A simple definition using the 'BESO' and 'resulting element forces' - components of the latest release to evolve a topology and get evenly distributed axial stress.

is this addon something like sap2000 component? for frame structure ?

thanks for your reply.hope it will be as powerful as the general fea software, such as sap& midas. good job. i am learning it now.

Hello David, we will update Karamba as soon as possible.

I was wondering if Karamba can identify a compression members in a truss/space frame?
Is there a Karamba definition that will allow me to identify the compression members for any kind of truss or space frame?

For example, I want to select my truss/space frame from Rhino, then define the supports, nodal forces and some other parameters too, and then Karamba definition will allow me to get all members under the compression to be selected.

Can this be done in Karamba?

If it can, can anybody help me with it please?

Thank you.

Hey Najna,

this will do it:

... assuming you already built up your model. Your question was hypothetic? Karamba gives a multitude of results, including the ones you asked for. It also includes a BESO-designer considering the characteristic 'force' of your choice (bending, normal force, deformation energy...), and in the new release (to be available in the next days) also a 'Tensile / Compressive -designer' where you can set tension-only or compression-only elements (this technically also, like BESO, means a solution has to be found iteratively by the system).

Best, Robert

Thanks Robert :D

The solution you presented in the image means, that I need to add the parameter "curve" on the beginning of the your definition, then right click on it, "Set multiple curves" and select my whole space frame structure in Rhino. Then on the end I need to add the "data" parameter, which will gather all my members under compression?

Like this:

What about the supports and the nodal forces? How can I define them?

By the way the solution you presented is the one that works with Karamba 0.9.06? Karamba 0.9.06 is not compatible with Grasshopper 0.8.0051?

I have no problem in using your solution. Just I am curious: what will be benefits in using the solution in the newest Karamba in comparison to this one?

It's a little bit more. There are sample definitions for download at http://twl.uni-ak.ac.at/karamba/ that basically should provide what you need.

The new release also will contain better learning examples.

Here is a sample structure under self weight:

The green lines are the ones under axial compression.

cheers

Thank you Robert.

The last image you provided is from Karamba 0.9.06 or from the newest version that will be released in few days?

So basically I need to right-click on "Line" parameter, "select multiple lines" and select my whole space frame/truss structure in Rhino?

Then I need to right-click on "Point" parameter, and define the points in Rhine, where the supports will be.

And that is it? What about the nodal forces and choosing points in which they will be taken?

The sample files you mentioned are simple .ghx files. I think we need some sort of at least pdf tutorial or video for Karamba analysis.

I installed newest Grasshopper 0.8.0051 and newest Karamba 0.9.07.

I created the .ghx defintion the way you told me, but for some reason, my deformation does not look like yours. Take a look:

Can you help me? Where am I wrong?

Here are both .3dm and .ghx files:

Hey Najna,

the scale of your structure and the profiles don't match up. You either have to increase your profile heights with 'modify beam' component between 'line to beam' and 'assemble' or scale down your truss.

Hope you get where you want :)

Nice set of components. Could you tell me how you managed to add the drop down option box to many of yourcomponents? Im currently trying to release some components for Excel and the ability to use a dorp down box for optional settings would really stream line my components,

cheers

Thank you for advice. It worked! :)


The thing I am confused now, is the far left member. For some reason, the karamba does not treat it, nor as a member under compression, nor as a member under tension.
Why is that???

I see now. I have a "null" member. It has no force in it.

Sorry for disturbance.

Simple%20Beam%20Karamba.gh

Building a basic model to calibrate for a paper I am working on. I noticed that the length can cause issues with the model results. When it is set to 40m on the first slider, it doesnt work. Then set it to 39.75m and it works. This happens across the whole slider range at random points.

Have I missed something?

J

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

...

?

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.

Dear RubberDuck,

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

Clemens

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.

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.

Haha good timing Luke!

I am writing a paper on Parametric structural analysis and just ran through all my analysers to see where I went wrong. I have it pretty much the same.

Example - CHS 100mm x 4mm

Deflection Calcs:

Manual - 64.6m

SG - 60.6m

Karamba - 61.5

Egret - 74.3

Now I am CERTAIN Egret is a result of a bug (I sincerely doubt Jon has made an error and it has been playing up on my computer probably because its full of shit).

I ran another model at 50mm depth of CHS to see if they maintain similar ratios. They do. I wanted to check that I could use Karamba and Egret for Galapagos modelling, so they are both pretty good.

Thank you for the check, its good to have a second set of eyes on problems like this.

Karamba uses a Young's Modulus of 21000[kN/cm2] and by default the thickness is 1/30 of the diameter of the tube. For D=100mm this results in t=3.33333 (etc.).

If you set both values according to the hand-calculation below you get the exact result of 74.844504m.

Here the definition:

Hi Josh,

Thanks for the confidence, but I would certainly double check anything computed by Egret (I haven't had the time or opportunity I'd like to progress and validate it).  I did quickly set up your verification model, the file can be downloaded here:

http://www.grasshopper3d.com/group/geometrygym/forum/attachment/dow...

I would suggest updating Egret from http://www.geometrygym.com/downloads , if you do, you should also see a deformation of 74.844504 (my gh definition assumes mm rhino document units).  If you want to send me the spacegass model, I'll take a look at it for you.

Ok here are the modules I have used to verify.

Karamba Cantilever

Egret Cantilever

I just built the same model in SG:

30m Cantilever

Incaste

2kN point Load at end

And drew the section in the section creator based on the Chinese steel manuals (S235).