Can you take torsion at distance dv from the face of the supports? 1

[GalileoG]

I am curious if we can take torsion at distance dv from the supports like we can with shear? I have heard mixed feelings about this and was curious what ACI but especially CSA A.23 has to say about this.

Also, if I have a cantilevered slab on top of a beam, this slab will introduce torsion into the beam. I was told to take the eccentricity from the center of the slab to the FACE of the beam as opposed to the center of the beam. I am not convinced at all but wanted some second thoughts on this.

Clansman

 

[BAretired]

The critical section for torsional stress may be taken as dv away from the support, same as shear...because torsional stress is, in fact shear stress.

If a slab cantilevers from a beam with no back span, then torsion in the beam is wL^2/2 where L is the distance from the centroid of the beam to the end of the cantilever.

Moment in the slab, however, may be measured to the face of support.

Best regards,

BA

 

[asixth]

Agree with BAretired, the beam you have described is working in equilibrium torsion and torsion must be designed for. I would analyse the eccentricity to the centreline of the beam.

You are really getting into the r/c design questions today.