## 4 Structural Modeling  
### Definition of Loading Conditions  
Load conditions were defined according to the Italian code [6]. Regarding the building decks, structural dead loads (\(g_{1k}\)) were distinguished from non-structural dead loads (\(g_{2k}\)) according to NTC2018 [10]. Table 3 shows the characteristic values of structural and non-structural dead loads for the different stories and stair landings. Moreover, the weight of the staircases was applied along the walls of the RC cores, while the load of the cladding walls was distributed along the external perimeter (Table 4). Finally, the weight of the mechanical systems, at the top of the RC cores, is 5.34 kN and was distributed along their walls. The weight of the metal members and the reinforced concrete walls are automatically included in the structural model (\(g_{1k}\)). The live loads (\(q_{k}\)) are dependent on the category of use of the various parts of the structure, and they are defined in Table 5 according to Chapter 3 of NTC2018 [10]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Structural Element** & \(\mathbf{G_{1k}}\) **[kN/m]** & \(\mathbf{G_{2k}}\) **[kN/m]** \\ \hline \hline
\begin{tabular}{c} Stair elements \\ Infill masonry (with windows) \\ Infill masonry (without windows) \\ \end{tabular} & - & 6.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Characteristic values of linearly distributed loads. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Structural Elements** & **Declared Class/Grade** & **Experimental Results** \\ \hline Steel beams (HEA 260-IPE 240) & Fe37 & \(f_{ym}=327.30\) MPa; \(f_{tm}=451.50\) MPa \\ \hline Steel columns (HEB 260) & Fe37 & \(f_{ym}=327.30\) MPa; \(f_{tm}=451.50\) MPa \\ \hline Steel bolts and nuts & Class 8.8 & \(f_{yb}=640\) MPa; \(f_{ub}=800\) MPa \\ \hline Concrete (RC walls) & C 20/25 & \(f_{ck}=20\) MPa; \(R_{ck}=25\) MPa \\ \hline Steel smooth bars (RC walls) & FeB 32k & \(f_{ym}=434.70\) MPa \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical properties of the structural elements. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Story** & \(\mathbf{g_{1k}}\) **[kN/m2]** & \(\mathbf{g_{2k}}\) **[kN/m2]** \\ \hline \hline \begin{tabular}{c} Intermediate story \\ Roofing story \\ Stair landing \\ \end{tabular} & \
\begin{tabular}{c} 1.84 \\ 5.00 \\ 4.25 \\ \end{tabular} &
\begin{tabular}{c} 3.07 \\ 1.56 \\ 1.74 \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristic values of structural and non-structural dead loads. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Structural Element** & \(\mathbf{G_{1k}}\) **[kN/m]** & \(\mathbf{G_{2k}}\) **[kN/m]** \\ \hline
\begin{tabular}{c} Stair elements \\ Infill masonry (with windows) \\ Infill masonry (without windows) \\ \end{tabular} & - & 6.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Characteristic values of linearly distributed loads. The snow load was evaluated according to the following relationship [10]:  
\[q_{s}=\mu_{i}\:q_{sk}\:C_{E}\:C_{t} \tag{2}\]  
where \(q_{sk}\) represents the characteristic value of the snow, which, in this case, is 0.66 \(\mathrm{kN/m^{2}}\) according to the geographical position of the building. The coefficient \(\mu_{i}\) is the shape factor of the covering roof, which here is 0.80. Finally, \(C_{E}\) and \(C_{t}\) are, respectively, the exposure and thermal coefficients, both assumed to be 1.00. So, the final value of the snow load was 0.53 \(\mathrm{kN/m^{2}}\). The gravitational loads were combined according to the fundamental load combination for the ultimate limit state verification (SLU) and in the characteristic combination to check the serviceability limit state conditions (SLE). The loads were amplified with the partial safety factors and the combination coefficients prescribed in Section 2.5.3 of the current Italian provisions [6].