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Conference programme 

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Poster session

Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Manuel Beauvais STX France Solutions, France
Co-authors:

(1) STX France Solutions, Saint-Nazaire, France (2) INNOSEA - Ecole Centrale Nantes - IFSTTAR, NAntes, France (3) IFSTTAR, Nantes, France

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Poster
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Presenter's biography

Biographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited

R&D project engineer at STX France Solutions, Manuel beauvais is graduated from UTT (Technology University of Troyes) as mechanical engineer.

Working for three years in its company, Manuel Beauvais has acquired major skills in offshore wind turbine loads prediction, structural calculations and optimisation and soil behaviour.

Abstract

Towards an updated analysis method concerning the resistance of pile foundations subjected to vertical and lateral loads.

Introduction

The growth of the renewable energy market and especially the offshore wind energy sector leads to an increasing number of offshore wind turbines installed on soils with varying mechanical properties. Pile foundation and support structure design is strongly dependent on soil behaviour. In this context, predicting soil reactions for axially or laterally loaded piles is a major concern for optimizing pile foundations and support structure.

Approach

Empirical formulas for the (t-z), (Q-z) and (p-y) curves recommended by API and DNV were generated from tests with piles foundation having a size limited to a diameter of 610mm and a length of 21m. Since the realization of these tests, offshore structures have evolved in size. Nowadays, piles installed in European wind farms could have wider diameter than 2000mm and could have longer penetration than 40m.

Main body of abstract

For this reason, research studies have been carried out by STX France, IFSTTAR, INNOSEA, and ECN within an R&D project named CHARGEOL. Laboratory soil tests using new piles dimensions have been performed and new (t-z), (Q-z) and (p-y) curves have been generated.

In parallel of such laboratory studies, a dedicated numerical tool for a better evaluation of pile foundation response to axial and lateral loads has been developed. This tool does not merely take into account the classical (t-z), (Q-z) and (p-y) curves proposed by API and DNV, but it offers the possibility to use recent curves based on the new laboratory soil tests.

As a validation procedure, results from the analytical method developed for the tool have been compared to a classical finite element method and experimental results. Moreover, in order to improve accuracy, this tool allows the user to take into account cyclic effect, group effect due to pile-soil-pile interaction and presence of rock layers.


Conclusion

Geotechnical constraints can be now estimated with more reliability and development of new tool based on laboratory tests allows designers to optimize pile foundation and substructure for offshore wind market.


Learning objectives
With this updated methodology, STX France and its partners are able to adapt to varying soil behaviour and new structural requirements.