# Analyzing the Economic Performance of a TLS-Based Structural Safety Diagnosis Process
## 3 Results
### Visual Inspection and TLS-Based 3D Scanning Reverse Modeling Process  
Structural safety diagnosis typically involves identifying defects and damage in structures through an initial visual inspection followed by a detailed second-stage investigation, then establishing appropriate repair and reinforcement measures. The conventional manpower-based diagnostic approach largely relies on visual inspections by on-site experts and measuring equipment, where estimations for the entire structure are made based on sampled measurements from specific areas. This approach has limitations, especially in large-scale facilities, fire-damaged sites, or high-altitude work environments, as it often requires significant manpower and extended periods of time. In contrast, the TLS-based 3D scanning reverse modeling method utilizes 3D scanning technology to quickly measure and document the entire structure, generating BIM models through automated and post-processing workflows from point cloud data. Structural safety analyses are subsequently conducted, and the outcomes are documented as maintenance records. Thus, repetitive visual inspections and sampling tasks by field personnel can be reduced, significantly enhancing investigation reliability and accuracy while also shortening the overall inspection duration. Project A involved investigating a fire-damaged area in an apartment complex. Under the traditional approach, four personnel were deployed for approximately 40 days to visually inspect damaged sections, conduct precise measurements in selected areas, assess damage levels, and prepare a report. In contrast, using the TLS-based 3D scanning reverse modeling method, 89 scanning points were established for comprehensive 3D scanning. Three personnel completed scanning, analyzed component deformation and damage using the 3D model, and calculated restoration quantities within 14 days. In Project B, which involved a structural safety assessment of an aging steel-frame structure, the conventional approach employed visual inspections and sample measurements, followed by separate drawing preparation and detailed analysis, requiring a total of 10 personnel over approximately 80 days. With the TLS-based 3D scanning reverse modeling method, however, 192 scanning points were used to capture comprehensive \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multicolumn{2}{c}{**Classification**} & \multicolumn{2}{c}{**Project A**} & \multicolumn{2}{c}{**Project B**} & \multicolumn{2}{c}{**Project C**} \\ \hline \multicolumn{2}{c}{Customer} & \multicolumn{2}{c}{21,550} & \multicolumn{2}{c}{5200} & \multicolumn{2}{c}{2743} \\ \hline Professional & Person & 1 & 1 & 1 & 1 & 1 \\ \cline{2-7} engineer & cost & 432,440 & 432,440 & 432,440 & 432,440 & 432,440 \\ \hline Senior & Person & 2 & 1 & 8 & 4 & 8 & 3 \\ \cline{2-7} engineer & cost & 282,545 & 282,545 & 282,545 & 282,545 & 282,545 & 282,545 \\ \hline Junior & Person & 1 & 1 & 1 & 1 & 1 \\ \cline{2-7} engineer & cost & 175,259 & 175,259 & 175,259 & 175,259 & 175,259 & 175,259 \\ \hline Total cost & 1,172,789 & 890,244 & 2,868,059 & 1,737,879 & 2,868,059 & 1,455,334 \\ \hline Equipment & - & TLS + BIM & - & TLS + BIM & - & TLS + BIM \\ \hline Equipment cost & 120,000,000 & 120,000,000 & 120,000,000 & 120,000,000 \\ \hline Service contract period & 2 months (44 days) & 4 months (88 days) & 8 months (176 days) \\ \hline Service fee & 30,000,000 & 28,5000,000 & 120,000,000 \\ \hline \end{tabular}  
* The unit is KRW.  
\end{table} 
Table 2: Cost and staffing comparison of as-is vs. to-be. point cloud data. Six personnel performed point cloud integration, modeled steel member dimensions and corrosion conditions, conducted structural analysis, and formulated repair strategies within 55 days. Finally, Project C was a case examining the displacement and deformation of pipe racks totaling 2743 m. The traditional approach divided the entire section into intervals, manually created drawings, and performed structural analysis, involving 10 personnel over approximately 7 months (154 days).