topic Problem with calculation nodes in Robot Structural Analysis Forum

Problem with calculation nodes

Anonymous — Fri, 11 Jan 2013 03:23:30 GMT

Hi guys,

I'm getting large (220kNm) moment in bracing!

It seems that the moment is coming from shear in the beam crossing almost mid brace;

Calculation nodes are being applied at the intersection of diagonal members which it should not be doing. Where members 492 and 493 intersect 106

The settings are not turned on to allow this. So it seems strange calculation nodes appear.

When I copy the 3 members to a sub-model and re-analyse, the problem goes away.

Can you guys explain why the forces are being transferred through calculation nodes that should not be there?

Model attached in private message.

Cheers,

Tony

Re: Problem with calculation nodes

Anonymous — Fri, 11 Jan 2013 04:02:15 GMT

Update,

I did the CTRL+A and paste into a new model trick. This did not stop the problem. The only thing that made the problem go away was adding the bracing members to the "Bars neglected in generation" list.

Cheers,

Tony

Re: Problem with calculation nodes

Artur.Kosakowski — Fri, 11 Jan 2013 15:03:08 GMT

The only thing that made the problem go away was adding the bracing members to the "Bars neglected in generation" list.

and this is what should be done ~~as the vertical/horizontal intersection includes also vertical/horizontal~~ to avoid intersection of the horizontal cladding with diagonal bars

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

Re: Problem with calculation nodes

Anonymous — Fri, 11 Jan 2013 11:37:38 GMT

Artur,

Sorry, I disagree with your answer and also your screen capture.

I set up two system with same load, one has perpendicular members, one has angle of 135deg

Picture 1 - Setup

See results below;

Picture 2 - With "normal" settings

Picture 3 - calculation nodes

Picture 4 - With both diagonal and vertical intersection checked ON.

By your explanation, picture 2 should show bending moment on ALL 4 bars. I only ever get bending moment on 3 of them. I use this as one of the first examples I do when teaching people how to use Robot. I have NEVER had diagonal bracing form a connection with a horizontal member UNLESS I turn on the checkbox to achieve it.

Regards,

Tony

Re: Problem with calculation nodes

Artur.Kosakowski — Fri, 11 Jan 2013 14:58:26 GMT

Tony,

I'm sorry my mistake. Of course it should be the intersection with the cladding (498). I will remove the attachment and update my previous answer so that nobody gets wrong information any more.