Question:
If I do not specify any basic reinforcement in RF‑CONCRETE Surfaces, I obtain the value X as an additionally required reinforcement. If I enter this value X as the provided basic reinforcement, I correctly do not get any additional required reinforcement.
However, if I enter a value lower than the determined required total reinforcement as the basic reinforcement, the additionally required reinforcement is increased in such a way that the originally required reinforcement content is exceeded. Why?
Answer:
Please check the concrete covers of the basic reinforcement and the additional reinforcement. In this case, a higher concrete cover is probably defined for the additional reinforcement than for the basic reinforcement.
If the existing basic reinforcement is so small that the additional reinforcement is required, but a lower effective depth is available due to the higher concrete cover, the program must adjust the reinforcement content accordingly; that is, increase it.
Therefore, the concrete covers in the "Reinforcement Layout" tab in Window 1.4 "Reinforcement" have to be considered; see the image.