Structural Parameter Identification of Ancient Stone Arch Bridge via Three-Dimensional Laser Ranger Scanning

Stone arch bridges are symbols of a shared civil engineering heritage worldwide, but they suffer from damage caused by various natural disasters that have occurred during their long service. The basis of ancient bridge preservation is the current situation assessment. This study proposes a structural parameter identification method for stone arch bridges via three-dimensional (3D) laser scanning. An automatic algorithm of arch axis extraction from massive point cloud data is developed and applied to the 800-year-old Lugou Bridge (LGB) in Beijing, and its structural parameters are identified from the extracted arch axis. The results reveal that the LGB’s arch axis is close to the arc curve. The axis extraction is accurate and the identification method is reliable, when compared to field measurement. The relative deformation between the upstream and downstream sides of each arch and the relative deviations of the clear rise and span between two longitudinally symmetric arches are manifestly large. This study extends the current identification methods for bridge heritage based on a 3D point cloud and provides a useful basis upon which to protect ancient arch bridges.