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Prediction of wear in grouted connections for offshore wind turbine generators

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journal contribution
posted on 2017-03-30, 14:08 authored by Paul Dallyn, Ashraf El-HamalawiAshraf El-Hamalawi, Alessandro Palmeri, R. Knight
Insufficient axial capacity of large-diameter plain-pipe grouted connections has recently been observed in offshore wind turbine substructures across Europe. Aimed at understanding the implications of this phenomenon, a campaign of structural condition monitoring was undertaken. The measurements showed significant axial displacements occurring between the transition piece and the monopile, which in turn resulted in a considerable amount of wear. Given the existing lack of technical data on the implications that this relative movement has on the wear of grouted connections, a methodology was developed to quantify the likely risk to the foundation integrity of the wear failure mode. The proposed approach consists of a numerical model which applies the wear rate derived from previous experimental testing to the conditions experienced by typical offshore grouted connections, as indicated by the wind turbine generators' supervisory control and data acquisition systems. The output of this model showed that, for a representative sample of the wind farm substructures analysed as a case study, the accumulated lifetime wear would be minimal in the majority of the grouted connection, i.e. less than 0.4 mm over 75% of the connection, but a much greater loss in thickness, of the order of 4 mm, was predicted at the very top and bottom of the connection. This assessment is based on the assumptions that no significant changes occur in the surrounding environmental conditions and that the degradation in the grouted connection does not significantly affect the dynamic response of the foundation structure over its life span. Importantly, these assumptions may affect the model's predictions in terms of cumulated wear over time, not in terms of identifying the individual connections to be prioritised when performing remedial work, which is indeed the main intended use of the model.

Funding

This study has been developed as part of the first author's EngD (Engineering Doctorate) project, co-sponsored by the ESPRC (the UK Engineering and Physical Sciences Research Council) (Grant code EP/G037272/1) and E.ON, whose financial support is gratefully acknowledged.

History

School

  • Architecture, Building and Civil Engineering

Published in

Structures

Volume

10

Pages

117-129

Citation

DALLYN, P.A. ... et al, 2017. Prediction of wear in grouted connections for offshore wind turbine generators. Structures, 10, pp. 117-129.

Publisher

Elsevier Ltd on behalf of Institution of Structural Engineers (© The Authors)

Version

  • VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/

Acceptance date

2017-02-02

Publication date

2017-02-03

Copyright date

2017

Notes

This is an Open Access article published by Elsevier and distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0). Further details are available here: https://creativecommons.org/licenses/by/4.0/

ISSN

2352-0124

Language

  • en