PSI - Issue 84

Tommaso Pivetta et al. / Procedia Structural Integrity 84 (2026) 1286–1293 T. Pivetta et al. / Structural Integrity Procedia 00 (2026) 000–000

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Table 3. Comparison between Experimental and Numerical natural frequencies after model calibration. Vibration mode Exp. Freq. (Hz) FEM Freq. ( Hz ) Error (%) Mode 1 3.919 3.887 0.816 Mode 2 4.302 4.325 0.535

4.2. Deflection Validation Once the model was successfully calibrated with respect to the dynamic response, a linear dynamic analysis reproducing the passage of the two heavy vehicles employed in the experimental campaign was performed. The total duration of the analysis was set to 20 seconds. Within the same analysis, the crossing of the 44-tonne vehicle and subsequently the 108-tonne vehicle was simulated, both travelling at a speed of 70 km/h. The two vehicles were set to cross the structure with a temporal separation of about 10 seconds, in order to ensure the decay of the free vibrations after the passage of the first vehicle. The time history response of the external girder at midspan is presented in Fig. 8.

Fig. 8. Numerical vertical deflection.

From the results, a maximum vertical deflection of 2.41 mm was reached during the crossing of the 44-tonne vehicle, while a peak value of 5.76 mm was obtained for the heavier vehicle. A comparison between experimental deflections, measured through a radar system at the same position, and the numerical deflection is presented in Table 4. For both load cases, the error is approximately 5%, confirming a satisfactory correspondence not only in terms of dynamic parameters but also with respect to the displacement response under controlled moving loads.

Table 4. Comparison between Experimental and Numerical vertical deflections after model calibration. Vehicle Exp. Dz. (mm) FEM Dz. ( mm ) Error (%) 44 tonnes 2.54 2.41 5.12 108 tonnes 6.01 5.76 4.16

5. Conclusion This paper presented a case study concerning the development and calibration of a high-fidelity finite element model of an existing bridge located in northern Italy. The bridge was first subject to an extensive geometric and