Cast in Place Slab on Grade Minimum Reinforcement 1

[bigmig]

After happily paying $90 for the ACI 360R-10, Guide to Design of Slabs on Grade so I
can actually "design slabs on grade" I am now having regrets. No where that I can find, does it give a formula or table for
minimum reinforcement requirements for plane old cast in place slabs on grade.

I found a subgrade drag equation in a Concrete Construction Article which is great.
I can see ACI318-11, Section 7.12.2.1 with the 5h, or 18 inches etc. Which is great

I found a great post from 2015 on this site where someone ways that 7.12.2.1 does not apply to on grade conditions
and that the commentary says this....I cannot find where the commentary says this.

In this post 12 people offer 12 different ways of reinforcing slabs.

https://www.eng-tips.com/viewthread.cfm?qid=392997

Why in the world does the ACI 360R-10 just blank this entire topic when
the title of the document is exactly what they are blanking?

Super frustrated.

 

[phamENG]

I have 360-06, and it's in 7.3 and 7.4 depending on what you're putting the reinforcing in for.

 

[fel3]

Very often, slabs on grade are not reinforced. This is why ACI 360R, Chapter 7, covers the design of unreinforced concrete slabs.

In addition to ACI 360R, you might be interested in US Army Technical Manual 5-809-12 "Concrete Floor Slabs on Grade Subjected to Heavy Loads" (

https://wbdg.org/FFC/ARMYCOE/COETM/ARCHIVES/tm_5_809_12.pdf)

and the Portland Cement Association document "Slab Thickness Design for Industrial Concrete Floors on Grade." When I design concrete traffic slabs and slabs for temporary equipment storage, I use the methods in ACI 360R, but I also pay attention to the recommendations in TM 5-809-12 and the PCA document.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[RattlinBog]

Sections 8.3 and 9.3 attached from 360R-10.

8.3 - Reinforcement for crack-width control only:
Min 0.005*Ag

9.3 - Reinforcement for shrinkage-compensating concrete slabs
Min 0.0015*Ag

 

[Celt83]

ACI removed the subgrade drag equation in the most recent update to 360R because it did not appropriately account for stresses from differential shrinkage (curling) and in place slab on grades designed with the method were exhibiting larger crack widths that most deemed serviceable when joint spacing was exceeding the 360 recommendations. There was a Q&A document released by ACI addressing this, Link

 

[WesternJeb]

Our firm has happily used the following guidelines from a 1960s CRSI manual and it has worked for my firm for the past 20 years with minimal kickback. I am sure there have been cracks in slabs, but no one has come to us crying about it and blaming us. You will have to find a conversion table for the old style of WWF callouts versus the new though.

 

[TLHS]

Yeah, that article isn't my basis, but that's pretty in line with my gut check numbers and if the math doesn't work out for a given site I tend to fix it with granular layers rather than bigger slabs.

 

[dik]

Fel3... when using a stiffener under a masonry wall, I sawcut the slab at the transition of the thin slab to the thick slab. The thickener tends to restrain shrinkage and it cracks at the sawcut, anyway.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik