The different verifications required by EN 1992-1-1 are assessed based on the direct results provided by the model. ULS verifications are carried out for concrete strength, reinforcement strength, and anchorage (bond shear stresses).

The **concrete strength** in compression is evaluated as the ratio between the maximum principal compressive stress σ_{c3} obtained from FE analysis and the limit value σ_{c3,lim}. Then:

\[\frac{σ_{c3}}{σ_{c3,lim}}\]

\[σ_{c3,lim} = f_{cd} = α_{cc} \cdot \frac{f_{ck,red}}{γ_c} = α_{cc} \cdot \frac{k_c \cdot f_{ck}}{γ_c} = α_{cc} \cdot \frac{\eta _{fc} \cdot k_{c2} \cdot f_{ck}}{γ_c}\]

\[{\eta _{fc}} = {\left( {\frac{{30}}{{{f_{ck}}}}} \right)^{\frac{1}{3}}} \le 1\]

where:

*f** _{ck}* characteristic cylinder strength of concrete,

*k** _{c2}* compression softening factor (see 5.1.1),

γ_{c }is the partial safety factor for concrete, γ_{c} = 1,5,

α_{cc} is the coefficient taking account of long term effects on the compressive strength and of unfavourable effects resulting from the way the load is applied. The default value is 1,0.

The **strength of the reinforcement** is evaluated in both tension and compression as the ratio between the stress in the reinforcement at the cracks σ_{sr} and the specified limit value σ_{sr,lim}:

\[\frac{σ_{sr}}{σ_{sr,lim}}\]

\(σ_{c3,lim} = \frac{k \cdot f_{yk}}{γ_s}\qquad\qquad\textsf{\small{for bilinear diagram with inclined top branch}}\)

\(σ_{c3,lim} = \frac{f_{yk}}{γ_s}\qquad\qquad\,\,\,\,\textsf{\small{for bilinear diagram with horizontal top branch}}\)

where:

*f** _{yk}* yield strength of the reinforcement,

*k* the ratio of tensile strength f_{tk} to the yield stress,

\(k = \frac{f_{tk}}{f_{yk}}\)

γ_{s }is the partial safety factor for reinforcement γ_{s} = 1,15.

The **bond shear stress** is evaluated independently as the ratio between the bond stress τ_{b} calculated by FE analysis and the ultimate bond strength f_{bd,} according to EN 1992-1-1 chap. 8.4.2:

\[\frac{τ_{b}}{f_{bd}}\]

\[f_{bd} = 2.25 \cdot η_1\cdot η_2\cdot f_{ctd}\]

where:

*f*_{ctd } is the design value of concrete tensile strength. Due to the increasing brittleness of higher strength concrete, *f*_{ctk,0,05 }is limited to the value for C60/75,

η_{1} is a coefficient related to the quality of the bond condition and the position of the bar during concreting (Fig. 33):

* *η_{1} = 1,0 when ‘good’ conditions are obtained and

* *η_{1} = 0,7 for all other cases and for bars in structural elements built with slip-forms, unless it can be shown that ‘good’ bond conditions exist

η_{2} is related to the bar diameter:

η_{2} = 1,0 for Ø ≤ 32 mm

η_{2} = (132 - Ø)/100 for Ø > 32 mm

*\[ \textsf{\textit{\footnotesize{Fig. 33\qquad Description of bond conditions.}}}\]*

These verifications are carried out with respect to the appropriate limit values for the respective parts of the structure (i.e., in spite of having a single grade both for concrete and reinforcement material, the final stress-strain diagrams will differ in each part of the structure due to tension stiffening and compression softening effects).