Creation of 3D Geometry in Scan-to-CAD/BIM Environment

Abstract

Scan-to-BIM brings the documentation of existing buildings into line with the modern digital planning methodology called building information modelling (BIM). This article describes how scan-to-BIM uses 3D laser scanning to capture digitally an existing building as a point cloud, for the creation and updating of a BIM model. Renovation of an existing old lattice grid structure, out of service for more than ten years, was a real challenge for investigation, capturing geometry and determining the rest load-carrying capacity. The original structure was calculated and produced in Italy and assembled at Bulgaria during the 80s of 20th century and was covered with a single layer membrane. It was used for 30 years before it was left without service and maintenance for more than 10 years. Strong corrosion processes was investigated for some of the members and almost all applied bolts which reduce seriously the rest load-carrying capacity. Laser scanning technology was chosen for getting the complex 3D geometry of the lattice grid structure. It was a real challenge to find a software for processing the scanned data and extracting the axial geometry of structure. Investigations for determining of the applied steel class and class of bolts was done on the site and at laboratory. Different concepts for rehabilitation was discussed before choosing the double layered stressed textile membrane. Numerical FEM models was used for proofing the adequacy of chosen structural solution. Modelling is a necessary process for converting the point cloud to a useful CAD representation. It provides a complete picture of the as-built situation by filling the gaps coming from occlusions, by averaging the effects of noise and by providing the quality measures about the final results.