Analyze wheel load, support, stiffness, and design repetitions. View charts, exports, formulas, and worked examples. Create reliable pavement sections using transparent engineering calculations today.
This rigid pavement design calculator estimates a practical slab thickness for preliminary engineering studies. It combines wheel load, contact pressure, flexural strength, slab stiffness, subgrade support, safety factor, and traffic repetitions into one workflow. The result helps you screen whether a trial slab thickness is likely to meet stress and fatigue requirements.
The method uses a Westergaard style edge stress approach with iterative thickness checks. Each candidate slab thickness is tested from 150 mm to 500 mm. The tool then identifies the first thickness that keeps calculated design stress below allowable flexural stress and provides fatigue life at least equal to the selected design repetitions.
This is useful for concept design, comparison studies, classroom work, and fast sensitivity checks. It also gives a graph, export options, and an example table so the design process is easier to review. Final pavement design should still be checked against local code provisions, drainage conditions, load transfer details, shoulder support, dowel design, temperature effects, and project specific reliability requirements.
1) Effective design wheel load: P = W × LDF × IF
2) Contact radius: a = √(P / πp)
3) Radius of relative stiffness: l = [Eh³ / 12k(1 − μ²)]1/4
4) Edge stress: σe = [0.572P / h²] × [4log10(l/a) + 0.359]
5) Joint spacing adjustment: σd = σe × Joint Factor
6) Allowable stress: σallow = MR / Safety Factor
7) Stress ratio: SR = σd / MR
8) Fatigue life estimate: Nf = 1012(1 − SR) for practical screening when 0.45 ≤ SR < 1.00
This tool selects the first slab thickness where design stress is not greater than allowable stress and fatigue life is not less than required repetitions.
| Parameter | Sample Value | Unit |
|---|---|---|
| Wheel load | 65 | kN |
| Lane distribution factor | 1.00 | - |
| Impact factor | 1.10 | - |
| Tire pressure | 0.80 | MPa |
| Modulus of rupture | 4.50 | MPa |
| Elastic modulus | 30000 | MPa |
| Poisson ratio | 0.15 | - |
| Subgrade reaction k | 55 | MPa/m |
| Load repetitions | 500000 | repetitions |
| Safety factor | 1.20 | - |
| Joint spacing | 4.50 | m |
| Recommended slab thickness | 240.00 | mm |
| Design stress | 2.3140 | MPa |
| Allowable stress | 3.7500 | MPa |
It estimates a trial concrete slab thickness for rigid pavement using wheel load, support stiffness, concrete properties, safety factor, and traffic repetitions. It is best for preliminary design and comparison studies.
Wheel load directly affects contact radius and slab stress. Higher wheel loads generally require thicker slabs because the pavement must resist greater bending stress at critical locations.
It represents how strongly the foundation supports the slab. A higher k value means better support, lower deflection, and often a thinner required slab under the same loading conditions.
The safety factor lowers allowable flexural stress. It adds conservatism to account for uncertainties in construction, traffic, support conditions, and material variability during service life.
It is an estimated repetition capacity based on stress ratio. If estimated fatigue life is above your design repetitions, the selected thickness is more likely to perform acceptably in this simplified screening method.
Yes. Longer joint spacing can increase slab stress because curling and slab action become more demanding. The calculator applies a small adjustment factor to reflect that influence during screening.
Yes. The chart helps explain how stress changes with slab thickness. CSV and PDF downloads make it easier to document results, compare options, and include summaries in design notes.
No. Final design should also check local standards, load transfer, edge support, dowels, temperature effects, drainage, reliability, construction details, and project specific traffic spectra.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.