Question:
I am designing surfaces in RF‑CONCRETE Surfaces and get a high minimum reinforcement in some areas as a result of the SLS design. In other areas, however, the minimum reinforcement is significantly smaller. Why?
Answer:
By default, the determination of the minimum reinforcement is based on the stress distribution in the tension zone before initial cracking (coefficient k-c according to EN 1992‑1‑1, 7.3.2 [7.2.]), which depends on the external loading (Image 01). This means that k-c is variable by default.
Depending on the state of stress (for example, pure bending, bending and tension, bending and compression, and pure tension), the minimum reinforcement can vary along the surface.
However, it is also possible to adjust the presetting. It is possible to select a bending constraint (k-c = 0.4) or a centric constraint (k-c = 1.0) (Image 02).
As soon as the constant value for k-c is assumed, the minimum reinforcement is independent of the external load and is applied uniformly over the structural component.
In this context, you can also select the direction in which the force should be considered (Image 03).