# Productivity Analysis of Documentation Based on 3D Model in Plant Facility Construction Project
## 4 Productivity Analysis of 3D-Model-Based Documentation
### Productivity Analysis of Assembly Drawing Extraction  
#### 4.2.1 Detailed Task Comparison in Documentation  
(1) 2D-Drawing-Based Documentation vs. 3D-Model-Based Documentation  
In the case of this project, the 3D-model-based documentation method was used. In contrast to the 2D drawing-based documenting method, four engineers with the same engineering competency were invested and analyzed the time taken to produce the production drawing. Fabrication documents (e.g., general arrangement drawing, assembly drawing, single part drawing, single plate drawing) using AutoCAD are used on site and must be delivered prior to fabrication of the part. Assembly drawing, single part drawing, and single plate drawing are prepared by referring to general arrangement drawing such as floor plan, elevation, section, and detail. After that, a lot of time is spent to cross-check the completed production drawings to ensure the integrity of the drawings. Therefore, the 2D-drawing-based documentation method is divided into documentation work and reviewing drawings. Cooperation is required in the cross-checking of individually generated 2D fabrication drawings. However, human error is very likely to occur when comparing the consistency of a large amount of 2D fabrication drawings without a 3D model. On the other hand, the 3D-model-based documentation method using TEKLA does not take time to examine the integrity of the drawing because the view extracted in the relevant drawing is created from the 3D model. In 3D modeling work of Module A-D, 3D model for Module A was first constructed according to fabrication documents delivery schedule. By sharing the 3D model, four engineers simultaneously perform 3D modeling for each part or floor connection for the same module. In the 3D modeling process, if the modeling work is interrupted and collaboration is difficult, some personnel perform 3D modeling work on the subsequent module. In order to deliver the fabrication documents, detailed information on the joints is required for each module. Therefore, when the 3D modeling work for the main joints for one module unit is completed, one person additionally proceeds with 3D modeling for the detail area. The remaining three engineers will work on the 3D modeling of modules B-D. When detailed 3D modeling for Module A is completed, a total of four engineers perform documentation editing for 3D modeling completed module. 3D modeling work and 3D-model-based documentation can flexibly distribute the manpower according to the delivery date and situation, enabling efficient work. As mentioned above, this study was analyzed the productivity data for assembly drawing, which has the highest proportion of drawing work in Table 4.  
As a result of the analysis, in the 2D-drawing-based documentation method, the documentation time per unit drawing for column and girder was 60 min and 55 min, respectively. The documentation time per unit drawing for BEAM and BRACE/POST was relatively low as 25 min and 10 min, respectively. The assembly drawing documentation time for BEAM and Girder was 9500 and 4015 min, respectively, accounting for 56.26% and 23.78% of total work time. In the 3D-model-based documentation method, the documentation time per unit drawing for Column and Girder was 40 min and 40 min, respectively. However, productivity is improved by 33.33% and 27.27% compared to 2D-drawing-based documentation method. The documentation time per unit drawing for BEAM