Loadbearing structures and detailed design - Concrete Structures for Wind Turbines - page 114

Fig. 4.5 Dynamic model of the structure

Replacing the distributed dead load g (x) by discrete dead loads G i acting horizontally,
with the associated ordinates of the deflection curve y i (see Figure 4.5), converts the
integrals into summation expressions:

P i G i

y i

2

v ¼

P i G i

y i

g

4.3.2.1 Practical vibration analysis [8]
The self-weight of the tower itself, the loads of the fitting-out and the quasi-permanent
imposed loads are applied to the nodes of the bar structure as individual loads G i acting
horizontally (see Figure 4.5).
The deflection curve with the ordinates y i at the nodes of the bar structure is then
calculated. From that we get the period of oscillation of the fundamental frequency: 2)

s

P i G i

y i 2 p

v g P i G i

T ¼ ¼ 2 p

y i

4.3.2.2 Example of application
Calculating the first period of oscillation T 1
Example: prestressed concrete wind turbine structure, hub height 130m (see
Section 5.2)

2) This equation can also be found in DIN 4131 [14].