Loads on full model Detailed knowledge of loads must be available for definition and assignment on LUSAS FEM model. They are: - Wind load (velocity and direction) - Wave load (height and period) - Water level - Flow load (velocity and direction)
The external loads can be simplified to single concentrated actions on the foundation as show to the right. It yields the following considerations, cf. [2] § Vertical, shear forces and significant overturning moments are transmitted to foundation by tower
§ Must be resisted within tolerances for foundation settlement and tilt
§ Manufacturers typically specify horizontal and rotational foundation stiffness criteria
§ Loading direction changes with wind direction and nacelle orientation
§ Circular foundation shape is therefore optimal, but straight-sided (e.g. octagonal, hexagonal) is easier to construct
§ Anchors can be used to add rotational strength
Analysis of the results
List of task for full static documentation is outlined in ICDAS Basis of Design . In short, they are: - Phases analyse using LUSAS 15.2-3 new features
- Stresses in two directions in concrete cylindrical shaft element elements
- Verification of reinforcement and concrete thickness in SLS and ULS after Eurocode
- Natural mode shapes and frequencies
- Wave-induced seabed response around the foundation
Additional dynamic analysis - Natural mode shapes and frequencies of the wind turbine (including the foundation and the tower) depended on the selected type of foundation and the assumed properties of the subsoil. - Passive/Active damper installation on top of the turbine tower related to the lowest natural mode shapes of the entire model.
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