Pavements & traffic · Pavement design
Mechanistic pavement criteria (subgrade & asphalt) calculator
Allowable repetitions from subgrade vertical strain N = (9300/µε)⁷ and asphalt fatigue N = RF[6918(0.856Vb + 1.08)/(Smix^0.36 µε)]⁵.
Standard: Austroads AGPT02 (2012) performance relationships
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Subgrade vertical strain | 600 | µε |
| Asphalt horizontal strain | 180 | µε |
| Binder volume | 11 | % |
| Asphalt modulus | 3000 | MPa |
| Reliability factor | 1 | |
| Design traffic | 5000000 | ESA |
| SAR/ESA (asphalt 5, subgrade 7 adjustment) | 1.1 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Subgrade allowable | 214,942,298 | ESA |
| Asphalt fatigue allowable | 5,886,283 | rep |
| Subgrade damage | 0.023 | |
| Asphalt damage | 0.934 | |
| Limit | 1.00 |
- ✓ Subgrade damage ≤ 1
- ✓ Asphalt damage ≤ 1
Method, formulas and assumptions
- Subgrade allowable = (9300/600)^7 = 2.149e+8 ESA
- Asphalt fatigue allowable = 1*(6918*(0.856*11+1.08)/(3000^0.36*180))^5 = 5.886e+6 rep
- Subgrade damage = 5.000e+6/2.149e+8 = 0.023262
- Asphalt damage = 5.000e+6*1.1/5.886e+6 = 0.93438
- Limit = 1 = 1
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.