The ultimate limit states are associated, among others, with the failure of a structural member and they generally concern safety of people.
For the verification of the ultimate limit state, design actions will not exceed the design resistance of the structure.
Once Ɛo is calculated, the analysis of the critical cross section for the ULS (Ultimate Limit State) is performed on the basis of Fig. 2-7,which shows the strain profile and internal forces at the Ultimate Limit State.
Forces equilibrium is carried out by using a parabola-rectangular stress block, as provided by Eurocode 2 (Fig. 2-8).
Concrete stress is determined according to the following equations: