# Automatic Bridge Design Parameter Extraction for Scan-to-BIM
## 1 Introduction  
The construction industry has been rapidly developing through its synergy with information technology (IT). An article entitled, \"The Vision for Civil Engineers in 2025,\" published by ASCE(American Society of Civil Engineers) in the US in 2007, predicted that civil engineers would be using sensors and IT technology at construction sites in 2025 [1]. As of 2020, most of these predictions have been realized through emerging technologies that improve existing processes, such as predicting the health of structures using drones and imaging equipment, identifying cracks using deep learning techniques, automatically recognizing structural components, and construction project simulation based on extended reality (XR). [2; 3; 4; 5; 6; 7]. Building information modeling (BIM) is also one of the core technologies in construction IT, which entails the management of data, such as design, construction, and maintenance information, throughout the life cycle of the structures by integrating the information into digital 3D models. The most well-known book on BIM, _BIM Handbook: A Guide to Building Information Modeling for Owners, Managers, Designers, Engineers, and Contractors_, stressed that BIM was a requirement for the future of the construction industry [8]. In addition, governments and companies have realized the importance of BIM and are making substantial efforts to promote it. In the US, integrated project delivery (IPD) has become mandatory for projects with construction cost estimates greater than US$500 million, and several BIM guidelines and standards have been published. In the EU, the _BIM Handbook for the EU Public Sector_ was published through the EU BIM Task Group to encourage widespread BIM adoption [9]. In Korea, BIM guidelines were provided in the _BIM Application Guide for Architecture_, and the use ofBIM became mandatory for projects costing more than US$50 million [10]. Companies have leveraged BIM to improve productivity and reduce costs on projects such as the Admiralty Station project in Hong Kong, the Danjiang Bridge project in Taiwan, and a Zaha Hadid Architects project in the UK [11]. Numerous studies regarding the application of BIM are currently underway worldwide. Experts have attempted to establish a framework for BIM by developing the concept of level of detail/level of development (LOD), which represents the level of informatization [12]. In addition, various software products, such as Revit and Navisworks (Autodesk), Tekla and Vico Office (Trimble), and ArchiCAD (Graphisoft), have been developed to facilitate BIM. However, the research on the application of BIM to the maintenance of existing structures is not fully developed [13]. Applying BIM to new construction is relatively straightforward. However, the use of existing infrastructure is much more complex [14; 15; 16; 17; 18]. It is difficult to produce BIM for existing infrastructure due to problems such as omission of design drawings, differences in design and construction structure, and structural deformation due to aging. The scan-to-BIM process can produce BIM models that represent the structure and its current status. Scan-to-BIM involves scanning the structure to obtain its 3D model data and producing a BIM model from the collected data [19; 20]. Most of the current scan-to-BIM technologies build 3D models by scanning the structure with imaging equipment such as cameras or laser scanners [21]. However, a 3D model built in this way only contains information regarding the shape of the structure based on point cloud data (PCD). Because PCD is only a set of points, semantic information must be assigned to each point in order to utilize the PCD in BIM. Various studies have investigated semantic segmentation to assign this information in an automated fashion [22; 23]. Recently, studies on semantic segmentation using deep learning have been performed [24; 25]. However, even PCD obtained in this way that contains semantic information may not be directly used to produce a BIM model.