Reinforcment Design 12" Thick Concrete Slabs 1

[LakeNormanTiger]

Friends,

I am a utilities precast engineer that usually deals with slabs and wall thickness that are 10" or less.

A project that we have been chasing requires 12" thick walls and a 16" base slab that will be monolythcally poured.

Original Design calls for one layer of steel in the center of the walls and the slab. Original design was rejected because it violates ACI-318. Basically telling me that because my slab is greater than 10" thick two matts of reinformement are required. I figured I was wrong and needed to reread the section, but I have not found anything in either section 7 or 10 regarding this. I still think the other guy is right, but could someone point me in the right direction.

Thanks

LNT

 

[DaveAtkins]

That rule refers to walls, not slabs.

DaveAtkins

 

[UcfSE]

The rule is only for walls, as Dave pointed out, 14.3.4.

If you look however at 10.6.4 you'll see the requirement for the limit on bar spacing due to crack width. If you use the assumed fs= 36 ksi and 8 inches of clear cover, your minimum spacing is less than zero. That implies that you can't have bars in the center of a 16" slab. That doesn't mean you have to have two layers of reinforcing but that you have to reduce the clear cover down so that you get a reasonable maximum bar spacing, bascially that you can't have your bars in the middle. If you have negative moments in your slab then you will need two layers in order to get your clear cover for the top and the bottom adequate for your maximum spacing due to 10.6.4.