A reduced integration method for the coupled analysis of floating production systems

•This paper proposes an efficient method for the coupled analysis of FPS.•It combines a strong coupling formulation with a Ritz-Wilson reduction technique.•The reduced equations are uncoupled and solved analytically.•The method is tailored for the nonlinear dynamic behavior of FPS.•Accurate solutions are obtained with lower computational costs.

This work presents a reduced integration method for the nonlinear coupled analysis of floating production systems, combining a “strong coupling” formulation with a variation of the Ritz-Wilson basis reduction technique. This leads to an uncoupled formulation for the reduced equations of motion, which may be solved analytically by the Duhamel integral expressing the convolution of the Green functions. These equations are implemented in a recursive time-domain step-by-step solution procedure where the convolution integrals are calculated numerically, with the range of the integration being simply the time step Δt. The method is tailored for the particular characteristics of the nonlinear dynamic behavior of FPS, including the selection of time steps between basis reevaluations: they are triggered according to the natural periods of the horizontal motions. The results from the case studies indicate that the goal of obtaining an efficient solution method has been reached, allowing an accurate evaluation of the response with lower computational costs.