Eccentric load in wide flange

[JStructsteel]

How much eccentricity do you allow in a wide flange beam before you start worrying about torsion? I would have 1" ecc of the line load on the beam. Its lightly loaded, LL=300lbs/ft, DL 50lbs/ft, span 10ft.

 

[phamENG]

Best bet is to run the calculation a few times. That way you can get a feel for it yourself. For sections that are especially narrow when compared to their depth, the torsion can add up quickly and become a design factor.

 

[KootK]

In order of preference:

1) I'll brace the torsion away if possible which, presumably, it is not in your case.

2) I'll often ignore to the torsion implied in an applied load of that load crosses the beam web such that a small amount of beam rotation would eliminate the torsion.

3) I'll run a quick torsion check using the very simple bi-moment method. If that check would use up less than 5%-ish of the available flange stress, I'll not bother with a detailed torsion check.

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[r13]

An uniform line load with 1" ecc, just make sure the beam end connections can handle the twist T = 350*1*10/(2*1000) = 1.75 kips-in, in addition to the shear/bolt.

 

[JLNJ]

If this is due to something like a hollowcore member sitting on a steel beam, does the hollowcore span to (or beyond) the beam centerline? If it does, then the case is probably "self-righting". The hollowcore reaction will work its way toward the beam centerline rather than the reaction being centered on the hollowcore bearing length. This will happen instead of the beam resisting any torsional load because the steel beam is relatively flexible in torsion. I believe this is the case KootK makes in his #2 above.

If it's hollowcore and it has embedded plates which are welded to the beam, the beam likely can't twist, even if the hollowcore bearing stops short of the beam centerline.