Experimental and Numerical Studies on Plate with Ribs–Monopile Foundations for Extra-Large Offshore Wind Turbines

Abstract

The expansion of offshore wind energy is essential to meet rising energy demands and reduce fossil fuel dependence. This demands next-generation extra-large offshore wind turbines (XL-OWTs) with robust foundations. Conventional monopiles may not withstand significant lateral environmental loading, necessitating innovative, practical foundation systems with enhanced lateral load capacity. This study introduces a Plate with Ribs–Monopile (PRM) foundation developed for XL-OWTs. The National Renewable Energy Laboratory (NREL) offshore wind turbine was adopted as the prototype in this study. Physical model tests were conducted to determine the ultimate load capacity of the PRM foundation, and its performance was compared with that of the Conventional Monopile (CM). Compared with the CM foundation, the PRM foundation exhibited a 65.7 percent increase in lateral load capacity, a 113 percent increase in initial stiffness, and a 74.3 percent reduction in lateral displacement. Numerical simulations were carried out using the finite-element method to investigate the mechanisms involved. The study also presents an extensive parametric analysis to determine the effects of various important parameters, such as load eccentricity, soil properties, and stratification of seabed soils. In addition, sensitivity analyses were conducted to determine the effects of the orientation of ribs in the PRM foundation. The study also presents a field installation procedure for the PRM, thereby providing installation guidelines for its practical application by the offshore wind industry. Finally, a comparative cost-capacity index was obtained, and the proposed PRM foundation was found to have greater cost efficiency. Therefore, the developed PRM foundation not only increases lateral load capacity but is also economical.