Laser-based multilevel framework for bridge deflection monitoring: Field implementation and structural health insights

This study presents and validates a novel, multilevel framework for real-time bridge deflection monitoring using cost-effective Time-of-Flight (ToF) laser sensors. The proposed framework enhances structural health monitoring (SHM) by providing scalable configurations depending on the availability of traffic information: (1) deflection-based anomaly detection under assumed stationary traffic, (2) correlation with video-based vehicle recognition, and (3) rapid load testing using vehicles of known mass. The approach was validated on the Volto Santo Viaduct in Naples, Italy, an operational highway bridge where the system was tested for nearly a year. The results demonstrate that the proposed deflection metrics provide a stable representation of the bridge’s behavior under variable operational conditions. In Level 3 experiments, a strong correlation (R = 0.92) was observed between controlled vehicle loads and measured deflections, confirming the system’s reliability. This research highlights the practical feasibility of using ToF laser sensors for establishing a robust performance baseline, essential for long-term structural health assessment.