About corner reinforcement

[tanvir.ce12]

Hi,

I've some confusion about corner reinforcement in two way slab.

We know corner reinforcement is provided in discontinuous edge of two way slab to prevent corner slab from lifting and prevents cracks. It is provided upto L/5 distance.

My question is whether top corener reinforcement has to provided avobe main reinforcement or below reinforcement? what about bottom corner reinforcement?

Thanks in advance.

 

[Tommy385]

you can just provide orthogonal reinforcement without additional diagonal reinforcement. Quantity: look at your FEM Moments including Mxy or use your code respectively
p.s. unless you anchor this this rebar in corner column it will not prevent uplift, if its is not the last slab you shouldn't normally have problem with corner uplift.

 

[tanvir.ce12]

@Tommy385

Thanks for your response.

I understand your point. According to ACI 318-14 (8.7.3), it is suggested to use corner reinforcement. I am curious to know, If i want to provide corner reinforcement, do i have to provide it below main top bar? If it has to be provided above top bar, clear cover in the corner region will be reduced.

 

[WARose]

I don't have 318-14.....but in 318-11 it says:

R13.3.6 — Unrestrained corners of two-way slabs tend to lift
when loaded. If this lifting tendency is restrained by edge
walls or beams, bending moments result in the slab. This
section provides steel to resist these moments and control
cracking. [red]Reinforcement provided for flexure in the primary
directions may be used to satisfy this requirement. See
Fig. R13.3.6.[/red]

In other words: that [red]is[/red] your steel in that area. (All of it.) And it can be parallel to the edges.

From Fig. R13.3.6, I take it that the corner zone for that reinforcement should be the longest distance to a adjacent column (in either direction) divided by 5. (Squared.) Potentially that is a different number than your column strip width (by Chapter 13 if you are using the direct design method).