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Valued Contributor
Jorgew09
Posts: 52
Registered: ‎01-11-2012
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instability type 3 RX direction

1502 Views, 16 Replies
03-09-2012 05:23 AM

When I calculate my modell i get the following error: instability of type 3 in RX direction

I have looked at the node but everything seems to be correct. I the releases box I have tried to tick off RX, but that did not help.

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Rafal.Gaweda
Posts: 5,070
Registered: ‎04-26-2010

Re: instability type 3 RX direction

03-09-2012 06:05 AM in reply to: Jorgew09

Open calculatin Report , find there Max min values on stiffeness matrix diagonal and write here these two values.



Rafal Gaweda
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Valued Contributor
Jorgew09
Posts: 52
Registered: ‎01-11-2012

Re: instability type 3 RX direction

03-09-2012 06:31 AM in reply to: Rafal.Gaweda

Min/Max after decomposition:    7,463808e+006         6,847539e+019

precision: 1 

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Rafal.Gaweda
Posts: 5,070
Registered: ‎04-26-2010

Re: instability type 3 RX direction

03-09-2012 07:04 AM in reply to: Jorgew09

if the difference between these values is greater than 1e11 \ 1e12 program reports instability number 3.

It is related to big differences in stiffenes of elements for example very short elements exist in model = some inaccuracies.

You can check it this way: on dummy model select everything, make intersection, then open Bars table on View tab. Find shortests bars. Then locate nodes \ places on original model and correct location of nodes.

If it is not the case. Send me model. You already know how.



Rafal Gaweda
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Valued Contributor
Jorgew09
Posts: 52
Registered: ‎01-11-2012

Re: instability type 3 RX direction

03-09-2012 07:15 AM in reply to: Rafal.Gaweda

I don't understand how to do what you told me to do

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Valued Contributor
Jorgew09
Posts: 52
Registered: ‎01-11-2012

Re: instability type 3 RX direction

03-09-2012 07:28 AM in reply to: Jorgew09

I'm sending the file:smileyhappy:

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Rafal.Gaweda
Posts: 5,070
Registered: ‎04-26-2010

Re: instability type 3 RX direction

03-09-2012 07:33 AM in reply to: Jorgew09

Example below

 

leng.jpg

 

 

If not - send me the file. 



Rafal Gaweda
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Rafal.Gaweda
Posts: 5,070
Registered: ‎04-26-2010

Re: instability type 3 RX direction

03-09-2012 07:54 AM in reply to: Rafal.Gaweda

Inacurracies in your model:

 

4243.jpg



Rafal Gaweda
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Valued Contributor
TraitCarré
Posts: 65
Registered: ‎07-26-2012

Re: instability type 3 RX direction

11-06-2013 03:24 AM in reply to: Rafal.Gaweda

Hi,

please find attached 2 files.

https://dl.dropboxusercontent.com/u/79282449/AUVENT_V2.zip

the first, AUVENT_V2, is calculated without sismic load and is free of instability.

the second, AUVENT_V2_SISMIQUE, contains sismic loads and shows instability.

Calculation report :

Elém. diagon. de la matrice de rigidité  
                Min/Max après décomposition:    4.067231e+002     2.066486e+015
     Précision:    2
Shortest calculaltion element : 0.16 m -> I think it's not too short

 

- Why?

- How be sure than we can ignore this instability (after checking node displacements, shorts elements)?

- Is it possible to highlight calculation node?

 

thanks

 

benoît

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Rafal.Gaweda
Posts: 5,070
Registered: ‎04-26-2010

Re: instability type 3 RX direction

11-06-2013 06:16 AM in reply to: TraitCarré
the first, AUVENT_V2, is calculated without sismic load and is free of instability.

 

I do not think so :
i3.jpg

 



Rafal Gaweda
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