why x brace bay beam does not have axial force

[donnabean]

Hi all,
i am working on one story steel structure with steel deck as roof. I noticed all x brace bay beams don't have axial force at all, the reaction force shows that columns take horizontal force, some of the columns don't belong to lateral resisting system. How to solve this problem? Thx in advance.

 

[slickdeals]

You probably assigned it as a rigid diaphragm. As a result, there is no relative displacement of the two nodes at each end of the beam and no axial force.

Change it to a semi-rigid diaphragm. Or select on of the nodes and remove it from the rigid diaphragm constraint.

 

[donnabean]

Thx, slickdeals.
I did notice if I run a 2d x brace frame, there is axial force in the beam. I did assign a rigid diaphragm in this project.But how can I remove those nodes from rigid diaphragm constraint? thx.