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# Location of Critical Perimeter (per ACI) for Concrete Pile Cap (single square cap for one pile)

## Location of Critical Perimeter (per ACI) for Concrete Pile Cap (single square cap for one pile)

(OP)
Introduction:
For punching (2-way) shear check, the ACI says to assume the critical perimeter location along a line located d/2 from face of pile. However, ACI 318-19 Sect. 22.6.4.3 also says that if an opening (or presumably an edge?) is located closer than 4h from the face of the column (in my case, a pile), then the concrete beyond that boundary shall be considered ineffective (or words to that effect?).

Subject:
48"x48"x15" reinforced concrete pile cap atop (1) 12"x12" precast concrete pile
H = 15"
d = 12"

Question:
For the above subject pile cap, would the critical perimeter be located at a distance from the face of the pile = (d/2 = 12"/2) = 6", or, (h/4 = 15"/4) 4.25"?

There are several of these pile caps associated with this potential construction project, so the cost differential could be significant.

Thank you.

### RE: Location of Critical Perimeter (per ACI) for Concrete Pile Cap (single square cap for one pile)

I would go with the 6". The 4h is for establishing whether or not you have to treat your piles as perimeter or corner conditions where the punching perimeter does not extend all of the way around the pile.

### RE: Location of Critical Perimeter (per ACI) for Concrete Pile Cap (single square cap for one pile)

An opening is an opening (a penetration), not an edge. The edge rules are also explained!

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