axial force in beams in rigid diaphragm

[mohamad reza]

hello
i have modeled some 2D concrete moment frames for my thesis , I have assumed diaphragms in all stores are rigid , so according to this assumption ,in beams should exist no axial force , what should I do in program for eliminating axial force in beams?I used Equal DOF in 'nodal constraint' but after running analysis I checked beams and axial force existed in beams. I also used Rigid diaphragm in 'nodal constraint' and axial force again existed in beams.generally is it true that axial force exists in beams in push over analysis ?considering that we have assumed rigid diaphragm for floors

regard

[huffte]

If only x-direction translation is included in the EqualDOF constraint, then the vertical displacement at the two ends of the beam are not necessarily different. So the distance between the beam ends does change, resulting in axial forces in the beams.

[mohamad reza]

thank you huffte

so what should i do to eliminate this axial force in beams?what is your opinion?i do not know is it correct that axial force exists in beams or not?
because we consider rigid diaphragm in preliminary model .

[huffte]

mohamad, it seems to me that the axial loads in the beams would be realistic. I believe they will be relatively small and I would not try to eliminate them. Physically, I believe it is realistic to accept that column tops on a given floor do not have to displace the same vertically.