Subdyn usage for onshore concrete foundation

[GBA217]

Hi,

Is Subdyn capable of modelling an onshore concrete gravity-based shallow foundation defined using 6x6 mass, stiffness and damping matrix? If yes, how is it done?

Thanks in advance.

[jjonkman]

Dear @GBA217,

Can you clarify how you want to represent the concrete gravity-based foundation? If I understand correctly, you want to define 6x6 mass, stiffness, and damping matrices representing the rigid-body characteristics of the gravity foundation with tower cantilevered on top, and represent the hydrodynamic loads via HydroDyn; is that correct?

Best regards,

[GBA217]

Dear @jjonkman ,

Thank you for the clarification question.

You are correct about the first two points:
Yes, I intend to define the 6x6 mass, stiffness, and damping matrices to represent the rigid-body characteristics of the concrete gravity-based foundation.
And yes, the tower is considered cantilevered on top of this foundation.

However, regarding the third point, please note that the query is about an onshore wind turbine. Sorry if I'm missing a point here but I'm not sure how HydroDyn is relevant in that case. Could you please clarify? My interest is purely in modeling the onshore concrete gravity-based shallow foundation using Subdyn.

Best regards!

[jjonkman]

Dear @GBA217,

Thanks for clarifying. I typically think of concrete gravity-based foundations as for offshore applications; I didn't realize you were talking about an onshore foundation, but I see now that you mentioned that in the Issue title.

For your case, I would suggest enabling the external platform MCKF module (ExtPtfm) instead of SubDyn (CompSub = 2). With this module, you can specify the 6x6 mass, stiffness, and damping of the substructure directly through an input file. (You should keep only the 6 Guyan modes, disable all Craig-Bampton modes, and set the external force to zero, resulting simply in 6x6 mass, stiffness, and damping matrices.)

Best regards,