Environmental Engineering Reference
In-Depth Information
2.3.1.3 Example of application
Prestressed concrete wind turbine structure, hub height 130m (see Section 5.2):
d
!
2
¼
r
h
ref
h
r
h
h
ref
h
þ
b
b
þ
0
:
125
04
25
129
0
:
0
:
04
!
2
¼
2
¼
0
:
0067
p
4
p
5
r
r
129
:
66
þ
0
:
125
:
19
129
:
7
þ
5
:
6
:
7
7
þ
0
:
125
:
5
:
6
25
x
s
=
h ¼ y
36
=ðz
36
z
1
Þ¼4
:
274
=ð130
:
174 0
:
500Þ¼0
:
0330
>
0
:
0067
The tower is therefore susceptible to vibration.
According to [9] 8.3.1, the vibration effect of the tower in the direction of the wind caused
by the gustiness of the wind for a wind turbine in the “non-operational” condition (see
Section 4.5.2) must be taken into account by way of an equivalent static load, which
according to [9] Section B.3 or DIN 1055-4 [12] annex C may be calculated as follows:
Resultant equivalent static wind load in structure segment j ([12] C.2)
F
Wj
¼
G
c
fj
q
m
ð
z
j
Þ:
A
j
where
G gust response factor to DIN1055-4 [12] C.3
c
fj
aerodynamic force coefficient for segment i to DIN 1055-4 [12] 12.6 or 12.7
q
m
(z
j
) average dynamic pressure at location z
j
z
j
average height of segment j above ground level
A
j
reference area of segment j
Average dynamic pressure (10-min average) ([12] C.2 (3))
q
m
z
j
¼
2
2
v
m
z
j
2
ð
v
m
m
½
=
s
Þ
or
q
m
kPa
½
¼
1600
r
density of air:
r¼
1.25 kg/m
3
v
m
average wind speed (Table 2.3)
Table 2.3 Average wind speed (to DIN 1055-4 [12] Table B.2).
v
m
z
j
¼ a v
ref
b
z
j
=
10
or
a
min
v
ref
for z
j
<
z
min
Terrain category
I
II
III
IV
a
Factor
1.18
1.00
0.77
0.56
Exponent
b
0.12
0.16
0.22
0.30
z
min
2.00
4.00
8.00
16.00
a
min
0.97
0.86
0.73
0.64
