Instability in nodes

[Anonymous]

Hi

When I run a calculation I got a warning of instability in for example node 50. If I stabilize that node and run the calculation once again I got a new warning of instability in a totally different node in the model, if I stabilize that node I got a new warning in another node and so on… Why is it like this and is it possible to get all warnings in the first calculation?

[Artur.Kosakowski]

If the instability is of the 1st or 2nd type then yes but for the 3rd one only the first detected is displayed.

[Anonymous]

Why does the instability occur. In the steel design the profile is calculated and OK? What's the difference between instability type 1, 2 and 3?

[Artur.Kosakowski · Accepted solution]

Please check the already existing topic of this forum:

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/instability/m-p/3108640/highlight/true#M453

In general the instabilities of types 1 and 2 cannot be ignored. The type 3 in some cases may be ignored but in all cases you should determine the cause of this instability first as well as examine the results (especially displacements and rotations of nodes as well as reactions vs. applied load) very carefully.

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