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BS EN IEC 61400-8:2024 Wind energy generation systems - Design of wind turbine structural components, 2024
- undefined [Go to Page]
- Annex ZA (normative)Normative references to international publicationswith their corresponding European publications
- English [Go to Page]
- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms, definitions, symbols and abbreviated terms [Go to Page]
- 3.1 Terms and definitions
- 3.2 Symbols and abbreviated terms
- 4 Reliability considerations [Go to Page]
- 4.1 Approaches to reliability based design
- 4.2 Models and basic variables for structural verification [Go to Page]
- 4.2.1 Reliability assessment
- 4.2.2 Material properties
- 4.3 Partial safety factors and reliability targets
- 5 Application of loads and analysis models [Go to Page]
- 5.1 Loads models
- 5.2 Analysis model [Go to Page]
- 5.2.1 General
- 5.2.2 Load path modelling
- 5.2.3 Application of load components
- Tables [Go to Page]
- Table 1 – Component classes as in IEC 61400-1:2019 [Go to Page]
- 5.2.4 Boundary conditions
- 5.3 Modelling of nonlinear mechanical behaviour [Go to Page]
- 5.3.1 General
- 5.3.2 Nonlinear stress effects
- 5.3.3 Application of ultimate loads
- 5.3.4 Application of fatigue loads
- 5.4 Partial safety factors
- Table 2 – List of potential sources for modelling deviations
- Table 3 – Modelling partial safety factor γmodelling: yielding where coefficient of variation of yield strength is less than 15 %
- 5.5 Partial safety factor for resistance
- Table 4 – Modelling partial safety factor, γmodelling: fatigue of welded details and cast iron
- Table 5 – Minimum resistance partial safety factors, γM, for welded steel for different survival probabilities of the characteristic S-N curve
- Table 6 – Minimum resistance partial safety factors γM, for cast iron, forged and steel components (if not utilizing relevant design standards such as EN 1993-1-9) for different survival probabilities of the characteristic S-N curve
- 5.6 Nacelle and hub component considerations [Go to Page]
- 5.6.1 General
- 5.6.2 Hub structure and bolts
- Figures [Go to Page]
- Figure 1 – Illustration of a nacelle structure, where for examplea direct drive generator is mounted behind the hub [Go to Page]
- 5.6.3 Nacelle front structure (alternatively: mechanical drive-train structure)
- 5.6.4 Gearbox structure
- 5.6.5 Yaw structure
- 5.6.6 Nacelle rear structure
- 5.6.7 Nacelle cover and spinner
- 6 Deflection analysis
- 7 Strength verification [Go to Page]
- 7.1 General
- 7.2 Determination of stress and strain
- 7.3 Material properties [Go to Page]
- 7.3.1 Material data
- 7.3.2 Influence of size
- 7.4 Static strength assessment [Go to Page]
- 7.4.1 Assessment process
- 7.4.2 Cast, forged and steel components
- Figure 2 – Idealized elastic plastic stress-strain curve [Go to Page]
- 7.4.3 Welded structures
- 7.4.4 Bolted joints
- 7.4.5 Fibre reinforced material
- 7.5 Fatigue strength assessment [Go to Page]
- 7.5.1 Fatigue strength methods
- 7.5.2 Determination of local stresses
- 7.5.3 Stress hypothesis for fatigue
- 7.5.4 S/N curves
- 7.5.5 Influence on fatigue strength
- Figure 3 – Representative S /N curve [Go to Page]
- 7.5.6 Partial safety factors for fatigue
- 7.5.7 Damage accumulation
- Table 7 – Partial safety factors γM for S/N-curves of cast iron materials [Go to Page]
- 7.5.8 Bolted joints
- 7.5.9 Fibre reinforced material
- 7.6 Fracture mechanics assessment [Go to Page]
- 7.6.1 General
- 7.6.2 Define objective
- 7.6.3 Material parameter
- Figure 4 – Fracture mechanics calculation – process flow chart [Go to Page]
- 7.6.4 Defect model
- Figure 5 – Idealized crack types [Go to Page]
- 7.6.5 Structural model
- 7.6.6 Loading
- 7.6.7 Strength assessment
- Figure 6 – Failure assessment diagram (FAD)
- Figure 7 – Crack growth under cyclic loading by Paris/Erdogan
- 7.7 Fracture mechanics-based design
- Figure 8 – Crack propagation and critical crack length in failure assessment diagram
- 8 Material data for design from testing [Go to Page]
- 8.1 Qualification of material
- 8.2 Derivation of static strength and impact energy properties (base material)
- 8.3 Derivation of fatigue strength properties (base material)
- 8.4 Welded joints
- 8.5 Cast, forged and steel [Go to Page]
- 8.5.1 Derivation of static strength properties
- 8.5.2 Fracture toughness
- 8.5.3 Derivation of fatigue strength properties
- 8.6 Bolts
- 8.7 Nacelle cover
- 9 Model verification and validation
- Annex A (informative)Model verification and validation methods [Go to Page]
- A.1 General
- A.2 Verification
- A.3 Validation (laboratory testing)
- A.4 Validation (field testing)
- Annex B (informative) Welded joint stresses [Go to Page]
- Figure B.1 – Fatigue analysis procedure for the weld toe
- Annex C (informative) S-N curve determination by test, statistical evaluation and influencing factors [Go to Page]
- C.1 General
- C.2 S-N curve
- C.3 Specimens
- C.4 Test procedure [Go to Page]
- C.4.1 General
- C.4.2 Finite lifetime
- C.4.3 Long life fatigue regime
- C.5 Influencing factors of S-N curve
- Annex D (informative) Limit state equations [Go to Page]
- D.1 General
- D.2 Yielding failure
- D.3 Fatigue limit state equation
- Figure D.1 – Haigh diagram with Re as the yield stress and Rm as the tensile limit
- D.4 Fatigue assessment based on fracture mechanics
- Table D.1 – Representative stochastic model for fatigue analysis of cast iron
- Annex E (informative) Load effect uncertainty computation [Go to Page]
- Figure E.1 – Model example
- Table E.1 – Test cases combination
- Table E.2 – Result comparison validation vs simplifiedmodels and ratio δmf calculation
- Annex F (informative) Considerations for structural elements [Go to Page]
- F.1 General
- F.2 Global and local failures
- Figure F.1 – Locations of failure for local (A) and global (B) failure
- F.3 Mean stress influence
- Figure F.2 – Local and global failure for two different notch radii
- Figure F.3 – Haigh-diagram for evaluation of mean stress influence
- Bibliography [Go to Page]
