Identifying the compressional members in a space frame?

Ok this is what I would like to do:

Is there a way to determine which members of a space frame are compressed, and then replace those compressed one with new ones? For example all the members of the space frame structure have tube cross sections. And I would like to determine which one of them are under the compressional load, and then increase the size of their cross sectional area.

Is this possible to do in grasshopper and Rhino tools, addons and scripts?

Thank you.

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Replies to This Discussion

Permalink Reply by djordje on February 12, 2011 at 6:05pm

Is that possible?

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Permalink Reply by Jacek Jaskólski on February 13, 2011 at 9:34am

Hi Djordje,

Is this what you're after?

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Permalink Reply by djordje on February 13, 2011 at 6:51pm

YES, this is what I am looking for !!!

I downloaded your karamba_test04.ghx, and .3dm files, and I can not figure out how to select the compressional members only, in order to change their cross sections.

Permalink Reply by Chris Tietjen on February 13, 2011 at 9:14pm

Chris

Attachments:

Space_frame_Karamba2.png, 276 KB

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Permalink Reply by djordje on February 14, 2011 at 5:41am

Thank you Chris. It seems I do owe a couple of beers to each member in this topic.

So, the code now continues from me past compressional members "Line" parameter? How can I do the same effect like Jacek did, in his last reply two posts above this one?

Permalink Reply by Jacek Jaskólski on February 14, 2011 at 12:54pm

Here's the definition for the example above.

It's a bit messy, didn't have time to clean it up.

btw. here's the video with increasing loads on the space frame.

btw2. I'm pretty sure that you can check multiple load scenarios within one gh definition by inserting additional karamba assemblies... haven't testet it though.

Attachments:

karamba_test05.ghx, 754 KB

Permalink Reply by Jacek Jaskólski on February 12, 2011 at 5:43pm

Hi guys,

This is a very interresting and practical discussion.

I took a shot at the problem using Karamba, here are the results:

(left: load&support case, right: stress identification; red=compression, blue=tension, black=zero or very little stress (there's an adjustable treshold slider for that))

the members are dispatched into separate lists according to stress types, so you can easily apply different cross-sections - see attached definition.

Cheers,

Attachments:

karamba_test04.3dm, 33 KB
karamba_test04.ghx, 373 KB

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Permalink Reply by djordje on February 14, 2011 at 3:39pm

Thank you for the file Jacek.

But that one you gave me, automatically creates a space frame structure. I want to assign a compressional members on my own structure, drew in Rhino. So I want to draw a space frame structure in Rhino, on my own, then apply the nodal loads and support positions (in this case with Karamba), and then to identify the compressional members and continue to edit them, further.

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Permalink Reply by Thorsten Strathaus on February 14, 2011 at 3:59pm

Hi Djorde,

since Karamba does not allow Loadgroups at the moment and you are using Rstab/Rfem, I would recommend the use of the implemented scripting interface "RS-COM".

We did this several times to create Rstab analysis models directly out of Grashopper and evaluate the results/change the design. These result data (negative/positive normal forces for tension or compression) could affect your definition in grasshopper and create elements which will get only tension forces or increase the size of its section.

The "RS-COM" interface is basicly written in VB, examples and the documentation is available at http://www.dlubal.de/download/manual/de/rs-com10.zip

Thorsten

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Permalink Reply by Daniel Piker on February 14, 2011 at 4:08pm

Did you take a look at the file I posted the other day ?

It does exactly this - takes a spaceframe you draw in Rhino, applies loads and supports of your choosing, and separates them into tension and compression members.

Guess I should have posted a screenshot...

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Permalink Reply by djordje on February 14, 2011 at 6:29pm

@Daniel Piker:

Sorry mate, I did not. I will take a look at it, during the day tomorrow. My intention was not to be unpolite, or to ignore your post, it's just, I am quite busy these days, and even 5 minutes of my spare time are fortune. I saw a screenshot of Jacek's work, and it looked interesting. Sorry if I insulted you in any way, by did not download and check your files. That was not my intention.
Which one of these replies of yours, do you have in mind: the one from the 6:22am or 6:51am 12th of February?

@Thorsten Strathaus:

Thank you for the files, I will do a thorough insight tomorrow.
And what about the license? As far as I know, all RFEM/RSTAB add-ons need to be paid. What about this one?