IEC 61400-6:2020

Wind energy generation systems - Part 6: Tower and foundation design requirements

IEC 61400-6:2020 specifies requirements and general principles to be used in assessing the structural integrity of onshore wind turbine support structures (including foundations). The scope includes the geotechnical assessment of the soil for generic or site specific purposes. The strength of any flange and connection system connected to the rotor nacelle assembly (including connection to the yaw bearing) are designed and documented according to this document or according to IEC 61400-1. The scope includes all life cycle issues that may affect the structural integrity such as assembly and maintenance.
The contents of the corrigendum of November 2020 have been included in this copy.

Systèmes de génération d'énergie éolienne - Partie 6: Exigences en matière de conception du mât et de la fondation

l'IEC 61400-6:2020 spécifie les exigences et les principes généraux à utiliser pour évaluer l'intégrité structurelle des structures de support d'éolienne terrestre (y compris les fondations). Le domaine d'application inclut l'évaluation géotechnique du sol en fonction des besoins génériques ou spécifiques au site. La résistance d'une bride et le système de connexion relié à l'ensemble rotor – nacelle (y compris la connexion au palier du dispositif d’orientation) sont conçus et documentés selon le présent document ou selon l'IEC 61400-1. Le domaine d'application inclut toutes les questions liées au cycle de vie qui peuvent avoir un impact sur l'intégrité structurelle (le montage et l'entretien, par exemple).
Le contenu du corrigendum de novembre 2020 a été pris en considération dans cet exemplaire.

General Information

• Status: Published
• Publication Date: 20-Apr-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: MT 6 - TC 88/MT 6
• Current Stage: PPUB - Publication issued
• Start Date: 27-Mar-2020
• Completion Date: 21-Apr-2020

Relations

• Corrected By: IEC 61400-6:2020/COR1:2020 - Corrigendum 1 - Wind energy generation systems - Part 6: Tower and foundation design requirements
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61400-6 ®
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
colour
inside
Wind energy generation systems –
Part 6: Tower and foundation design requirements
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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International Standards for all electrical, electronic and related technologies.

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IEC 61400-6 ®
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
colour
inside
Wind energy generation systems –

Part 6: Tower and foundation design requirements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-8004-1

– 2 – IEC 61400-6:2020 © IEC 2020
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 12
3 Terms and definitions . 13
4 Symbols and abbreviated terms . 17
4.1 Symbols . 17
4.2 Abbreviated terms . 19
5 Design basis including loading . 20
5.1 General . 20
5.2 Basis of design . 20
5.2.1 Basic principles . 20
5.2.2 Durability . 21
5.2.3 Principles of limit state design . 21
5.2.4 Structural analysis . 21
5.2.5 Assessments by tests . 22
5.3 Materials . 22
5.4 Loads. 22
5.4.1 Use of IEC 61400-1 or IEC 61400-2 load cases and partial safety
factors for loads . 22
5.4.2 Superseding of IEC 61400-1 or IEC 61400-2 partial safety factors for
materials . 22
5.4.3 Serviceability load levels . 23
5.4.4 Load combinations in ULS . 24
5.4.5 Structural damping values to be used in load calculations . 25
5.4.6 Definitions and methods for use of internal loads . 25
5.4.7 Definition of required load data for fatigue analysis . 25
5.4.8 Definition of required load data for extreme load level . 25
5.4.9 Vortex induced vibration . 26
5.4.10 Loads due to geometric tolerances and elastic deflections in tower
verticality . 26
5.5 Load data and interface reporting requirements . 27
5.5.1 Purpose . 27
5.5.2 Wind turbine specification . 27
5.5.3 Time history data . 28
5.5.4 Load origins . 28
5.5.5 Load components . 28
5.6 General structural design requirements . 28
5.6.1 Secondary structural influence . 28
5.6.2 Fatigue analysis . 28
5.7 Delivery documentation . 28
6 Steel towers . 29
6.1 General . 29
6.2 Basis of design . 29
6.3 Materials . 29
6.3.1 General . 29
6.3.2 Structural steels . 29

6.3.3 Bolts and anchors . 32
6.4 Ultimate strength analysis for towers and openings . 32
6.4.1 General . 32
6.4.2 Partial safety factors . 32
6.4.3 Verification of ultimate strength . 32
6.4.4 Tower assessment . 32
6.4.5 Detail assessments. 33
6.5 Stability. 33
6.5.1 General . 33
6.5.2 Partial safety factor. 34
6.5.3 Assessment . 34
6.5.4 Door frames/stiffeners . 34
6.6 Fatigue limit state . 35
6.6.1 General . 35
6.6.2 Partial safety factor for materials . 35
6.6.3 Assessment . 36
6.6.4 Details . 36
6.7 Ring flange connections . 36
6.7.1 General . 36
6.7.2 Design assumptions and requirements, execution of ring flanges . 36
6.7.3 Ultimate limit state analysis of flange and bolted connection . 38
6.7.4 Fatigue limit state analysis of bolted connection . 38
6.8 Bolted connections resisting shear through friction . 40
6.8.1 General requirements . 40
6.8.2 Test-assisted design . 41
6.8.3 Design without test . 42
7 Concrete towers and foundations. 42
7.1 General . 42
7.2 Basis of design . 42
7.2.1 Reference standard for concrete design . 42
7.2.2 Partial safety factors . 43
7.2.3 Basic variables . 43
7.3 Materials . 45
7.4 Durability . 46
7.4.1 Durability requirements . 46
7.4.2 Exposure classes . 46
7.4.3 Concrete cover . 46
7.5 Structural analysis . 46
7.5.1 Finite element analysis . 46
7.5.2 Foundation slabs . 47
7.5.3 Regions with discontinuity in geometry or loads . 47
7.5.4 Cast in anchor bolt arrangements . 48
7.6 Concrete to concrete joints . 48
7.7 Ultimate limit state . 48
7.7.1 General . 48
7.7.2 Shear and punching shear . 48
7.8 Fatigue limit state . 49
7.8.1 General . 49
7.8.2 Reinforcement and prestressing steel fatigue failure . 49

– 4 – IEC 61400-6:2020 © IEC 2020
7.8.3 Concrete fatigue failure .
...

IEC 61400-6 ®
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 6: Tower and foundation design requirements

Systèmes de génération d'énergie éolienne –
Partie 6: Exigences en matière de conception du mât et de la fondation

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

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3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

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IEC 61400-6 ®
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –

Part 6: Tower and foundation design requirements

Systèmes de génération d'énergie éolienne –

Partie 6: Exigences en matière de conception du mât et de la fondation

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-8803-0

– 2 – IEC 61400-6:2020 © IEC 2020
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 12
3 Terms and definitions . 13
4 Symbols and abbreviated terms . 17
4.1 Symbols . 17
4.2 Abbreviated terms . 19
5 Design basis including loading . 20
5.1 General . 20
5.2 Basis of design . 20
5.2.1 Basic principles . 20
5.2.2 Durability . 21
5.2.3 Principles of limit state design . 21
5.2.4 Structural analysis . 21
5.2.5 Assessments by tests . 22
5.3 Materials . 22
5.4 Loads. 22
5.4.1 Use of IEC 61400-1 or IEC 61400-2 load cases and partial safety
factors for loads . 22
5.4.2 Superseding of IEC 61400-1 or IEC 61400-2 partial safety factors for
materials . 22
5.4.3 Serviceability load levels . 23
5.4.4 Load combinations in ULS . 24
5.4.5 Structural damping values to be used in load calculations . 25
5.4.6 Definitions and methods for use of internal loads . 25
5.4.7 Definition of required load data for fatigue analysis . 25
5.4.8 Definition of required load data for extreme load level . 25
5.4.9 Vortex induced vibration . 26
5.4.10 Loads due to geometric tolerances and elastic deflections in tower
verticality . 26
5.5 Load data and interface reporting requirements . 27
5.5.1 Purpose . 27
5.5.2 Wind turbine specification . 27
5.5.3 Time history data . 28
5.5.4 Load origins . 28
5.5.5 Load components . 28
5.6 General structural design requirements . 28
5.6.1 Secondary structural influence . 28
5.6.2 Fatigue analysis . 28
5.7 Delivery documentation . 28
6 Steel towers . 29
6.1 General . 29
6.2 Basis of design . 29
6.3 Materials . 29
6.3.1 General . 29
6.3.2 Structural steels . 29

6.3.3 Bolts and anchors . 32
6.4 Ultimate strength analysis for towers and openings . 32
6.4.1 General . 32
6.4.2 Partial safety factors . 32
6.4.3 Verification of ultimate strength . 32
6.4.4 Tower assessment . 32
6.4.5 Detail assessments. 33
6.5 Stability. 33
6.5.1 General . 33
6.5.2 Partial safety factor. 34
6.5.3 Assessment . 34
6.5.4 Door frames/stiffeners . 34
6.6 Fatigue limit state . 35
6.6.1 General . 35
6.6.2 Partial safety factor for materials . 35
6.6.3 Assessment . 36
6.6.4 Details . 36
6.7 Ring flange connections . 36
6.7.1 General . 36
6.7.2 Design assumptions and requirements, execution of ring flanges . 36
6.7.3 Ultimate limit state analysis of flange and bolted connection . 38
6.7.4 Fatigue limit state analysis of bolted connection . 38
6.8 Bolted connections resisting shear through friction . 40
6.8.1 General requirements . 40
6.8.2 Test-assisted design . 41
6.8.3 Design without test . 42
7 Concrete towers and foundations.
...