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123456789_123456789_1123456789Wind Turbine Jacket Foundation

Analysis model
ICDAS WTF 2017.00R

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WTF Model Examples

Model description


Geometry model

Analysis model

Landscape model

ICDAS Basis of Design


Additional features

Rendering & Animation 

Trial Version

Case Study 


123456789Automatic creation of Jacket Foundations

Figure: Jacket foundations, LUSAS FEM 3D View

Show above is example of four jacket foundations carrying the same platform of 7.4m diameter.

The water depth is increased 5m between the models, corresponding to one more leg is

designed for the foundation (npoints = 3, 4, 5 and 6).


Figure: Elevation of jacket foundations

Input of levels and radii is shown as an example for the jacket 40m. The radius at each level is

reduced 500m from the bottom, and keep constant 3500mm at the topmost two levels. Thus,

the vertical inclining can be varying individual from the one to the next level by given two radii

to the points of the legs from centre of the jacket foundation.

The piles are design in three elements fixed to the bottom of the legs. The two lowermost

elements have 2500mm length with V-shaped form towards the seabed. The case of longer pile

below the seabed it is just the parameter of height of piles to be modify in input.


ICDAS offer also verification of elements of the jacket foundation according to

ICDAS Basis of Design for a given site condition (design and static documentations).




Figure: Jacket foundations, Input elevation


Figure: Jacket foundations, FEM Top view





123456789_123456789_123456789_ Natural mode shapes and frequencies jacket foundation 

Infinite stiff support (2.018Hz)

Finite stiff support (0.393Hz)


Figure: Natural frequencies depending on support conditions.


Example of jacket foundation (Height, diameter top, diameter bot) = (40000, 14000, 7000)mm  


Shows above are the 1st mode shape of the two assumptions of support. The case of fixed support

the bottom points are fixed. The case of finite stiff support (linear) the bottom points are vibrated up

and down according to the assumed linear springs 10000kN/m translation and 10000kNm/rad rotation.

This numerical test shows that the ratio of natural frequency is up to 2.018/0.393=5.1 between the cases.

The following remarks can be drawn:


§       Soil-structure interaction needed to analysis at the points assuming to be support. The soil surrounding

      the pile element (here assumed point) does not keep the pile moving up and down with the same force,

      as assuming with linear spring kUZ=10000kN/m. It is about the shear modulus G of the soil and also

      the external actions on the structure.

§       Natural frequency of the full model is lower with the structural turbine and components model above

      the jacket foundation.

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Updated 17-07-2016