The growing demand for clean renewable energy sources and the lack of suitable near shore sites is moving the offshore wind industry toward developing larger wind turbines in deeper water locations. This adds significant uncertainty to the geotechnical design of monopiles since soil testing becomes more challenging, rigid monopile behaviour is less certain, and design methods are exceeding the bounds of the datasets from which they were originally derived. This paper examines the impact of geotechnical uncertainty on monotonic load-displacement behaviour and design system natural frequency of an example offshore wind turbine. Geotechnical uncertainty is considered in terms of spatial variability in soil properties, parameter transformation uncertainty, and design model choice. Results show that spatial variability has limited impact on design load-displacement characteristics of monopiles as variability tends to be averaged out in the process to develop discrete p-y models. This highlights an issue related to data loss and requires careful checking. Soil spatial variability has a noticeable effect on predicted system frequency response of OWTs, and the influence of subgrade reaction model choice is significant. The results in this paper will be of interest to the offshore geotechnical community tasked with designing emerging large-diameter offshore wind turbines.
|Journal||ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems Part B: Mechanical Engineering|
|Early online date||21 Jul 2021|
|Publication status||Published - 31 Dec 2021|