1. Evaluation of shell thicknesses Prof. Ch. Baniotopoulos I. Lavassas, G. Nikolaidis, P.Zervas Institute of Steel Structures Aristotle Univ. of Thessaloniki, Greece

2. Hand calculation

3. Hand calculation

4. Linear model Computational model (Linear):
All sections of the tower are simulated via linear beam elements.
Rotor & blade system is simulated as a mass at the top of the tower placed with eccentricity in x and z axes
Soil-structure interaction is simulated by the use of translational spring in z direction & rotational springs along X and Y directions
Kz=15400 kN/m3

5. Linear model Wind loading
Bending moment
& shear force diagrams
M= kNm
V= kN

6. Linear model Response spectrum analysis
Bending moment
& shear force diagrams
M= kNm
V= kN
(almost 30% of the corresponding for wind loading)
Need to be combined with
18 m/s wind loading when load data on the tower top are available

7. FE model
Rotor & blade system is simulated as a mass at the top of the tower placed with eccentricity in x & z axes
Soil-structure interaction is simulated by unilateral contact springs below the foundation.

8. Model details to the flange positions
FE model details
Model details to the flange positions
Connection type for the flanges

9. FE model detrails (foundation)‏
Foundation shape is octagonal.
Equivalent circular diameter (Beq=17.46 m) has been used for the model
Rotor & blade system is simulated as a mass at the top of the tower placed with eccentricity
Soil-structure interaction is simulated by unilateral contact springs below the foundation.
Ground load above foundation has been taken into account

10. Tower Loads: Tower loads a) Vertical loads
Self mass & weight is estimated directly by the FE software
the total mass on the tower top, is kg
(eccentricity of m horizontal, +0.50m vertical).
b) Wind loads
Top of the tower (estimated):
F=550 kN , M=4000 kNm
Tower stem (calculated acc. EC1-1-4)‏
z ≤ 2,00m : FW = 0,51•D
z > 2,00m : FW = 0,013•ln(20•z)•
• [ln(20•z) + 7]•D
Pressure distribution along the circumference

11. Eigenvalue analysis results
Types of analysis
LA (Linear analysis)‏
MNA & LBA (Material non-linear analysis & Linear buckling analysis)‏
GMNA (Geometric & material non-linear analysis)‏
Eigenvalue analysis & Response spectrum analysis
Eigenvalue analysis results

12. Eigenvalue analysis results (linear model)
1St & 2nd , 3rd & 4th , 5th & 6th mode shapes

13. Eigenvalue analysis results (FE model)
1St & 2nd , 3rd & 4th , 5th to 8th (not participating) , 9th & 10th mode shapes

14. GMNA analysis results (wind loading)
Tower displacements & foundation uplift for the wind loading

15. GMNA analysis results (wind loading)
Von mises stress distribution
Max Vm (334 Mpa) stress to the door position
Vm variation around the door occurs due to the coexistence of circumferencial stress

16. GMNA analysis results (wind loading)
Meridional stress (max 297 Mpa) distribution
Skirts 1 & 2 are stiffer than the needed for pure bending due to the presence of the door

17. GMNA analysis results (wind loading)
Negative circumferencial stress distribution
Mainly to the flange position (min -90 Mpa)
Almost disappears in a distance <10 cm
Affects the areas above & below the door
(min -64 Mpa)

18. Response spectrum analysis
Seismic loading:
Response spectrum analysis for the seismic loading
Three eigenmodes are mainly participating.

19. Response spectrum analysis results
(almost 30% of the corresponding for wind loading)
Need to be combined with
18 m/s wind loading when load data on the tower top are available
In this type of analysis negative circumferencial stresses are very small
due to the absence of
loading variation along the circumference as in wind loading
Displacements, Von mises stresses & circumferencial (~zero) stresses