# Productivity Analysis of Documentation Based on 3D Model in Plant Facility Construction Project
## 5 Discussion  
This study compared the productivity of documentation methods using 3D models with the documentation methods using 2D drawings. Existing studies have also been carried out on the premise of the advantage of the 3D model drawing method [42, 44, 47]. [PERSON] et al. (2019) [42] analyzed the productivity of documentation of more than 30,000 fabrication documents for the irregular shaped building. In addition to the engineer's documentation work, technologies such as automated algorithm and robotics using CNC machine were considered in the productivity analysis of documentation. Therefore, there is a limit to purely analyzing the engineer's productivity for documentation. [PERSON] and [PERSON] (2018) [44] analyzed the process, productivity and economics of multi-trade prefabrication based on BIM. However, it does not provide productivity data for producing fabrication drawings using 3D models. [PERSON] et al. (2019) [47] analyzed the effects of BIM-based steel construction management from the perspective of SMEs and examined the merits of the documentation method based on the 3D model. However, the number of documents extracted from the 3D model is insufficient to discuss productivity. On the other hand, this study divides the productivity of 5295 drawings into two documentation methods. The following are the implications and limitations of the study comparing the productivity of 2D-drawing-based documentation method and 3D-model-based documentation method, in which engineers perform all documentation tasks. First, the documentation method that extracts the shape (e.g., plan view, elevation view, section view, etc.) and property (e.g., member list, member size, etc.) information required for the documentation of general arrangement drawing, assembly drawing, single part drawing, and single plate drawing from the 3D model has been found to improve the working time significantly. However, in addition to the 3D modeling and documentation tasks, there is also a task of continuously checking the consistency of the 3D model and reviewing and verifying the shape and property information extracted from the documentation. However, this study does not reflect this task in productivity measurement. Second, 3D modeling work is performed repeatedly, not just once during the construction project. In this study, 3D modeling work time was analyzed based on the experience of the engineers who produce shop drawings. However, assuming that the integrity of the 3D model is secured, the 3D modeling time spent on Module A and Modules B-D fully demonstrates the learning effect of repeated use of libraries. In future studies, analyzing the productivity of 3D modeling and documentation when the 3D models and libraries built in the case project of this study were recycled into a new \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**(Unit: min/1 drawing)**} \\ \cline{3-10}  & & \multicolumn{4}{c}{**2D Drawing Based Documentation**} & \multicolumn{4}{c}{**3D Model Based Documentation**} \\ \cline{3-10}  & & \multicolumn{4}{c}{**Type of Documentation**} & \multicolumn{4}{c}{**Type of Documentation**} & \multicolumn{4}{c}{**Type of Documentation**} \\ \cline{3-10}
**Module** & **Documents** & \multicolumn{4}{c}{**General**} & \multicolumn{4}{c}{**Assembly**} & \multicolumn{4}{c}{**Single Part**} & \multicolumn{4}{c}{**Single**} & \multicolumn{4}{c}{**Single**} & \multicolumn{4}{c}{**Single**} \\ \cline{3-10}  & **Review** & **90** & **25** & **5** & **5** & & & **60** & **13** & **2** & **1** \\ \hline Module A & 0.98 & 90.98 & 25.98 & 5.98 & 5.98 & 2.44 & 62.44 & 15.44 & 4.44 & 3.44 \\ Module B & 1.58 & 91.58 & 26.58 & 6.58 & 6.58 & 1.18 & 61.18 & 14.18 & 3.18 & 2.18 \\ Module C & 2.04 & 92.04 & 27.04 & 7.04 & 7.04 & 1.53 & 61.53 & 14.53 & 3.53 & 2.53 \\ Module D & 1.63 & 91.63 & 26.63 & 6.63 & 6.63 & 1.23 & 61.23 & 41.23 & 3.23 & 2.23 \\  & & & & & & & & (33.18\%) & (46.56\%) & (51.28\%) & (66.37\%) \\ \hline \hline \end{tabular}
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