Max bar spacing in concrete columns 4

[WillisV]

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?

 

[cap4000]

I have the CRSI 2002 Design Handbook and on page 3-15 they have a 40 x 40 column with 4-#18 in the corners. Only one bar in each corner or 1% steel.

 

[IDS]

I have the CRSI 2002 Design Handbook and on page 3-15 they have a 40 x 40 column with 4-#18 in the corners. Only one bar in each corner or 1% steel.

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/

 

[STATICPH]

the SABS 0100-1 say area 0.4 – 6% for cols in vertical,
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

 

[jheidt2543]

Excuse my coming late to this thread, but I have a question related to this topic, but in reverse. The best way to illistrate my question is in the case of a metal building corner column (see attached sketch). The columns tend to be inset pretty far sometimes and it is generally less expensive to "square off" the concrete pier with excess concrete than to form all the ins and outs for an exact pier size. So, how then do you arrange the reinforcing for the conc. col. pier? Around the base plate where the load is or around the perimeter of the oversized pier?

 

[hetgen]

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."

 

[BAretired]

jheidt2543,

I think I would place the bars as shown in red in the attached. These are not really columns, more like short pedestals.

BA

 

[jheidt2543]

hetgen
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.

 

[BAretired]

Yes, that would be my choice. The concrete is so lightly stressed in this situation that you need little more than plain concrete to do the job. Balancing the reinforcement about the baseplate, in such a situation would, in my view, be unnecessary because of the extremely low stresses in the concrete.

BA