Answer:
Yes, you can use "orthotropic surfaces" for reinforced concrete design in RF‑CONCRETE Surfaces.
If you only want to perform ultimate limit state designs, no further settings are required in RF‑CONCRETE Surfaces with regard to the surface type.
For serviceability limit state designs, you need the RF‑CONCRETE NL add-on module. Select the "Nonlinear..." method of check in the "Serviceability Limit State" tab (in Window "1.1. General Data"). See Image 01.
Then, in Window "1.3 Surfaces", you can change the surface type to "Constant" to also enable the serviceability limit state design. See Image 02.
