topic Re: Bridge Columns - Openings in Robot Structural Analysis Forum

Bridge Columns - Openings

Anonymous — Mon, 06 May 2013 14:08:31 GMT

Hi i want to modelate the columns seen in the atachment. They belong to a bridge and they make the connection betwen the arch and the deck. The problem is that i´m using a bar model and i dont know how to do it. The only away i came up with is to create a secction with a width equal to the sum of the massive parts not counting with the opening.

Re: Bridge Columns - Openings

Rafal.Gaweda — Mon, 06 May 2013 14:07:40 GMT

Attachment missing

Re: Bridge Columns - Openings

Anonymous — Mon, 06 May 2013 14:12:01 GMT

Sorry i forgot. Its there now 🙂

Edit: I forgot to mention that the main objective of the model its to do a modal analysis.

Re: Bridge Columns - Openings

Anonymous — Mon, 06 May 2013 16:18:43 GMT

hm can anyone help me?

Re: Bridge Columns - Openings

Rafal.Gaweda — Tue, 07 May 2013 07:10:56 GMT

Maybe like that.

(It depends how the rest of structure is modeled)

Re: Bridge Columns - Openings

Rafal.Gaweda — Tue, 07 May 2013 07:22:02 GMT

or this way:

Re: Bridge Columns - Openings

Anonymous — Tue, 07 May 2013 09:03:56 GMT

Thanks a lot for the answer. You can see how the rest of the bridge is being modeled on the attachment. Witch of the approaches do you think is the best? I´m thinking in the second one.

Thanks a lot 😄

Re: Bridge Columns - Openings

Anonymous — Tue, 07 May 2013 09:18:03 GMT

here´s one more foto of the brige so you can have a better idea of what i´m talking about.

Re: Bridge Columns - Openings

Rafal.Gaweda — Tue, 07 May 2013 10:40:56 GMT

Now, it is more clear.
Second approach much convenient.

Re: Bridge Columns - Openings

Anonymous — Wed, 08 May 2013 16:14:20 GMT

Hi I´ve created the model. Unfortunately the results I am receiving are absurd. Plus for some reason I´m getting instability of type 3 on one of the nodes. I believe the problem i on the rigid links created, Can you give me some tips of how to fix it?

I´ve attached the model. Sorry for all the bother.

Thanks for all the help .

Re: Bridge Columns - Openings

Rafal.Gaweda — Thu, 09 May 2013 06:50:21 GMT

This instability can be neglected

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Instability/m-p/3855698/highlight/true#M12465

in your case

Stiffness matrix diagonal elements
Min/Max after decomposition:3.034729e+004 2.523399e+020

if you replace all sections by C 18x18 it will disappear(Min/Max after decomposition:8.557681e+005 9.945693e+015 ).

Re: Bridge Columns - Openings

Anonymous — Thu, 09 May 2013 08:00:38 GMT

OK thanks. But still, the results for the modal analysis are absurd. Look at those modes of vibration. Can you find a reason for that?

Thanks a lot.

Re: Bridge Columns - Openings

Rafal.Gaweda — Thu, 09 May 2013 11:50:04 GMT

I do not know how you did it but rigid links between nodes 208to214 216to218 224to226 232to234 240to242 248to250 260 274 281 302 309 are either corrupted or not well defined or ....

Corrected file attached.

Re: Bridge Columns - Openings

Anonymous — Thu, 09 May 2013 12:15:59 GMT

Again Thanks for all the help 😄