huangyhg

damaged steel girder
i have a w27x84 steel girder that supports steel roof joists. the girder is stressed to 80 percent allowable. the girder was hit by equipment and bottom flange is deflected laterally about an inch. how do i repair this girder?
if it is the tension flange, then the tendency under load is to straighten the flange back towards its original shape. this distortion and straightening will allow more vertical deflection to a degree.
you may not have to do much of anything in the tension case. perhaps add some lateral brace angles to ensure that its stable.
heating to straighten, under load, is not probably a wise choice. you can add additional shapes, such as a tube, or double angles, along the bottom flange, lapping past the distortion and tying into the beam in the straight flange areas on either side of the bend.
how much collateral damage has been done ?
how strong is the plastically deformed section ?
me, i'd replace the flange with a tee ... brace up the beam, cut out the offending flange, splice in the replacement flange (tee).
can you give a better description of the damaged shaped? has the bottom flange moved parallel to be web? certainly the bottom flange hasn't slid laterally, while the web and top flange remained stationary. has the bottom flange rotated at the area damaged? is it now straight or curved? did the end of the bottom flange moved closer to the web and the flange become bowed down? is the flange damaged on only one side of the web or both sides? what is the length along the beam of the damaged area?
if you can unload it during repair, why would replacing material be better than heat-straightening (with proper controls against overheating)? splicing in a replacement patch comes with its own problems, like transversely loaded welds, the second of which will be welded in a fairly restrained condition.
hg
as jae suggested... i'd first take a real close look at not having to do anything and then maybe locally reinforce it if needed...
dik
answering bagman254 questions:
the bottom flange moved about 1 inch.
web was dragged locally with flange.
deosn't appear to flange rotation or twist.
damage is about four feet long.
i think i will weld a 3/4" thick plate by 10 feet long to bottom flange
i suggest you check the connections at each end of the girder just to be safe, to verify they haven't been damaged as well.

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