reinforcement of concrete slab
reinforcement of concrete slab
(OP)
Hello, Im wondering how do you guys solve the problem when a concrete slab has a sudden change of thickness (above a wall).
I have a cantilever slab (balcony) on the left side - 18 cm thick and the rest of the plate is 12 cm.
I have to model this plate as one element (because of cantilever part that has to be 'fixed') but im wondering what is the best solution for reinforcement detail. I dont like the first sketch very much because i think there is too much unreinforced concrete above (upper reinforcement mesh) i think it may crack?!
Im also not a fan of 2nd sketch since the reinforcement is not in one line (upper reinforcement in the cantilever part is disconnected from the rest of the slab - there is a disconnect of reinforcement at the area with the biggest bending moment.
Id really appreicate some suggestions or sketches.
TNX

I have a cantilever slab (balcony) on the left side - 18 cm thick and the rest of the plate is 12 cm.
I have to model this plate as one element (because of cantilever part that has to be 'fixed') but im wondering what is the best solution for reinforcement detail. I dont like the first sketch very much because i think there is too much unreinforced concrete above (upper reinforcement mesh) i think it may crack?!
Im also not a fan of 2nd sketch since the reinforcement is not in one line (upper reinforcement in the cantilever part is disconnected from the rest of the slab - there is a disconnect of reinforcement at the area with the biggest bending moment.
Id really appreicate some suggestions or sketches.
TNX







RE: reinforcement of concrete slab
The second approach is dead wrong, as you do not have continuity of the reinforcement. But you know that.
Your situation is the opposite of a normal balcony, as you want the step the other way for weatherproofing purposes.
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
That is NOT a good detail. While it will have sufficient strength, it would be much better to fully develop the hook. There is nothing stopping a shallow angle crack at the step from basically causing delamination .
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
Structurally, for a ~2.5" step, I think that OP's original option one would be fine. My only concern there is durability. With ~3.5" cover on the top bars, I might be concerned with top side crack widths should the balcony slab ever actually crack. I'm curious to know what others think of that supposition.
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.
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
I assume it is an external/internal junction, and internally there is a lower slab level to allow finishes to be installed. Also assuming it's carrying a 60mm unreinforced topping is not a good idea in my opinion. It might be OK for strength, but a balcony slab should have reinforcement near the top face to control cracking.
I agree with KootKs detail. Or, for larger steps, a Z bar so the vertical face of the step can fully develop.
RE: reinforcement of concrete slab
RE: reinforcement of concrete slab
Dik
RE: reinforcement of concrete slab
The sloping bar - yes, as per Koot's detail, with a bit more slope than yours.
The open U,s no, development is still inadequate, and would be painful to install.