Mining Vehicle & Underground Equipment worked example

Structural Fatigue Reserve at 18% joints likely to crack: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop joints likely to crack to 18%, then walk the calculation through step by step. Estimate a reserve to cover fatigue cracking and weld repair across the fatigue-critical structure of a mining vehicle over its service life.

The inputs for this scenario

  • Fatigue-critical joints: 40 joints (held at the documented default)
  • Reserve per joint: 2,200 $/joint (held at the documented default)
  • Joints likely to crack: 18 % (the input this scenario stresses; the baseline uses 25)
  • Inspection program setup: 6,000 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Fatigue reserve = critical joints x reserve per joint x crack-likelihood % + inspection setup.
  • Total structural fatigue reserve cost works out to 21,840 $ at these inputs, and this is the headline figure for the scenario.
  • Structural fatigue reserve cost per unit works out to 546 $ / piece at these inputs.
  • Variable structural fatigue reserve cost works out to 15,840 $ at these inputs.
  • Fixed structural fatigue reserve adder works out to 6,000 $ at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where joints likely to crack sits at 25% and the headline result is 28,000 $, this scenario comes in 22% below the baseline at 21,840 $.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to joints likely to crack, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. Crack likelihood is treated as one average across all joints; a frame with a few known high-stress hot spots needs those joints reserved separately at higher probability.

Results at a glance

  • Total structural fatigue reserve cost: 21,840 $ (headline result)
  • Structural fatigue reserve cost per unit: 546 $ / piece
  • Variable structural fatigue reserve cost: 15,840 $
  • Fixed structural fatigue reserve adder: 6,000 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Structural Fatigue Reserve calculator, set joints likely to crack to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.