IEC 61400-8:2024 outlines the minimum requirements for the design of wind turbine nacelle-based structures and is not intended for use as a complete design specification or instruction manual. This document focuses on the structural integrity of the structural components constituted within and in the vicinity of the nacelle, including the hub, mainframe, main shaft, associated structures of direct-drives, gearbox structures, yaw structural connection, nacelle enclosure. It also addresses connections of the structural components to control and protection mechanisms, as well as structural connections of electrical units and other mechanical systems. This document focuses primarily on ferrous material-based nacelle structures but can apply to other materials also as appropriate<\/p>\n
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| 2<\/td>\n | undefined <\/td>\n<\/tr>\n | ||||||
| 5<\/td>\n | Annex ZA (normative)Normative references to international publicationswith their corresponding European publications <\/td>\n<\/tr>\n | ||||||
| 8<\/td>\n | English CONTENTS <\/td>\n<\/tr>\n | ||||||
| 11<\/td>\n | FOREWORD <\/td>\n<\/tr>\n | ||||||
| 13<\/td>\n | INTRODUCTION <\/td>\n<\/tr>\n | ||||||
| 14<\/td>\n | 1 Scope 2 Normative references <\/td>\n<\/tr>\n | ||||||
| 16<\/td>\n | 3 Terms, definitions, symbols and abbreviated terms 3.1 Terms and definitions <\/td>\n<\/tr>\n | ||||||
| 18<\/td>\n | 3.2 Symbols and abbreviated terms <\/td>\n<\/tr>\n | ||||||
| 20<\/td>\n | 4 Reliability considerations 4.1 Approaches to reliability based design <\/td>\n<\/tr>\n | ||||||
| 22<\/td>\n | 4.2 Models and basic variables for structural verification 4.2.1 Reliability assessment 4.2.2 Material properties 4.3 Partial safety factors and reliability targets <\/td>\n<\/tr>\n | ||||||
| 23<\/td>\n | 5 Application of loads and analysis models 5.1 Loads models 5.2 Analysis model 5.2.1 General 5.2.2 Load path modelling 5.2.3 Application of load components Tables Table 1 \u2013 Component classes as in IEC 61400-1:2019 <\/td>\n<\/tr>\n | ||||||
| 24<\/td>\n | 5.2.4 Boundary conditions 5.3 Modelling of nonlinear mechanical behaviour 5.3.1 General 5.3.2 Nonlinear stress effects 5.3.3 Application of ultimate loads 5.3.4 Application of fatigue loads <\/td>\n<\/tr>\n | ||||||
| 25<\/td>\n | 5.4 Partial safety factors <\/td>\n<\/tr>\n | ||||||
| 26<\/td>\n | Table 2 \u2013 List of potential sources for modelling deviations Table 3 \u2013 Modelling partial safety factor \u03b3modelling: yielding where coefficient of variation of yield strength is less than 15 % <\/td>\n<\/tr>\n | ||||||
| 27<\/td>\n | 5.5 Partial safety factor for resistance Table 4 \u2013 Modelling partial safety factor, \u03b3modelling: fatigue of welded details and cast iron Table 5 \u2013 Minimum resistance partial safety factors, \u03b3M, for welded steel for different survival probabilities of the characteristic S-N curve Table 6 \u2013 Minimum resistance partial safety factors \u03b3M, 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 <\/td>\n<\/tr>\n | ||||||
| 28<\/td>\n | 5.6 Nacelle and hub component considerations 5.6.1 General 5.6.2 Hub structure and bolts Figures Figure 1 \u2013 Illustration of a nacelle structure, where for examplea direct drive generator is mounted behind the hub <\/td>\n<\/tr>\n | ||||||
| 29<\/td>\n | 5.6.3 Nacelle front structure (alternatively: mechanical drive-train structure) 5.6.4 Gearbox structure 5.6.5 Yaw structure <\/td>\n<\/tr>\n | ||||||
| 30<\/td>\n | 5.6.6 Nacelle rear structure 5.6.7 Nacelle cover and spinner 6 Deflection analysis <\/td>\n<\/tr>\n | ||||||
| 31<\/td>\n | 7 Strength verification 7.1 General 7.2 Determination of stress and strain 7.3 Material properties 7.3.1 Material data <\/td>\n<\/tr>\n | ||||||
| 32<\/td>\n | 7.3.2 Influence of size 7.4 Static strength assessment 7.4.1 Assessment process 7.4.2 Cast, forged and steel components <\/td>\n<\/tr>\n | ||||||
| 33<\/td>\n | Figure 2 \u2013 Idealized elastic plastic stress-strain curve <\/td>\n<\/tr>\n | ||||||
| 34<\/td>\n | 7.4.3 Welded structures 7.4.4 Bolted joints <\/td>\n<\/tr>\n | ||||||
| 35<\/td>\n | 7.4.5 Fibre reinforced material 7.5 Fatigue strength assessment 7.5.1 Fatigue strength methods 7.5.2 Determination of local stresses 7.5.3 Stress hypothesis for fatigue <\/td>\n<\/tr>\n | ||||||
| 36<\/td>\n | 7.5.4 S\/N curves 7.5.5 Influence on fatigue strength Figure 3 \u2013 Representative S \/N curve <\/td>\n<\/tr>\n | ||||||
| 37<\/td>\n | 7.5.6 Partial safety factors for fatigue <\/td>\n<\/tr>\n | ||||||
| 38<\/td>\n | 7.5.7 Damage accumulation Table 7 \u2013 Partial safety factors \u03b3M for S\/N-curves of cast iron materials <\/td>\n<\/tr>\n | ||||||
| 39<\/td>\n | 7.5.8 Bolted joints 7.5.9 Fibre reinforced material 7.6 Fracture mechanics assessment 7.6.1 General <\/td>\n<\/tr>\n | ||||||
| 40<\/td>\n | 7.6.2 Define objective 7.6.3 Material parameter Figure 4 \u2013 Fracture mechanics calculation \u2013 process flow chart <\/td>\n<\/tr>\n | ||||||
| 41<\/td>\n | 7.6.4 Defect model Figure 5 \u2013 Idealized crack types <\/td>\n<\/tr>\n | ||||||
| 42<\/td>\n | 7.6.5 Structural model 7.6.6 Loading <\/td>\n<\/tr>\n | ||||||
| 43<\/td>\n | 7.6.7 Strength assessment Figure 6 \u2013 Failure assessment diagram (FAD) <\/td>\n<\/tr>\n | ||||||
| 45<\/td>\n | Figure 7 \u2013 Crack growth under cyclic loading by Paris\/Erdogan <\/td>\n<\/tr>\n | ||||||
| 46<\/td>\n | 7.7 Fracture mechanics-based design Figure 8 \u2013 Crack propagation and critical crack length in failure assessment diagram <\/td>\n<\/tr>\n | ||||||
| 47<\/td>\n | 8 Material data for design from testing 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) <\/td>\n<\/tr>\n | ||||||
| 48<\/td>\n | 8.4 Welded joints 8.5 Cast, forged and steel 8.5.1 Derivation of static strength properties 8.5.2 Fracture toughness <\/td>\n<\/tr>\n | ||||||
| 49<\/td>\n | 8.5.3 Derivation of fatigue strength properties <\/td>\n<\/tr>\n | ||||||
| 50<\/td>\n | 8.6 Bolts 8.7 Nacelle cover 9 Model verification and validation <\/td>\n<\/tr>\n | ||||||
| 52<\/td>\n | Annex A (informative)Model verification and validation methods A.1 General A.2 Verification A.3 Validation (laboratory testing) A.4 Validation (field testing) <\/td>\n<\/tr>\n | ||||||
| 53<\/td>\n | Annex B (informative) Welded joint stresses Figure B.1 \u2013 Fatigue analysis procedure for the weld toe <\/td>\n<\/tr>\n | ||||||
| 54<\/td>\n | Annex C (informative) S-N curve determination by test, statistical evaluation and influencing factors C.1 General C.2 S-N curve C.3 Specimens C.4 Test procedure C.4.1 General <\/td>\n<\/tr>\n | ||||||
| 55<\/td>\n | C.4.2 Finite lifetime C.4.3 Long life fatigue regime C.5 Influencing factors of S-N curve <\/td>\n<\/tr>\n | ||||||
| 56<\/td>\n | Annex D (informative) Limit state equations D.1 General D.2 Yielding failure <\/td>\n<\/tr>\n | ||||||
| 57<\/td>\n | D.3 Fatigue limit state equation <\/td>\n<\/tr>\n | ||||||
| 59<\/td>\n | Figure D.1 \u2013 Haigh diagram with Re as the yield stress and Rm as the tensile limit <\/td>\n<\/tr>\n | ||||||
| 61<\/td>\n | D.4 Fatigue assessment based on fracture mechanics Table D.1 \u2013 Representative stochastic model for fatigue analysis of cast iron <\/td>\n<\/tr>\n | ||||||
| 64<\/td>\n | Annex E (informative) Load effect uncertainty computation Figure E.1 \u2013 Model example Table E.1 \u2013 Test cases combination <\/td>\n<\/tr>\n | ||||||
| 65<\/td>\n | Table E.2 \u2013 Result comparison validation vs simplifiedmodels and ratio \u03b4mf calculation <\/td>\n<\/tr>\n | ||||||
| 66<\/td>\n | Annex F (informative) Considerations for structural elements F.1 General F.2 Global and local failures Figure F.1 \u2013 Locations of failure for local (A) and global (B) failure <\/td>\n<\/tr>\n | ||||||
| 67<\/td>\n | F.3 Mean stress influence Figure F.2 \u2013 Local and global failure for two different notch radii Figure F.3 \u2013 Haigh-diagram for evaluation of mean stress influence <\/td>\n<\/tr>\n | ||||||
| 69<\/td>\n | Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Wind energy generation systems – Design of wind turbine structural components<\/b><\/p>\n |