Torsional Loading on a concrete beam 1

[iengineerstuff]

I have a concrete beam, 8"Dx32"W spanning 16'. I have a concrete "eyebrow" cantilevering off the edge of concrete beam. This is causing a torsional load on my beam. On the other side of my beam I have a floor system that is bearing eccentrically on an embeded steel angle causing a torsional load. The torsional load from the floor system is on the opposite side of the torsional load from the concrete "eyebrow". Lets say the torsional load from the floor system is 10k-ft CCW (counter clockwise) and the torsional load from the concrete "eyebrow" is 5k-ft CW (clockwise), would I be correct in assuming the stresses induced by these opposite torsional effect would negate each other up to the point where I would need to design for a 5k-ft CCW torsional load on my beam? My other option I am considering would just be design the beam for the greater torsional load and being able to sleep easy tonight. Any advice, as always, is appreciated. Let me know if this requires any more information.

 

[bobbyboucher]

Yes you're right you could counteract torsion on one side with the other. But also make sure to check the live load for either 0 live load or 100% live load. Will the eyebrow have wind loads on it? Uplift wind load will push in the same torsional direction as the floor load. I also agree with your intuition for designing the beam for the worst case of either the eyebrow or the floor. The eyebrow is an appendage and your main structure should not be worse off with the appendage removed.

8"x32" is a pretty deep beam, are you getting any hoops in there? I don't have a good sense as to the magnitude of the torsion versus the threshold torsion, etc. but I would also double check that the load path/design concept makes sense as the design is set up.

 

[iengineerstuff]

Good reminder for the uplift, I had not yet considered that in my calculations. I will be using hoops and adding additional longitudinal steel to resist any torsional moments.