PSI - Issue 84

Ivan Beltracchi et al. / Procedia Structural Integrity 84 (2026) 1015–1022

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The monitoring system was conceived by the University of Brescia and implemented with an industrial partner to ensure safety, reliability, and robust long-term management of the collected data. It integrates a dynamic vehicle weighing system (weigh-in-motion, WIM) with structural health monitoring (SHM) system based on fibre-optic sensing, enabling high-frequency (100 Hz) real-time acquisition and centralized data processing. As shown in Fig. 3, the system comprises 18 sensors (namely accelerometers, tiltmeters, extensometers and laser displacement meters) connected via a fibre-optic network, together with two WIM platforms embedded in the asphalt layer on both sides of the outer lanes used by heavy vehicles. The platforms are located 35m upstream of the bridge in the Milan-bound direction and 100m upstream in the Verona-bound direction, allowing effective monitoring of traffic loads in both travel directions. The instruments used allow the load (measured using WIM) caused by heavy vehicles on the bridge span to be correlated with the structural response of the bridge in terms of both bending (measured through rotations and deflections) and shear (measured using extensometers positioned near the supports). The SMH system interface allows the filtering, storage, downloading and tracking of a large amount of available data relating to each mobile load detected and structural information. N.1 Vertical displacement (lower flange of the

beam in the centreline) N.10 Uniaxial tiltmeters N.3 Biaxial tiltmeters N.3 Extensometers (lower flange of the beam in the centreline) N.1 Extensometers (support beam core) N.2 Wheighing system (on one lane for each direction)

Fig. 3 Schematic of the SHM system installed on the bridge. The SHM system was validated through a load test using an exceptional 200 tons transport vehicle. During the test, traffic on the road beneath the bridge was temporarily halted, allowing displacement transducers mounted on telescopic poles to be installed at selected locations to independently verify the monitoring system readings. The vehicle was then moved through several positions along the bridge under quasi-static conditions. The analysis focused on the peak responses recorded by the devices, in particular the net deflections and the maximum rotations measured at both ends of the target beams directly beneath the outer lane. Overall, the load test confirmed the reliability of the data and it was set as a reference for the validation of the numerical models developed afterward. 3. Data analysis and processing To compare the deflections and rotations measured on the instrumented beams with the structural responses predicted by the structural models, an analytical approach was adopted to quantify transverse load redistribution for heavy vehicles travelling in the outermost lane. Specifically, a redistribution coefficient was estimated for each beam, representing the fraction of the total load carried by the individual member.

Fig. 4 Validation of the analytical approach with FEM model to evaluate the load redistribution coefficients for each beam.