A Numerical Procedure for Deriving p-y Curves for Monopiles Installed in Sand

The design of monopile foundations for offshore wind turbines (OWTs) is usually performed using simplified (1D) models based on the p-y method. When deriving p-y curves, the main issues arise from the soil reaction profiles (p), commonly obtained by double differentiating the bending moment profiles. Several authors have proposed modified p-y curves for OWT applications derived from experimental analysis conducted using small-scale in situ models, centrifuge models, or numerical analysis using three-dimensional finite element (3D FE) models. This article presents a 3D FE model simulating a monopile installed in sand, which was used to derive monotonic p-y curves. Typical curve fitting methods adopted in the literature for adjusting the bending moment data were investigated, such as the high-order global polynomial, the piecewise polynomial, the smoothing cubic spline, and the single-term Fourier series methods. Moreover, a parametric study was conducted to quantify possible deviations in generating the p-y curves. The number of points used to create each p-y curve and the number of nonlinear soil springs adopted in the 1D model varied. Finally, a guideline for deriving p-y curves from 3D FE models is provided.