## 4 Mock-up Fabrication
### Mock-Up Data Analysis  
The laser scanning technology was used once again to analyze the as-built quality of the mock-up panels. In doing so, among the eight mock-up panels, the author focused on the two double-curved panels with three coordinate curvatures (the third panel of each row in Figure 8a) since that type of panels had been known the most difficult to form, showing critical discrepancy harming the beauty of overall free-form facade. The study expected that the analysis of the two panels would deliver valuable lessons that would be applicable to other types of panels for the small/mid-scale contractors. Differently from the case study of [PERSON], the study did not use data superimposition. Instead, the two mock-up panels were scanned and using the practice in Figure 7, the as-designed and as-built X, Y, Z coordinate values at four corners of each panel were compared. Each of the scanned panels was labeled (C), i.e., aluminum panel and (C-1), that is, GFRC panel, and the four corners labeled p1, p2, p3, and p4 as shown in Table 2. Table 2a,b present the coordinate values. The origin of the X, Y, Z coordinates was at the lower right-hand side corner of the bottom right-hand side panel. Figure 12: Procedures to produce mock-up GFRC panels. Table 3 summarizes the discrepancy of the coordinate values at each corner of the as-designed and as-built aluminum panels. Considering the maximum difference value of the GFRC panel shapes is 4 mm (Z direction) at p1, it is very obvious that the aluminum panel demonstrated much bigger discrepancy than the GFRC panel. The study inferred this tendency would be explained in conjunction with material features, forming methods, or craftsmanship level in handling free-forms. The inferred issues became the main subjects to be discussed with the experts in the interview. The following section of the study \"Lessons Learned\" will summarize the findings from the interview. Table 4 shows the numerical amount of the as-built discrepancy of the two panels (C) and (C-1). The linear distances between two points at four edges as well as the diagonal distances of the panels were measured based on the laser scanned data. Table 5 presents the aluminum production allowance designated by the Korean industrial standard [5]. Since the allowance is for a planar panel, it is questionable to apply it to the mock-up test results in Table 4. However, considering the size of the mock-up panels, the as-built quality of the aluminum panels were too big to accept as reasonable. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Materials** & **Edges, Diagonals** & **As-Designed Length (mm)** & **As-Built Length (mm)** & **Discrepancy (mm)** \\ \hline \multirow{4}{*}{Aluminum, Panel (C)} & P1 – P2 & 756.6 & 720.9 & \(-35.7\) \\  & P2 – P3 & 602.1 & 602.2 & 0 \\  & P3 – P4 & 707.1 & 734.7 & 27.6 \\  & P4 – P1 & 600 & 613 & 13 \\  & P1 – P3 & 927.4 & 957.4 & 30 \\  & P2 – P4 & 965.7 & 938.7 & \(-27\) \\ \hline \multirow{4}{*}{GFRC, Panel (C-1)} & P1 – P2 & 707.1 & 713.2 & 6.1 \\  & P2 – P3 & 608.3 & 605.8 & \(-2.5\) \\ \cline{1-1}  & P3 – P4 & 806.2 & 803 & \(-3.2\) \\ \cline{1-1}  & P4 – P1 & 600 & 594 & \(-6\) \\ \cline{1-1}  & P1 – P3 & 1005 & 1003.32 & \(-1.7\) \\ \cline{1-1}  & P2 – P4 & 927.4 & 926.5 & \(-0.9\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: As-designed vs. as-built length discrepancy of panels (C) and (C-1).