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Linear releases / instability check

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Message 1 of 12
michaelcpetersen
806 Views, 11 Replies

Linear releases / instability check

Hi guys

 

Can you take a look at the attached pictures and maybe see what my problem here is?

I think it has something to do with the use of releases.

All the plates are modelled as shell elements with one-way distribution of forces.

Only shear forces can be transferede to the walls in the longitudinal direction.

 

The model is 150mb so i could not upload it for you to check it in RSA.

11 REPLIES 11
Message 2 of 12

Also, my meshing options is:

Kinematic Links off and meshing parameters without regular...

 

 I found out what the problem with the load overlap was: X-direction of one-way shells was wrong so it could not distribute load to the steelframes.

 

Now i only have the secret hidden node and instability on the pictures...

 

Message 3 of 12

File please.


Rafal Gaweda
Message 4 of 12
Message 5 of 12

I do not think this is important distance in your model.

 

3mm.jpg

 

Corrected file here: http://we.tl/Ekr3r2e3hn 



Rafal Gaweda
Message 6 of 12

Hi Rafa

 

Thank you very much for looking into my model. Instead of just using your corrected model I would like to learn how to fix it myself.

I have made some geometrical changes to the model and have been able to delete the isolated nodes. The 3mm gab you found have also been corrected.

 

Now im stuck with the instabilities of invisible nodes, can you please explain how i can deal with it?

 

The new model is found here:

http://www.4shared.com/zip/qJNQwnxlba/rev_FEM_design_test.html

 

Thanks alot

Message 7 of 12

Please check http://forums.autodesk.com/t5/Robot-Structural-Analysis/Node-that-does-not-exist/m-p/4655919

 

I'm not able to download files from 4shared.com. If the above will not help you to solve the instability errors upload the fine on some other site please.

 

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.



Artur Kosakowski
Message 8 of 12

Here is another link:

Download

 

Im trying to use elastic linear relases to reduce the load transfered from the slabs to the wall. Is it possible to set a restriction on the join? Ex. 30 kN/m max transfered from slab to wall?

 

I can see on the deflection view that this model is not correct as it has a slip in the wall, see pictures. Can you help me correct this and get the connection between wall/slabs?

And please if possible explain how

 

Thanks

Message 9 of 12

Do you really want to apply releases for horizontal directions allowing for walls moving "under" slabs whereas bending moments are fully transferred from slabs to walls?

 

In addition i would recommend removing RX releases from bar elements. To correct model geometry run Detailed Correction option with adjustment to structural axes and re-mesh the panels.

 

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.



Artur Kosakowski
Message 10 of 12

Hi

 

No that is not really what i want, but i tried different solutions to get the horizontal force distributed better to the steel frame. My guess was that the walls have a much higher stiffness than the steel frames, which leads to almost all horizontal loads go into the wall.

 

If i want to reduce how much load that can be transferred from the slab to the wall, what release should i put on? An elastic release between slab-wall dosent seem to work for me.

Message 11 of 12

And another question.... You wrote that i transfer moment from slabs to walls, but in linear release dialog box i can see that RX is release (xxxf) so i do not transfer moment?
Message 12 of 12


No that is not really what i want, but i tried different solutions to get the horizontal force distributed better to the steel frame. My guess was that the walls have a much higher stiffness than the steel frames, which leads to almost all horizontal loads go into the wall.

 

In such case you perhaps a better solution is to reduce E for walls and remove elastic releases from walls? This should not influence the vertical loads transfer allowing the horizontal ones go to frames.

 

If i want to reduce how much load that can be transferred from the slab to the wall, what release should i put on? An elastic release between slab-wall dosent seem to work for me.

 

You cannot define nonlinear linear release - the equivalent would be to connect walls with slabs with short bars with such releases instead.

 

And another question.... You wrote that i transfer moment from slabs to walls, but in linear release dialog box i can see that RX is release (xxxf) so i do not transfer moment?

 

I'm sorry - my mistake. Writing this I overlooked the releases defined for slabs.

 

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.

 

 



Artur Kosakowski

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