## 2 Testing the Cho'ponota L1 Bridge
### Operational Modal Analysis Tests  
This section presents the details and results of the OMA conducted to determine the structural behavior of the bridge in its current state, specifically focusing on its dynamic characteristics, such as frequencies and mode shapes. Dynamic characteristics are also referred to as the behavior exhibited by the structure under environmental or forced vibrations and are unique to each structure. These characteristics are particularly important as they serve as an indicator of whether a finite-element model (FEM), which is created as a three-dimensional representation in a computer environment, accurately represents the constructed, real structure. Therefore, the results obtained from the finite-element model and the operational measurements must be closely aligned. For the OMA tests of the Cho'ponota L1 Bridge, sensitive accelerometers were placed at specific points on the bridge. The locations of the accelerometers were determined based on the mode shapes obtained from the modal analysis of the bridge's initial finite-element model. Figure 9 presents the mode shapes corresponding to the first 10 bending modes obtained from the initial finite-element model of the Cho'ponota L1 Bridge. Figure 9: Frequencies and mode shapes of the first 10 bending modes of the Cho’ponota L1 Bridge. In Figure 9, mode shapes with different amplitudes are observed for each mode in the finite-element model of the bridge, and each span moves in distinct patterns. Based on this visualization, the placement of accelerometers in spans S1, S2, and S3 of the bridge has been determined. Figure 10 summarizes the accelerometer placement plan for spans S1, S2, and S3 of the bridge. In each span, six sensitive accelerometers were placed at equal intervals in the vertical direction to capture the bending modes. The tests used B&K 8340 type single-axis accelerometers, with a dynamic range of 120 dB and a frequency range of 0-1500 Hz. The raw signals captured by these high-sensitive sensors were recorded using the B&K Type 3560C data acquisition unit and transferred to the PULSE Labshop Software Release 11.2 [82]. The raw signals processed in PULSE Labshop were then transferred to Dynamic Modal Release 1.0 [83] and Operational Modal Analysis Software Release 4.0 [84], where they were digitized using frequency and time domain methods to obtain the structure's frequencies and mode shapes. In the OMA tests conducted separately for the three spans, the first 10 frequency values and mode shapes of the bridge were determined. The frequency range was selected as 0-8 Hz, and measurements were taken for 15 min per span, resulting in a total measurement duration of 45 min. The OMA measurements were repeated twice, once before and once after the loading tests. The frequencies and mode shapes obtained prior to the loading tests were accepted as the reference values of the bridge. The results of the measurements conducted after the loading tests were compared with these reference values to determine whether any damage occurred in the structure due to the loading tests. In the conducted OMA tests, the Singular Values of the Spectral Density Matrices (SYMSV) obtained from all measurements for each span are presented in Figures 11-16. As a result of the OMA tests conducted on the Cho'ponota L1 Bridge, the operational mode shapes obtained for each span were found to be consistent with the mode shapes from the finite-element model. The visuals of the first 10 bending mode shapes for the three spans of the bridge are presented in Figure 17.  
The frequency values obtained from the OMA tests conducted on the bridge before and after the vehicle loading tests are comprehensively summarized for each span in Table 6. As detailed in Table 6, the comparison of frequency values derived from OMA measurements before and after the loading tests reveals a maximum of 1.95%. This maximum value suggests that the structural integrity of the bridge remains largely unaffected by the vehicle loading tests.