Grasshopper

algorithmic modeling for Rhino

Help with Converting Parametric Building Model to Elements for Assemble Module

Hello! I'm an undergrad working on a summer research project with the aim of minimizing embodied carbon by optimizing the material quantities used in a low rise concrete building.  I am totally new to structural modeling, but Karamba and Galapagos seem promising for this application.  With the help of some video tutorials, I have created a basic parametric model building in Grasshopper that has floor slabs and columns and sliders to change the number of floors among several other parameters.  But even after watching tutorials and looking through the Karamba manual, I'm struggling with converting that model into the list of beam and shell elements that must be fed into the Assemble module that allows you to see the results of adding loads.  I'm also trying to calculate the overall volume of materials used in the building, because we are trying to optimize the volume of materials used versus the useful interior space of the building.  My .gh file is attached and any help or direction to additional resources would be appreciated.  Thanks! 

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Hello Tess Hegarty, the attached definition contains the Karamba model. The easiest way to get the volume is use the mass which comes out of the assemble-component and divide it by the mean material density.

Best,

Clemens

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Clemens, thank you so much for the quick and thorough reply!  This is exactly what I was looking for, and I'm looking forward to learning more about Karamba as I work with it.  Thanks for the tip about calculating the volume as well, makes a lot of sense.

Best, 

Tess

Hi Clemens,

Is it the same if we use the G (resulting force of gravity = weight in KN for the gravity own weight load case) coming out from the Analyze ThI component and then dividing by the material density ? instead of using the mass then multiplying by g = 9.81 m/s2 to get the weight then dividing by the material density ..

What do you think ?

Thanks ..

the physical unit of density rho is e.g. kg/m3, the specific weight gamma of a material is e.g. measured in kN/m3. In order to arrive at the volume you can either use the total mass M of the structure (V[m3] = M[kg]/rho[kg/m3]) or the total weight W (V[m3]=W[kN]/gamma[kN/m3]). The total mass has the advantage that you get it after assembling the model whereas for the weight you have to analyze the structure.

Best,

Clemens 

Hello Clemens,

Sorry for posting in the old topic but I am trying to calculate volume of my structure and have some problems. I can see that assembled model has Mass output, but Karamba materials don't include density rho. On the other hand they include gamma, but after analyzing structure (TH1) I do not see weight output.

I could just check tables for density rho for my material but I am optimizing both cross sections and materials (reinforced concrete - values would be estimated by % of steel used) - f.ex two possible classes of concrete + 2 types of steel. That gives 4 combinations and estimating density could get problematic.

Have you got an idea how i could encounter that problem?

Hello Wujo,

you could disassemble the model and assemble it again, using only one custom material for all elements.

Best,

Clemens

Hi again Clemens!  So I've been refining my parametric building model, and one change that I've been struggling with is making the columns decrease in width as the number of stories increases.  For example, the columns are a 40 cm x 40 cm square for the first two floors and then a 35 cm x 35 cm square for the third and fourth floors, etc.  I have been able to figure this out for 2, 4, and 6 floors but not beyond, due to the following error when I tried to make an 8 floor model: Singular Stiffness-matrix: Can not solve static system.

It's also "hard coded" so floor number no longer works as a parameter (I have to make a new file for each number of floors, which is not ideal).  I'm wondering if there is an easier/better way to achieve this goal?

My .gh files for the 6 floor building and 8 floor building (which produces the error) are attached.  Any suggestions or ideas?  Thanks in advance!

Best, 
Tess

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Actually, I figured out why I was getting that error message for my 8 story setup, so nevermind about that part.  Any suggestions to to improve the setup of my model would still be appreciated though!

Thanks,

Tess

There is a Karamba example called 'OptimizeBeam.gh' in the installation folder of Karamba under 'C:\Program Files\Rhinoceros 5.0 (64-bit)\Plug-ins\Karamba\Examples\WebsiteExamples'. It contains a custom C# component which calculates the optimum circular cross section for given section forces. You could use this for designing the columns. 
If there are no shear walls or wind bracing in your building, the horizontal forces (e.g. wind, earthquake) cause bending moments in the columns and thus govern the column design. You could apply wind - say 1kN/m2 - via the Meshload-component.

Best,

Clemens

Thank you for the advice, I will give those suggestions a try.

Best, 

Tess

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