Concrete Column - Development Length
Concrete Column - Development Length
(OP)
Folks,
How do you typically handle the column reinforcing at the last lift (roof)?
If you have a 8" flat plate with columns at 28'-30' on center, I assume it is impossible to develop reinforcing inside the 8" slab with hooks unless you are using very small bars (#5 or #6).
In that case, do you analyze the building with a slab supported on hinged columns at the top?
I am curious as to how you detail/analyze/design them?
How do you typically handle the column reinforcing at the last lift (roof)?
If you have a 8" flat plate with columns at 28'-30' on center, I assume it is impossible to develop reinforcing inside the 8" slab with hooks unless you are using very small bars (#5 or #6).
In that case, do you analyze the building with a slab supported on hinged columns at the top?
I am curious as to how you detail/analyze/design them?






RE: Concrete Column - Development Length
I recall my mentor many years ago - we were driving somewhere to a meeting and we drove past a multi-story concrete building. I noted to him that there were 90 degree hoooked bars at the top floor columns. We typically didn't do that - just extended the column bars as far into the roof structure as possible and called it good.
He stated to me that day, "Well, where would that floor ever go? The wind certainly can't lift the concrete floor system off the columns."
I suppose that in a seismic area you'd have to deal with some shear or something possibly. But if you have a pinned condition at the top of your columns, and you've taken story shear out some other way, there really shouldn't have to be a full blown developed connection there.
RE: Concrete Column - Development Length
30' is too big a span for an 8" flat plate.
RE: Concrete Column - Development Length
RE: Concrete Column - Development Length
asixth: was your slab post-tensioned?
RE: Concrete Column - Development Length
RE: Concrete Column - Development Length
RE: Concrete Column - Development Length
flat slab or flat plate? flate plate would be struggling.
An expert is a man who has made all the mistakes which can be made in a very narrow field
RE: Concrete Column - Development Length
Reinforced flat plate, L/26 end, L/30 internal
Posttensioned flat plate, L/36 end, L/42 internal
Reinforced flat slab, L/33 end, L/37 internal
Posttensioned flat slab, L/37 end, L/46 internal
RE: Concrete Column - Development Length
flat slab, the same one I posted in the AS/NZS forum a few months back.
RE: Concrete Column - Development Length
Aixth,
I will have to go back and review because I don't remember.
An expert is a man who has made all the mistakes which can be made in a very narrow field
RE: Concrete Column - Development Length
I think this is the thread asixth is talking about.
thread744-265955: Long Term Deflection & Compression Reinforcing