Max bar spacing in concrete columns
Max bar spacing in concrete columns
(OP)
Is there a limit in ACI pr elsewhere for the maximum spacing between longitudinal reinforcing bars in a column resisting only compression loads? For instance if I have a 48"x48" column, is it allowed to only place say bundles of 4 no. 11 bars in each corner without any reinforcement in between?






RE: Max bar spacing in concrete columns
Either way, 4-#11 is not adequate.
DaveAtkins
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
Why do you say engineers disagree on the min. reinforcement, I think ACI 10.9.1 is pretty clear that it's 1%. Is this one of those relatively recent changes to the provisions that has older engineers crying foul?
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
I usually limit the space between bars at about 12" on a column...no specific reasn - just a feel good.
RE: Max bar spacing in concrete columns
So my initial example of a 48x48 with bundles of 11s in each corner is code compliant - but maybe not a good idea!
RE: Max bar spacing in concrete columns
Sorry! I didn't read the word "bundles."
frv--
The Code says that if a column which is half the area of the column you are designing would theoretically be adequate, you only need to use half of the normally required area of steel.
DaveAtkins
RE: Max bar spacing in concrete columns
I have even thought the same about T&S steel. Intuitively it seems more logical to me to have the steel even dispersed.
RE: Max bar spacing in concrete columns
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
So really it comes down to judgment, but I'm not sure why you would bundle the bars when you have plenty of room to spread them out along the column perimeter. It's just not standard practice.
RE: Max bar spacing in concrete columns
If your column receives large bending moments and is a beam-column element, then perhaps sections 10.6.4 and 10.6.6 might apply.
RE: Max bar spacing in concrete columns
I can't agree with that. Confinement of the core is an important requirement, and a the core of a large column with bars only at the corners will not be adequately confined.
The requirement to provide confinement to every bar when the spacing exceeds 150 mm but every other bar when the spacing is below 150 mm suggests to me that the intended maximum spacing is 300 mm, even if the code does not explicitly state that.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Max bar spacing in concrete columns
Spread out the vertical steel you need - 12" max as JAE suggests is a good start. Blown out columns are not good for your reputation.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
Dik
RE: Max bar spacing in concrete columns
BA
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
It would be interesting to know what the load capacity of such a column was, compared with one with a properly confined core.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Max bar spacing in concrete columns
max spacing of vert bars 300mm (out of my head), I won't bundle if I can spread them,
less grip in concrete, and I'm not genius enough to do that calc.
Anyway, we are busy adopting all the euro codes here, I don't know if you would accept the SABS
RE: Max bar spacing in concrete columns
RE: Max bar spacing in concrete columns
Eurocode-2 9.5.2-6
"Every longitudinal bar or bundled bars placed in a corner should be held by transverse reinforcement. No bar within a compression zone should be further than 150 mm from a restrained bar."
RE: Max bar spacing in concrete columns
I think I would place the bars as shown in red in the attached. These are not really columns, more like short pedestals.
BA
RE: Max bar spacing in concrete columns
The detail shows the corner bars & verticals in the 8" wall. The note calls out for this example/question that I don't show the #2 ties around the column verticals.
BAretired
I don't disagree with what you suggest, it is what I would call the traditional correct way to do a column pier. However, much of the concrete is "excess" to what is needed to carry the loading; in fact I would guess the pier capacity is 2-3 times what is required. The addition concrete is filled in to reduce the formwork. So, your answer would be to reinfore the pier in the "normal" way and ignor the column base plate/load eccentricty rather then "balance" the vertical rebar around the base plate adn load. That's the crux of my question.
RE: Max bar spacing in concrete columns
BA