A New Identification Method for Bolt Looseness in Wind Turbine Towers
Table 1
The bolt looseness ratio statistics of the six wind turbine towers.
Tower ID
Theoretical design value of the first-order natural frequency (Hz)
The looseness ratio of three flange plates from the bottom up
Notes
1
0.380
28%; 7%; 12%
Height 75 m, four section towers
2
0.380
15%; 14%; 8%
Height 75 m, four section towers
3
0.311
10%; 8%; 6%
Height 80 m, four section towers
4
0.311
32%; 18%; 9%
Height 80 m, four section towers
5
0.311
64%; 24%; 15%
Height 80 m, four section towers
6
0.311
34%; 17%; 6%
Height 80 m, four section towers
Note. The bolt looseness ratio refers to the percentage of loose bolts (nuts) between the upper and lower flanges divided by the total number of flange bolts (nuts).
