Limits of ACI 318 Chapter 22?

[jropert]

I have an existing unreinforced concrete slab-on-grade to check for new machine loads. Is ACI318 chapter 22 (Structural Plain Concrete) allowed to be used for such design checks (such as section 22.5)?

The reason I ask is that section 22.1.1.2 states that "Design and construction of soil supported slabs, such as sidewalks and slabs on grade, shall not be governed by this code UNLESS they transmit vertical loads or lateral forces from other parts of the structure to the soil."

I would interpret that since the new machine loads would transmit vertical loads thru this unreinforced slab-on-grade to the soil, that I could use chapter 22 for design checks? The commentary section R22.1.1.2 states that "It is not within the scope of this code to provide design and construction requirements for nonstructural members of plain concrete such as soil-supported slabs (slabs on grade)".

Wouldn't my slab be "structural" thus allowing the use of chapter 22? I don't have a copy of ACI 360 or the PCA design book for slab-on-grade design, but are these necessary if I could check the slab with ACI318?

 

[Ron]

More rampantly ludicrous code wording....yes, in my opinion Chap. 22 applies in your case

 

[TXStructural]

ACI 360R-10 is the current slab on ground design resource from ACI.

ACI 318 does NOT apply for slabs on ground which are loaded on top and supported directly below. You can apply the Code, but it will likely be excessive, and the most difficult task is figuring soil support conditions and applying the usual bending and shear computations appropriately.

The caveat in 318 about load path is to require use of 318 where the slab is part of the gravity system (like a raft slab supporting a building) or lateral (like slab used as a tie between foundation elements or drag strut to move forces as part of the lateral load path). It is not that you can't use it for slabs, only that you are not required to use it.

 

[SlimSE]

ACI 360R-10 and the Portland Cement Association have design resources that would be much more suitable for the type of application you are describing.