rebar connection between existing and new concrete slab 2

[greznik91]

Hi, Id like to know how do you guys suggest to connect existing concrte slab (14 cm thick) with new slab (same thickness).
I was thinkin about connecting it with rebar (in the middle of the thickness of existing slab).

Im wondering about modeling supports for a new slab at the edge of the slab which is beside existing slab (building). Is it alright, to use pinned support and then choose rebars (diameter and spacing) based on support reaction there (shear forces)?

How do you guys do it?

 

[SteynvW]

I would normally chip a bit into the existing slab so that a bit of the shear gets transferred with bearing on the wall and is not 100% relying on the reinforcing for shear transfer althoug I would stil supply enough reinforcing for the shear transfer (belt and braces). 140cm slab might still be thick enough for 2 layers of reinforcing as well (top and bottom) and then you will model it as simply supported.

 

[KootK]

Similar to Styn, I would:

1) Chip a continuous bearing key into the bottom of the existing slab. This will increase reliability and encourage the entire slab to participate in resisting shear.

2) move the dowels to the top of the slab where they will be most advantageous for shear friction and crack control.

Technically, to achieve proper anchorage of your bottom steel (assuming pin connection), you either need to create a bearing ledge or you need to lap the bottom steel with properly anchored dowels.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[greznik91]

thank you very much for quick answers.

'Chip a continuous bearing key'

Can you please post a sketch/picture of this... if you can find one of course...
Sorry but English is not my 1st language so i have some trouble understanding some of expressions.

 

[SteynvW]

See attached. What I described is option 1
and what I interpret Kookt meant is option 2,he can confirm this
or pull my drawing apart!

 

[jayrod12]

I like the second option in the sketch personally. Then there's no concerns about the wall above not having full bearing.

 

[DaveAtkins]

Also remember if you will be using shear-friction provisions per ACI 318, you need to develop the rebar on both sides of the joint. The bar could get to be quite long.

DaveAtkins

 

[greznik91]

Thanks! I appreciate it! Regards