Truss model, check value different than zero.

[jorgealexvieira]

Hi,

I'm using Robot to try to get the diagrams for a 2D strut and tie model. I'm only interested in the axial diagrams, i don't need the robot to give me deformations or nothing else. So i've define the model using as section a simple pipe, with very little diameter and a matheria without self weight. 

This is my model, my supports are, a simple support in the top and double supports in the bottom. As it was supposed there is no reactions in the top support, but robot gives me 3 instability errors in 3 points. Does this affect the axial forces or just the displacements?
The other question i have is what is the check value and if the cause of that value being different than zero is because of the instability warnings.

Thank you! JPV

[Rafal.Gaweda]

File please

[jorgealexvieira]

Here it is, thank you!

[Rafal.Gaweda]

Check displacement first.

Either this structure should not be truss or every field should be made as trangle.

Additionaly you should use section with real properties