Instability Type 2 in Curtain Wall Model

[SamKa85]

Hello, 

I am trying to analyse an aluminium curtain wall in Robot but I am getting instability type 2 in Ry direction ( and sometimes in Rz direction) at several nodes. I tried to remove the bars connected to these nodes and re-drew them to make sure no separate structure is present but I am still getting the warning message . 

Could anyone have a look at the rtd file and shed a light on what might be the cause of this warning message?

Thank you 

[Artur.Kosakowski]

Try to redefine the releases e.g. like that:

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.

[SamKa85]

Thank you for your reply. 

I have followed your instructions and applied a rotation release about z axis (Rz ). Now, I am not receiving the warning message but the the horizontal members (transoms) are still showing end moments which is not correct. 

Attached is the modified rtd file. 

[Artur.Kosakowski]

I'm sorry my mistake. Please restore your original definition of releases but change the definition of the support.

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.

[SamKa85]

I have restored the bar releases to xxxfff and changed the definition of supports as follows: 

Top Supports: 

Fixed directions: Ux, Uy, Uz & Rz

Mid & Bottom Supports: 

Fixed directions: Ux, Uy & Rz

Now, I am getting the following error message: "excessive releases at the bar" 

Attached is the rtd file. 

[Artur.Kosakowski · Accepted solution]

The default pinned - pinned release definition is:

This is to avoid a bar rotation about its own axis.

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.

[SamKa85]

Thanks Artur, 

This worked for me but now I have a query: 

I have understood why Rx in bar releases should not be released but I could not figure out why Rz should be blocked for roller support (Mid & Btm supports).

Also, I re-did the model from scratch but now, for some reason, planar loads applied on cladding are not being distributed to bars and hence the moment diagram for the frame is not generated. 

P.S. We have just upgraded to RSA 2013 so I do not know if this has any effect.

[Artur.Kosakowski · Accepted solution]

I have understood why Rx in bar releases should not be released but I could not figure out why Rz should be blocked for roller support (Mid & Btm supports).

To prevent the vertical bars to rotate along their own axes. You may add that to the top support instead if you prefer.

Also, I re-did the model from scratch but now, for some reason, planar loads applied on cladding are not being distributed to bars and hence the moment diagram for the frame is not generated. 

It seems that you accidentally created them as acis objects that are intended for solids. Try the followindg steps:

1. Delete them

2. Open Preferences and mark View Parameters

3. Switch off the default definition in the Solid modeler format

4. Save the file under a new name

5. Restart Robot

6. Open the file and define the claddings again.

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.

[SamKa85]

Thank you for your support and help 

Just to clarify 

"To prevent the vertical bars to rotate along their own axes "

Does this mean  

preventing the vertical bars from rotating about their local axes X (i.e.  about Z in global axes in this case)

Or

preventingthe vertical bars from rotating in ZY plane in glabal axes ?

[Artur.Kosakowski]

The prior.