In this study, the results of a vast experimental campaign on the applicability of a smartphone-based technique for bridge monitoring are presented. Specifically, the vehicle–bridge interaction (VBI)-based approach is exploited as a cost-effective means to estimate the natural frequencies of bridges, with the final aim of possibly developing low-cost and diffused infrastructure monitoring system. The analysis is performed using a common hybrid vehicle, fully equipped with classical piezoelectric accelerometers and a smartphone MEMS accelerometer, to record its vertical accelerations while passing over the bridge. In this regard, the experimental campaign is carried out considering the vehicle moving with a constant velocity on a bridge in the city of Palermo (Italy). Appropriate identification procedures are then employed to determine the modal data of the bridge from the recorded accelerations. Further, comparisons with the results of a standard Operational Modal Analysis procedure, using accelerometers directly mounted on the structure, are presented. Experimental VBI-based analyses are performed also considering the effect of several different vehicle velocities. Further, the applicability of smartphone-based sensor data is investigated, exploiting the possibility of using up-to-date smartphone accelerometers for recording the vehicle accelerations. In this regard, comparison between piezoelectric accelerometers and MEMS ones is performed to assess the reliability of these sensors for the determination of bridge modal properties.

The issue of monitoring the structural condition of bridges is becoming a top priority worldwide. As is well known, any infrastructure undergoes a progressive deterioration of its structural conditions due to aging by normal service loads and environmental conditions. At the same time, it may suffer serious damages or collapse due to natural phenomena such as earthquakes or strong winds. For this reason, it is essential to rely on efficient and widespread monitoring techniques applied throughout the entire road network. This paper aims to introduce an integrated procedure for structural and material monitoring. With regard to structural monitoring, an innovative approach for monitoring based on Vehicle by Bridge Interaction (VBI) will be proposed. Furthermore, with regard to material monitoring, to evaluate concrete degradation, a non-invasive method based on the continuous monitoring of the pH, as well as chloride and sulfate ions concentration in the concrete, is presented.