What it checks
The module designs a square isolated column footing for soil bearing, one-way and punching shear, and flexural steel. It supports both strength (LRFD) and service (ASD) design methods, deriving loads from basic load cases or accepting pre-factored values. The sequence of checks begins with soil bearing capacity, followed by shear and flexure, with specific handling for biaxial moment and uplift cases.Inputs
- Geometry - Footing plan dimension (ft), footing thickness (in), and square column dimension (in).
- Loads - Service axial load (kips) for bearing, factored axial load (kips) for concrete, or axial load by basic load case (kips) to derive both automatically.
- Combinations - Project load combinations; if absent, the module falls back to ASCE 7-22 §2.3 strength and §2.4 service sets.
- Seismic - Ev toggle (SDS) to fold vertical seismic effects into combinations when provided.
- Soil - Allowable soil bearing pressure (net) in ksf.
- Materials - Concrete compressive strength (psi), steel yield strength (psi), and clear cover to reinforcement (in).
What it reports
- Loads Used - Service and factored axial loads actually used, with the specific ASD and strength combination labels.
- Load Warning - A flag if the supplied pre-factored pair is inconsistent with any ASCE 7 gravity combination.
- Effective Depth - Calculated effective depth d, assuming a #8 bar.
- Bearing Pressure - Net factored and service bearing pressures compared against allowable limits.
- Cantilever Length - The cantilever length derived from footing and column dimensions.
- Reinforcement - Required steel area for flexure, governing rho, and bar options for selection.
Code references
The engine cites ACI 318-19 §22.5, §22.6, and §9.6.1.2, as well as ASCE 7-22 §2.4 bearing. Load combinations default to the ASCE 7-22 §2.3 strength set and §2.4 service set when project combinations are not provided.Limits
The module assumes a square footing and a #8 bar for effective depth calculations. Service and factored loads are ignored when axial load is given by basic load case. Results are engineering aids; the engineer of record is responsible for the design.Try it free in your browser
The Spread Footing calculator runs this module's engine with no install and no signup.