Fatigue Design of Wind Turbines - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 669

As an example, Table 12-1 contains a listing of a sequence of loads calculated for a wind
turbine blade, normalized by the maximum load expected in the sequence. This is one of
several load spectra developed during the conceptual design of the 2.5-MW Mod-2 HAWT
[Boeing 1979]. A run period is first divided into “layers” of various durations during which

Table 12-1.
9.0-Hour Blade Fatigue Design Spectrum for the DOE/NASA Mod-2 Wind Turbine
in Time Order

Layer
No.

Wind
speed
(m/s)

Cycle
per
layer

Flatwise Blade Load / Maxmax Load,
L F / L maxmax

R-Ratio
R f

Max Min Cyclic Average

Start 5.4 0 -0.400 -0.400 0.000 -0.400 1.00

1 " 908 0.433 0.061 0.186 0.247 0.14

2 " 333 0.496 -0.002 0.249 0.247 -0.00

3 " 605 0.383 0.111 0.136 0.247 0.29

4 " 1,059 0.463 0.030 0.217 0.247 0.06

5 " 91 0.525 -0.030 0.278 0.248 -0.06

6 " 30 0.550 -0.055 0.303 0.248 -0.10

7 9.4 613 0.880 0.446 0.217 0.663 0.51

8 " 56 0.923 0.405 0.259 0.664 0.44

9 " 1,951 0.855 0.473 0.191 0.664 0.55

10 " 1,115 0.787 0.540 0.124 0.664 0.69

11 " 1,673 0.828 0.498 0.165 0.663 0.60

12 " 167 0.903 0.423 0.240 0.663 0.47

13 15.6 237 0.645 0.192 0.227 0.419 0.30

14 " 415 0.798 0.038 0.380 0.418 0.05

15 " 356 0.740 0.098 0.321 0.419 0.13

16 " 36 0.918 -0.080 0.499 0.419 -0.09

17 " 12 0.968 -0.130 0.549 0.419 -0.13

18 " 130 0.863 -0.025 0.444 0.419 -0.03

19 18.3 3 0.838 -0.471 0.655 0.184 -0.56

20 " 37 0.710 -0.343 0.527 0.184 -0.48

21 " 67 0.447 -0.080 0.264 0.184 -0.18

22 " 118 0.632 -0.265 0.449 0.184 -0.42

23 " 101 0.561 -0.195 0.378 0.183 -0.35

24 " 10 0.778 -0.411 0.595 0.184 -0.53

25 13.0 1,305 0.890 0.520 0.185 0.705 0.58

26 " 130 0.976 0.433 0.272 0.705 0.44

27 " 870 0.841 0.568 0.137 0.705 0.68

28 " 1,522 0.918 0.491 0.214 0.705 0.54

29 " 44 1.000 0.410 0.295 0.705 0.41

30 " 478 0.950 0.460 0.245 0.705 0.48

31 7.2 927 0.527 0.206 0.161 0.367 0.39

32 " 139 0.702 0.031 0.336 0.367 0.04

33 " 1,622 0.626 0.108 0.259 0.367 0.17

34 " 1,390 0.588 0.145 0.222 0.367 0.25

35 " 46 0.732 0.002 0.365 0.367 0.10

36 " 510 0.666 0.068 0.299 0.367 0.10

Stop 5.4 0 -0.400 -0.400 0.000 -0.400 1.00

Spectrum: 9.6 19,105 0.724 0.299 0.212 0.511 0.37