Offshore wind in the Asia-Pacific region is quickly gaining momentum, with the installed capacity expected to significantly increase in the near future. At variance with offshore wind turbines in the North Sea, those installed in the Asia-Pacific region are prevalently exposed to typhoons. This results in severe wind speeds and, consequently, extreme waves. Such conditions become driving for the design of the support structures. This paper explores the impact of using a non-linear hysteretic foundation model on the dynamic response of an offshore wind turbine. First, the adopted non-linear macro-element model is verified for the extreme load levels that occur in the Asia-Pacific region. Further analyses, that evaluate the hysteretic foundation damping, indicate that the frequently used logarithmic decrement method may not be a valid damping estimation method for an offshore wind turbine. Compared to non-linear elastic foundation models calibrated against API p-y functions, the macroelement model calibrated against 3D finite element analyses gives a reduction of the magnitude of the response along the height of the support structure.
Sara C. van Hoogstraten, Sebastiaan J. Hermans, Willem G. Versteijlen, Ana M. Page, Gustav Grimstad, Federico Pisanò and Andrei V. Metrikine
Keywords: macro-element model, non-linear hysteretic behaviour, foundation stiffness, foundation damping, offshore wind turbine, support structure
Publisher: DFI