Answer:
For the calculation of deformations in cracked sections (state II), the RF‑CONCRETE Deflect extension is available in the RF‑CONCRETE Surfaces add-on module.RF‑CONCRETE Deflect requires an explicit load situation for the analytical calculation of deformations in cracked sections (state II), which is only given using the load combinations (CO). Result combinations do not provide an explicit load situation, no matter if it is an additive or an enveloped OR combination. Therefore, when applying an RC for the calculation of deformations in RF‑CONCRETE Surfaces using RF‑CONCRETE Deflect, you receive the mentioned error message. See Image 01.
To avoid this problem, you can simply generate load combinations (CO) instead of result combinations (RC). If you still want to perform the ultimate limit state design with RCs, you can manually create an LC in addition to the existing RCs for which you want to calculate the deformations by means of RF‑CONCRETE Deflect. See Image 02.
It is important that for the calculation of the deformations, RF‑CONCRETE Surfaces applies the loads from a quasi-permanent design situation by default. See Image 03. This means that the LC for which the deformations are to be calculated must be defined as "quasi-permanent". As an alternative, it is also possible to user-define the check boxes for the settings of design situations (see Image 03).