The motivation for this research is to inspire and facilitate the development of more sustainable foundation concepts, coined "green" foundations. The work is advancing a fundamental understanding of soil-structure interactions to develop a novel and sustainable foundation concept for offshore wind turbines: a Flying Wing Anchor. This anchor is a steel plate in the shape of an aerodynamically efficient winged aircraft. The anchor is installed silently and efficiently using gravity from free fall through the water column and penetration into the sea floor. Tension in the line that attaches the wind turbine structure to the anchor causes the anchor to dive and pitch toward the horizontal in service, maximizing the available holding capacity in bearing over the full wing surface in an extreme load. The intellectual challenges are (1) modeling the resistance of soil against a foundation in shear and bearing over the orders-of-magnitude range of strain rates corresponding to free-fall penetration, line pre-tensioning and ultimately storm loading and (2) capturing the dynamic, fully six-degree-of-freedom movement of a foundation as it "flies" through the soil during installation and service. The research plan comprises a comprehensive approach to physically testing scale models of a Flying Wing Anchor during penetration and in-service loading and numerically modeling the three-dimensional behavior with time of a Flying Wing Anchor with the Finite Element Method (FEM) and advanced constitutive models. It capitalizes on a U.S.-Ireland Research and Development Partnership Program to bring together a multidisciplinary, multiple-institution team that represents the European state-of-the art in offshore wind development and the U.S. state-of-the-art in offshore foundations. The project partners include The University of Texas at Austin, the University of Rhode Island, University College Dublin and Queen's University Belfast. With external funding from Invest NI and Science Foundation Ireland, the U.S. investment in this project is leveraged at a ratio of nearly 3 total dollars for each dollar invested from NSF.
This research has the potential to improve foundation systems over a wide range of offshore and onshore applications by developing a green foundation concept, where nature initially "installs" it through gravity and then completes the "installation" through in-service loading. This research aims to reduce the economic and environmental cost of harnessing offshore wind energy, which is a key challenge to increasing the availability of renewable energy. This research will benefit society at large by providing cross-country and cross-Atlantic education and research opportunities for graduate and undergraduate students, by fostering excitement in engineering and science for school children through exposing them to the development of a novel concept and giving them an opportunity to examine it themselves through a model testing facility, and by increasing public awareness of the promises and challenges of renewable energy through public demonstrations and workshops.
