EngiMetric Arena / Interpret & Validate
Is a 2.8 % rebar delivery difference a problem?
Competency Evidence interpretation primary Quantitative reasoning supporting
What you should take away: Interpret a theoretical rebar weight against a delivery ticket, recognising laps, cutting waste and mill tolerances.
The situation
What is happening
A slab schedule calls for 120 bars of 16 mm reinforcement, each 12 m long. The theoretical weight is 2.276 t. The delivery ticket shows 2.34 t, about 2.8 % more. The site engineer asks whether the delivery should be rejected. Choose the defensible interpretation.
Given
| Quantity | Value | Unit | Note |
|---|---|---|---|
| Bar diameter | 16 | mm | Scheduled reinforcement. |
| Bar length | 12 | m | Each bar. |
| Bar count | 120 | bars | Scheduled quantity. |
| Theoretical weight | 2.276 | t | From the bar schedule and unit weight. |
| Delivered weight | 2.34 | t | Delivery ticket. |
Assumptions this challenge makes
- The theoretical weight is based on nominal bar dimensions and density.
- The delivery ticket is a weighed or mill-certified quantity.
- Laps and cutting waste are not included in the theoretical bar schedule.
Your call
Your answer
Hints
- Compute the theoretical weight from nominal unit weight, length and count. Then compare the percentage difference.
- Ask what the theoretical schedule leaves out: laps, cutting waste and the mill’s permissible weight tolerance.
- The question is not whether the numbers differ, but whether the difference is evidence of an error.
Your answer Engine result
Where that comes from
Each limit, checked
Why
- The engine gives a unit weight of about 1.58 kg/m for 16 mm bar. For 120 bars of 12 m, the theoretical weight is 2.276 t.
- The delivery is 2.34 t, a difference of 0.064 t or about 2.8 %.
- That difference is consistent with laps, cutting waste and normal mill weight tolerance, none of which are in the theoretical schedule.
- The defensible interpretation is therefore that the delivery is not evidence of an error. It should be reconciled against the approved bar list, lap details and mill certificates.
- A theoretical weight is a design and estimating quantity; a delivery ticket is a commercial quantity. Treating them as the same number confuses two different purposes.
What this challenge does not establish
- The 2.8 % difference is plausible but not proven acceptable; the actual laps, waste and mill tolerance must be checked.
- The unit weight is nominal. Real bar weight varies within the mill tolerance.
- The calculation does not verify bar diameter, grade, length or certification.
- Contractual acceptance criteria may set a different reconciliation process.