TheStructuralCalc

Pile Foundation Layout

Every column and wall from ETABS on one plan: the piles each needs at your spacing and capacity, the cap arrangement, caps that overlap flagged to combine, every cap designed automatically, and DXF of the layout and cap sections.

ACI 318-08ACI 318-19
Save calculationFree account — your numbers come with you.

Building

Demo building

12 columns, 1 walls · 7 grid lines · 2 strength · 2 service

Piles

The allowable loads are the pile's working capacities — take them from the Pile Design calculator. 0 uplift = piles take no tension; 0 lateral = not checked.

Caps

Design code

Everything you have entered is in the address bar, so the link reproduces this exact calculation.

Caps sized

1 group of caps crowd each other — combine?

Caps

13

Piles

44

Arrangements

3

Cap concrete

65.3 yd³ · 50.0 m³

Plan

ABCD123PC-A1: 3 piles, 90 × 99 in — pile 46.0 kip3PPC-B1: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-C1: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-D1: 3 piles, 90 × 99 in — pile 46.0 kip3PPC-A2: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-B2: 4 piles, 90 × 90 in — pile 85.4 kip — crowds a neighbour4PPC-C2: 4 piles, 90 × 90 in — pile 85.4 kip — crowds a neighbour4PPC-D2: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-A3: 3 piles, 90 × 99 in — pile 46.0 kip3PPC-B3: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-C3: 3 piles, 90 × 99 in — pile 74.2 kip3PPC-D3: 3 piles, 90 × 99 in — pile 46.0 kip3PPC-Core: 6 piles, 306 × 36 in — pile 99.4 kip — crowds a neighbour6PA1B1C1D1A2B2C2D2A3B3C3D3Core
Designed, passesCrowds a neighbour — combine?FailsSized, not yet designedClick a cap for its design; shift-click to pick several. Wheel zooms, drag pans.

Combine caps

  • PC-B2, PC-C2, PC-Core overlap by 36 in

Pile groups

CapCapsPilesL × W, inR/Qa
PC-A1A1390 × 990.46
PC-B1B1390 × 990.74
PC-C1C1390 × 990.74
PC-D1D1390 × 990.46
PC-A2A2390 × 990.74
PC-B2B2490 × 900.85
PC-C2C2490 × 900.85
PC-D2D2390 × 990.74
PC-A3A3390 × 990.46
PC-B3B3390 × 990.74
PC-C3C3390 × 990.74
PC-D3D3390 × 990.46
PC-CoreCore6 (6×1)306 × 360.99

Drawings (DXF)

AutoCAD R12 DXF, layers GRID, SUPPORT, CAP, PILE, REBAR, CLASH, DIM, TEXT; 1 unit = 1 mm. The cap details come once every cap is designed.

Supports (13)

SupportGridX, ftY, ftcx, incy, inWallMax P, kipLeave out
A1A-1156
B1B-1268
C1C-1268
D1D-1156
A2A-2268
B2B-2412
C2C-2412
D2D-2268
A3A-3156
B3B-3268
C3C-3268
D3D-3156
Core2648

Design checks

CheckDemandCapacityDCRStatus
PC-A1 — 3 piles, compression46.023 kip100.000 kip0.460✓ OK
PC-B1 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-C1 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-D1 — 3 piles, compression46.023 kip100.000 kip0.460✓ OK
PC-A2 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-B2 — 4 piles, compression85.430 kip100.000 kip0.854✓ OK
PC-C2 — 4 piles, compression85.430 kip100.000 kip0.854✓ OK
PC-D2 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-A3 — 3 piles, compression46.023 kip100.000 kip0.460✓ OK
PC-B3 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-C3 — 3 piles, compression74.162 kip100.000 kip0.742✓ OK
PC-D3 — 3 piles, compression46.023 kip100.000 kip0.460✓ OK
PC-Core — 6 piles, compression99.390 kip100.000 kip0.994✓ OK

Calculation

  1. 1Pile reactions (rigid cap on equal piles, about the pile group's centroid)
    R_i = \frac{\sum P + W_{cap}}{n} + \frac{\left(\sum M_x + \sum P\,\Delta y\right) y_i}{\sum y^2} + \frac{\left(\sum M_y + \sum P\,\Delta x\right) x_i}{\sum x^2}
    \text{PC-Core (6 piles, D+0.75L+0.525E)}:\ R_{max} = 99.4
    R_{max}99.4 kip

    The fewest piles whose reactions stay within the allowable compression and uplift in every service combination; Δx, Δy are each support's offset from the group centre.

  2. 2Cap weight carried by the piles (service)
    W_{cap} = A\,(t\,\gamma_c + h_s\,\gamma_s)
    \text{PC-Core}:\ W_{cap} = 36.3
    W_{cap}36.3 kip

Warnings

  • PC-B2, PC-C2, PC-Core overlap (by 36 in) — combine B2 + C2 + Core on one cap.

What this calculator does not check

  • Pile reactions of a rigid cap on equal piles (R = P/n ± M·c/Σc²), with each support's offset from the group centre adding P·offset to the moment; pile stiffness, group efficiency, block failure and negative skin friction are not considered. The allowable pile loads are taken as entered (from the pile design).
  • A single support gets the Bowles/CRSI standard arrangement at spacing S (either way round for the unsymmetric ones); a wall or a group of supports gets a rectangular grid, centred on the resultant of its heaviest service combination and large enough to cover every support by 3 in. A single pile, or a single row, has no lever arm for the moment across it: it is used only where that moment is zero, unless tie beams are to take it — and then the tie beams are not designed here.
  • Each cap is designed by the pile-cap engine (punching at every pile and support, one-way shear, flexure, top steel between supports, bar development) for every strength combination; the thickness is the thinnest in whole steps from the minimum whose concrete checks pass. See the Pile Cap Design calculator for the full calculation of any cap.
  • Caps with the same arrangement are made one type: the thickest cap and the heaviest bars of the group, checked again for every member.
  • Caps closer than the clear gap are flagged; combining them is the engineer's choice. Tie beams, the pile design itself and the cap-to-pile connection are outside this tool.

Results are for preliminary sizing and educational use. They are not a design and must be reviewed, verified and sealed by a licensed or registered engineer before being used in construction.

pile-foundation-layout v1.0.0 · ACI 318-08 · input b4bad4159cfb417a