Torsion
Torsion
(OP)
Dear everyone!
Could you tell about torsional constant modifier value in Etabs to as code requirement?
when reduce it, effect on other local and global stability design?

Could you tell about torsional constant modifier value in Etabs to as code requirement?
when reduce it, effect on other local and global stability design?







RE: Torsion
DaveAtkins
RE: Torsion
As I recall ACI has some varying provisions for design of torsion in beams.
a) If the torsional moment is below some threshold amount then it can just be ignored.
b) If above the threshold then it must be considered in one of the following ways
It's the 2nd option that this section of the ETABs help file is talking about. They are trying to point out that they do not do anything in the program to automatically re-distributed these torsional moments. My guess is that they also don't consider the torsion in the design of the beams. But, that's just a guess as I'm not an ETABs expert. They are emphasizing that you (as the engineer) are responsible for adding this moment into the adjacent beams or designing / detailing the beam to resist the torsion.
IMO this is merely good practice in documenting some program limitations that the user needs to be aware of.
RE: Torsion
RE: Torsion
RE: Torsion
RE: Torsion
when design, Etabs have option for user to consider torsion or not.
but if we let Etabs ignore torsion in design phase, it will be our fail because moment in slab will be smaller than we release in analysis phase.
so we should release in analysis to ignore torsion transfer to slab resist.
The question for engineer how much we need release for torsion cause by slab deflection(statically indeterminate structure) ? It depend on your judgement to make sure the torsion Tu=min(Tcr,Tu)for statically indeterminate structure.