PSI - Issue 84

Marco Civera et al. / Procedia Structural Integrity 84 (2026) 1206–1213

1207

1. Introduction Structural Health Monitoring (SHM) plays a crucial role in ensuring the safety and longevity of civil infrastructure. However, traditional (i.e., direct) SHM relies on sensors installed directly on the structure; hence, its high cost and limited scalability make widespread deployment impractical. Drive-by or indirect Bridge Health Monitoring, which uses sensors mounted on passing vehicles, has therefore emerged as a promising alternative, especially for a first diagnostic scan, as it potentially offers a more cost-effective solution for bridge management. The number of scientific articles reporting the results of comprehensive full-scale tests involving a prototype instrumented vehicle has been increasing in recent years, but remains quite low. Among the most influential contributions are the pioneering field tests by (Benedetti et al., 2022; OBrien & Malekjafarian, 2016; Tan et al., 2019), which demonstrated the feasibility of using instrumented vehicles for the extraction of bridge modal properties. However, to the Authors' current knowledge, almost all full-scale tests reported in the literature underscore, in one way or another, the need for further development and validation of practical indirect SHM systems, as noted in a recent state-of-the-art review (Massarelli et al., 2024). More recent examples, published in the international literature over the year and a half since that previous work, show advances in data processing and technology (Cronin et al., 2025; Gkoktsi et al., 2024), but also that more systematic full-scale testing is still limited. For this reason, a collaborative effort was initiated to develop a novel multi-task instrumented prototype vehicle for bridge monitoring, called iBHM+ and introduced for the first time in this article. This initiative brought together industrial and academic expertise to design and experimentally validate an innovative mobile platform capable of acquiring multiple measurements, including accelerometric data for indirect SHM, on real-life, real-world road infrastructure. The system has been tested across different case studies and under various operational conditions to determine optimal monitoring configurations for the infrastructure owner, as illustrated in the following Sections. 2. The prototype vehicle The primary goal of this joint industrial and academic collaboration was to create an instrumented prototype vehicle, therefore called iBHM+, or indirect Bridge Health Monitoring and More , which will help the infrastructure owner/manager to achieve more rapid and flexible bridge management. The focus on operational and technical details, together with thoughtful state-of-the-art research, enabled us to design and realise the presented prototype vehicle, with optimal features for the intended use. A commercial vehicle, the Mercedes EQV 300 Extralong van, was selected for outfitting (see Fig. 1). The rationale was that the vehicle is fully electric, with very high battery capacity and efficiency, and, importantly, a large claimed autonomy (about 320 km). The choice of an electric vehicle (EV) was motivated by the need to eliminate the vibrations typical of combustion engines; this aspect helps to improve the quality of measurements (Fiandaca et al., 2022). The vehicle is approximately 5.37 × 1.93 × 1.90 m (length × width × height), with a longitudinal wheelbase of 3.43 m. Its weight, excluding the carried instrumentation and payload, is estimated at about 2.9 tons (front axle/rear axle distribution: circa 53% – 47%, i.e., ~1580 kg – ~1380 kg), with a maximum gross weight of 3.5 tons. The choice of this EV model was also motivated by its large interior space and stable configuration, which makes it suitable for accommodating the instrumentation, Data Acquisition (DAQ) system, and all the necessary auxiliary components. The EV was equipped with several sensors, not only limited to bridge dynamic identification. In particular, a total of four high-sensitivity, low-noise triaxial accelerometers (model Columbia SA-307LN) were mounted on the front and rear suspension control arms (Fig. 1 (a)), with one in correspondence of each wheel, to measure the bridge vibrations just above the wheel–suspension interface, avoiding additional vibration components that would be introduced if the sensors were placed inside the vehicle chassis. Fig. 1 (d) reports a schematic representation of the direction of the triaxial accelerometers with their local reference frames (in red). However, all measurements in the same direction are corrected and reported with respect to the global vehicle reference system (in blue). Apart from the accelerometers, a temperature probe and a GNSS antenna (Fig. 1 (b)) were also installed on the roof of the vehicle. The GNSS provides accurate positioning data, while an inertial navigation system (INS), namely the OxTS RT3000 v4, equipped with a CAN bus interface, was installed in the rear cabin to supplement it with detailed motion data. Collectively, these sensors allow for monitoring of the vehicle's state (position and speed) during