Scaffolding Support Dependent on Normal Force
Tips & Tricks
In addition to their structural behaviour, the purpose of many temporary structures such as scaffolding or bracing is the adaptation to different geometric conditions. A stable state of the construction is usually achieved by a plated support situation.
However, this plated support situation affects the stability of the entire structure. Then the support acts no longer as a singular support but as a ‘flat foundation’.
The non‑flexible support plate reacts initially flexible in this situation. With increasing rotation of the support member, there is a certain moment resistance. This special relation is described in the following standards according to the structure type:
- EN 12811‑1: Temporary works equipment - Part 1: Scaffolds - Performance requirements and general design
- EN 1065: Adjustable telescopic steel props - Product specifications, design and assessment by calculation and tests
RFEM provides the nonlinearity option ‘scaffolding’ for the degrees of freedom of the node support φX' and φY', as required by the standards. After you select the option in the nodal support dialog box, you can create the Mφ diagram for the respective support points:
- φ0 = slip
- C = rotational spring stiffness
- e0 = slip eccentricity (depends on ke0 and D)
- emax = maximum eccentricity (depends on kemax and D)
- ke0 = slip eccentricity factor
- kemax = maximum eccentricity factor
- D = outer diameter of the member
- PZ' = support force in the Z'‑direction
The support remains moment-free until the rotation angle φ0 is reached. Then, the rotation does not change anymore until the moment Me0 = ke0 × D × PZ' is reached. Between the moment Me0 and the moment Memax = kemax × D × PZ', the support reacts with a rotational spring stiffness C. After the Memax is reached, the yielding starts.
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