Project
Design traffic in heavy vehicle axle groups (Section 10.5.2)
Rigid pavements are designed for the number and load of each heavy vehicle axle group (HVAG), not for equivalent standard axles: concrete is sensitive to axle load magnitude (overloading) but much less to the number of repetitions (Section 10.5.2). Design period 30–40 years.
Design period, growth and design lane
| Growth period | Years | Growth rate (% a year) |
|---|
Heavy vehicles and axle loads
One row per vehicle type and load state (laden and empty as two rows): daily number in each direction in the count year and the load on each axle group (Table 2-1 vehicle types, Pakistan truck types at the NHA limits, or your own). Every axle group of every vehicle becomes one load in the spectrum.
| # | Vehicle (Table 2-1) & description | Dir. 1 per day | Dir. 2 per day | Axle groups & loads | Axle groups / vehicle | ESA / vehicle (n = 4) | ESA / day dir. 1 | ESA / day dir. 2 |
|---|
Use this when you know the total design traffic in HVAG but have no axle load survey. The load distribution is the example traffic load distribution of Austroads AGPT02 Appendix F (as used in its Appendix M worked example): 39.3% SAST, 0.9% TAST, 19.1% SADT, 25.9% TADT, 14.8% TRDT, each with a spread of loads. It is not from Road Note 31 and may not represent your road — use an axle load survey where possible.
Subgrade (Sections 3.3, 10.5.4.1)
Where the subgrade within 1 m below the sub-base is layered: CBRE = [Σ(hi CBRi0.333) / Σhi]3, layers top down to a depth of 1.0 m. Austroads conditions: combine layers thinner than 200 mm with a neighbour (using the lower CBR), stronger layers on top, no filter layers, maximum 15%.
| Layer (top down) | Thickness (m) | CBR (%) |
|---|
Concrete, shoulders, reliability & sub-base (Table 10-4 steps 2–6)
Concrete pavement options (Tables 10-4 and 10-7)
Costs (your rates, in place)
| Item | Rate | Unit |
|---|
Leave a rate blank if you don’t know it: options are then ranked by total thickness instead of cost.
Life-cycle cost (Chapter 12)
| Pavement type | Periodic maintenance per km | Every (years) |
|---|---|---|
| JUCP undowelled Jointed unreinforced concrete pavement, no dowels at the joints | ||
| JUCP dowelled Jointed unreinforced concrete pavement, dowels at the joints | ||
| JRCP Jointed reinforced concrete pavement | ||
| CRCP Continuously reinforced concrete pavement |
Road Note 31 gives no maintenance quantities: enter your own estimates (0 is allowed). Every type needs an entry before the options are ranked by life-cycle cost.
Options for this traffic and subgrade
Pavement types: JUCP = jointed unreinforced concrete pavement (plain slabs, no steel mesh); JRCP = jointed reinforced concrete pavement (longer slabs with steel mesh); CRCP = continuously reinforced concrete pavement (no transverse joints, continuous longitudinal steel). Dowelled = steel dowel bars across the transverse joints transfer load between slabs; undowelled = no dowels, load passes by aggregate interlock.
Selected design
Reinforcement, dowels, tie bars & joints (Sections 10.5.5.2, 10.6)
Concrete pavement types (Table 10-1)
Method, assumptions & references
- Traffic. Each axle group of each vehicle row is one load in the spectrum; repetitions = daily number in the design lane (Table 2-5 rule; for “heaviest direction” rules the direction with more axle groups) × seasonal factor × growth summed year by year (Equation 2-6). The MESA shown (for the Table 10-7 catalogue) uses the Table 10-2 standard loads with n = 4.
- Thickness design (Table 10-4). Effective subgrade CBR from Figure 10-2 (straight lines read from the figure, maximum 75%; below CBR 2 use 150 mm LCS and 5%). Equivalent stress Se and erosion factor F3 from Equation 10-5 with the coefficients of Tables 10-8 to 10-10 (CRCP and JRCP use the dowelled erosion table). Fatigue: Equations 10-2 to 10-4 (unlimited below Sr = 0.45); erosion: Equation 10-6 (F2 = 0.94 with, 0.06 without concrete shoulder; unlimited when the bracket is zero). The thickness is the least multiple of 5 mm with total fatigue and erosion damage ≤ 100%, and not less than Table 10-6.
- Verification. The engine reproduces the Austroads AGPT02-26 Appendix M worked example (40 million HVAG, CBRE 75%, 4.5 MPa, LSF 1.3, undowelled with shoulders): equivalent stresses and erosion factors of all five groups to 3 decimals, total fatigue 125% / erosion 119% at 210 mm and 66% / 93% at 215 mm, design thickness 215 mm.
- Catalogue. Table 10-7 gives slab and sub-base by MESA and foundation class (F1–F4 from the subgrade class and the capping of RN31 Key 3).
- Below the sub-base RN31 asks for at least 150 mm of unbound granular or selected subgrade material (Section 10.5.4.2); it is added to every option unless capping already provides it.
- Steel. JRCP mesh and transverse / tie steel by subgrade drag (Equation 10-7, fs = 0.6 fsy, ρ = 2400 kg/m³); CRCP longitudinal steel by Equations 10-8 and 10-10 with the 0.67% minimum; cover Table 10-11; dowels Table 10-14 (450 mm long at 300 mm).
- Costs. Construction quantities per km over the carriageway width at your rates; joint sealing, formwork and curing are not priced.
- Not covered: RCC and CRCB thickness (RN31 gives none), steel fibre concrete, roundabouts (LSF + 0.3), mix design (Section 10.5.6).
Road Note 31 misprints found against the Austroads source
- References: Road Note 31, 5th edition, TRL 2023 (FCDO / ReCAP), Chapter 10; Austroads AGPT02-26 Guide to Pavement Technology Part 2: Pavement Structural Design, Chapter 9 and Appendix M. Check every design against your road agency’s requirements.