Legend
L = Clear span [ mm ]
W = Width [ mm ]
bq = Load width from Pointload (Fp) in crossbar direction [ mm ]
bt = Load width from Pointload (Fp) in bearingbar direction [ mm ]
Fp = Pointload [ kN ]
Fv = Distributedload [ kN / m2 ]
ϒ = Safety factor variable load [ - ]
ν = Reductionfactor pressedgratings [ - ]
ulim = maximum deformation limit [ mm ]
mat = material [ - ]
t = bearingbar pitch [ mm ]
tcross = crossbar pitch [ mm ]
Basis of design
- Calculations are based on quality standard RAL-GZ 638 and cover the situation with one span and one load acting on the grating stairtread. The load can be a pointload in the middle of the span or a distributed load.
- Defelection limit of pressed gratings stairtreads is ulim = L*(1/300) with a maximum of 6 mm ( RAL-GZ 638 par 2.2.4 )
- RAL-GZ 638 describes the spread of the load over the bearing bars. The number of bearing bars activated depend on the width of the pointload and the spreading factor 'm' according RAL-GZ 638 table 1. For stairtreads, as a conservative approach, besides the bearing bars directly under the load no additional spreading is taken into account.
- When the point load deflection and stress checks are performed the nose of the stairtread is added. The dimensions of this stair tread nose is 33.33 x 2.0 mm and are based on the minimum stair tread nose dimensions.
- Horizontal forces are not taken into account.
- RAL-GZ 638 does not cover (local) instability checks
Material characteristics
| Steel quality: |
S235 |
|
| Specific weight: |
7850 |
kg/m3 |
| Material factor: |
1.0 |
|
| Design yield stress: |
235 |
N/mm2 |
| Modulus of elasticity: |
210000 |
N/mm2 |
| Steel quality: |
S355 |
|
| Specific weight: |
7850 |
kg/m3 |
| Material factor: |
1.0 |
|
| Design yield stress: |
355 |
N/mm2 |
| Modulus of elasticity: |
210000 |
N/mm2 |
| Steel quality: |
AISI 304 / AISI 316L |
|
| Specific weight: |
7980 |
kg/m3 |
| Material factor: |
1.1 |
|
| Design yield stress: |
209 (230/1.1) |
N/mm2 |
| Modulus of elasticity: |
200000 |
N/mm2 |
| Steel quality: |
AW-5754/H22 |
|
| Specific weight: |
2755 |
kg/m3 |
| Material factor: |
1.1 |
|
| Design yield stress: |
118 (130/1.1) |
N/mm2 |
| Modulus of elasticity: |
70000 |
N/mm2 |
This calculation tool is to be treated as a help tool only, no rights should be derived from its results. All technical projects of platforms and traffic arteries must be based on qualified strength calculations by the project structural engineer.
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