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Spread Footing Sizer

Size square isolated footings: required plan dimension from soil bearing, plus one-way (beam) shear, two-way (punching) shear and flexural steel checks per ACI 318 / NSCP 2015.

Inputs

kN
kN
kPa
mm (square col.)
mm
mm
MPa
MPa
mm
Notes & assumptions
  • Loads are service; factored Pu = 1.2D + 1.6L. Self-weight of footing ignored in q_a check (typical for light footings — increase D as needed).
  • Effective d = h − cover − 1.5·d_b (average two layers of bottom mat).
  • One-way shear: Vc = 0.17·λ·√f'c·b·d. Two-way: Vc = min[0.17(1+2/β), 0.083(αs·d/bo+2), 0.33] · √f'c·bo·d.
  • φ_v = 0.75; α_s = 40 (interior column).
  • Square footing assumed unless rectangular selected (uses given B and computed L from B·L = Areq).

Results

P_factored (P_u)
Required Footing Area
Required B (square)
q_u (factored bearing)
Effective d
One-way shear demand / capacity
Two-way (punching) demand / capacity
Bending moment Mu (per m)
As,req per direction
Suggested mat
Overall statusOK