Wind turbine - rotational stifnness

[totutomek]

Hello

I'm working on windturbine foundation.
There is one criteria that rotation stiffness ratio have to be more than 6*10^10 Nm/rad.
Do you know how to assume that value properly ?
Do you know any computational solution?
I have: demensions of foundation, ground conditions (mostly clay, sandy clay), loads on the buttom of foundation.

Thank for your help

Best Regard
TOM

 

[FixedEarth]

You need to get a copy of the RISOE publication-"Guidelines for Design of Wind Turbines" latest edition. Luckily for you, the pages you need are posted here by the publisher:

http://www.risoe.dk/en/business_rel...hvervskontakt/VEA/Documents/Page_204 205.ashx

 

[Mccoy]

It's interesting to realize that the posted RISOE formulas, even though wind turbines are undoubtedly a significant source of vibrations, do not include the imaginary term of the spring-dashpot equation, which models the damping phenomena in such a configuration (see for example Gazetas, 1991 in Feng: FEH).

I reckon that might turn out to be overconservative especially in soft soils, where damping phenomena are significant.

Also, that way if there is a strong acoustic impedence contrast, eventual multiple refraction and reflection phenomena are ignored, and this would result in an underconservative design.

Unless dynamic conditions are illustrated in other parts of the same publication.