## 5 Discussion of the Results
When applying the dynamic amplification, the values of the Load Rating Factors \(V\) for the 1925 design loads are, therefore, lower or just slightly higher than one, even for spans above 5 m.  
Figure 11: Load Rating Factor of arches verified with B2 loads. Figure 12: Load Rating Factor of arches verified with C3 loads. Figure 14: Load Rating Factor of arches verified with B2 loads, with dynamic amplification. Figure 13: Load Rating Factor of arches verified with D4 loads. Based on the results of the parametric analysis, some indications can be gathered for masonry arches designed according to Italian codes. For bridges with spans \(L<10\) m, or designed according to the 1926 design code, no evidence of capacity reserve was found. With regards to bridges designed according to 1925 code, they resulted in being verified for \(L\geq 10\) m when dynamic amplification is neglected. Instead, when dynamic amplification is considered, a capacity reserve is found only when the B2 verification line load is used on bridges with spans \(L\geq 25\) m. As far as the 1945 code is concerned, when dynamic amplification is neglected, only bridges with spans \(L\geq 10\) m are able to withstand the current loads, whereas when dynamic amplification is accounted for, different results are presented. Figure 16: Load Rating Factor of arches verified with D4 loads, with dynamic amplification. Figure 15: Load Rating Factor of arches verified with C3 loads, with dynamic amplification. between 1945A and 1945B codes can be observed. In particular, when using the 1945A code, a reserve capacity is found for arches with spans \(L\geq 15\) m, while for bridges designed according to the 1945B code a capacity reserve is observed for structures with spans \(L\geq 20\) m, or for spans \(L\geq 15\) m if the B2 verification line load is used. The minimum spans found for the generic arches, to show a reserve capacity, are summarized in Table 5.  
As a final remark, it is important to note that applying dynamic amplification does not necessarily imply that the reserve capacity decreases. This can be observed by comparing the Load Rating Factor obtained for the 1945 codes with and without dynamic amplification (Figures 17-19). The trend shown by the curves can be explained looking at the dynamic amplification factors applied (Figure 10). The dynamic amplification factor for the 1945 design code \(\Phi_{1945}\) is equal to 1.25, and similar values of the amplification factor are prescribed for 25 m span bridges in the B2, C3, and D4 line loads. Accordingly, for \(L=25\) m the Load Rating Factor \(V\), with and without dynamic amplification, is almost the same (Figures 17-19). Instead, the factors for the B2, C3, and D4 line loads, respectively \(\Phi_{B2}\), \(\Phi_{C3}\), and \(\Phi_{D4}\), are higher than \(\Phi_{1945}\) for spans \(L<25\) m, and lower than \(\Phi_{1945}\) for spans \(L>25\) m (Figure 10). In a similar way, for \(L<25\) m, lower values of the Load Rating Factor \(V\) are obtained, since the verification load becomes more severe compared to the design loads, whereas for \(L>25\) m, the verification load becomes less burdensome, resulting in higher values of the Load Rating Factors \(V\) (Figures 17-19). Figure 17: Load Rating Factor of arches designed according to the 1945 code and verified with B2 loads, both with and without dynamic amplification comparison. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Minimum Span of the Arch \(L\) (\(m\)) for Obtaining a Load Rating Factor \(V\) \textgreater{} 1**} & & & & \\ \hline \hline \multirow{2}{*}{**Design**} & \multirow{2}{*}{**Loads Verification**} & \multicolumn{2}{c}{**Without Dynamic Amplification**} & & & \\ \cline{2-6}  & & **B2** & **C3** & **D4** & **B2** & **C3** & **D4** \\ \hline
1925 & 10 & 10 & 10 & 25 & / & / \\
1926 & / & / & / & / & / & / \\
1945A & 10 & 10 & 10 & 15 & 15 & 15 \\
1945B & 10 & 10 & 10 & 15 & 20 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Minimum spans of bridges highlighting Load Rating Factor \(V>1\).