PEMB foundations - using slab to resist wind

[CCox]

I am designing a PEMB foundation. I've designed multiple of these. For DL and SL thrust, usually I use hairpins or ties/grade beams to resist loading. For wind loading, the tension tie can be used to resist the outward thrust from the column in the leeward side. Has anyone used the slab and grade beam to resist in part or all of thrust on the windward side?

There are many posts on here for PEMBs that I looked through. If there is an appropriate thread, please reply with it for me to review.

 

[KootK]

If anything, I'd think it easier in the windward direction. Depending on your details, the column may be able to bear directly against concrete. And, if not, you can probably lean into the hairpins as they're restrained from buckling by the surrounding concrete.

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.

 

[CCox]

I was curious as to what others have done. KootK, I was thinking something similar. The thrust force is naturally reconciled in bearing against the slab. Traditionally, I have designed the foundation to handle the inward direction of horizontal wind force. Obviously, I get a larger footing to resist the overturning. I got to thinking about how the building would actually respond under wind loading. In reality, the heavily reinforced slab and grade beam is much stiffer than the footing and pier. Since the slab/grade beam is located at the steel column basepate elevation, it is going to provide considerable resistance against overturning in this direction.

 

[KootK]

Agreed. You're one up on me as I've never even thought to check this. I think it's healthy to consider it though, at least qualitatively. In my estimation, a good structural engineer cycles though all possible failure modes in their mind and then spends time checking only those with a snowball's chance in hell of actually governing. The designers that tell me that they've "checked everything" are the ones that worry me. Everything that matters? Quite possibly. Everything everything? No way.

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.