## 5 Discussion of the Results  
The results reported in Tables 3 and 4 are shown in Figures 11-16 for a more immediate understanding of the outputs. It emerges that, for very short bridges with spans in the order of 5 m, the Load Rating Factor always results in a value much lower than one. The analysis also outlines how design loads prior to the World War 2 were less demanding than more recent ones, whereas design loads subsequent to 1945 highlight the presence of a capacity reserve with respect to the current line loads. With reference to the line loads, they are ordered by burdensomeness as well; thereby, the reserve capacity is higher for B2 line loads and lower for D4 line loads. It appears evident that the reserve capacity for each line is strongly influenced by the design code. Indeed, the 1945A code allows for remarkable capacity reserves, whereas lower Load Rating Factors \(V\) were found for the 1945B code. In fact, the most severe load in the 1945 code is the single-axis wagon, which in the 1945A design load has a higher value than in 1945B (see Figure 9), resulting in higher \(s_{min}\), and, as a consequence, a higher capacity. Reserve capacities similar to 1945B were obtained for 1925 code (Figures 11-13), although for the latter almost no capacity reserves were found when considering the dynamic amplification (Figures 14-16). Significant capacity deficits were always found for the analysis conducted with the 1926 design code, since distributed loads, such as the ones prescribed in such codes, are less critical, as the Load Rating Factor \(V\) is a function more of the shape of the bending moment than of its entity. As a consequence, the 1926 code allows for designing arches with depths \(s_{min}\) so low that they are not sufficient to meet the verification loads (B2, C3, and D4). It follows that it cannot be assumed that arches designed according to such a code are automatically verified for the line loads, as the obtained Load Rating Factors are always lower than one. Furthermore, verification against the 1925 and 1926 codes results in considerably lower capacities when dynamic amplification is considered (Figures 14-16). This is due to the fact that the dynamic amplification factor \(\Phi\) equals one for the 1925 and 1926 codes, i.e., no dynamic amplification was prescribed in the codes, whilst for the verification loads (B2, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{10}{c}{**Load Rating Factors \(V\)**} \\ \hline \hline \multirow{2}{*}{**Codes**} & \multicolumn{8}{c}{**Arch Bridge Length L (m)**} \\ \cline{2-9}  & **5** & **10** & **15** & **20** & **25** & **30** & **40** & **50** \\ \hline
1925 vs. B2 & 0.43 & 0.74 & 0.88 & 0.98 & 1.04 & 1.08 & 1.05 & 1.08 \\
1925 vs. C3 & 0.39 & 0.67 & 0.78 & 0.88 & 0.93 & 0.96 & 0.95 & 0.95 \\
1925 vs. D4 & 0.35 & 0.6 & 0.7 & 0.79 & 0.83 & 0.9 & 0.87 & 0.89 \\
1926 vs. B2 & 0.25 & 0.38 & 0.46 & 0.56 & 0.64 & 0.58 & 0.33 & 0.14 \\
1926 vs. C3 & 0.22 & 0.34 & 0.41 & 0.51 & 0.59 & 0.53 & 0.29 & 0.15 \\
1926 vs. D4 & 0.2 & 0.31 & 0.37 & 0.45 & 0.53 & 0.49 & 0.27 & 0.12 \\
1945A vs. B2 & 0.64 & 0.99 & 1.4 & 1.78 & 2.37 & 2.28 & 2.45 & 2.35 \\
1945A vs. C3 & 0.57 & 0.89 & 1.26 & 1.6 & 2.08 & 1.98 & 2.2 & 2.12 \\
1945A vs. D4 & 0.51 & 0.8 & 1.13 & 1.44 & 1.92 & 1.89 & 2.01 & 1.93 \\
1945B vs. B2 & 0.52 & 0.96 & 1.08 & 1.34 & 1.53 & 1.49 & 1.54 & 1.49 \\
1945B vs. C3 & 0.47 & 0.87 & 0.97 & 1.2 & 1.34 & 1.28 & 1.39 & 1.34 \\
1945B vs. D4 & 0.42 & 0.78 & 0.87 & 1.08 & 1.24 & 1.23 & 1.27 & 1.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Load Rating Factors \(V\) for the 1925, 1926, 1945A, and 1945B design loads, and the B2, C3, and D4 lines, with dynamic amplification. C3, and D4) it is always higher than one (Figure 10). Hence, the design \(s_{min}\) and \(H_{MAX,d}\) remain unchanged, as compared to the analysis without dynamic amplification, but higher verification loads are applied, resulting in more burdensome verifications.