## 4 Experimental Results at Birago Palace Tests  
In the impact test carried out at Birago Palace in Turin (Italy), every masonry vault was divided into survey areas as shown in Figure 7, labeled with alphabet letters, within which both apparently intact and potentially damaged points were tested. For each point, at least three impacts were performed to obtain a better statistical response, and the return coefficient \(e\) was evaluated. The maps of the areas tested and the force-time curves of some tested points are shown, respectively, in the Pelagi (Figures 8 and 9), Blu (Figures 10 and 11), and Giunta rooms (Figures 12 and 13). Tables 1-3 show the coefficient averages for each point. Figure 7: Survey area on the Pelagi room vault. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Area** & **Test Point** & \(e=A_{2}/A_{1}\) & **Notes** & **Adhesion Plaster** \\ \hline \multirow{4}{*}{A} & P1 & 0.77 & & safe \\  & P2 & 1.21 & stuccoing & not safe \\  & P3 & 0.83 & & safe \\  & P4 & 1.08 & & not safe \\  & P5 & 1.33 & stuccoing & not safe \\ \hline \multirow{4}{*}{B} & P6 & 0.74 & & safe \\  & P7 & 0.73 & & safe \\  & P8 & 0.71 & & safe \\ \hline \multirow{4}{*}{C} & P9 & 0.66 & & safe \\  & P10 & 0.91 & & safe \\  & P11 & 1.36 & & not safe \\ \hline \multirow{4}{*}{D} & P12 & 0.66 & & safe \\  & P13 & 0.62 & & safe \\  & P14 & 0.65 & & safe \\  & P15 & 0.73 & & safe \\  & P16 & 0.75 & & safe \\ \hline \multirow{4}{*}{F} & P17 & 0.91 & & safe \\  & P18 & 0.69 & & safe \\  & P19 & 0.73 & & safe \\  & P20 & 1.43 & & not safe \\  & P21 & 0.68 & & safe \\ \hline \multirow{4}{*}{G} & P22 & 0.60 & & safe \\  & P23 & 0.62 & & safe \\ \cline{1-1}  & P24 & 1.19 & & not safe \\ \cline{1-1}  & P25 & 0.69 & & safe \\ \hline \end{tabular}
\end{table} 
Table 1: Results of impact test on Pelagi room vault. Figure 8: Map of the points and areas tested on the vault of the Pelagi room. Figure 11: Impact test on Blu room vault: Force–time curve of **(a)** P7 test; **(b)** P4 test. Figure 10: Map of the points and areas tested on the vault of the Blu room. Figure 9: Impact test on Pelagi room vault: force–time curve of **(a)** P13 test; **(b)** P5 test. It is possible to observe that most of the points tested had a return coefficient \(e\) lower than 1. This means that the energy returned was lower than that emitted, because part of this energy was dissipated by the tested structure through sufficient bonds in the interface between the plaster and the masonry surface. On the contrary, the return coefficient \(e>1\) showed a returned energy greater than the one emitted: in this case the material was already damaged [4; 5] because it was partly or \begin{table}
\begin{tabular}{c c c c c} \hline
**Area** & **Test Point** & \(e=A_{2}/A_{1}\) & **Notes** & **Adhesion Plaster** \\ \hline \multirow{4}{*}{A} & P1 & 0.68 & & safe \\  & P2 & 0.75 & & safe \\  & P3 & 0.71 & & safe \\  & P4 & 1.98 & Stuccoing & not safe \\ \hline \multirow{4}{*}{B} & P5 & 0.78 & & safe \\  & P6 & 0.65 & & safe \\ \hline \multirow{4}{*}{C} & P7 & 0.77 & & safe \\  & P8 & 0.76 & & safe \\  & P9 & 0.84 & & safe \\  & P10 & 0.79 & & safe \\  & P11 & 0.78 & & safe \\ \hline \multirow{4}{*}{D} & P12 & 0.75 & & safe \\  & P13 & 1.11 & & not safe \\  & P14 & 0.87 & & safe \\  & P15 & 0.70 & & safe \\  & P16 & 0.56 & & safe \\ \hline \multirow{2}{*}{E} & P17 & 0.83 & & safe \\  & P18 & 0.63 & & safe \\ \hline \multirow{4}{*}{F} & P19 & 0.72 & & safe \\  & P20 & 0.66 & & safe \\ \cline{1-1}  & P21 & 0.66 & & safe \\ \cline{1-1}  & P22 & 0.70 & & safe \\ \cline{1-1}  & P23 & 0.73 & & safe \\ \hline \end{tabular}
\end{table} 
Table 2: Results of impact test on Blu room vault. Figure 12: Map of the points and areas tested on the vault of the Giunta room. stuccoing, lower values of the maximum force and more asymmetric curves were recorded in which the area after maximum force was greater than that which preceded it (Figures 9b, 11b and 13b).