Tension Leg Platform Response to Drag Forces by Equivalent Stochastic Quadratization

by P. D. Spanos, Rice Univ, United States,
M. G. Donley, Rice Univ, United States,



Document Type: Proceeding Paper

Part of: Structural Safety and Reliability

Abstract:

An equivalent stochastic 'quadratization' method is described for performing nonlinear stochastic response analyses of offshore platforms subject to wave and current forces. The method is applied on a three degree-of-freedom model of a deepwater platform called the tension leg platform. The nonlinear drag force is replaced with an 'equivalent' nonlinear drag force which has polynomial terms up to quadratic order. The resulting nonlinear equivalent system is in a form which can be solved approximately by a Volterra series expansion. The non-gaussian probability distribution of the response is approximated by a Gram-Charlier expansion. The power spectrum of the response determined by the proposed method compares well with the one obtained by simulation.

Subject Headings: Stochastic processes | Offshore platforms | Probability | Tension members | Dynamic structural analysis | Water waves | Probability distribution

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