关键词: 地面激光扫描, 点云切片, 钢桁拱桥线形, 全站仪测量

Abstract:

The alignment measurement of railway bridge plays an important role in bridge health detection and the safe operation of railway. In order to improve the efficiency of alignment measurement of steel truss arch bridge in operation railway, this study constructed a complete “pure” bridge point cloud model. It took a three-span steel truss arch bridge as an example and used the terrestrial laser scanning (TLS) technology to scan the bridge members as a whole. From the three aspects of bridge alignment measurement accuracy, scanning integrity and point cloud number, the optimal number of bridge scanning stations was determined as 10. The 3DNDT point cloud registration algorithm was used to register each station one by one. The accuracy of bridge point cloud registration is 2 mm. The bridge point cloud was projected onto the xoy plane and the noise points were removed by the radius filter. The point cloud equidistant slicing and point cloud plane slicing algorithm were proposed to extract the bridge alignment, and the alignment point cloud data was exported to Auto CAD to pick up the coordinates. The point cloud slicing method was used to extract the TLS measurement value, and the total station method measurement result was compared with the original bridge alignment. In the analysis of the bridge deck alignment, the two methods measured the maximum deformation at the mid-span A₅ point as 12.69 mm and 10.29 mm. The maximum mutual difference R of the two methods is 2.4 mm, and the correlation coefficient is better than 99.93%. In the analysis of arch axis alignment, the maximum deformation of point cloud slicing method and total station method is 6.2 mm and 3.9 mm at B₄ point in the upper chord span of main truss, and 5.9 mm and 3.5 mm at B₁₀ point in the lower chord span of main truss. The maximum mutual difference R of the two methods is 3.2 mm, and the correlation coefficient is better than 99.87%, which verifies the effectiveness of point cloud slicing algorithm and the high precision of TLS measurement. There is no obvious lateral displacement in the transverse alignment of the arch axis. The verticality of the 19 suspenders obtained by the point cloud equidistant slicing remains good, and no torsion and offset occurs. The research results provide a reference for the alignment analysis and point cloud processing methods of the operating railway steel truss arch bridge, and have important practical value.

Key words: terrestrial laser scanning, point cloud slicing, alignment of steel truss arch bridge, total station measurement