A method for detecting construction deviations in large and complex building structures utilizing synthetic point clouds for segmentation

Point cloud-based construction quality assessment and quality control (QA/QC) are playing an increasingly important role in large-scale complex building projects. However, this approach faces several challenges, such as the laborious and time-intensive process of manual point cloud segmentation, the high cost of point cloud labeling, and the lack of sufficient training data for deep learning-based automatic segmentation methods. To address these issues, this paper proposed a method for detecting construction deviations in large-scale complex building structures by utilizing synthetic point clouds for segmentation. The method automatically generated labeled synthetic point clouds with Gaussian noise using BIM and a virtual engine, significantly augmenting the limited amount of real point cloud data to train the semantic segmentation model, enabling the achievement of 94.2% overall accuracy (OA) and 81.1% mean intersection over union (M_IoU). Furthermore, a point cloud instance segmentation method according to density-based spatial clustering of applications with noise (DBSCAN) and voxel-vs-BIM was proposed to independently compare each instance object of different building components with its corresponding BIM model, assessing the construction accuracy of each component based on root mean square error metric and the level of accuracy specification. For components with an LOA3 accuracy level, further deviation analysis was conducted. Taking the structural construction deviation detection of beams, columns, and concrete thick shells in the core area of the Shanghai Grand Opera House as a case, the proposed method significantly improved the efficiency of QA/QC.