PSI - Issue 84

Ana Avramova et al. / Procedia Structural Integrity 84 (2026) 560–568

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generally below 0.06 Hz and fluctuations limited to a few percentage points of the corresponding mean values. To verify the dependence of natural frequency variations on temperature changes, the coefficients of determination R 2 were computed and suggest that frequency variations are primarily driven by temperature variations for both viaducts. Moreover, the inspection of the results summarized in Errore. L'autoriferimento non è valido per un segnalibro. (VI03 viaduct) and Table 2 (VI04 bridge) shows that the VI03 bridge exhibits a stronger frequency temperature correlation than VI04. It is further noticed that identified modes exhibit different sensitivity to thermal effects, with torsion modes showing a stronger correlation with temperature (R² values between 0.921 and 0.755 for the VI03 viaduct and between 0.906 and 0.849 for the VI04 viaduct) compared to bending modes (R² values ranging from 0.905 to 0.861 and from 0.878 to 0.663, respectively).

Fig. 6 Measured temperature during the investigated period (from 05/06/2024 to 01/10/2025).

(a)

(b)

Fig. 7 Time evolution of the cleansed natural frequencies of (a) VI03 and (b) VI04 viaducts (from 05/06/2024 to 01/10/2025).