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Message 1 of 14
1426229
647 Views, 13 Replies

panel releases

hi guys,

I get some abnormal bending moment for some of the elements in my model (see attached picture). As I found out on the forum, it has something to do with linear release. but when I try to add linear releases to panel,  I get type 2 and type 3 instablity. I have attached a test model. Thanks in advance.


13 REPLIES 13
Message 2 of 14
Leader_Mohamed
in reply to: 1426229

I see you released every element of your model
Message 3 of 14
t.sautierr
in reply to: Leader_Mohamed

Mohamed is right, many of your instabilities is coming from a too large number of release. Analyse your elements, at one node you have to let at least one element blocked for each dof otherwise the problem is unsolvable.

 

example : 3 in plane bars intersecting in one point (like 1026) cannot be released at each end.

 

Then if your still have problem -> post your corrected model.

Message 4 of 14
1426229
in reply to: 1426229

Thank for the answer!

I just want to illustrate hollow-core slab in the model, which spans one-way and have pinned-connection to supporting beams. I have modeled this configuration in other FEM programs and I get correct bending moment with parabol shapes, but in Robot, I have not succeeded to get the correct results. I followed t.sautier advice and, but still I can't get a parabol shape bending moment. for example, look at the bar 1341 of the attached model.

Message 5 of 14
Rafal.Gaweda
in reply to: 1426229

Model without significant instabilities (supports and some bar releaeses corrected) attached

Results as follows (if you want different results , apply different correct releases) : 

 

dk.jpg

 

 



Rafal Gaweda
Message 6 of 14
t.sautierr
in reply to: Rafal.Gaweda

Rafal, how did you set the pannel properties in order it is not working with the beam ? I mean it seems that you don't have this "saw tooth" effect on the moment as Tony mentionned in one topic.

Linear release Ux ?

Message 7 of 14
Rafal.Gaweda
in reply to: t.sautierr

Instabilities = wrong results
I have not corrected any panel. Corrected supports and releases on bars 1331 1332 1352


Rafal Gaweda
Message 8 of 14
t.sautierr
in reply to: Rafal.Gaweda

Oki doki.

Works fine.

 

But the pannel is working with the beams in this model as a composite section. 

I say that because I'm not sure that he is aware of that.

 

Shall have spare Ux release on pannel edges if this effect has to be suppressed

 

Message 9 of 14
Rafal.Gaweda
in reply to: t.sautierr

 

Shall have spare Ux release on pannel edges if this effect has to be suppressed

 

Your choice. But do it in the way not to make model \ panel unstable.

 

 



Rafal Gaweda
Message 10 of 14
t.sautierr
in reply to: Rafal.Gaweda

Which not an easy part when you have a big number of pannels ... have to be wise when you built up the model.

Message 11 of 14
Rafal.Gaweda
in reply to: t.sautierr

That's why this is soft for engineers, not secretaries.


Rafal Gaweda
Message 12 of 14
t.sautierr
in reply to: Rafal.Gaweda

What are you suggesting about my degrees? 😛

 

Message 13 of 14
Rafal.Gaweda
in reply to: t.sautierr

It has no relation to degree 🙂


Rafal Gaweda
Message 14 of 14
t.sautierr
in reply to: Rafal.Gaweda

Good point, I'm hesitating to kudo for that!

Let's there some good technical secretaries and some bad sales engineer 😉

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