An Efficient FEA Tool for Offshore Wind Turbine Foundations-Paper

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The paper presents INFIDEP, a computationally efficient three-dimensional finite element program for designing offshore wind turbine foundations. It models foundation–soil interaction, including nonlinear soil behavior, displacements and rotations, structural forces, soil reactions, and hysteretic damping under cyclic loading.<br /><br />INFIDEP reduces computational demands by combining conventional finite element interpolation in vertical and radial directions with Fourier series to represent variation around the circumference. This approach suits axisymmetric foundations under non-axisymmetric loads while requiring fewer degrees of freedom than conventional 3D models. The soil domain is divided into a nonlinear near field and a linear-elastic far field; specialized skirt and shell elements represent foundation components. A corrected Euler, or second-order Runge–Kutta, procedure solves the nonlinear equations.<br /><br />The authors demonstrate the program using monopile foundations in uniform clay and a gravity-based structure (GBS) in layered clay. Predicted load–displacement responses generally agree well with results from PLAXIS 3D and, for the GBS, Abaqus. A back-analysis of a Cowden test-site pile also shows that including tension cut-off at the pile–soil interface is important: it improves agreement with measured behavior, while omitting it produces overly stiff predictions.<br /><br />For the cases studied, INFIDEP runs roughly 100 times faster than PLAXIS 3D, making it suitable for optimized foundation design. Differences between INFIDEP and PLAXIS are attributed largely to differences in soil-model formulations, as comparisons with Abaqus using a similar nonlinear soil model show good agreement. Overall, the results indicate that INFIDEP offers a robust and accurate, substantially faster alternative for analyzing monopile and gravity-based offshore wind foundations.

Keywords

offshore wind turbine foundations

INFIDEP

finite element analysis

nonlinear soil behavior

monopile foundations

gravity-based structure

hysteretic damping

soil-structure interaction

cyclic loading

computational efficiency