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Message 1 of 6
dJStefan
1078 Views, 5 Replies

Instability type 3

I've been working through a model and sorting out instabilities and I've reached a point where if I release (pin) any more members I get a type 3 instability somewhere else in the model.  After reading this thread I've made a copy of my model and changed all the members to one section size.  This seems to get rid of my instabilities.  Does this mean I can ignore the type 3 instabilities in my real model?

My model is 95MB so haven't been able to upload it.

5 REPLIES 5
Message 2 of 6
Rafal.Gaweda
in reply to: dJStefan
Message 3 of 6
dJStefan
in reply to: Rafal.Gaweda

Ok, I've saved the model without results and zipped it and it should be accessible by this link:

https://www.hightail.com/download/OGhjb256Y1MzS29LSk1UQw

Note that currently I am getting a type 3 instability in node 758 direction RZ.  This is because I have changed the releases of bar 3553 to xxxxff. If you moment connect this member then the instability goes away.

I currently have lots of bracing members which are moment connected but need to be pinned members (preferably with a torsional release at one end too).  However if I pin any of them then I get instabilities, but If I change all the section sixes to the same section then the instability goes away.

I would very much appreciate your thoughts on this!

Thanks

Message 4 of 6
Rafal.Gaweda
in reply to: dJStefan

mathematical instability - ignore it

if you change all sections onto CHS 406.4x10 instability is not reported



Rafal Gaweda
Message 5 of 6
dJStefan
in reply to: Rafal.Gaweda

Thanks for the response.  I thought that was probably the case but how can I tell if it is an error I can ignore or an error which needs to be addressed?

Message 6 of 6
Rafal.Gaweda
in reply to: dJStefan

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