## 3 Results
### Dynamic Identification Results  
Data for the dynamic identification of the west wall were collected with two, 30 min acquisitions. Using multiple acquisitions allowed for multiple recordings of data to be combined, thereby improving the amount of data collected on the wall. Using the same accelerometer and location for multiple acquisitions is essential for this. Fifteen accelerometer locations were selected; with eight accelerometers, this allowed for seven to be moved between setups, while one was kept in place. Five vertical lines across the wall were selected, allowing for three accelerometers to be placed vertically to record the shape and curvature of the wall at each line. An additional point below the lowest accelerometer was also added as a base, with no assumed movement or assigned measurement. The highest point on the midspan, shown as point 12 in the diagram, was selected as the reference point; for each acquisition, three accelerometers were placed along a line to the left of the reference, three accelerometers were placed in a line to the right, and one was placed below the reference point (Figure 9). It is important to note that accelerometers were only placed in the out-of-plane direction, as the stiffness of the wall in the in-plane direction was considered too high to present any descriptive mode shapes.  
The acquired data were processed using ARTeMIS 6.0 modal software for dynamic identification. The data were filtered to consider the frequency content from 0 Hz to 100 Hz  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test ID** & **Filtering** & \
\begin{tabular}{c} **Mean of Elastic** \\ **Modulus Before** \\ **Filtering (GPa)** \\ \end{tabular} &
\begin{tabular}{c} **Mean of Elastic** \\ **Modulus After** \\ **Filtering (GPa)** \\ \end{tabular} \\ \hline Crack & Type & 1.17 & 1.17 \\ Horizontal & Type & 2.54 & 1.89 \\ Vertical & Type & 1.35 & 1.35 \\ A (20–25 cm) & Distance & 2.39 & 1.10 \\ B (40–50 cm) & Distance & 1.74 & 1.74 \\ C (60–75 cm) & Distance & 1.81 & 1.54 \\ D (80–100 cm) & Distance & 1.65 & 1.65 \\ \hline Indirect * & Type & - & 1.56 \\ Indirect * & Distance & - & 1.54 \\ Direct & Type & 2.01 & 1.97 \\ \hline \hline \end{tabular}  
* Reconstructed datasets after separation and filtering.  
\end{table}
Table 3: Mean values from sonic testing before and after outlier filtering based on test type and distance.  
Figure 9: FE model of west wall with nodes for MAC calculations.  
for decimation, with a resolution of 1024. Raw signals were converted from a time domain to a frequency domain for processing in this way. Identification of the modes was performed using both a manual peak-selection process and the support of the Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification-Unweighted Principal Components (SSI-UPC) to validate the selected shapes (Figure 10a). Three modes were identified for the west wall setup, consistent with those from a fixed string vibration system due to the length of the wall. The frequencies for the first, second, and third mode were, respectively, 7.58 Hz, 10.84 Hz, and 14.13 Hz. Spatially, the first mode was composed of a single antinode at the midspan where the maximum displacement of the mode occurred, with two nodes at the ends of the wall. The second mode introduced an additional node and antinode, with the maximum displacement occurring at one-quarter of the length of the wall to effectively half the wavelength of the mode. The third mode introduced a final node and antinode pair, returning the maximum displacement to the midspan and introducing another half-wavelength to the system. These shapes are visible in Figure 10b.