Torsion in Beam due to earthquake 1

[AniMhj]

Dear everyone,
I am getting huge torsional moments in beams due to earthquake forces in ETABS.
The slab diaphragm is rigid.
Can anyone describe how torsion is induced in beams due to the earthquake force? How is it calculated manually?

 

[human909]

Your "huge torsional moments" aren't due to ETABS. They are due to YOU and the way you have modelled your structure. Don't blame the software, blame user. Trace back your model and its assumptions and work out what is causing this. (HINT: If the EQ forces are not on the same plane as the beam centroid then you can readily get high torsion. Resolve the load paths satisfactorily)

I'm half sorry if that sounded harsh but there has been a large number of inexperienced engineers asking naïve questions about software output. If you are going to rely on software at least understand the WHYs. (I say this as somebody who leans heavily on software.)