Question:
When performing the fire resistance design in RF‑CONCRETE Members, the acting internal forces (for example, My,Ed,fi) are applied that do not correspond to the internal forces of the applicable determination of internal forces. What is the reason?
Answer:
In the fire resistance design, the acting internal forces are determined again if taking into account the thermal expansion of the concrete and the reinforcing steel and the precamber due to the temperature difference (Image 01).
If the thermal expansions and the precamber are not taken into account, the acting internal forces should correspond to the internal forces of the calculation from RFEM or RSTAB (Image 02).
To what extent it is allowed to deactivate the thermal expansions and precambers, has to be checked in the context of the applicable standard.