## 3 Results  
### Modal Identification by Accelerometer Array  
The first two modal shapes at each measurement point are recognized by the particle movement technique [41] using accelerometer array. This technique requires filtering the signals on a narrow (e.g., 0.01 Hz) band-pass and setting the identified resonant frequencies as the center of the band-pass. For this purpose, a Butterworth band-pass filter was used. The width of the band-pass was sufficiently narrow to prevent nearby frequencies from contaminating the analyzed natural frequencies. The modal shape for the first resonant frequency of 2.49 Hz was estimated for each of the measured points. For this, a third-order Butterworth band-pass filter was applied in all the channels between frequencies 2.485 and 2.495 Hz. Figure 18a shows the particle movement of the acceleration signals in both directions for each of the points. The mode corresponding to the aforementioned frequency is torsional, generating greater accelerations along the T-axis of the N-W facade, corresponding to the axis of the more flexible direction of the structure. The rotational mode can explain the presence of the same resonant frequencies in the PSD of the signals in both directions. It can also be observed that point P5 has the lower accelerations in this frequency range. This fact could be due to the possible coupling with another building on the S-W facade, or superior stiffness in the S-W and N-W facades due to the absence of windows and openings. For the second frequency identified, the acceleration component corresponding to the frequency of 2.79 Hz was isolated using a band-pass filter between the cutoff frequencies of 2.785 and 2.795 Hz. In Figure 18b, the acceleration particle motion results for each of the five points measured on the roof of the studied building are shown. It can be observed that this frequency relates to a combined translational mode between both the L and T directions. The amplitude of the acceleration for this mode is similar in the five measured points of the structure and follows an E-W direction. Figure 17: Mean MSCs between each Rbin signal and the array of the rest of the selected signals (black). A 1 indicates high coherence and 0 indicates no coherence at all; the grey lines indicate the different MSCs for each of the combinations of signals. The frequencies 2.49 and 2.71 Hz are indicated with red and blue dashed lines, respectively. The modal shapes are described in Figure 19, where the first and second modes of the building are depicted. The first mode (Figure 19a), corresponding to a frequency of 2.49 Hz, is mainly rotational and the second mode (Figure 19b) is a combined translation mode with a frequency of 2.79 Hz. Finally, in order to find the fundamental frequencies and modes of the structure, it was necessary not only to find the highest energy peaks of the PSD by applying the widely used PPM, but also to isolate and study the dynamics corresponding to each of the selected frequencies. This is required to find out whether the natural frequencies correspond to the structure motion and not to an isolated or external element, inducing high-energy peaks in the PSD. In fact, the isolation of these two frequencies for all of the acceleration sensors allows us to depict the particle motions corresponding to each frequency (Figure 18) at different sites of the structure, which, in this case, are located on the roof. This allows us to link the recorded motion and the vibration modes. The first frequency clearly corresponds to a rotation mode, while the second frequency corresponds to a translation mode. The results of the first two frequencies and modes, corresponding to the studied building, are shown in Table 2.  
Figure 19: Modal shapes of the first (**a**) and second (**b**) modes of the _“La Vina”_ building, corresponding to a frequency of 2.49 and 2.79 Hz, respectively, determined by the particle motion method. The blue and red lines indicate the positive and negative maximum acceleration of one vibration cycle.