Mining Vehicle & Underground Equipment worked example

Structural Fatigue Reserve at 29% joints likely to crack: a worked example

What does the result look like when joints likely to crack reaches 29%? The full calculation is worked below with real intermediate numbers. A reliability engineer reserving for fatigue crack repairs on a haul-truck frame subjected to high-cycle dump and load duty.

The inputs for this scenario

  • Fatigue-critical joints: 40 joints (unchanged)
  • Reserve per joint: 2,200 $/joint (unchanged)
  • Joints likely to crack: 29 % (raised for this scenario; the documented default is 25)
  • Inspection program setup: 6,000 $ (unchanged)

Working through the calculation

  • Applying the documented formula (Fatigue reserve = critical joints x reserve per joint x crack-likelihood % + inspection setup) to the inputs above produces each figure below.
  • At this operating point the engine returns 31,520 $ for total structural fatigue reserve cost, the number this scenario is built around.
  • At this operating point the engine returns 788 $ / piece for structural fatigue reserve cost per unit.
  • At this operating point the engine returns 25,520 $ for variable structural fatigue reserve cost.
  • At this operating point the engine returns 6,000 $ for fixed structural fatigue reserve adder.

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 12.57% above the baseline at 31,520 $.
  • A figure at this level is achievable when joints likely to crack is genuinely sustained, not just peaked for a shift. 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: 31,520 $ (headline result)
  • Structural fatigue reserve cost per unit: 788 $ / piece
  • Variable structural fatigue reserve cost: 25,520 $
  • Fixed structural fatigue reserve adder: 6,000 $

Run it with your numbers

  • Every input above is editable in the live Structural Fatigue Reserve calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.