Grasshopper

algorithmic modeling for Rhino

Hello everyone.

I'm new to Karamba and I'm wondering if it is possible to optimize the cross-section of a shell, but not by picking from a list of standardized cross-sections.

The picture below is that of the attached example file from Karamba.

I have three questions:

1) How can you visualize the chosen cross-section from the Optimize Cross Section component?

2) Can Karamba perform an optimization on the cross-section, in order to obtain a freeform cross-section?

3) If yes, can Karamba also vary this freeform cross-section along the length of the bridge?

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Hi Clemens,

I have the same problem with replying you.

This is the definition but I used Kangaroo for the form finding. 

Please let me know if now it's better.

Thanks a lot,

Marinella

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Dear Marinella,

for some reason, when I open your definition there are many components missing. Could you please internalize the geometry and remove dependencies from all plug-ins except Karmba3D?

Do you use Rhino5 or 6?

Best,

Clemens

Hi Clemens,

I baked everything from other plug-ins and I run the simulation.

Now it should work.

Thanks a lot,

Marinella

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Hi Marinella,

the reason why a constant shell cross section resulted from the above definition was that the smallest cross section was already sufficient for the given loads.

In order to see a variation of cross sections, the range of thicknesses needs to be adapted (see attached definition).

Your mesh looks a bit coarse. Test the effect of a refined mesh. Also consider non-symmetric loads due to e.g. wind.

Best,

Clemens

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Hi Clemens,
thanks a lot for your answer.

I opened the definition but there is this error. "236 cross-sections need to be bigger than their biggest family members".
If I am not wrong I've already added different load cases like wind load, anyway I try to change something.

Thanks a lot,
Marinella

Hi Marinella,

in that case you have to increase the upper bound of the number range which limits the maximum shell thickness at the 'Cross Section'-component.

Best,

Clemens

Hi Clemens,
sorry If I am bothering you with these questions but I'm trying to understand how to control better this process: if I want to reduce the stresses (in my case I want to reduce tensile stresses) generated on the structure the only way to do in the case of this optimization is to change the range of thickness? Or is there another way to optimize it as an objective?

Thanks a lot.
Marinella

Hi Marinella,

there are two options for lowering the stresses: either reduce the value for 'MaxUtil' or set 'MaxDisp'. Both input-plugs are part of the 'Optimize Cross Section'-component. See the manual for details.

Best,

Clemens

Hi Clemens, 

after carrying out the optimization of cross section, to run the analysis in order to get stresses on the structure can I connect "analyze" component directly to the model output of "opticrosec" component? Or do I have to connect the analyze component in the model output of "disassemble" component? Because I tried to do both and the results of principal stress1 of shell view are pretty different from each other.

Thanks a lot,

Marinella

The model which comes out of the cross section optimization component has displacements and stresses calculated. It is not necessary to add an 'Analyze'-component. The reson for the difference coud be that there was a problem in the disassemble-assemble process.

Best,

Clemens

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