Operations-aware structural monitoring of a 46-year-old bridge using traffic-induced vibrations and frequency-domain analysis

Abstract

This article proposes an integrated approach for structural health monitoring (SHM), as demonstrated on the 46-year-old Rayhanna Bridge that connects visual inspection data with operational dynamics and provides mitigation strategies. This approach starts with a condition survey indicating severe bearing conditions with elastomeric pads reduced in size from 74 to 48 mm. Accelerometers were installed for tri-axial data collection, and acceleration data were recorded over 3 weeks with live traffic conditions. Operational modal analysis was used to identify three stable frequencies at 2.5, 5.1, and 7.8 Hz with the highest dynamic demand in the central girder (G2). A physics-based vehicle–bridge interaction model was created with a higher order fractional beam and compliant bearings and validated against the data. The model has produced decision support tools such as resonance proximity maps, damage rate maps, and tuned mass damper (TMD) charts. The results indicate that the vehicle speeds between 12 and 19 m/s, or 43 and 68 km/h, produce a high-risk resonance band, which explains the observed amplification phenomena. A TMD designed to target the 5.1 Hz mode (mass ratio μ = 0.04, damping ζ = 0.12) has been shown to attenuate the resonant peaks by 3–5 dB. This work has created a defensible link between the degraded bearings and the asymmetric modal energy and second mode vulnerability. Finally, the process has developed operational interventions such as the development of a speed/lane management strategy for heavy vehicles, the prioritization of the central girder bearings, and TMD implementation criteria. This low-intrusion, data-driven approach has significant implications for operations-aware SHM, which will allow modest operational interventions and retrofit actions to be undertaken to extend the life of aged bridges.