An investigation into the effect of scour on the natural frequency of an Offshore Wind Turbine

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Title: An investigation into the effect of scour on the natural frequency of an Offshore Wind Turbine
Authors: Prendergast, Luke J.
Gavin, Kenneth
Doherty, Paul
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Date: 1-Jun-2015
Abstract: Rapid expansion of the offshore wind industry has stimulated a renewed interest in the behaviour of offshore piles. There is widespread acceptance in practice that pile design methods developed for the offshore oil and gas industry may not be appropriate for designing wind turbine foundations. To date, the majority of offshore wind turbines are supported by large diameter monopiles. These foundations are sensitive to scour which can reduce their ultimate capacity and alter their dynamic response. In this paper, the use of a vibration-based method to monitor scour is investigated. The effect of scour on the natural frequency of a model monopile was measured in a scale model test. A spring-beam finite element numerical model was developed to examine the foundation response. The model, which used springs tuned to the small-strain stiffness of the sand, was shown to be capable of capturing the change in frequency observed in the scale test. This numerical procedure was extended to investigate the response of a full-scale wind turbine over a range of soil densities, which might be experienced at offshore development sites. Results suggest that wind turbines founded in loose sand would exhibit the largest relative reductions in natural frequency resulting from scour.
Funding Details: Higher Education Authority
Type of material: Journal Article
Publisher: Elsevier
Journal: Ocean Engineering
Volume: 101
Issue: 1
Start page: 1
End page: 11
Copyright (published version): 2015 Elsevier
Keywords: ScourAccelerationWind turbinesFrequencySoil stiffnessMonopiles
DOI: 10.1016/j.oceaneng.2015.04.017
Language: en
Status of Item: Peer reviewed
Appears in Collections:Civil Engineering Research Collection

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