This document provides specifications for calculating wind loads on a wind turbine tower. It specifies the materials used in the tower as structural steel with ultimate and yield strengths. It describes the dead loads from tower materials and wind loads as dynamic loads depending on wind speed, structure shape and height, and topography. It assumes a cylindrical tower and lattice wind turbine and provides the basic wind speed, importance factor, surface roughness, velocity pressure coefficients, topographic factor, and force coefficients to calculate design wind loads and moments on the tower and turbine.

1. WIND TURBINE TOWER
LOADINGS
CALCULATION

2. Tower Specification
 Structural Steel JIS SS400.
 Ultimate Strength 415 MPa.
 Yield Strength 230 MPa.

3. Dead Loads
 Dead loads consist of the weight of all
materials of construction incorporated
into the structure (i.e. tower and wind
turbine).

4. Wind Loads
 Wind loads are
randomly applied
dynamic loads.
 It depends on the
wind speed, shape
and height of the
structure and
topographic of the
region.
 Most calculations
using US customary
systems, which is
applicable to ASCE
7-02 and ASCE 7-
05.

5. Assumption
Components Assumption for Analysis
Tower Cylindrical Poles
Wind Turbine Lattice Frameworks (Є= 0.36)

6. Basic Wind Speed, V
and Wind Directionality Factor,
Kd The basic wind speed, V, assumed as
134.216 mph or 60 m/s.
 The wind directionality factor, Kd, for
wind turbine tower is 0.95 for tower
and 0.85 for the DS wind turbine.

7. Importance Factor, I
 An importance
factor, I, for the
wind turbine tower
(Building Category
III or IV) is 1.15.
Building Type I
Category I -
Buildings and other
structures with low
hazard to human life
in the event of
failure, such as
agricultural facilities.
0.77
Category II – Other
buildings.
1.00
Category III and IV -
Buildings and other
structures with a
substantial hazard to
human life in the
event of failure, such
as hospitals,
communication
towers and power
generating stations
1.15

8. Surface Roughness and
Exposure
 It is assumed that
the tower would be
installed on a
terrain with surface
roughness and
exposure category
of C (town/ small
city).
Exposure
Category B,
ex. 臺北
Exposure
Category C,
ex. 板橋
Exposure
Category D,
ex. 金門

9. Velocity Pressure Exponent
Coefficient, Kz
 Velocity pressure
exponent, Kz, depe
nds on the site
relative height to
the ground, z.
 This means for
rooftop
structure, z, would
be the total height
of the component
and the building its
installed.
Nominal height
above ground level,
z
K z for
Exposure
C
ft m
0-15 0-4.6 0.85
20 6.1 0.90
25 7.6 0.94
30 9.1 0.98
40 12.2 1.04
50 15.2 1.09
60 18 1.13
70 21.3 1.17
80 24.4 1.21
90 27.4 1.24
100 30.5 1.26

10. Topographic Factor, Kzt and
Force Coefficient, Cf
 The value of Kzt
was taken as 1 with
assumption flat
region
environment.
 The values of Cf
were taken from
Figures 6-19 and
6-21 of the code.
 The values are 1.2
for the tower and
1.1 for the wind
turbine.

11. Velocity Pressure, qz
 The velocity pressure, qz, evaluated at
height z shall be calculated by:

12. Gust Effect Factor, G
 Gust effect factor, G, could be
calculated by Eq. 6-4 of the code.
 This factor increased with structure
height.

13. Design Wind Loads, F
 Design wind force for
each component shall
be determined by:
 Moment because of
wind force calculated
as:
FWT
FTOWER
a
b
bFaFM WTTOWER