Maximum permitted spacing of vertical bars in a basement wall

[cliff234]

ACI 318-08 Section 10.6.4 has an equation for computing the maximum permitted spacing of flexural steel in order to control cracking in "beams and one-way slabs". Question: Does this spacing limitation apply to basement walls? My gut tells me no. Section 10.6.1 specifically states "beams and one-way slabs". Also, I have never seen horizontal cracks in reinforced basement wall. I have seen plenty of vertical cracks, but that's a different story. If this section applies to walls, then I need to limit my bar spacing to 12". If the section does not apply to walls then I can space my bars at 18". I usually try to limit my bar spacing to 12" but lately we've been under pressure to squeeze whatever economy we can out of our design and details. Spacing the vertical bars at 18" will save some money.

 

[Archie264]

Check out Ch. 14. I think 14.3.5 might apply, which requires not less than three times wall thickness nor further apart than 18".

 

[XR250]

18" O.C. is what I have always used. Although, I do not see why 32" or even 48" O.C. will not work as long as a large enough bar is used. Is the wall going to crack between the rebar over a 4 ft. length - I think not. FYIW, I specify #4 @ 32" O.C. each way for slabs in lieu of WWF or fiber and have never had a shrinkage crack.

 

[Archie264]

Whoops, a correction to the earlier post regarding Sect. 14.3.5: not greater than three times wall thickness nor further apart than 18".

 

[a7x1984]

If this is an R-3 use group (one or two-family dwellings 3-stories for less) per the IBC, the following applies:
IRC 2012 TABLES R404.1.2(2),(3), and (4) will find you an answer.

I would save yourself time and the client money, by not reinventing the wheel beyond the applicable building code. There is no reason to even crack open the ACI for this, as long as the usage group is R-3. The ACI-318 requirements are met by following the tabulated values in the IRC.

Cheers!


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