Punching shear on slab on grade 1

[civg]

Consider an existing, 4" thick, unreinforced slab on grade that must support a new concentrated load. I want to check punching shear with the equation Vc = 4*(sqrtf'c)*bo*d (base plate is square). My question is what do I use for d? The ACI code defines d in this case as the effective depth, but I'm assuming the slab is not reinforced. Because the slab is on grade, can I take d as the full depth? Any feedback would be much appreciated.

 

[ishvaaag]

Not very technical proof nor punch case

http://answers.yahoo.com/question/index?qid=20070902040320AA0FUSv

this does better, still no punch proof

page 48 in

http://books.google.com/books?id=PQ...ge&q="mass concrete" "shear strength"&f=false

will try to find something directly for punching unreinforced slabs on grade

 

[JAE]

Well, technically ACI 318 requires a minimum thickness for footings which is more than 4" so your slab can't serve as a footing.

But if this is a minor loading, not part of a major load carrying column, then a check for punching shear might be referenced through the "Plain Concrete" section 22 of 318.

Short of that I'd use 0.8T to 0.6T to be conservative.
But with no reinforcing, I'd stick to what Chapter 22 of
ACI says.

 

[civg]

Got it. Equation (22-10) from ACI Chapter 22 is what I was looking for. Good thing because the punching shear capacity I got from using the equations in Chapter 11 was adequate, and that would have been wrong in this case. Thanks a lot!

 

[jheidt2543]

Sorry this is so late, but here is an article that may be of some help.