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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
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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 .
...