reinforcing the edge of a concrete slab

[greznik91]

I understand that its mandatory to reinforce the end of a free edge of a slab (balcony) with "U" shaped rebars. (image A)

But what in a case that a free edge of a slab ends with a beam (image B1 and B2). Since beam has shear reinforcement, is it really necessary to add "U" shaped rebars as shown in image B2 or is OK to do it as its shown in image B1?

Another example is when there is a horizontal tie at the odge of a slab (image C - bearing masonry wall bellow). There is no need in my opinion to add "U" shaped rebars since shear reinforcement of horizontal ties can also have this function.

I have seen different things in field (Europe). How do you do it and why?

 

[hokie66]

I don't know about "mandatory" in your code, but I think common practice, in all three situations, is to cog (90 degree hook) the top bars, or if the slab is thin, a 180 degree hook works better. The slab top bars should normally be placed over the beam bars, in the same layer as the top of the stirrups. Watch the edge cover on those cogs in the field, and one way of ensuring the cover is to place the cogs inside the beam bar which is closest to the exterior.

 

[MotorCity]

You need some way to develop the slab bars. Whether you choose to develop the bars within the slab or the beam is up to you.

 

[robyengIT]

Reinforced concrete structures - Park/Paulay - chapter 13 The art of detailing

 

[KootK]

You may be thinking of slab edges in two way slab system where there is a slab torsion to be considered. I support hokie's hooked bar recommendation. With a uniformly loaded cantilever, even the need for the hook is debatable. I'll include it for good measure and railing connection "feel good" though. That, and it costs nothing.

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.

 

[dik]

Unless you are looking for a horizontal crack at mid depth of the slab, Detail A is 'silly'. Detail B1 and C, the top bars of the slab should/could hook into the beam. Detail B2 achieves this and accommodates any +ve moment at the beam (wouldn't normally use this)...

Dik