rebar detailing

[tclat]

Hi

I have a cantilever slab 10' long for a balcony in a house. Between inside and outside, the architect shows a 4" level difference. Outside slab thickness is 10" and inside slab thickness is 6"

My question is regarding the bar bending detail at the level change. ACI detailing manual shows a 1:6 max for cranking bars for columns between floor levels.

Is this detail applicable for my condition?

Thanks

 

[civilperson]

Is the exterior and interior finish floor elevations the same?

 

[JAE]

I wouldn't use a tapered/bent top bar in this condition. Then tension in the bar would compel the bar to straighten out and that would spall the concrete on the top.

Your top bar in the cantilever should extend directly into the main slab horizontally and your "d", depth for design should be based on the 4" thickness.

 

[apsix]

I doubt if a 4" design thickness will work.

You'll need sufficient overlap of the exterior and interior slabs, and extend the top bars of the inside slab to the bottom face of the balcony slab. Balcony top bars as noted by JAE above.
Provide full development length to the inside slab and balcony top bars beyond the point where they intersect.

 

[hokie66]

If you have a 6" internal slab and a 4" step, you have 2" of effective depth at the soffit step, which is not going to work. You must extend the 10" depth a considerable distance inside the building in order to provide sufficient backspan for the cantilever and to allow for adequate bar lapping.

As JAE and apsix said, you can't crank the top bars under the 4" step, they will break out the corner concrete as they try to straighten.

It sounds like you need to consult with one of the senior engineers in your firm, as this issue has been dealt with many times over many years.