Bridge Strain Monitoring Using Distributed Fiber Optics: Application and Validation under Traffic Loading

This study investigates the use of distributed fiber optic sensing (DFOS) with Optical Frequency Domain Reflectometry (OFDR) to monitor strain in reinforced concrete bridges under typical traffic loading. OFDR technology offers exceptional spatial resolution, uniquely suited for capturing localized behavior and detecting potential damage such as cracking. Sensing cables were strategically installed within the main span of the box girder to monitor load distribution in the bridge deck, with configurations spanning both longitudinal and transverse directions. Additional cables were embedded in the primary bridge column to detect axial and bending deformations. The system captures dynamic responses, including vehicle-induced vibrations and seismic excitations, with measurements taken along cables up to 50 meters in length. The first phase of the project focused on sensor installation and data acquisition, yielding detailed insights into both global and localized structural responses, including load distribution patterns under vehicular traffic. In the subsequent phase, strain measurements will be validated against computational models to compare real load distributions with design assumptions, providing crucial insights into the bridge’s actual structural behavior. Overall, this study highlights the potential of OFDR for high-resolution monitoring of critical infrastructure. The findings aim to enhance bridge safety and resilience by validating performance against design expectations and enabling rapid detection of structural anomalies or damage, an essential capability for post-earthquake assessments and long-term structural health monitoring.