, Norway, June.
2.
Bradshaw, I. J., 1988, “Jack-Up Behaviour and Analysis Methods,” Mobile Offshore Structures, eds., L. F. Boswell, C. A. D’Mello, and A. J. Edwards, Elsevier Applied Science, pp. 125–155.
3.
Brekke, J. N., Campbell, R. B., Lamb, W. C., and Murff, J. D., 1990, “Calibration of a Jackup Structural Analysis Procedure Using Field Measurements from a North Sea Jackup,” 22nd Annual Offshore Technology Conference, OTC 6465, Houston TX, May, pp. 357–368.
4.
Chen, Y. N., Chen, Y. K., and Cusack, J. P., 1990, “Extreme Dynamic Response and Fatigue Damage Assessment for Self-Elevating Drilling Units in Deep Water,” SNAME Annual Meeting, San Francisco, CA, Oct.
5.
Hambly, E. C., Imm, G. R., and Stahl, B., 1990, “Jackup Performance and Foundation Fixity Under Developing Storm Conditions,” 22nd Annual Offshore Technology Conference, OTC 6466, Houston, TX, May, pp. 369–380.
6.
Hansen, H. T., 1984, “Dynamic Analysis of Jack-Up Platforms,” Proceedings of the Third International Offshore Mechanics and Arctic Engineering Symposium, New Orleans, LA, Feb.
7.
Karunakaran, D., Leira, B. J., Haver, S., and Moan, T., 1992a, “Parametric Influence on Extreme Dynamic Response of Drag-Dominated Platforms,” Proceedings of the Second International Offshore and Polar Engineering Conference, Vol. III, San Francisco, CA, pp. 463–471.
8.
Karunakaran, D., Gudmestad, O. T., and Spidso̸e, N., 1992b, “Nonlinear Dynamic Response Analysis of Dynamically Sensitive Slender Offshore Structure,” Proceedings of the 11th International Conference on Offshore Mechanics and Arctic Engineering, Calgary, Canada, pp. 207–214.
9.
Kjeo̸y, H., Bo̸e, N. G., and Hysing, T., 1989, “Extreme Response Analysis of Jack-Up Platforms,” Marine Structures, pp. 305–334.
10.
Manuel, L., 1992, “A Study of the Nonlinearities, Dynamics, and Reliability of a Drag-Dominated Marine Structure,” Technical Report RMS-12, Stanford University, Reliability of Marine Structures Program, Stanford, CA.
11.
Manuel, L., Cornell, C. A., and Winterstein, S. R., 1991, “Nonlinear Dynamic Response of a Jack-up Rig under Random Wave Loading,” Sixth International Conference on Applications of Statistics and Probability in Civil Engineering, Mexico City, Mexico, pp. 969–976.
12.
Manuel, L., and Cornell, C. A., 1994, “An Efficient FORM-Based Strategy for the Reliability Analysis of Marine Structures,” Proceedings of the Sixth IFIP WG7.5 Working Conference on Reliability and Optimization of Structural Systems, Assisi, Italy, pp. 193–200.
13.
McDonald, D., 1990, “Reliability Estimates of a Jack-Up Drilling Unit in the North Sea and in the Gulf of Mexico,” Master’s thesis, Coastal and Hydraulic Engineering, Department of Civil Engineering, University of California, Berkeley, CA.
14.
Osborne, J. J., Trickey, J. C., Houlsby, G. T., and James, R. G., 1991, “Findings from a Joint Industry Study on Foundation Fixity of Jackup Units,” 23rd Annual Offshore Technology Conference, OTC 6615, Houston, TX, May, pp. 517–533.
15.
Perol, C., and Meimon, Y., 1990, “Cyclic Storm Loading Soil-Structure Interaction for a Three Independent Leg Jack-Up,” The Jack-Up Drilling Platform: Design, Construction and Operation, eds., L. F. Boswell and C. A. D’Mello, Elsevier Applied Science, pp. 223–243.
16.
Pyke
R. M.
,
1979
, “
Nonlinear Soil Models for Irregular Cyclic Loadings
,”
Journal of the Geotechnical Engineering Division
, ASCE, Vol.
105
(
GT6
), June, pp.
715
–
726
.
17.
Ramberg, W., and Osgood, W. R., 1943, “Description of Stress-Strain Curves by Three Parameters,” Technical Note 902, National Advisory Committee for Aeronautics, Washington, DC.
18.
Spidso̸e, N., Karunakaran, D., and Gudmestad, O. T., 1992, “Nonlinear Effects of Damping to Dynamic Amplification Factors for Drag-Dominated Offshore Platforms,” Proceedings of the 11th International Conference on Offshore Mechanics and Arctic Engineering, Calgary, Canada, pp. 231–240.
19.
Winterstein
S. R.
,
1988
, “
Nonlinear Vibration Models for Extremes and Fatigue
,”
Journal of Engineering Mechanics
, ASCE, Vol.
114
, No.
10
, Oct., pp.
1772
–
1790
.
20.
Winterstein, S. R., and Lo̸seth, R., 1990, “Jackup Structures: Nonlinear Forces and Dynamic Response,” Proceedings of the Sixth IFIP WG7.5 Working Conference on Reliability and Optimization of Structural Systems, Berkeley, CA., pp. 349–358.
21.
Winterstein, S. R., and Torhaug, R., 1993, “Estimating Extreme Response of Jack-Up Structures from Limited Time-Domain Simulations,” Proceedings of the 12th International Conference on Offshore Mechanics and Arctic Engineering, Vol. II, Glasgow, Scotland, June, pp. 251–258.
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