Bridge Clearance Evaluation Based on Terrestrial LIDAR Scan

Low vertical clearance bridges over the roadway are vulnerable to overheight vehicle collision damage. Collisions can cause driver and passenger injuries/fatalities and property loss to the vehicle and bridge owners and can severely jeopardize the bridge structural capacity. However, accurate measurements of bridge vertical clearance can be difficult, especially when height differentials occur either as a result of site topography or a superelevated bridge deck. An automated measurement technique using light detection and ranging (LIDAR) scan is introduced to provide high-precision clearance data for bridge surfaces, from which minimum vertical clearance locations can be easily identified. Traffic can induce noises in terrestrial LIDAR imaging, hence, an approach to reduce noise is proposed. The results from field measurements on four bridges in Mecklenburg County, North Carolina, demonstrated the value of LIDAR-based measurement techniques and confirmed the deviation measurements from design criteria, which can be associated with the collision damage caused by deficient clearances.