Size a rectangular isolated footing under a concentric column: service bearing, one-way shear at d, two-way punching at d/2, and the flexural steel per direction, all live as you drag.
Size a rectangular isolated footing under a concentric column: service bearing, one-way shear at d, two-way punching at d/2, and the flexural steel per direction, all live as you drag.
Basis: ACI 318-19 (φ = 0.75 shear, 0.90 flexure; U = 1.2D + 1.6L). Building-code footing checks, offered as a companion to the AASHTO LRFD bridge tools.
Punching usually governs thickness and bearing usually governs plan size — if flexure is governing your design, something unusual is going on and worth a second look. The service bearing check includes pad and soil weight; forgetting them is the most common hand-calc error. Real footings also need development length and, on sloped sites, sliding checks — not covered here.
Inputs are saved on this device · reset to defaults
With Eurocode selected the footing is designed to EN 1992-1-1 with the bridge value αcc = 0.85 from EN 1992-2 and the EN 1990 road-bridge factors 1.35 on both permanent and traffic load. Material partial factors (γc 1.5, γs 1.15) replace the φ factors. One-way shear uses the EC2 empirical expression, which depends on the size factor k and on the steel ratio, so the bars chosen in the flexure check feed into the shear checks. Punching is the main change: instead of one perimeter at d/2, Eurocode checks a family of rounded perimeters out to 2d, removes the soil reaction acting inside each perimeter from the punching force, and lets the resistance grow as 2d/a for the closer perimeters; the tool scans them and reports the critical one, plus the crushing limit at the column face.
With KDS selected the loads follow the Korean bridge ultimate combinations: I (1.25 on dead load, 1.80 on live load) and IV (1.50 on dead load alone), whichever is larger, which matters when dead load is more than about 7.2 times the live load, and the concrete checks follow KDS 24 14 21, which works like Eurocode but multiplies material strengths by φc = 0.65 and φs = 0.90 instead of dividing by partial factors, uses a parabola-rectangle stress block and caps the neutral axis at 0.4d. One-way shear and the footing punching rule (perimeters out to 2d, soil reaction deducted, 2d/a enhancement) mirror the Eurocode forms. The KDS punching equations are printed with 100ρl where the one-way equation has ρ; read literally that would make punching 4.6 times stronger than one-way shear, so the tool uses ρl, consistent with the one-way equation and Eurocode 2, until KCSC confirms. In both codes the bearing check stays a service-pressure check against the qa you enter, read as a presumed (presumptive) bearing value, because the tool has no soil strength parameters for a full bearing calculation.