An Integrated Framework for BIM Development of Concrete Buildings Containing Both Surface Elements and Rebar

As-built Building Information Models (BIM) are increasingly used to facilitate the management of all aspects of built infrastructure’s life cycle. Existing studies mainly focus on automating as-built BIM development for surface elements but often ignore embedded elements such as rebar due to the inaccessibility with typical sensing devices, such as image-based or time-of-flight-based methods. To tackle the issue, this research utilizes Ground Penetrating Radar (GPR) together with the photogrammetry method to generate BIMs for in- service buildings considering both surface elements (e.g., column, slab, wall, etc.) and rebar. As the first step, as-built BIM for surface elements is generated and then existing rebar is identified by using GPR. A calibration label is designed and attached to elements which are scanned by GPR device, and a series of images are captured from those elements and then used with other images to generate point clouds. Faster RCNN is then utilized to recognize labels among all images. Next, an inverse photogrammetry approach is deployed to identify the scanned elements in BIM. By matching the recorded timestamps of GPR data and labeled images, links between the rebar in GPR data and elements in BIMs are successfully established. Finally, IFC (Industry Foundation Classes) is developed to generate as-built BIM models. Six case studies demonstrate that the system is capable of automatically developing as-built BIM, while embedded rebar could be efficiently localized and projected into corresponding elements in BIM.