Karamba3D

Comment

Comment by Lucas Epp on September 28, 2011 at 6:50am

Hi Joshua - I think part of the problem with your Karamba model may be the document accuracy - If you have a document with [m] units the tolerance is only +/-.001m by default in Rhino; Grasshopper uses these same tolerances.
The theoretical deflection of your cantilever beam is 

delta = P*L^3/(3*E*I)

= (2000 N) * (30,000 mm)^3 / (3*205000 N/mm^2*1173164mm^4)

= 74,844.5mm

So in your image below Karamba is slightly out, but your SpaceGass model is somehow much different or wrong - have you checked your material /section properties?

I did a quick model in Karamba with the document in [mm] units and got a deflection of 73,062.5mm which is only a 2.5% difference from the theoretical answer.  I did a quick model in Autodesk Robot as well and got exactly 74,844.5mm deflection as expected.

Comment by Joshua Seskis on September 28, 2011 at 5:43am

I have set up this model for a Cantilever with a 2kN point load. Displacement is 72m for a 30m CHS 100x3.3. I then set up the same model in SpaceGass and get the following results:

 

How do you calibrate your models? I am just trying to work it out so I can start using this for my paper on parametric structural analysis.

Comment by Karamba3D on September 28, 2011 at 5:29am

Dear RubberDuck,

Christoph will make a separate assembly of the custome components and publish it on Food4Rhino. But this may take some time.

Clemens

Comment by Joshua Seskis on September 28, 2011 at 4:10am

Effectively thats right. If you have two pins in the same support plane then the second pin will restrict the model from utilising the rollers.

 

Restraint conditions are, in my opinion, one of the trickiest things to understand when you start modelling.

Comment by Najna Sorin on September 28, 2011 at 3:40am

Thank you for the tip Joshua.

So If I want to lean my space truss on:

2 supports, I need:

1 pinned and 1 roller support?

 

3 supports, I need:

1 pinned, and 2 roller supports

 

4 supports, I need:

1 pinned, and 3 rollers supports

 

5 supports, I need:

1 pinned, and 4 roller supports

 

...

 

?

Comment by Joshua Seskis on September 28, 2011 at 3:10am

Might be valuable to those playing with this. If you don't understand how these affect your model you might want to do some research on statics and have a read of this little pdf here.

Comment by Joshua Seskis on September 27, 2011 at 4:04pm

Thanks, That was dumb of me. Model Working.

Comment by Karamba3D on September 27, 2011 at 1:44pm

Joshua, fix the beams rotation about its longitudinal axis (Rx) at one support then your example works. Otherwise the example is kinematic.

Comment by Karamba3D on September 27, 2011 at 1:39pm

we have examples and will upload them on the karamba website as soon as possible.

Comment by Joshua Seskis on September 27, 2011 at 8:40am

Do you have functioning models we can use to learn with? I looked on the website but I couldn't find any. It would be a very useful learning tool especially for a simple problem like a beam so we can start calibrating our results against other software i.e. space gass.

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