Answer:
Since concrete has a nonlinear material behavior that can only be simulated with the CONCRETE NL module, it is not possible to analyze it using the RF‑STABILITY add-on module.
The use of another material model, such as isotropic linear elastic or isotropic plastic, would not represent the crack formation correctly, and the results are, therefore, not usable.
Stability analysis on columns can be performed with RF‑CONCRETE Columns or RF‑CONCRETE NL. You can find a small example under Downloads.
This example includes the design of a column using the RF‑CONCRETE Columns add-on module. Make sure that the calculation of the internal forces in RFEM is performed according to the geometrically linear analysis and that no imperfections are required, because the method used in the add-on module takes them into account.
The example also includes the design with RF‑CONCRETE NL. Here, it is also necessary to calculate according to the second-order analysis, and it requires imperfections in the form of inclinations. For better comparability, the layout of the longitudinal reinforcement was aligned with the result from RF‑CONCRETE Columns, as shown in Image 01 and Image 02. Since the reinforcement is optimized by the module after a new calculation, the desired reinforcement was saved as a template (see the red arrow).
