tall stemwall foundation design
tall stemwall foundation design
(OP)
When a typical slab on grade/cmu stem wall foundation (see attached) starts getting higher lets say over 6 ft (exposed face above grade) would you analyze as a cantilever retaining wall? or could you assume you have a pin-pin with the keyed in slab holding back the wall? I often detail dowels in the slab hooked into the top of the chair block an effort to help with any differential settlement but I don't think I these could be adequately(per code) developed into the masonry or 4" thick slab?






RE: tall stemwall foundation design
Respect reinforcement one needs to follow the applicable code specs. You may need more or less depending on your situation, but you will see examples in the generic literature of reinforced masonry where the particular aspects of effective anchorage are (at least) not even addressed or warned about.
RE: tall stemwall foundation design
As an alternative, you could leave the fill out behind the wall, pour the slab for a distance "H" of the wall back from the inside face, stub out bars from the slab, extend and bend the vertical wall steel up and bend 90 degrees to meet the stubbed out bars and field weld them together, then backfill and tamp by hand, after which you pour the remainder of the slab.
I have used this metho many times for higher walls where the owner did not want the larger footing required by a standard retaining wall.
Mike McCann
MMC Engineering
RE: tall stemwall foundation design
If this block wall is to be exposed, you need to waterproof the earth side. And fill all the cores.
RE: tall stemwall foundation design
running through some quick calcs under retaining wall assumption the foundation does get large (as I expected) but reqd. wall thickness for flexure got larger than I expected. The asd provisions required a much thicker wall then lrfd.
RE: tall stemwall foundation design
RE: tall stemwall foundation design
RE: tall stemwall foundation design
Mike McCann
MMC Engineering
RE: tall stemwall foundation design
1. Consider how this wall gets built. If you design it as a basement wall (pinned top and bottom) then the top will need to be braced until the top slab gets cured to take the load.
2. If you transfer structural loads into the slab on grade (probably the top and the bottom slabs), the SOG will need to be designed to ACI 318 requirements.
3. You will need to develop the hooks into the wall at the top enough to transfer the required loads. Ref 12.5 for ldh
RE: tall stemwall foundation design
I can't see a contractor installing bracing to resist the back-fill until the slab is cured... although I guess bracing could be handled by loading the left side of the wall temporarily with dirt.
RE: tall stemwall foundation design
RE: tall stemwall foundation design
RE: tall stemwall foundation design
RE: tall stemwall foundation design
RE: tall stemwall foundation design
RE: tall stemwall foundation design
regarding your statement "I wouldn't worry about the footing rotating" so even if the allowable soil bearing capacity at the edge of the footing was exceeded by some rotation due to fixity of the wall to footing...you agree this would be negliable and not cause any setllement etc.?
RE: tall stemwall foundation design