This study presents a new statistical cubicization approach for predicting the stochastic response of offshore platforms subjected to a Morison-type nonlinear drag loading. Statistics of the original system are obtained from an equivalent nonlinear system, which is constructed by replacing the Morison drag force by a cubic polynomial function of the relative fluid-structure velocity, up to cubic order. A Volterra series expansion with a finite Fourier series representation is used to approximate the response of the equivalent system. Exact solutions are developed to express the Fourier coefficients of the second and third-order response as functions of the Fourier coefficients of the first-order relative fluid-structure velocity. Response statistics are then computed by ensemble averaging over a suitable number of realizations of the first-order Gaussian response. Response statistics up to the sixth order, computed for a variety of sea conditions, show accuracy and efficiency of the proposed method as compared to digital simulation.
Stochastic Response of Offshore Structures by a New Approach to Statistical Cubicization
Contributed by the Offshore Mechanics and Arctic Engineering Division and presented at the 20th International OMAE Conference, Rio de Janeiro, Brazil, June 3–8, 2001, of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS. Manuscript received by the OMAE Division, July 17, 2000; revised manuscript received July 31, 2001. Guest Associate Editor: C. Guedes Soares.
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Di Paola, M., and Failla, G. (July 31, 2001). "Stochastic Response of Offshore Structures by a New Approach to Statistical Cubicization ." ASME. J. Offshore Mech. Arct. Eng. February 2002; 124(1): 6–13. https://doi.org/10.1115/1.1425395
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