Automated flatness assessment for large quantities of full-scale precast beams using laser scanning

Prefabrication has been widely used in bridge construction, for which precast beams are produced from a beam yard and constructed with a cast-in-suit bridge deck. The developments recently are focusing on large dimensions or large quantities of beam units, which leads to the inevitable challenge of beam quality control. Among them, beam surface flatness as one of the important indicators for manufacturing quality needs to be strictly controlled to ensure structural performance. However, the commonly used methods still rely heavily on manually contact-based inspection, which is not only time-consuming but also error-prone. This paper presents an automated flatness assessment for large quantities of full-scale precast beams by using terrestrial laser scanning techniques. Through axis calibration, target surface segmentation, and flatness deviation calculation, flatness deviations of the segmented surfaces from the point cloud of the entire beam are calculated, and colored maps are generated to visually assess the flatness quality. The proposed approach was applied to numerical simulated models as well as laboratory-scale specimens for accuracy validation. Besides, its processing time was also compared to conventional contact-based inspection during a field test. Moreover, efforts are devoted to applying the proposed method on nearly a thousand precast beams in an in-field bridge construction project. Results can demonstrate its outperformance not only on accuracy but also the efficiency and practicality when applied to large quantities of full-scale precast beams.