Down turned slab

[StrEng007]

Guys,
I'm trying to use a downturned slab edge to support a kneewall and glazing. I'm considering the linear reaction from the glazing (negative wind load) to cause a point load at the top of my kneewall, which in turn creates outward shear and overturning about the outer edge of my down turned slab. I don't have enough concrete in my footing to counteract the overturn. Can I use my slab reinforcing, hooked into the thickened edge of the slab, as a tie to counter the overturning? Basically like a tie-rod.

 

[KootK]

Yeah, for small loads this is probably alright.

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.

 

[StrEng007]

KootK,
Are you familiar with Alexander Newman's Foundation and Anchor Design Guide for Metal Building Systems? I've read this text and questions like the one I have above aren't completely addressed.

Where can I find a finite answer on this sort of question?

 

[mike20793]

I don't know if you're going to find a discrete answer, but Koot would likely be the person that has the reference document if there is one. This type of situation is probably mostly based on engineering judgement and depends on the loads, the area over which they are applied, etc. What kind of loads are we dealing with and how thick is the turndown? How far does the glazing continue? Can you provide a sketch of what you were thinking of doing? We, especially the more seasoned engineers on here, can give much better answers with this kind of information.

 

[KootK]

Are you familiar with Alexander Newman's Foundation and Anchor Design Guide for Metal Building Systems?

I own a copy but confess that I've done nothing with it to date other than flip through it casually.

Where can I find a finite answer on this sort of question?

I doubt that you'll find it anywhere. Structural engineers are smart cookies. Too smart to attach their names, in print, to a sketchy detail like this.

If you turn the detail on its side for the critical opening moment case, you'll find that it quite resembles a retaining wall. And that ought to inform our detailing I think. Of course, you'll have closing moments as well and probably a 6" knee wall with only room for a single curtain of rebar. C'est la vie.

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.

 

[XR250]

There is usually an eccentricity on turned down slabs. As KootK shows, I always reinforce back far enough to engage a sufficient amount of slab to balance the moment.
They build 3 story apartments here on TD slabs - aahhh!

 

[KootK]

Proportions permitting, I suppose that there is another story that could be told. Based on OP's use of the term "tie rod", I'm guessing that this was the original intent.

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.