Temporary works & site · Cranes & lifting
Mobile crane outrigger pad / crane mat calculator
Worst outrigger load for a mobile crane slewing over a corner (crane + load share plus the load moment over the outrigger diagonal), the pad or timber-mat size for the allowable bearing pressure, and the bending stress in the mat as a cantilever beyond the outrigger float. Plan and section to scale.
Standard: AS 2550.5 · CIRIA C703 (crane stability & ground pressure) · AS 1720.1 timber bending
Open the live calculator → All temporary works & site calculators
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 |
|---|---|---|
| Crane mass in lifting configuration | 48 | t |
| Load incl. rigging | 6 | t |
| Radius | 12 | m |
| Outrigger spread (longitudinal) | 6.6 | m |
| Outrigger spread (transverse) | 6.2 | m |
| Outrigger float diameter | 0.5 | m |
| Mat width | 1.8 | m |
| Mat length | 1.8 | m |
| Mat thickness (timber) | 300 | mm |
| Timber bending strength f'b | 30 | MPa |
| Allowable bearing pressure | 200 | kPa |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Worst outrigger load (incl. 10 % dynamic) | 231 | kN |
| Bearing pressure under mat | 71 | kPa |
| Mat area required | 1.16 | m² |
| Mat cantilever beyond float | 0.65 | m |
| Mat bending stress | 1.0 | MPa |
- ✓ Bearing pressure ≤ allowable — 36 %
- ✓ Mat bending ≤ 0.8·f'b (k1 short-term) — 1.0 vs 24.0 MPa
- ✓ Outrigger load on one corner < 75 % of total — 44 %
Method, formulas and assumptions
- Worst corner load ≈ (crane + load)/4 + load × radius / (2 × half-diagonal), increased 10 % for dynamic effects; use the crane's outrigger-load calculator where available.
- Mat checked as a uniformly loaded cantilever from the float edge (one-way, full width). Rates of bearing pressure should come from a geotechnical assessment of the ground under the mat.
Related temporary works & site calculators
- Crawler crane lift check (radius, capacity, ground bearing) — Checks a crawler-crane lift against a load chart (radius vs rated capacity, interpolated), adds hook block…
- Spreader beam (lifting) — CHS strut, AS 4100 — A tubular spreader carrying a load from two lower slings with a two-leg upper sling to the hook. Sling…
- Lifting lug (padeye) plate check — A plate padeye with a pin hole: bearing on the plate, net-section tension across the hole, shear tear-out to…
- Precast pile lifting & pitching moments — A square precast concrete pile lifted horizontally at two points (0.207L from each end, equal hogging and…
- Driven pile: Hiley formula (set, capacity, blows per 250 mm) — Relates the final set per blow to the pile resistance for a drop or hydraulic hammer: R = ηh·W·h·ηb/(s +…
- Bored pile: concrete volume, cage and pour — Concrete and reinforcement quantities for a bored pile: theoretical and overbreak volume, trucks, tremie…
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.