Removing a portion of a flange from a web tapered steel column
Removing a portion of a flange from a web tapered steel column
(OP)
I have a client who is attempting to place a ten pound load in a five pound bag. In order to fit a new section of electric switch gear in an existing building, the electric contractor would like to cut a section out of the flange of a web tapered steel metal building column. The strip removed from the flange would begin 2" above finish floor and extend up to 92" above finish floor.
I have been asked if this would work structurally. Although AISC Design Guide 25 covers the design of web tapered members, it does not give any guidance if the flanges are of unequal width. Am I too far off base if I weld a slightly wider flat plate to the affected flange if the built up section has greater section properties than the original section (I, Sx, r)?
Any suggestions would be appreciated.
I have been asked if this would work structurally. Although AISC Design Guide 25 covers the design of web tapered members, it does not give any guidance if the flanges are of unequal width. Am I too far off base if I weld a slightly wider flat plate to the affected flange if the built up section has greater section properties than the original section (I, Sx, r)?
Any suggestions would be appreciated.






RE: Removing a portion of a flange from a web tapered steel column
RE: Removing a portion of a flange from a web tapered steel column
You'd be going from what is a doubly symmetric section to something that's asymmetric. You're primary mechanism for failure had likely been flexural buckling, but after modification you've opened things up to torsional and flexural-torsional buckling as well. You'll get a twist in your buckling failure.
The AISC spec has a section about this. I've never used it, but it looks like it's pretty similar to the one in the CISC code. You'll get to do some fun things like work out the torsional constants for your section.
RE: Removing a portion of a flange from a web tapered steel column
If you have to cut from one side, dont you have to cut from both, or is the compression side smaller?
RE: Removing a portion of a flange from a web tapered steel column
Also, I am not sure whether to shore the column before adding the reinforcing or add the reinforcing and then remove the flange section.
I may tell my client to relocate the equipment. That solution may be cheaper.
RE: Removing a portion of a flange from a web tapered steel column
That being said, if you do add additional strips on top of the web, balance the strips to either side of the web, trying to balance the area on each side of the centerline, as well as re-providing the original S value.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Removing a portion of a flange from a web tapered steel column
I hate to disappoint the sparkies, because if you ask them to change something, they're likely to make it worse, but even they understand that if you cut into a building column, it's a bad thing. Can they fit their gear into a slightly smaller box?