Deflection Measurement through 3D Point Cloud Analysis



Moghaddame-Jafari, Bahman

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Point cloud technology is now used in inspection of bridges and tunnels where it is desired to remotely measure the structure’s movements such as settlements and member deformations. Current methods of point cloud analysis for measuring structural deflections require meshing or line/curve fitting to the point cloud data. This step adds an error to the overall accuracy of this technology and is not computationally stable. This study presents a novel method in measuring structural deflections through a per-point sampling method in which the point cloud is directly analyzed without the need for meshing or line/curve fitting. The 3D point cloud data is collected using Photogrammetry and the Structure-from-Motion (SfM) algorithm. The deflections are computed using Cloud-to-Cloud (C2C) distance measurement and Multiscale Model to Model Cloud Comparison (M3C2) algorithms. Through three-point flexural testing, series of aluminum specimens were deflected for validation. Two different statistical methods were used to determine the deflections along the member. The results indicate sub-millimeter accuracy in measuring vertical deflection. Furthermore, results suggest that this technique can be a tool to update locally the structure’s Finite Element Model to account for deformations in the structure.



3D point cloud analysis, Structure-from-Motion, Beam deflection measurement, Photogrammetry, Point cloud comparison, Structural health monitoring