Footing Size Calculator (Preliminary) mechanism

Model scope

The algebra is correct for preliminary sizing under a centered axial load, positive allowable pressure, compatible units, and a square footing assumption. Verdict is NEEDS_REVIEW because the specification leaves the load basis, gross-versus-net pressure convention, unit contract, and applicability constraints ambiguous. The existing honest label is appropriate but should explicitly state that self-weight, eccentricity/moments, settlement, shear, stability, code minimums, and constructible rounding are excluded.

• A_req=P/qallow is the standard preliminary formula only for a concentric axial load and a uniformly distributed allowable bearing pressure; the specification does not state those constraints.
• The formula does not account for footing self-weight, overburden, eccentricity, moment, shear, settlement, sliding, overturning, or code-required minimum dimensions and rounding.
• The square-footing dimension formula is valid only when a square plan shape is explicitly selected; rectangular footing dimensions are not determined by the provided formulas.

Units and conventions

• P and qallow must use compatible force units, with qallow expressed as force per unit area.
• Examples using kN and kPa rely on 1 kPa=1 kN/m², so P/qallow produces m².
• Examples using N and kPa require converting qallow from kPa to N/m² before division.
• The calculation assumes P is the load basis appropriate for comparison with the stated allowable soil pressure, but the specification does not identify whether P is service, factored, net, or gross load.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "P": 600,
    "P_unit": "kN",
    "qallow": 200,
    "qallow_unit": "kPa",
    "shape": "square"
  },
  "expected_outputs": {
    "required_area": 3,
    "required_area_unit": "m²",
    "square_side": 1.73205,
    "square_side_unit": "m"
  },
  "working": "1. Since 1 kPa=1 kN/m², qallow=200 kN/m². 2. A_req=P/qallow=600 kN ÷ 200 kN/m²=3 m². 3. Square side=√A_req=√3 m=1.73205 m."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The plain formula has no stated input validation or load-sign convention. Zero or negative allowable pressure can cause division-by-zero or invalid negative areas, zero load produces a nonphysical zero footing, and a signed compressive load can produce an undefined square root.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json