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PaulGrimes2282
Posts: 41
Registered: ‎05-28-2012

Instability errors in model with no releases

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10-08-2012 02:11 AM

I have a model which was created by a colleague of mine and i've now taken over. It was giving instability errors, and i could not get rid of them so i went through and deleted all the releases but i was still getting instabilities.

 

Is there any common reason that this might happen? If not would someone be able to have a look at the model and see if they can find any errors in it that might be causing this? I will upload it somewhere if so.

 

thanks!

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Active Contributor
PaulGrimes2282
Posts: 41
Registered: ‎05-28-2012

Re: Instability errors in model with no releases

10-08-2012 02:47 AM in reply to: Rafal.Gaweda
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Rafal.Gaweda
Posts: 5,189
Registered: ‎04-26-2010

Re: Instability errors in model with no releases

10-08-2012 08:33 AM in reply to: PaulGrimes2282

IN short - too many or wrong releases in some (many) nodes.

It will take me some  time to correct.



Rafal Gaweda
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Active Contributor
PaulGrimes2282
Posts: 41
Registered: ‎05-28-2012

Re: Instability errors in model with no releases

10-09-2012 02:07 AM in reply to: Rafal.Gaweda

Yes - i thought this might be the case. But when I removed all the releases I was still getting instability errors - is there some further underlying problem?

 

file with no releases:

 

https://www.yousendit.com/download/TEhYZm1kbThCMTd2WnRVag

 

 

 

Thanks for looking into it.

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Rafal.Gaweda
Posts: 5,189
Registered: ‎04-26-2010

Re: Instability errors in model with no releases

10-09-2012 02:28 AM in reply to: PaulGrimes2282

Should I correct file with releases or not?



Rafal Gaweda
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Rafal.Gaweda
Posts: 5,189
Registered: ‎04-26-2010

Re: Instability errors in model with no releases

10-09-2012 02:29 AM in reply to: PaulGrimes2282

 I was still getting instability errors - is there some further underlying problem?

 

 

merge nodes 796 1402

 



Rafal Gaweda
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Rafal.Gaweda
Posts: 5,189
Registered: ‎04-26-2010

Re: Instability errors in model with no releases

10-10-2012 01:53 AM in reply to: Rafal.Gaweda

Model corrected http://wtrns.fr/oZNEZn3anfttNz - check diagrams etc.

I have removed some releases, new releases added : PP  and Fixed Pinned no rx ; nodes merged.



Rafal Gaweda
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Active Contributor
PaulGrimes2282
Posts: 41
Registered: ‎05-28-2012

Re: Instability errors in model with no releases

10-10-2012 08:47 AM in reply to: Rafal.Gaweda

Hello, thanks for your help so far. However when I open your fixed model and run it – I get a warning that says ‘Matrix is not positive definite’. This suggests that the model is unstable? (see image below)

 

<error1.PNG>

If I run the analysis with the DSC Algorithm turned on then I am still getting unstable nodes where they should be stable. (see image below)

 

<error2.PNG>

 

Is there any reason why this would be happening for me, but the model runs cleanly for you?

 

Thanks!

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Rafal.Gaweda
Posts: 5,189
Registered: ‎04-26-2010

Re: Instability errors in model with no releases

10-10-2012 09:05 AM in reply to: PaulGrimes2282

PaulGrimes2282 wrote:

Hello, thanks for your help so far. However when I open your fixed model and run it – I get a warning that says ‘Matrix is not positive definite’. This suggests that the model is unstable? (see image below)

 

Read the warning to the end ... check buckling.

 

Critical coeffs below 1 for nonlinear selfweight - check "upper branches of trees"

 

bucklingtrees.jpg

 



Rafal Gaweda
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