oSIST prEN IEC 61400-8:2022
(Main)Wind energy generation systems - Part 8: Design of wind turbine structural components
Wind energy generation systems - Part 8: Design of wind turbine structural components
Windenergieanlagen – Teil 8: Design von Windenergieanlagen-Strukturkomponenten
Systèmes de génération d'énergie éolienne - Partie 8: Conception des composants structurels des éoliennes
Sistemi za proizvodnjo energije na veter - 8. del: Projektiranje delov konstrukcije vetrnih turbin
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN IEC 61400-8:2022
01-november-2022
Sistemi za proizvodnjo energije na veter - 8. del: Projektiranje delov konstrukcije
vetrnih turbin
Wind energy generation systems - Part 8: Design of wind turbine structural components
Systèmes de génération d'énergie éolienne - Partie 8: Conception des composants
structurels des éoliennes
Ta slovenski standard je istoveten z: prEN IEC 61400-8:2022
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
oSIST prEN IEC 61400-8:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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88/897/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61400-8 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2022-09-02 2022-11-25
SUPERSEDES DOCUMENTS:
88/797/CD, 88/896/CC
IEC TC 88 : WIND ENERGY GENERATION SYSTEMS
SECRETARIAT: SECRETARY:
Denmark Mrs Christine Weibøl Bertelsen
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
Other TC/SCs are requested to indicate their interest, if any, in this
CDV to the secretary.
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TITLE:
Wind energy generation systems – Part 8: Design of wind turbine structural components
PROPOSED STABILITY DATE: 2026
NOTE FROM TC/SC OFFICERS:
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CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Definitions . 10
4 Symbols and abbreviations . 13
5 Reliability Considerations . 15
5.1 Approaches to reliability based design . 15
5.2 Models and Basic Variables for Structural Verification . 16
5.2.1 Material Properties. 17
5.3 Partial Safety Factors and Reliability Targets . 17
6 Application of Loads and Analysis Models . 18
6.1 Loads Models . 18
6.2 Analysis model. 18
6.2.1 Load path modelling . 18
6.2.2 Application of Load components . 18
6.2.3 Boundary Conditions . 19
6.3 Modelling of nonlinear mechanical behaviour . 19
6.3.1 Nonlinear stress effects . 19
6.3.2 Application of Ultimate loads . 19
6.3.3 Application of Fatigue loads . 19
6.4 Partial Safety Factors . 20
6.5 Partial safety factor for resistance . 22
6.6 Nacelle and Hub Component Consideration . 24
6.6.1 Hub structure and bolts. 24
6.6.2 Nacelle front structure (Alternatively : Mechanical drive train structure) . 25
6.6.3 Gearbox structure . 25
6.6.4 Yaw structure . 25
6.6.5 Nacelle rear structure . 26
6.6.6 Nacelle cover and spinner . 26
7 Deflection analysis . 28
8 Strength Verification . 28
8.1 Determination of stress and strain . 28
8.2 Material properties . 28
8.2.1 Influence of size . 29
8.3 Static strength assessment . 29
8.3.1 Cast, forged and steel components . 29
8.3.2 Welded structures . 31
8.3.3 Bolted joints . 31
8.3.4 Fiber reinforced material . 32
8.4 Fatigue strength assessment . 32
8.4.1 Fatigue strength methods . 32
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8.4.2 Determination of local stresses . 32
8.4.3 Stress hypothesis for fatigue . 32
8.4.4 S/N curves . 32
8.4.5 Influence on fatigue strength . 33
8.4.6 Partial safety factors for fatigue . 34
8.4.7 Damage accumulation . 35
8.4.8 Bolted joints . 36
8.4.9 Fiber reinforced material . 36
8.5 Fracture mechanics assessment . 36
8.5.1 Define objective . 37
8.5.2 Material Parameter . 37
8.5.3 Defect Model . 38
8.5.4 Structural model . 39
8.5.5 Loading . 39
8.5.6 Strength Assessment . 39
8.6 Fracture mechanics-based design . 42
9 Material data for design from testing . 43
9.1 Qualification of Material . 43
9.2 Derivation of static strength and impact energy properties (base material) . 43
9.3 Derivation of fatigue strength properties (base material) . 43
9.4 Welded Joints . 44
9.5 Cast, Forged and steel . 44
9.5.1 Derivation of Static strength properties . 44
9.5.2 Fracture toughness . 44
9.5.3 Derivation of fatigue strength properties . 44
9.6 Bolts . 46
9.7 Nacelle Cover . 46
10 Model verification and validation . 46
Annex A - Model Verification and Validation Methods (informative) . 47
A.1 Verification . 47
A.2 Validation( Laboratory testing) . 47
A.3 Validation (Field experience) . 47
Annex B : Welded Joint Stresses (informative) . 48
Annex C (Informative) . 50
S-N Curve determination by test, statistical evaluation and influencing factors . 50
C.1 General . 50
C.2 S-N Curve . 50
C.3 specimens . 50
C.4 Test Procedure . 50
C.4.1 Finite life line . 51
C.4.2 Long life fatigue regime . 51
C.5 Influencing factors of S-N curve . 51
Annex D : Limit State Equations (Informative) . 52
D.1 Yielding failure . 52
D.2 Fatigue Limit State Equation . 53
D.3 Fatigue Assessment Based on Fracture Mechanics . 56
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Annex E Load Effect Uncertainty Computation (Informative) . 59
Annex F (informative) : Considerations for structural elements. 62
F.1 General . 62
F.2 Global and local failures . 62
F.3 Mean stress influence . 63
Bibliography . 65
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IEC CDV 61400-8 IEC 2022 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS
Part 8: Design of Wind Turbine Structural Components
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced
publications is indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may
be the subject of patent rights. IEC shall not be held responsible for identifying any or all
such patent rights.
International Standard IEC 61400-8 has been prepared by IEC technical committee 88: Wind
energy generation systems.
The text of this International Standard is based on the following documents:
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FDIS Report on voting
XX/XX/FDIS XX/XX/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
reconfirmed,
withdrawn,
replaced by a revised edition, or
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The National Committees are requested to note that for this document the stability date
is 20XX.
THIS TEXT IS INCLUDED FOR THE INFORMATION OF THE NATIONAL COMMITTEES AND WILL BE DELETED
AT THE PUBLICATION STAGE.
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IEC CDV 61400-8 IEC 2022 – 7 –
1 INTRODUCTION
2 This part of the IEC 61400 series outlines the minimum requirements for the design of wind
3 turbine nacelle-based structures and is not intended for use as a complete design specification
4 or instruction manual.
5 Several different groups may be responsible for undertaking the various elements of the design,
6 manufacture, assembly, installation and maintenance of a wind turbine nacelle and for ensuring
7 that the requirements of this standard are met. The division of responsibility between these
8 parties is a contractual matter and is outside the scope of this standard.
9 The requirements stated in this standard may be altered if it can be sufficiently demonstrated
10 that the safety of the system is not compromised. Compliance with this standard does not relieve
11 any person, organization, or corporation from the responsibility of observing other applicable
12 regulations.
13 The specific scope of the standard is provided in clause 1. For cases out of the scope of this
14 standard, reference should be made to relevant IEC/ISO standards.
15
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16 WIND ENERGY GENERATION SYSTEMS –
17 Part 8: Design of Wind Turbine Structural Components
18
19 1 Scope
20 The IEC 61400-8 outlines the minimum requirements for the design of wind turbine nacelle-
21 based structures and is not intended for use as a complete design specification or instruction
22 manual. This standard focuses on the engineering integrity of the structural components
23 constituted within and in the vicinity of the nacelle, including the hub, mainframe, main shaft,
24 associated structures of direct-drives, gearbox structures, yaw structural connection, nacelle
25 covering and other structural connections to subsystems of control and protection mechanisms,
26 electrical units and mechanical systems. The standard focuses primarily on Ferrous material-
27 based nacelle structures, but can apply to other materials also as appropriate. The design of
28 bolted and welded joints in the nacelle structures is included, as well as cast and forged
29 components. Material testing requirements to use in the design process for nacelle structures
30 are specified. Structures or components outside of the nacelle, such as the tower, foundations
31 or blades are not in the scope of this standard. Further, the standard does not address non-
32 structural components or systems such as hydraulics or electrical units. While the structural
33 connections of the gearbox and the main shaft, are in scope, the design of the gears and
34 bearings are not included.
35 This standard shall be used together with the appropriate standards mentioned in Section 2. In
36 particular, this standard is consistent with the requirements of IEC 61400-1 Ed.4. The safety
37 level of the wind turbine designed according to this standard shall be at or exceed the level
38 inherent in IEC 61400-1 Ed.4. Probabilistic methods to calibrate partial safety factors and for
39 use in the design process are provided.
40 2 Normative references
41 The following documents are referred to in the text in such a way that some or all of their content
42 constitutes requirements of this document. For dated references, only the edition cited applies.
43 For undated references, the latest edition of the referenced document (including any
44 amendments) applies.
45 ASTM-E466-21: Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue
46 Tests of Metallic Materials.
47 BS 7919:2013. Guide to methods for assessing the acceptability of flaws in metallic structures
48 FKM Guideline, Fracture Mechanics Proof of Strength for Engineering Components, 2018
49 (FKM - RBM-04-18)
50 IEC 61400-1 Design Requirements, Ed. 4, 2019
51 IEC 61400-3, Wind turbines – Part 3: Design requirements for offshore wind turbines, Ed. 2,
52 2019
53 IEC 61400-4 Design requirements for wind turbine gearboxes Ed. 2, in process
54 IEC 61400-5 Wind Energy Generation systems – part 5: Wind turbine blades, 2020
55 IEC 61400-6 Tower and Foundation Design requirements Ed. 1, 2019
56 IEC 61400-13, Wind turbines – Part 13: Measurement of mechanical loads, 2015
57 ISO 148-1:2016 Metallic materials – Charpy pendulum impact test – Part 1: Test method
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58 ISO 898-1:2013 Mechanical properties of fasteners made of carbon steel and alloy steel - Part
59 1: Bolts, screws and studs with specified property classes - Coarse thread and fine pitch
60 thread
61 ISO 945-1:2019 Microstructure of cast irons – Part 1: Graphite classification by visual analysis
62 ISO 1143:2010 Metallic materials -- Rotating bar bending fatigue testing
63 ISO 2394: 2015 General principles on reliability for structures
64 ISO 3800:1993 Threaded fasteners -- Axial load fatigue testing -- Test methods and evaluation
65 of results
66 ISO 6892-1:2019 Metallic materials – Tensile testing – Part 1: Method of test at room
67 temperature
68 ISO 12107 Fatigue Testing – Statistical Planning and Analysis of Data, 2012
69 ISO 16269 – 6:2014 Statistical interpretation of data, Determination of Statistical Tolerance
70 Levels
71 ISO 12108: 2018 Metallic materials -- Fatigue testing -- Fatigue crack growth method
72 ISO 14345: 2012 Fatigue Testing of welded components
73 EN 12680-3:2011, Ultrasonic examination. Spheroidal graphite cast iron castings
74 EN 13445-3 "Unified pressure vessels", Part-3, Design, 2014
75 ISO 7500-1:2018 Metallic materials – Calibration and verification of static uniaxial testing
76 machines – Part 1: Tension/compression testing machines – Calibration and verification
77 of the force-measuring system
78 ISO 12135:2016 Metallic materials – Unified method of test for the determination of quasistatic
79 fracture toughness
80 ISO/IEC 17025:2017 General requirements for the competence of testing and calibration
81 laboratories
82 EN 1011-4/A1:2004 Welding - Recommendations for welding of metallic materials - Part 4: Arc
83 welding of aluminium and aluminium alloys
84 EN 1090-1 + A1:2012 Execution of steel structures and aluminium structures – Part 1:
85 Requirements for conformity assessment of structural components
86 EN 1090-2:2018 Execution of steel structures and aluminium structures - Part 2: Technical
87 requirements for steel structures
88 EN 1090-3:2019 Execution of steel structures and aluminium structures – Part 3: Technical
89 requirements for aluminium structures
90 EN 1999-1-1:2008 Eurocode 9: Design of aluminium structures - Part 1-1: General structural
91 rule
92 EN 1999-1-3:2007 Eurocode 9: Design of aluminium structures - Part 1-3: Structures
93 susceptible to fatigue
94 EN 50308:2004 Wind turbines. Protective measures. Requirements for design, operation and
95 maintenance
96 Eurocode 3: 2010. Design of steel structures – Part 1-9: Fatigue
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97 IIW document IIW-2259-152259-15, Hobbacher A., Recommendations for fatigue design of
98 welded joints and components, International Institute of Welding, 2014
99 IIW document XIII-2240r2-08/XV-1289r2-08, Fricke W., Guideline for the Fatigue Assessment
100 by Notch Stress Analysis for Welded Structures, 2010
101 VDMA 23901, Components and Systems for Wind Turbines in Cold Environments, Verband
102 Deutscher Maschinen- und Anlagenbau e.V., 2016
103 VDMA 23902, Guideline for fracture mechanical strength assessment of planet carriers made
104 of nodular cast iron EN-GJS-700-2 for wind turbine gear boxes, Verband Deutscher
105 Maschinen- und Anlagenbau e.V., 2014
106 VDI 2230 Blatt 1:2015-11Systematic calculation of highly stressed bolted joints - Joints with one
107 cylindrical bolt
108 VDI 2230 Part 2: 2014-12- Systematic calculation of high duty bolted joints –Joints with
109 several cylindrical bolts
110
111 DIN50100: Load controlled fatigue testing – Execution and evaluation of cyclic tests at
112 constant load amplitudes on metallic specimens and components
113
114
115 3 Definitions
116 For the purposes of this document, the following terms and definitions apply.
117 ISO and IEC maintain terminological databases for use in standardization at the following
118 addresses:
119 IEC Electropedia: available at http://www.electropedia.org/
120 ISO Online browsing platform: available at http://www.iso.org/obp
121
122 3.1
123 Basquin equation
124 Power law representation of S-N curves
125 3.2
126 component capacity
127 The maximum loading (e.g. stress) the component can withstand / static strength criterium
128 3.3
129 component loading
130 The loading (e.g. stress) acting on the component
131 3.4
132 component tests
133 Full scale tests or sample tests that sufficiently represent the component
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134 3.5
135 damage equivalent load
136 The load which when repeated a certain number of cycles causes the same amount of damage
137 as the original combination of several loads and cycles.
138 3.6
139 defect model
140 A model which is used to substitute the geometrical dimensions of an idealized defect type
141 3.7
142 design limits
143 Maximum or minimum values of a parameter as used in design
144 3.8
145 design life
146 Minimum intended life of the structure used in the design process that structure shall survive
147 3.9
148 design load
149 The mechanical loads whether dynamic or static that the structure shall withstand in its lifetime
150 3.10
151 failure assessment diagram (FAD)
152 A diagram which is used to check if there is any risk of brittle failure of plastic collapse while
153 performing a fracture mechanic strength assessment
154 3.11
155 fail-safe
156 design property of a structure or system which prevents its failure from resulting in critical
157 consequences
158 3.12
159 global Stresses
160 Stresses in terms of nominal stresses which are applicable for simple continuous structures
161 (e.g. beams, shells, plates), where the stress can be derived out of sectional forces by analytical
162 methods. Notch factors may need to be considered
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163 3.13
164 impact Energy
165 Energy absorbed/required to break a V-notched test sample on pendulum impact testing
166 machine
167 3.14
168 limit state
169 state of a structure beyond which it no longer satisfies the design requirements
170 3.15
171 local Stresses
172 Local stress analysis points at specific regions of a global structure (e.g. at radii, notches) with
173 consideration of the notch shape
174 3.16
175 mode I / failure mode I
17
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