Resonance in offshore wind turbine systems due to seismic loading and extensive soil liquefaction
Resonance in offshore wind turbine systems due to seismic loading and extensive soil liquefaction
Offshore wind turbines in the North Sea are designed to ensure that fundamental frequencies of the turbine-substructure systems lie outside frequency ranges occupied by dynamic wind loads, wave loads and rotor and blade-passing frequencies. For wind farms located in areas of high seismicity, dynamic earthquake loading needs to be further considered to avoid resonance of the wind turbine system. High-intensity seismic ground shaking may lead to liquefaction of sand layers and a reduction in strength and stiffness within the soil. As the stiffness of the ground diminishes, the fundamental period of a deposit may elongate, enabling an amplification of the low-frequency content of an earthquake motion. Through advanced fully-coupled finite element analyses, this study illustrates the example of a 5 MW reference turbine supported by a large diameter monopile founded in a deep soil deposit consisting of stiff marine clay and liquefiable sand. The results show amplification of a strong motion input through a partially liquefied soil deposit within a frequency range near the fixed-based frequency of the turbine tower and illustrate the response of the wind turbine system near resonance.
Julia Katharina Moller; Stavroula Kontoe; David M. G. Taborda; David Malcolm Potts
10th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2023)
12. Offshore geotechnics
https://doi.org/10.53243/NUMGE2023-126
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