SOG Used To Reduce Retaining Wall Height

[TomWaggoner]

I have a retaining wall that was not built per plan and I need to find a way to justify the slab on grade support 1'-0" above the retaining wall footing. I am looking for an ACI section I could use to justify this support. Maybe like a baseplate type calculation. Any help for my response back to DSA would be appreciated today. Thanks!

-Tom

 

[msquared48]

Do you have to justify the sliding or the moment?

Sliding should be no problem to justify if it is large enough. Depends upon the sliding coefficient used.

The moment in the wall should be reduced also, receiving support from the slab level.

Create a model showing the slab pushing back on the wall, creating a counter moment to the wall moment and see if you can justify the footing size as constructed. Should work.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[TomWaggoner]

Yeah its for the moment. I did create a model as you suggested. When I did my hand calc of just reducing the wall height the moment made it just under the allowable. Not so much when I run it on the computer with multiple supports. It looks like I might have to not use calculations and just justify with a letter and suggest that the shear is taken out by the SOG. I can't think of anything else. 15' retaining by 200' long done and needing sign off. I tweaked everything even getting the prism test and mill certificate to get 98% stressed. Any other thoughts?

 

[JAE]

If you are depending on the slab to reduce your vertical stem moment - keep in mind that the new "fixity" of your stem probably shoudn't be taken as the top of slab elevation. The slab will have some give - and will not resist the moment at the top surface perfectly. You would theoretically have a second set of force couples - one force near the top of footing and one just BELOW the top of slab.

And with this new force couple, the slab will have to resist this force couple via flexure in the slab, or axial in the slab on top and shear friction between the slab bottom and top of footing - thus dowels into the top of footing might be warranted.

 

[a2mfk]

Is the slab and thickened edge already in place?

 

[TomWaggoner]

Thanks. This all pretty much helped me confirm my own conclusions on this end. I am working on an equivalent soil pressure that would work and going to see if the soils engineer can tweak his end to get me that number. As for the slab, it's poured and set. The dowels for the thickened portion do not hook into the CMU wall.

 

[hokie66]

To restrain the wall with the slab, you may have a gap to fill. If a soft joint was used, dig it out and grout. If it was cast directly against the wall, shrinkage may leave a narrow gap, which you may be able to fill after time with a low viscosity gap filling product.