Nonlinear Dynamic Analysis of Offshore Towers in Frequency Domain
Publication: Journal of Engineering Mechanics
Volume 113, Issue 4
Abstract
A frequency domain iterative method is proposed to solve the non‐linear dynamic equation of motion encountered in the dynamic analysis of offshore structures under regular and random waves. The nonlinearities due to the relative velocity‐squared drag term and variable submergence are considered and treated using an approximate Newton‐Raphson method. In order to facilitate the computation, the formulation makes use of the normal mode theory. The resulting iterative scheme, which introduces a modal hydrodynamic damping on both sides of a decoupled equation of motion in modal coordinates, is shown to be highly efficient for the analysis of fixed base offshore structures. The numerical study shows that only 3–5 iterations are required to obtain the converged solutions for hydrodynamic loadings on the structure produced by random and regular waves. The computational time is marginally greater than that required for the linearized methods which in certain cases may introduce considerable error in the results.
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References
1.
Chakrabarti, S. K. (1971). Discussion of “Dynamics of single point moorings in deep water.” by John H. Nath and Michael P. Felix. J. Waterways, Harbor and Coastal Engrg., ASCE, 97(3), 588–590.
2.
Dao, B. V., and Penzien, J. (1982). “Comparison of treatments of nonlinear drag forces acting on fixed offshore platforms.” J. Applied Ocean Research, 4(2), 66–72.
3.
Eatock Taylor, R., and Rajagopalan, A. (1981). “Superharmonic resonance effects in drag dominated structures.” Proc., Int. Symposium on Integrity of Offshore Structures, Glasgow, Scotland.
4.
Fish, P., and Rainey, R. (1979). “The importance of structural motion in the calculation of wave loads on an offshore structure.” Proc., Second Int. Conf. on the Behaviour of Offshore Structures, London, U.K., 2(50), 43–60.
5.
Gudmestad, O. T., and Connor, J. J. (1983). “Linearization methods and the influence of current on the nonlinear drag hydrodynamic force.” J. Appl. Ocean Research, 5(4), 184–194.
6.
Hogben, N., et al. (1977). “Estimation of fluid loading on offshore structures.” Proc., Inst. of Civ. Engrs., 2(63), 515–562.
7.
Laya, E. J., et al. (1984). “Hydrodynamic forces on flexible offshore structures.” J. Engrg. Mech., ASCE, 110(3), 433–448.
8.
Malhotra, A. K., and Penzien, J. (1970). “Nondeterministic analysis of offshore structures.” J. Engrg. Mech. Div., ASCE, 96(6), 985–1003.
9.
Penzien, J. (1976). “Structural dynamics of fixed offshore structures.” Proc., First Int. Conf. on the Behaviour of Offshore Structures, Trondheim, Norway, 1, 581–592.
10.
Shinozuka, M., Yun, C.‐B., and Vaicaitis, R. (1977). “Dynamic analysis of fixed offshore structures subjected to wind generated waves.” J. Struct. Mech., 5(2), 135–146.
11.
Taudin, P. (1978). “Dynamic response of flexible offshore structures to regular waves.” Proc., Tenth Annual Offshore Technology Conf., Houston, Tex., Vol. 2, Paper No. OTC3160, 975–986.
12.
Wu, S. C. (1976). “The effects of current on dynamic response of offshore platforms.” Proc., Eighth Annual Offshore Technology Conf., Houston, Tex., Vol. 3, Paper No. OTC2540, 185–196.
Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 113 • Issue 4 • April 1987
Pages: 610 - 625
Copyright
Copyright © 1987 ASCE.
History
Published online: Apr 1, 1987
Published in print: Apr 1987
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