2.6.4.2 Check of principal internal forces

Check of principal internal forces

The program first checks if the concrete cracks under the principal moment in the ULS. In the serviceability design details of the relevant grid point, we can see that this is indeed the case:

The linear-elastically determined stress σ_c,I,-z at the upper concrete edge is compared to the mean value of the axial tensile strength f_ctm of 2.9 N/mm² for concrete C30/37.

${\sigma }_{c,l,-z} = \frac{m_{l,-z}}{W} = \frac{m · 6}{b · h^2} = \frac{33.65 · 6}{1.0 · 0.2^2} = 5.05 {\text{N/mm}}^{2 }$

Thus, the concrete edge stress σ_c,I,-z = 5.05 N/mm² significantly exceeds the tensile strength f_ctm. The reinforcement is therefore also activated for the serviceability limit state.