# A Web-Based BIM-AR Quality Management System for Structural Elements
## 3 Quality Control System Development
In IfcQuality, the related quality parameter activities (the concrete placement in the case of wall geometrical quality parameters) are recorded in IfcInspectionplan, while the results of the inspection are recorded in IfcQualityAcceptance. The 4D BIM model in IFC format, inspection lots, their corresponding quality parameters and related activities in comma-separated values format (CSV) are prerequisites as input for the system. The application initially parses the CSV file and stores the data in a dictionary which will be used to determine the value of quality classes, their subtypes, and their attributes. Loading the IFC model, the system parses all the IfcBuildingElements that are in the model and retrieves their globally unique identifier (GUID) and type. For concrete structures, the type of IfcBuildingElement could be IfcColumn, IfcBeam, IfcWall, IfcFooting, IfcSlab, IfcReinforcementRebar, and IfcBuildingElementProxy. Based on such types, the associated quality classes will be dynamically loaded, also containing the GUID of the specific elements. Since each element has its own unique GUID, for each element a specific webpage  
Figure 5: Input/output scheme of the proposed QC system. address will be generated and this web address will be added as a user-defined property (IfcPropertySet) in the 4D IFC model, creating the link between this system and the web-based QC checklist. Opening this webpage will direct to the checklist of the related quality parameters, where the inspector can enter and record all the requested information. The results will be saved in IfcQualityAcceptance class and stored as two XML files. One of them is used to save the results of the latest inspection performed and the other to save all the inspection results and the documents related to each quality parameter. Whenever the checklist opens, the results of the latest inspection are shown. The other file can be imported into a spreadsheet for data queries, filtering, and quantification. Results can then be summarized to generate a quality dashboard of the project. Another output of the system is a color-coded IFC model, which provides the construction team with direct visual feedback on the contents of the inspection results. This reduces the time needed to analyze data and allows for a faster corrective action of quality defects to take place on site. The color coding is based on the legend reported in Figure 7.  
The on-site visualization of the color-coded model with a mobile device exploiting the integration with AR can be useful for both the inspector and the people responsible for rework. In the former case it will make up the basis for subsequent inspections, while in the latter case it can be used to access the inspection checklist to identify the element, its problem, and the inspector's comments. Through a central interface, projects are managed and IFC models are uploaded and visualized on site. Figure 8 shows the interface of the AR application and the steps needed to visualize the model on site and to access the web-based checklist; as an example, the figure reports the inspection of a column element. Figure 6: IFC-based process model. New entities are highlighted in blue. Figure 7: Color coding legend for the visual feedback on the inspection results.