Laterally supported top flange
Laterally supported top flange
(OP)
I have a group of parallel and relatively long 4" tall aluminum I-beams whose bottom flanges are continuously connected together by a thin membrane that effectively braces the bottom flange. The beams are simply supported at their quarter points and loaded with point loads between the supports. I've been using the quarter length as the unbraced length of the top flange to calculate the allowable compressive strength of the top flange. Is that overly conservative?






RE: Laterally supported top flange
In my opinion, my guts tell me that your assumption is not conservative enough. If there were transverse members at the 1/4 point support locations, I would concur, but not as you describe it. I think roll-over will be a problem.
Mike McCann
MMC Engineering
RE: Laterally supported top flange
RE: Laterally supported top flange
Mike McCann
MMC Engineering
RE: Laterally supported top flange
"I forgot to mention that at the quarter points where the load is applied, there are transverse beams"
If the beams are broken at the simple supports and not continuous over simple supports, then the beam top flange unbraced length is likely to be the length between the support and the loaded location. Can you post a picture of the elevation of the beam system and section where the transverse beams are framing into the girder so I can be sure what is going on?
RE: Laterally supported top flange
RE: Laterally supported top flange