Grasshopper

algorithmic modeling for Rhino

Hi Guys, I am working on a project about cable nets on Kangaroo. I found the form of the net with Kangaroo and now I would like to do a FEA with Karamba. Is it possible?

I am having some difficulties because it's like if on Karamba my beams (which are trusses) are recognized only in their initial form and not in the one I found with Kangaroo. How can I do a FEA on the final form I found? 

I have also another question about the supports. To assemble the model I had to create the supports but I think they are not correct but it was the only way to assemble the model. My cables work as trusses with only axial forces and my anchors of Kangaroo cannot be recognized by Karamba as supports.

Thanks in advance,

Roberto 

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Hi Roberto,

your definition does not contain a geometry - I think you forgot to internalize it.

I am not a Kangaroo expert, but in Kangaroo2 one can feed geometry via the 'Show'-component into the solver which then gets co-deformed (see attached definition).

Best,

Clemens

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Hi Clemens,

thank you for your reply.

Sorry I forgot to attach the rhino file. Please, find attached it now.

I tried to put the Show component into the solver but nothing happens.. maybe I am wrong with it.

My problem is that now that I found the form with Kangaroo, I would like to study the FEA of it. I could do it if I create the whole model with the new coordinates I found with Kangaroo on Karamba. In this example I am showing you it is very easy because the example is simple but I think it could be a problem if my project would be more tricky than this. 

Thank you again in advance,

Roberto

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Hi Clemens,

I tried to create the same cable net in the final configuration on Karamba abandoning, at the moment, the idea of doing the form finding and the finite element analysis together.

I am having some difficulties with the "Model" because it doesn't work and I think it's due to the fact I am wrong with the supports.

What kind of supports should I use with trusses since that they could have only axial forces? I put the toggle "False" in the "ModifyElement" in order to have trusses and not beams. So I didn't think I have to choose supports too since that trusses have only axial forces. 

Where am I wrong?

Thanks in advance for your help!

Best,

Roberto

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Hi Roberto,

I just looked at the definition quickly and noticed that you have separate models for each cable. You need to make sure to combine everything into one model so that Karamba calculates it as one system.

Please see the definition I uploaded.

best regards,

Matthew

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Hi Matthew, 

thank you so much for your answer. Now, I understand what I was wrong.

Thanks a lot again!

Bests,

Roberto

The only doubt I still have is if it's correct how I am applying the axial loads on the cables. Because from the "Results" I am seeing that everything is 0 and it could be since that the cables are in equilibrium but trying to apply axial forces it is still 0 so am I not applying it properly?

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Hi Roberto,

The point load you define goes directly into the support. Use a pre-strain load to create axial forces (see attached definition).

Best,

Clemens

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Ok now I see what you mean. Thank you so much Clemens! 

Best,

Roberto

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