Full field LiDAR-based measurement of deflection and support condition effects in a scaled bridge model: comparison with traditional point sensors

Abstract Bridge inspections are critical for ensuring structural safety, and Structural Health Monitoring (SHM) provides continuous information on bridge performance. Traditional SHM methods rely on contact sensors or visual inspection, which may not capture the full extent of structural behavior. This study evaluates Light Detection and Ranging (LiDAR) as a noncontact technique for measuring bridge deflection and settlement. Unlike single-point instruments, LiDAR provides full-field measurements of the structure, enabling spatially continuous measurements of girder and support behavior. A scaled bridge model was constructed using aluminum I-beams and plywood decking, supported by concrete masonry blocks to simulate abutments. Support conditions were varied from all pins to all springs across eleven tests. LiDAR measurements were compared against control baselines obtained from string potentiometers, a laser reference method, and reaction scales. Results showed that LiDAR captured deflections with an overall average difference of 1.82 mm across the scaled bridge model and measured settlement with an average agreement of over 87%, corresponding to a maximum difference of 5.00 mm. Importantly, LiDAR captured changes in deformation patterns across support-condition cases that were not consistently reflected by single-point measurements, highlighting the value of spatially distributed displacement data. These findings support LiDAR as a reliable approach for quantifying deflection and settlement under varying boundary conditions and motivate further validation under field and dynamic loading conditions.