Analysis of deepwater offshore structures: Issues and challenges

Abstract

A brief overview of analysis of deepwater offshore structures with reference to modeling issues is presented. Floaters with moorings and risers exhibit nonlinear response under environmental loads. The modeling of such structures poses many challenges because of the flexibility of the riser/mooring system, fluid–structure interaction and random nature of wave loads. Tensioned beam finite elements can be used for structural modeling of line elements. Computational fluid dynamic modeling may be used to firm up hydrodynamic coefficients required in the Morison equation for the estimation of fluid loads on structural elements, as well as to evolve simplified models to represent vortex-induced motions. While wave-body interaction of large-volume structures may be modeled using computational fluid dynamic tools, the use of numerical models employing the fully nonlinear potential flow theory is worth exploring. Simpler analytical models for use in design analysis may be developed by employing coupled models based on nonlinear structural finite element methods and computational fluid dynamic tools. Simpler methods of evaluating stress-range statistics required for fatigue damage estimation need to be developed for the case of nonlinear stochastic response of deepwater systems.