RF‑CONCRETE Surfaces displays failed design at some locations in Window 2.1 because the concrete compression stress is too high there (see Image 01). In this window, you can also use the [Info] button to check the design details for a result row selected in the table above. Based on the values shown in a new window, it is obvious that the membrane force resistance is smaller than the design membrane force in the strut direction (see Image 02).
As a result, the program displays a corresponding message of "not designable" on all finite elements with concrete compression stresses that are too great.
The theoretical background for this design can be found in the manual of RF‑CONCRETE Surfaces, among others. You can download it using the link under Reference or open it in the module by pressing the [F1] key.
In order to prevent non-designable situations, you can follow this procedure:
- The failed design may be caused by singularities.
- If there is no pure slab, the optimization of internal forces may be the cause. This should be deactivated in the case of shells and slabs (Image 03).
- It may be helpful to add a third reinforcement direction (Image 04).
- The concrete quality can be increased.
- The surface thickness can be increased.
![Spans Based on Figure 5.2 from [1]](/en/webimage/039540/3493372/01_Abmessungen_EN.png?mw=512&hash=3cc425f1463bd5981b358d5889e3109e07ae1233)
