Automated Inverse Modeling And Digital Pre-assembly Of Steel Box Arch Structure Using Point Cloud

In order to reduce the economic cost of physical assembly of steel box arch segmental components,the time cost of point cloud processing in digital pre-assembly engineering and the learning cost of processing personnel,this thesis studies the automatic reverse modeling and digital pre-assembly of the steel box arch structure point cloud,so as to more automatically predict the geometric shape of the assembled steel box arch structural components.The research content is as follows:1)This study proposes an automated method for inverse modeling of steel box arches based on laser scanning point cloud data.The method includes preprocessing the point cloud data,using the region growing algorithm to segment the data into web,top and bottom plates,and extracting features,and finally using the node coordinates to establish a quasi-uniform interpolation B-spline surface for modeling.2)This study analyzes the multipath errors of 3D laser scanners,which can lead to segmentation errors in point clouds.The study proposes a method to determine the threshold value of the normal vector of the region growing algorithm by using the structural characteristics of the arch structure itself,so as to avoid the influence of multipath error when cutting the laser scanning data.The conclusion proves that the modeling error using the proposed automated method is within the error range of the relevant regulations.3)The study compared the model with the original point cloud data,counted the number distribution of point clouds in different distance intervals,and finally analyzed the accuracy of the automatically generated inverse model.The study also analyzed errors that occurred at different stages of the automated modeling process.4)This study proposes a digital pre-assembly method using an inverse model of a steel box arch,which combines a virtual trial assembly method with drawings.The conclusion proves that the proposed method ensures the parallelism of all component webs,avoids the influence of the margin of the top plate and bottom plate on the assembly results during the manufacturing process,and can better simulate the physical assembly.5)This study proposes an analysis method for digital pre-assembly results,which is mainly divided into two aspects: arch structure base plate and base plate linear analysis and web welding and cutting area analysis.Line analysis involves comparing the line errors of the roof and floor plates of the design model and the assembled model after assembly.Deviation analysis evaluates the dimensions of cuts and welds required for preassembly and visualizes the deviation dimension information in model space.6)This study compared the GPA pre-assembly method with the virtual pre-assembly method based on the ICP algorithm which is proposed in this study.And finally believed that the virtual pre-assembly method based on the ICP algorithm could better simulate the actual engineering pre-assembly.7)This study applies the proposed method to the arch segmental members of the Liaozi Bridge,and proves that the proposed method is applicable to full-scale members in the project.