Source: https://guthlabs.ai/docs/instruments/unit-weight-self-weight-load-calculator-structural-members/
instrument / verified-clean
# Unit Weight / Self-Weight Load Calculator (Structural Members)
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Mechanical, Civil & Structural Engineering — Statics/Dynamics, Strength of Materials, Machine Design, Civil, HVAC, Vibration
**Tranche**: tranche-5
**Evidence ID**: t5-191
**Ledger rows**: 1
No ledger note is attached.
## Review findings
NEEDS_REVIEW because the exact ambiguity is whether the input is mass density ρ or weight density γ, and because g is unspecified for the ρ formulation. The honest label should explicitly state accepted units, the selected formulation, the gravity constant, the assumption of uniform member properties, and that the output is a downward distributed load.
### Formula and scope findings
- The formula w=ρ·A·g is correct only when ρ is mass density, such as kg/m³, A is in m², and g is in m/s²; the formula w=γ·A is correct only when γ is weight density, such as N/m³ or kN/m³.
- The input description 'material density/unit weight' is ambiguous because mass density ρ and weight density γ are different quantities and require different formulas.
- The specification does not state that the member is prismatic or that density and cross-sectional area are uniform along its length; otherwise w may vary with position.
### Unit assumptions
- For the density formulation, ρ is mass density in kg/m³, A is cross-sectional area in m², g is gravitational acceleration in m/s², and the result is w in N/m.
- For the weight-density formulation, γ is force per volume in N/m³ or kN/m³, A is in m², and w has corresponding units of N/m or kN/m.
- Test vectors use g=9.80665 m/s² unless another value is explicitly provided.
- The resulting self-weight load acts downward in the direction of gravity.
## Boundary hardening
### Recorded hazards
- Reject or clearly handle negative, non-finite, or missing density, weight density, area, and gravitational acceleration values.
- A zero area produces zero self-weight and should be accepted or explicitly defined as an invalid geometry boundary; negative area must be rejected.
- Do not apply g to γ because γ already includes gravitational acceleration.
- Unit mismatches, especially mm² versus m² and N/m³ versus kN/m³, can cause errors by factors of 10⁶ or 1000.
- The calculator should identify the load direction as downward and should not imply that the scalar magnitude alone fully defines a structural load.
- No division-by-zero operation is present in the stated formulas, but any later conversion or derived calculation must guard against zero denominators.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"density_rho": 7850,
"density_unit": "kg/m³",
"area_A": 0.01,
"area_unit": "m²",
"g": 9.80665,
"g_unit": "m/s²"
},
"expected_outputs": {
"w": 769.822025,
"w_unit": "N/m",
"w_kN_per_m": 0.769822025
},
"working": "w=ρ·A·g\n=7850 kg/m³ × 0.01 m² × 9.80665 m/s²\n=78.5 kg/m × 9.80665 m/s²\n=769.822025 N/m\n=0.769822025 kN/m"
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche5/tranche5-results.json`