INstability at nodes(Frame)

[ali.safiaddine]

Hello there, i am facing a problem in the analysis of a frame that contains a concrete column and a cantilever steel beam. when i run analysis a warning messege appears( instability at certain nodes).

This warning results in a high values of displacements

please find attached the fil.

Thanks in advance,

Ali

[Rafal.Gaweda]

Your structure is unstable - releases are wrongly defined. Look below.

[ali.safiaddine]

whats wrong with them??
and whats the correct way to define releases in this structure
the beam is cantilever and the upper point of the column is pinned
thank you in advance
Ali

[Rafal.Gaweda]

whats wrong with them??

Is is a mechanism = it is unstable.

fixed support + pinned release on column on the side of support = pinned support, no moment is blocked, no more supports, structure may collapse

cantilever beam released on one side, not supported on second -> mechanism -> collapse

and whats the correct way to define releases in this structure

tell me how this shoud work

the beam is cantilever and the upper point of the column is pinned

Upper node of column is not supported at all.

[tony.ridley]

c'mon Rafal!  magically make the cantilever work!