Steel · Cold-formed & secondary steel
Car-park vehicle barrier (impact energy) calculator
Steel-post edge barrier in a car park. The impact force is found from the kinetic energy ½mv² absorbed by the deformation of the car (δc) and of the barrier (δb), solving the quadratic because δb itself depends on the force and the post stiffness; or enter a specified force. Posts are checked as cantilevers for bending (AS 4100 section slenderness for C350 SHS) and shear, and the base anchors for tension.
Standard: AS/NZS 1170.1 Cl 3.8 barriers · EN 1991-1-1 Annex B / BS 6399-1 energy method F = ½mv²/(δc + δb) · AS 4100 hollow sections
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 |
|---|---|---|
| Force basis | Energy method (m, v, δc) | |
| Vehicle mass | 1500 | kg |
| Impact velocity | 4.5 | m/s |
| Car deformation δc | 100 | mm |
| Specified force (if chosen) | 30 | kN |
| Load factor on the force | 1 | |
| Load height above the floor | 500 | mm |
| Post (SHS, C350L0) | 150x150x5.0 SHS | |
| Post fy | 350 | MPa |
| Posts sharing the impact (rail spreads load) | 2 | |
| Anchor lever arm (tension to compression) | 300 | mm |
| Anchors in tension per post | 2 | |
| Anchor design tension φNt | 70 | kN |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Kinetic energy ½mv² | 15.19 | kJ |
| Barrier stiffness (2 posts) | 97,672 | N/mm |
| Energy-method force | 149.6 | kN |
| Rigid-barrier force E/δc (upper bound) | 151.9 | kN |
| Design force F* | 149.6 | kN |
| Barrier deflection δb | 1.5 | mm |
| Post M* / φMs (λe = 33.1) | 37.4 / 47.5 | kNm |
| Post V* / φVv | 74.8 / 265 | kN |
| Anchor tension per anchor | 62.3 | kN |
- ✓ Post bending M* ≤ φMs — 79 %
- ✓ Post shear
- ✓ Anchor tension ≤ φNt — 89 %
- ✓ Barrier deflection ≤ 150 mm
Method, formulas and assumptions
- F = ½mv²/(δc + δb) with δb = F/K and K = n·3EI/h³ (cantilever posts) solved as a quadratic; m = 1500 kg and v = 4.5 m/s for car parks with vehicles ≤ 2500 kg (EN 1991-1-1 Annex B), δc = 100 mm.
- Check the force your jurisdiction specifies (AS/NZS 1170.1 Cl 3.8 and the BCA) and use the larger; the force acts over a 1.5 m length, so a continuous rail shares it between posts.
- Section slenderness for cold-formed SHS: λep = 30, λey = 40 (AS 4100 Table 5.2); φ = 0.9. Also check the slab edge for the anchor forces (AS 5216).
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.