Column Rebar Configuration
Column Rebar Configuration
(OP)
I have a question about rebar configuration for column which I am not familiar too so hope you guys could help me with this.
This is for a building with 1st floor SOG, 2nd floor slab, 3rd floor transfer slab and wood framing above.
Typically for concrete column, our detail shows rebar from the top of footing to the second floor (extended above slab for as required for lap) and from 2nd to 3rd floor slab. Now someone is asking that is it OK to run the column rebar from top of footing directly to 3rd floor slab without breaking it at each floor level.
I personally have only seen seen doing it the conventional way with rebar from floor level to floor level. Has anyone designed their columns in such a way and if so is there any codes regarding using such method.
Please share your ideas and if you recommend or do not recommend doing it so. Other than workability, are there any issues. Thank you for your help in advance.
This is for a building with 1st floor SOG, 2nd floor slab, 3rd floor transfer slab and wood framing above.
Typically for concrete column, our detail shows rebar from the top of footing to the second floor (extended above slab for as required for lap) and from 2nd to 3rd floor slab. Now someone is asking that is it OK to run the column rebar from top of footing directly to 3rd floor slab without breaking it at each floor level.
I personally have only seen seen doing it the conventional way with rebar from floor level to floor level. Has anyone designed their columns in such a way and if so is there any codes regarding using such method.
Please share your ideas and if you recommend or do not recommend doing it so. Other than workability, are there any issues. Thank you for your help in advance.






RE: Column Rebar Configuration
1) Contructability, which you mentioned. All slab and beam bars will need to be threaded through the column cage.
2) Safety. Gotta keep that cage from buckling and crushing our builder friends.
From a structural performance perspective, the full height bars are probably an improvement. Can you share why your contractor wants to do this? It's an odd request to be sure.
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: Column Rebar Configuration
Well he did not give us a reason why but I am guessing probably because they can save a lot of steel from eliminating lap. Also, save labor for bending steel which will probably add a lot. Well that all I can think of.
RE: Column Rebar Configuration
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: Column Rebar Configuration
I guess you could only pour up to each floor level but then you're left with a 10ft cage sticking up swaying while you form and pour the second floor slab.
RE: Column Rebar Configuration
RE: Column Rebar Configuration
Well Brad805, it seems they have been in business for a while and I suppose they have used this method earlier as well.
The Project is located in Northern VA but honestly I do not have an idea of the cost around here compared to other places.
I do believe that structurally it is a better option but as noted by you all there are some constructability and safety factors with this method.
So we all agree that in terms of structural stand point we do not have any issues with it correct?
RE: Column Rebar Configuration
RE: Column Rebar Configuration
If they are concerned about rebar splices, use mechanical connectors. You can't run a column cage 2 stories and do two pours. The concrete will never consolidate and the cage would need to be braced while the lower slab is poured.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Column Rebar Configuration
RE: Column Rebar Configuration
RE: Column Rebar Configuration
RE: Column Rebar Configuration
The industry worked with CalTrans and the University of Nevada Reno to complete research and prepare a report on safe erection of rebar cages.
http://www.dot.ca.gov/newtech/researchreports/repo...
RE: Column Rebar Configuration
It cuts out quite a bit of rebar. If for whatever reason you're using tension laps and large bars (say #8 or #9), then your lap splice using the simple development formula (not reducing for cover/spacing, etc.) is going to be 5'-6' for 4 ksi concrete anyways. If you've got a floor to floor of 10', that's like 50% more bar just due to splice if you splice each floor because each bar has to be 15'-16' foot long.
Over two floors, that means you've got 30'-32' foot of bars. If you only splice once in that period (as opposed to twice) it's more like 25'-26' instead. Still fits on a truck and in a container. We usually see the cages stabilized with internal bracing once a floor or so, they're still relatively stout, especially after you pour the first half. But material cost is 10-20% less. Extend that over a whole building and it's a decent amount of steel/cash.