PSI - Issue 64

Mariniello Giulio et al. / Procedia Structural Integrity 64 (2024) 2101–2108 G. Mariniello, D. Coluccino, A. Bilotta, D. Asprone / Structural Integrity Procedia 00 (2019) 000 – 000

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longitudinal beam, targeting a concrete cube positioned under the bridge. Diagonal measurements are facilitated by sensors attached to a steel bracket on the column, aiming at the midpoint of the longitudinal girder. To effectively demonstrate the sensor's capability in measuring heavy loads, a camera was utilized to correlate the passage of trucks with the deflection measurements. System validation was performed on just one of the viaduct's four spans, specifically span 3. The bridge decks are composed of highly stiff elements that produce displacements below one millimeter under normal operational conditions. Monitoring displacements in such a complex scenario is a challenging objective, a methodology that offers good performance on this benchmark will be able to predict the monitoring decks characterized by lower stiffness. 3. Real-time monitoring of bridge deck deflection Analyzing videos from cameras installed on the bridge enables the assessment of the structural response, as measured by lasers, about the size of crossing vehicles. The authors define a step function, Vehicles size (t), to represent the time-dependent, user-estimated size of each heavy vehicle crossing the bridge. The function assumes the highest value in the presence of a heavy truck, while an intermediate value in the presence of a medium truck. A comparison between the Vehicles size(t) function and L3 measurements reveals a strong correlation between the measured data and crossing loads. Specifically, clear peaks are observed in the measurements during the passage of heavy vehicles. Although the bridge has limited capacity to deform, the sensors are sensitive enough to detect displacements on the order of millimeters. This is evident in Figure 4, which shows the relationship between the vertical distance from the bridge deck to a reference point (raw data) and the passage of heavy vehicles across the bridge.

Fig. 4 Measurements collected by L3 sensors compared with the size of trucks.

Furthermore, by observing the raw signal from the diagonal sensors as depicted in Figure 5, it can be noted that there are significant peaks corresponding to the passage of vehicles, despite the important role played by the phenomenon of ambient noise amplification on them. This suggests the sensitivity of laser sensor even for non-vertical measurement of beam deflection despite physiological misalignment between sensor and target and the inducted