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Design of wind turbine foundation slabs
2008 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this study the structural behaviour of wind turbine foundation slabs is analysed with various numerical and analytical models. The studied methods include models suitable for hand-calculations, finite element models with plate elements resting on springs as well as three dimensional models of both the foundation slab and the soil. Linear elastic as well as nonlinear behaviour including cracking of concrete and the complex load transfer from the tower into the foundation through a steel ring is considered in the study. The elastic analyses show, for example, that whereas in a concentrically loaded foundation slab a significant part of the load is carried through diagonal compression struts thus resulting in less flexure than what was found with the FE-models, the largest section forces and moments in a slab subjected to large overturning moment are obtained with a three-dimensional FE-model of both the slab and the underlying soil: i.e. the section forces increase together with the accuracy of the model. An important issue when designing members according to nonlinear analyses is to consider proper choice of material parameters. The results of a nonlinear plate element analysis verify the assumption that considerable redistribution of the section forces takes place due to flexural cracking of concrete. However, because of the large amount of simplifications of a simple plate element model no major conclusions of the structural behaviour should be made. A three-dimensional elastic analysis of a typical wind turbine foundation slab considering the complex load transfer through a steel ring reveals that the global flexural behaviour of the structure can be modelled sufficiently well by simpler models. This model, however, yields the largest section forces and moments: this has to be considered when simplifications are made. Additionally, the high local stress concentrations and the relative movement of the steel ring anchorage have to be taken into consideration when designing the reinforcement. A complete, three-dimensional nonlinear analysis of the foundation slab shows that the steel ring anchorage in the slab is the most critical part of the structure.

Place, publisher, year, edition, pages
Keyword [en]
Keyword [sv]
URN: urn:nbn:se:ltu:diva-51280ISRN: LTU-EX--08/128--SELocal ID: 87e0a775-b92e-451f-8fa2-4efba6c28becOAI: diva2:1024641
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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