Residential Slab on grade Epoxy rebar connection

[Eng.V-C]

Does Anyone know what is the min. code requirement for rebar length into new slab when connecting existing slab to new slab with epoxied rebars?
And how about max. spacing? ACI318 calls for 18" max. spacing for temp and shrinkage reinf. ... Is that applicable for nonstructural slabs on ground?
Both new and existing slab have wire mesh. This is a 3.5" Residential concrete slab.
I have done research on ACI codes/manuals, multiple residential building codes and online forums and have not found a clear answer.
Please see attached picture:

 

[phamENG]

Why are you connecting them? Is it just to maintain the floors in line under normal residential live loads? Is it in a garage with wheel loads? Is there a wall bearing nearby?

There is no code requirement to dowel them together, just good engineering sense. Take a look at ACI 360 for some approaches to doweling slabs. Though, 3.5" is really thin and doweling will be tough. You'll likely need small dowels at really tight spacing.

 

[WesternJeb]

A typical detail that I have seen done successfully for years is:

#3 bar@ 12" o.c
5" post-installed embed. using an adhesive
12" into the new slab.

As phamENG states above, this is just to keep the slabs from differential settlement under the loads. If this is forklift loading or semi loading then obviously this won't be satisfactory, but is a good detail for most conditions.

 

[TLHS]

For something that thin I wouldn't dowel it unless there was a structural reason like it's part of a tension tie load path.

I'd likely design the new slab so that I was pretty confident that it's stiffer than the old one and then excavate a few inches under the existing slab and kind of underpin it to give it a bearing surface.

 

[Eng.V-C]

Thank you for your responses.
This for a garage extension of a 1 story CMU house.
Is there any section of the ACI360 that you can guide me to? ... I have been looking for a requirement or guidelines there and I have not found anything specific for my condition.
So there is not a Code that regulates the spacing and length for these "dowels" that help prevent differential movements between floors?

 

[phamENG]

There's no prescriptive code for it, no. It has to be designed.

 

[Eng.V-C]

How do you design it? What Engineering Principles?
Do you have an example?

 

[WesternJeb]

What is your role on the job? That might help us gather what you may need, or point you in the right direction based on your role.

 

[Eng.V-C]

I am the structural engineer in charge of providing this detail.
The snip of the one I attached is an example I was provided with from another firm and I just wanted to know if it meets the code requirements.
I just wanted to know if there is a code for this type of connection or a design approach.
This is a non-structural slab on grade for a residential garage in Florida.

 

[WesternJeb]

If you're that concerned about it, use Hilti Profis (free) to design it with your anticipated loading.

Otherwise, the detail you provided and the one I have outlined as typical for our firm are very similar.

 

[Eng.V-C]

Thank you WesternJeb.

 

[Greenalleycat]

I will usually spec 100-150mm (4" to 6") based on how I feel or the direction of the wind on the day
Typically 150mm (6") though
This is just based on a gut feel - these connections don't really have loads on them per se (assuming typical residential slab-on-grade applications) so it's just about judgement as to what is needed to get a good connection

 

[JoelTXCive]

You can do a detail like this. We call it a 'headered connection' There are many different versions of it though.

This version is for a 6" thick piece of paving, but you could tweak it for your needs.

 

[phamENG]

An example for a 3.5" thick slab? No. But if you want to get into how they can be designed, this is a good document to review. It serves as a basis for the dowel design in one of the popular Alex Tomanovich spreadsheets for slab on grade design. ACI 360 is good, too, and has some guidance for spacings, but they don't consider much below 5 or 6" thick slabs. (For what it's worth, I won't go below 4" for a garage, and will usually specify 5" - especially if it's a nice house).

 

[Eng.V-C]

Thank you all for your contributions.