- I'll assume that the stiffening/reinforcing is in place to solve a flexural issue.
- I feel like this is something probably covered by Blodgett but I'm not feeling energetic enough to look into it.
- No matter what you do, you'll need hanger welds at the ends of the stiffener that transfer the shear in the stiffener back to the duct plate. This will be in addition to any shear demand. I'd be inclined to just double these welds as that should be more than enough to cover both bases.
- If you have considered the stiffener acting compositely with the plate then, at minimum, you'll need VQ/It consistent with that assumption. But, then, if you've underestimated the effective width of the plate acting compositely, you may also underestimate the demands on the welds. My gut feel is that this isn't something to get terribly excited about but we will anyhow for academic interest if nothing else.
- One approach to estimate weld demand conservatively, but not excessively conservatively, would be:
A) Imagine a system comprised of the stiffener plus another instance of the stiffener mirrored about the strong axis so that the two stiffeners are stacked and touching.
B) Do VQ/It at the center line using this system behaving compositely and double the real load applied to the stiffener.
C) Use this shear demand to size your welds.
This is essentially the same as assuming that your neutral axis in the real system occurs at the stiffened plate.
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.
