Allow moment in intermediate node

[Anonymous]

I have these 2 beams (equal section) connected at node 2, uniformly distributed loaded but with some point loads on beam 2 as well.

My question is, I guess, simple: how can I allow a moment in node 2? Note that this node doesn't have a support, and it shouldn't have. I just want to allow all rotations at node 2 so I can design properly my connection there.

[Rafacascudo]

allow a moment in node 2  = Release the moment ??

By your picture , moment is already close to zero on node 2 . But ,moment releases can be a assigned through Geometry/releases...

[Anonymous]

But what I want is exactly not to be zero, so my connection should hold also a possible moment there.

[Rafacascudo]

Without having the model, it seens that your short beam, which has the fixed support, does not have enough torsion stiffness( IX ) to generate a My bending moment on the longer beam at node 2.

[Anonymous]

I've modified the model due to the fact that I cannot have a moment at none of the 2 supports. So now, I need to model properly the node connecting the 2 beam so I can have my forces there in order to design my connection.

Should I use bar releases at that intermediate node? If so, how can I do that?

Sorry for the probably basic question but I'm not that familiar with Robot modeling.

[Rafacascudo]

Zip the model and send it here

[Anonymous]

Thank you for your fast reply.

In the meantime I've made some changes and included a release which partially solved the issue, however I still don't have equilibrium in the "corner" joint (node 2 in the model).

[Rafacascudo · Accepted solution]

   1st of all you should learn about the program a little more . Watch some very good official tutorials here. Webinar 16 is  about instabilities. You must pay attention to the analysis warnings!!

You cannot ignore instability type 1 warning!!

   If you really cannot have moments at the 2 supports , you need to get another support somewhere else or the structure will be unstable even without the midspan release on shorter beam. With the release at short beam midpoint. , it got worse!!!

  Check the model displacements. Very very large values are the 1st clue that there is something very wrong with your model.