615x
003331
2019-07-25

Question

When performing the fire resistance design in RF‑CONCRETE Members, 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 when taking into account the thermal expansion of the concrete and the reinforcing steel and precamber due to the temperature difference (Image 01).

If the thermal expansions and 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).

Check the context of the applicable standard to learn to what extent you are allowed to deactivate the thermal expansions and precambers.