huangyhg

bottom loaded wide flange
if a beam is loaded at the bottom flange only, does it still need to be laterally braced? in the case i am considering now, the bottom flange is equally loaded on each side of the web by a hanging wall. i realize there are several considerations such as flange bending, section modulus reductions because of connections, etc, but in regard to bracing i'm having trouble.
it seems to me that for the compression flange (the bottom flange)to buckel out of plane it has to overcome the "resisting" force which is the load itself. does anyone have any suggestions, or perhaps a code that describes these situations.
thanks
i do not understand your situation. you stat that the bottom flange is in compression. is the wall pushing upwards on the steel beam?
(continuation of previous post)
if the wall is hanging from the beam, then would not the top flange be in compression (i'm assuming it is simply supported)?
sorry, top flange in compression. for the beam to buckel out of plane the load is resisting the instability...right?
sorry for the bum description.
i wouldn't count on it (the load resisting the top flange buckling). if you can't brace the top flange laterally, use a section where the bending stress is acceptable for that unbraced length.
the bracing parameters are to prevent lateral torsional buckling of the member. loading the bottom flange will not keep the
perhaps another option might be to sufficiently stiffen the top flange with a channel for lateral bending due to lateral torsional effects, if the span is short enough. (see aisc 9th edition, p.1-83 for descriptive picture).
jtpe,
you are absolutely right. this topic just came up in our office today. a bottom load wide flange is stable because of the stabilizing moment produced by the load. as the top flange attempts to buckle sideways it produces an eccentricity that allows the load at the bottom of the beam to "torque it" back to the upright position.
it had been so long since school that i had forgotten about it. however it was taught in my graduate class in stability years ago.
for bottom flange loading, the beam top flange will buckle at a higher load than for a top flange loaded beam for the same unbraced length.
it does not mean that it won't laterally buckle just because it is loaded at the bottom flange.
the higher the load the higher the bracing force???
you cannot brace the compression flange if you do not connect to the compression flange.

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