Instability of type 3 in RY

[Anonymous]

Hi I am having an instability of type 3 in  Ry direction.

I have a a deck slab wiith secondary and primary beams so whenever i released the secondary beams i got an instability in the structure.

Can you please help me to solve it.

regards,

George 

[Rafal.Gaweda]

In this case in this model it is a mathematical instability - can be ignored.

For test - replace all sections by UC 356x406x634 then run calculations - no instability

[Anonymous]

Hi Rafal, could you please explain more about what is "mathematical instability"?

And why we can ignore mathematical instability problem?

And why this type 3 instability problem can be solved by changing the sections to UC 356x406x634?

[Romanich]

Hi @Anonymous ,

You can check the forum regarding the instability type 3:

https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-issues/m-p/3919282#M13456

https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-type-3-rx-direction/m-p/3365071#M3277