Is a slab depression considered a reentrant corner? 1

[astrctrlengr]

I have a slab-on-grade foundation system with several depressions for showers. Are these drops (3" drop in an 8" thick slab) considered re-entrant corners?

I have re-inforced for potential vertical cracks across the drop, but am concerned about possible re-entrant corner issues.

Do I need to reinforce for this?

Thanks.

 

[pittguy12]

Yes, I would consider this a reentrant corner but only for the portion that is actually being depressed. In other words, if you didn't get the diagonal bar in the 3" step, it wouldn't do you much good to prevent cracking. Although, with 5" acting beneath it that wasn't wanting to pull away at the corner, I wonder if the 3" portion would be enough to cause a crack here? It might depend on where your other reinforcing is located in the slab.

Is there anyway you could gradually depress the slab...slope it down towards the depressions? This might help alleviate the issue.

 

[astrctrlengr]

Pittguy12, thank you for the response.

The 8" slab thickness will be maintained across the drop location with slab reinforcing draped across the drop (#4 @ 12" O.C. Ea. Way Top & Bottom).

See attached for visual.

Given this image, do you still think the #3 corner bar is necessary?

Thanks.

 

[pittguy12]

Can't answer it for sure as I haven't seen how something similar works once it's constructed. In my experience, I wouldn't think it asking too much to put it in there but my background/training taught me to liberally reinforce before deciding not to reinforce!

If it was my detail, I would probably throw it in there.

 

[Ron]

Yes and put the corner bars at the center of the drop thickness or slightly above center, depending on cover requirements.

 

[hokie66]

Diagonal bars will help to control cracks initiated at the stress riser. Whether or not you use them depends on whether a bit of cracking will be objectionable.