Double-Deep Wide Flange Design
Double-Deep Wide Flange Design
(OP)
Hello, I am doing a retrofit project on an old industrial building with a central girder (W18x40) supporting roof joists. Sharing the columns with the roof girder is also another W18x40 crane girder. The crane will be removed and the budget is tight, so I would like to use the extra 18x40 to reinforce the roof girder already in place by welding the crane girder to the bottom. Should I design this as a doubly-symmetric wide flange that is 36" deep with a continuous longitudinal stiffener? This seems a little conservative to me, although the bottom flange of the top beam and the top flange of the bottom beam are very close to the neutral axis and won't contribute much to moment capacity.
The next step is to do this same thing along the edge of the building but with a W10x12 top and W18x40 below, so it becomes singly symmetric.
Has anyone else dealt with welding wide flange shapes on top of one another? Thanks!
The next step is to do this same thing along the edge of the building but with a W10x12 top and W18x40 below, so it becomes singly symmetric.
Has anyone else dealt with welding wide flange shapes on top of one another? Thanks!






RE: Double-Deep Wide Flange Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Double-Deep Wide Flange Design
RE: Double-Deep Wide Flange Design
I was thinking:
1) Weld an overhanging top flange plate to the reinforcing piece on the ground.
2) Top side fillet weld the flange plate to the existing beam bottom flange in the air.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Double-Deep Wide Flange Design
How much additional capacity or deflection reduction is needed for this project? There are other concerns, especially for the W10 / W18 combination you mention.
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RE: Double-Deep Wide Flange Design
RE: Double-Deep Wide Flange Design
you want higher capacity why not lace them together to create a mini truss and deeper overall section, shouldn't need too many lacings and cheap.