Minimum Reinforcement in Shallow Footings (Beam or Slab?)
Minimum Reinforcement in Shallow Footings (Beam or Slab?)
(OP)
We've recently opened up discussion in our office about minimum reinforcement requirements in shallow footings.
ACI318-11 13.3.2.1 states that the design, detailing of one-way shallow foundations, including strip footings, combined footings, and grade beams, shall be in accordance with this section and the applicable provisions of Chapter 7 and Chapter 9.
Chapter 7 "One Way Slabs" states that minimum reinforcement shall be: 0.0018x60000xAg/fy or 0.0014Ag
Chapter 9 "Beams" states that minimum reinforcement shall be: 3xsqrt(f'c)xBwxD/fy or 200xBwxD/fy
I've normally followed 0.0018Ag as my minimum guideline but as per Chapter 9, my minimum is greater.
ACI318-11 13.3.2.1 states that the design, detailing of one-way shallow foundations, including strip footings, combined footings, and grade beams, shall be in accordance with this section and the applicable provisions of Chapter 7 and Chapter 9.
Chapter 7 "One Way Slabs" states that minimum reinforcement shall be: 0.0018x60000xAg/fy or 0.0014Ag
Chapter 9 "Beams" states that minimum reinforcement shall be: 3xsqrt(f'c)xBwxD/fy or 200xBwxD/fy
I've normally followed 0.0018Ag as my minimum guideline but as per Chapter 9, my minimum is greater.






RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
Dik
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
Dik
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
In 318-11 the provisions for footings are in 10.5.4 as EngineerEIT indicates above....and are very very confusing to some - see this thread: thread507-251751: How to place minimum steel in a rectangular footing?
However, it appears that 318-14 has cleared up this mess from 10.5.4.
One thought I have on this is that it may be that this section, 13.3.2.1, refers to footings and then to "grade beams" and that the chapter 7 provisions are for general one-way footings while the chapter 9 provisions are for grade beams. That to me is rational.
Having said that I would possibly concur with you that the higher of 7 vs. 9 would be prudent.
But it does say "as applicable" when mentioning 7 and 9 in 13.3.2.1. which implies that 7 applies to some and 9 applies to some.
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RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
You're absolutely right. It is 2014 not 2011. I think I'm also onboard with Chapter 9 as my minimum.
The conversation came up as our min reinforcement has always been 5 @ 12 for a 12" thick footing under light loading. Now it is 6 @ 12.
RE: Minimum Reinforcement in Shallow Footings (Beam or Slab?)
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