calcnote ACI 318-19
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Footing result

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Pile cap 4 piles (4-square) cap 66 × 66 × 30 in piles Ø12 in at 36 in f′c 4,000 psi fy 60 ksi #6 bottom bars d 26.62 in
PASS

All checks pass: pile reactions, flexure, shear, punching shear, development length, column interface.

Pile reactions and capacity

PASS
D/C pile capacity (max service reaction / allowable) 0.62
Rmax (maximum service reaction)
50.0 kip
Ppile (allowable pile capacity)
80.0 kip
Pile x (in) y (in) R service (kip) R factored (kip) D/C
1 -18.0 -18.0 50.0 70.0 0.62
2 18.0 -18.0 50.0 70.0 0.62
3 -18.0 18.0 50.0 70.0 0.62
4 18.0 18.0 50.0 70.0 0.62
Rigid cap; coordinates measured from the column center; cap self-weight not included ACI 318-19 §13.4.2

Flexure

PASS

L-direction bars (parallel to L)

D/C moment 0.22
φMn (design moment capacity)
465.02 kip-ft
Mu (factored moment at column face)
105.00 kip-ft
Quantity Value
b (design width, in) 66.0
d (effective depth, in) 26.62
As,req (steel required for Mu, in²) 0.88
As,min (minimum steel, in², §13.3.3.2) 3.56
Bars (number of #6 bars) 9
As,prov (steel provided, in²) 3.96
s (center-to-center spacing, in) 7.41
Clear spacing (in, minimum max(db, 1 in), §25.2.1) 6.66
a (stress block depth, in) 1.06
φMn (design moment strength, kip-ft) 465.02
Status PASS

B-direction bars (parallel to B)

D/C moment 0.23
φMn (design moment capacity)
451.66 kip-ft
Mu (factored moment at column face)
105.00 kip-ft
Quantity Value
b (design width, in) 66.0
d (effective depth, in) 25.88
As,req (steel required for Mu, in²) 0.91
As,min (minimum steel, in², §13.3.3.2) 3.56
Bars (number of #6 bars) 9
As,prov (steel provided, in²) 3.96
s (center-to-center spacing, in) 7.41
Clear spacing (in, minimum max(db, 1 in), §25.2.1) 6.66
a (stress block depth, in) 1.06
φMn (design moment strength, kip-ft) 451.66
Status PASS
γs (fraction of short-direction steel in the central band, §13.3.3.3) 1.000
φ = 0.90; critical section at the column face ACI 318-19 §13.2.7.1 · Table 21.2.2 · §25.2.1

One-way shear

PASS

L-direction bars (critical section parallel to B)

D/C shear 0.00
φVc (design shear capacity)
87.42 kip
Vu (factored shear at d from the face)
0.00 kip
Quantity Value
ρw (As,prov / (bw·d)) 0.0023
Vc (concrete shear strength, kip) 116.57
φVc (design shear strength, kip) 87.42
Vu (factored shear, kip) 0.00
Status PASS

B-direction bars (critical section parallel to L)

D/C shear 0.00
φVc (design shear capacity)
85.78 kip
Vu (factored shear at d from the face)
0.00 kip
Quantity Value
ρw (As,prov / (bw·d)) 0.0023
Vc (concrete shear strength, kip) 114.37
φVc (design shear strength, kip) 85.78
Vu (factored shear, kip) 0.00
Status PASS
φ = 0.75; no shear reinforcement ACI 318-19 §13.2.7.2 · Table 22.5.5.1

Punching shear

PASS
D/C punching shear 0.00
φVc (design punching capacity)
881.56 kip
Vu (factored punching demand)
0.00 kip
Quantity Value
davg (average effective depth, in) 26.25
bo (critical perimeter at d/2, in) 177.0
Area inside perimeter (in²) 1,958
β (long side / short side of column) 1.00
αs (location factor, §22.6.5.3) 40
vc (a) (4λsλ√f′c, psi) 253.0
vc (b) ((2 + 4/β)λsλ√f′c, psi) 379.5
vc (c) ((2 + αsd/bo)λsλ√f′c, psi) 501.7
vc governing (minimum of (a), (b), (c), psi) 253.0
Vc (vc·bo·d, kip) 1,175.42
φVc (design punching strength, kip) 881.56
Critical perimeter fits in the footing Yes
φ = 0.75; concentric loading only ACI 318-19 §22.6.4.1 · Table 22.6.5.2

Pile punching shear (edge piles)

PASS

Only piles close enough to a cap edge to have an incomplete critical perimeter at d/2 are checked. Each pile is checked against its own factored reaction.

D/C edge pile 1 0.21
D/C edge pile 2 0.21
D/C edge pile 3 0.21
D/C edge pile 4 0.21
Edge pile Vu (kip) φVc (kip) bo (in) Status
1 70.00 333.13 66.9 PASS
2 70.00 333.13 66.9 PASS
3 70.00 333.13 66.9 PASS
4 70.00 333.13 66.9 PASS
φ = 0.75; round pile taken as the equivalent square ACI 318-19 §22.6.4.1 · Table 22.6.5.2

Development length

PASS

L-direction bars

D/C development length 0.57
Quantity Value
ld (development length, in) 17.1
ld adjusted (reduced for excess steel, minimum 12 in, in) 12.0
lavail (available length beyond the critical section, in) 21.0
cb (cover or half spacing term, in) 3.38
ψt (casting position) 1.00
ψe (coating) 1.00
ψs (bar size) 0.80
ψg (grade) 1.00
Status PASS

B-direction bars

D/C development length 0.57
Quantity Value
ld (development length, in) 17.1
ld adjusted (reduced for excess steel, minimum 12 in, in) 12.0
lavail (available length beyond the critical section, in) 21.0
cb (cover or half spacing term, in) 3.38
ψt (casting position) 1.00
ψe (coating) 1.00
ψs (bar size) 0.80
ψg (grade) 1.00
Status PASS
Straight bars in tension, no hooks ACI 318-19 §13.2.7.1 · Eq. 25.4.2.4a · Table 25.4.2.5

Column to footing interface

PASS
D/C bearing on concrete 0.19
φBn (design bearing strength)
1,432.08 kip
Pu (factored load)
280.00 kip
Quantity Value
A1 (loaded area, in²) 324
A2 (supporting area (frustum base), in²) 4,356
φBn (design bearing strength, kip, §22.8.3.2) 1,432.08
As,dowel,min (minimum dowel area, in², §16.3.4.1) 1.62

Feasible dowel sizes

Sizes whose compression development length fits in the footing depth. A design aid; detailing is the engineer’s responsibility.

Bar Number ldc (in)
#4 9 9.5
#5 6 11.9
#6 4 14.2
#7 3 16.6
#8 3 19.0
φ = 0.65 for bearing ACI 318-19 §22.8.3.2 · §16.3.4.1 · §25.4.9.2

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