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Note:
Alternatively, the actions of DLC 1.1 and 6.4 which occur more than 104 times are recommended as a
conservative approach.
(5) The extreme loads of the pitch drive actuator torque (min/max) shall be given for all load cases without pitch activity (braked pitch) and separately for all load cases with pitch activity. The simulation of the pitch drive actuator torque shall include effects from the aerodynamic pitch torque, the blade bearing and pitch gearbox friction and the pitching inertia of rotor blade and pitch drive.
(6) With regard to the maximum loads in the blade coordinate system, a table shall be compiled with all the corresponding loads from all the blade connec- tions.
(7) With regard to the maximum bending moment in the hub coordinate system, a table shall be compiled with all the corresponding loads from all the blade connections.
Note:
Following the evaluation of the extreme loads with or without partial safety factors, differing load cases may become relevant.
4.B.2.3 Fatigue loads
(1) In addition to the time series required in Section 4.B.2.1, all results of the evaluation shall be submitted in formats which can be edited by computer.
(2) For the evaluation of the fatigue loads, it is generally required that all design load cases of the fatigue strength shall be included (DLC 1.1, DLC 1.4, DLC 1.8, DLC 2.1, DLC 2.2, DLC 3.1, DLC 4.1, DLC 6.4 and DLC 9.1 to DLC 9.4, if applicable). (3) The assumptions made in the calculation of the fatigue loads shall be specified. These include e.g. the mean annual wind speed, the parameters of the wind speed distribution, the operating life etc.
(4) For all load components, accumulated fatigue spectra within the simulated operating life shall be given in tabular, and if necessary graphic, form. In addition, equivalent constant-range spectra shall be computed from the accumulated fatigue spectra and also specified. Here the reference load cycle number nref shall be stated. Equivalent fatigue loads can be
presented in tabular form for all material-relevant slope parameters of the S/N curves, in accordance with Table 4.B.2.
(5) For dynamically loaded components of fibre reinforced plastic (GRP/CRP), such as the rotor blade, the Markov matrices (range-mean matrix) shall be given in addition at the sections investigated.
(6) In particular, for the evaluation of the fatigue loads at the blade root, the following procedure shall be observed:
(7) Apart from the evaluation for the bending mo- ments in the flapwise and edgewise directions (Mx and My), the angular sector between these bending mo- ments and the subsequent sector up to 90° shall be examined, so that a total sector of 180° is obtained. These bending moments shall be computed at angular intervals of at least 15°.
(8) Without further evaluation, this examination can be dispensed with if the fatigue loads for the flapwise and edgewise directions are multiplied by a factor of 1.2.
(9) For the components of the blade pitching sys- tem, the drive train (main bearing, gear box, coupling etc.) and the yaw system, the average values from the fatigue loads as well as the distribution of the load duration distribution (LDD) shall be specified for the relevant load components (see also Chapter 7). For the blade pitching system, the LDD shall be specified for the pitch drive actuator torque. All LDDs consist of the respective load tables and the lists of applied DLCs including the number of occurrences.
(10) For the components of the blade pitching sys- tem, the root mean square value (RMS) of the 600 sec time series of the sensor “pitch actuator torque” is requested additionally for all load cases of DLC 1.1. (11) For the tower and the foundation, the investi- gated load components shall be verified with a state- ment of the mean value and the amplitudes, e.g. through specification of the Markov matrices.
4.B.3 Further evaluations
(1) Maximum blade deflection and minimum
tower clearance: In the case of wind turbines with a horizontal axis, the maximum blade deflection in the tower direction and the minimum clearance between the rotor blades and the tower or other parts of the turbine (determined for all load cases) shall be speci- fied for the deformation analysis. Here the deforma- tions of all blades shall be taken into account. The decisive load case shall be specified. See also Section 6.2.4.1, para 7.
(2) Maximum tower top acceleration: The maxi-
IV – Part 1 Appendix 4.B Evaluation of the Loads Chapter 4
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direction and in the tower lateral direction (x and y directions acc. to Fig. 4.A.5) shall be specified for the strength analysis. All load cases shall be considered. The acceleration values shall be multiplied with the partial safety factor for loads γF according to Tables
4.3.1 and 4.3.2.
(3) Maximum rotational speed: Statement of the
maximum rotational speed of the rotor and generator nmax occurring for the entire load case simulation, and
naming of the corresponding load case.
(4) Braking load cases: Graphic presentation of the time series of a braking load case with application of the mechanical brake or of the braking system bringing the turbine to standstill, in which the maxi- mum torque occurs (rotor torque versus simulation time).
Statement of the maximum rotor braking time that is required when the mechanical brake is applied.
(5) Operation within the tower resonance range: If the wind turbine is operated within the tower reso- nance range (see Section 6.6.5.1), the corresponding evaluation and definition of the limiting values shall be submitted and explained.
(6) Design loads for locking devices: For the di- mensioning of the locking devices for the blade pitch- ing, rotor and yaw systems, the relevant loads shall be specified with consideration of the partial safety fac- tors. This concerns the load cases DLC 8.1 and DLC 8.2.
(7) Design loads for appearance of a ground gap: In the case of slab foundations, the evaluation of load case combinations acting at the tower bottom shall be executed in tabular form in accordance with the specimen table for extreme load evaluation (see Table 4.B.1), including statement of the wind speeds and wind direction for the corresponding load situation. The essential load case combinations are given in Section 6.7.6, Table 6.7.1. For the analyses required in Section 6.7.6, Table 6.7.1, column 2 and Section 6.7.6.3 (4), the load case combinations listed in each case in column 1 shall be evaluated. In this evaluation, the partial safety factors may be applied with γF = 1.0
(analysis of the serviceability limit state). For the vari- ous load situations, the wind speeds and wind direc- tions prevailing at that time shall be specified.
Table 4.B.1 Recommended presentation of the calculation results of extreme loads (Fres – resulting transverse force, Mres – resulting bending moment)
Results of the extreme load evaluation
Load case γF Fx Fy Fz Fres Mx My Mz Mres
Fx Max Min Fy Max Min Fz Max Min Fres Max Mx Max Min My Max Min Mz Max Min Mres Max
Chapter 4 Appendix 4.B Evaluation of the Loads IV – Part 1
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Table 4.B.2 Recommended presentation of the calculation results of equivalent fatigue loads for various slope parameters of the S/N curve
Results of the fatigue load evaluation
nRef Fx Fy Fz Mx My Mz ma mb mc md me mf mg mh mi Slope par ame ter of the S/N cur ve m mj
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