## 3 Results
### Phase I: Defining PC On-site Assembly Optimization Principles via BIM-GA Hybrid System
#### 3.1.5 Interference of Works  
Construction projects, which are characterized by the simultaneous and consecutive execution of numerous tasks within a limited time and space, face a high probability of temporal and spatial interference among the tasks ([PERSON] et al., 2001) [36]. This interference is the primary cause of reduced productivity at construction sites ([PERSON] et al., 2018) [37]. Hence, it is imperative to minimize the interference in the workspace to ensure efficient construction progress ([PERSON], 2014) [38]. Furthermore, various challenges such as delays in element delivery or damage often render the installation of scheduled elements unfeasible because of non-compliance with quality standards. This study aimed to comprehensively assess such situations to determine the feasibility of element installation.  
To evaluate the feasibility of element installation at sites conducting composite construction, including the RC process, essential information such as installation dates and location details for each PC element is crucial. In addition, the schedule of the RC process must be incorporated into the analysis. By setting the assembly schedule based on the sequence of the PC element assembly, potential time-space conflicts are identified by considering the RC process's time and location information. In cases in which interference with other processes occurs, a penalty score of 1 is assigned; otherwise, a score of 0 is assigned, defined as the Interference Penalty Score (IPS). The sum of the Ips values is formalized as C, representing the total Interference Penalty Score, as expressed in Formula 3.  
\[C=\sum_{i=1}^{n}Ips_{i} \tag{3}\]  
\[Ips_{i}=\left\{\begin{array}{cc}1,&\quad\quad\text{when $i$th component is interfered}\\ 0,&\quad\text{when $i$th component is not interfered}\end{array}\right.\]  
\(C\) = sum of penalty score of interference  
\(Ips_{i}\) = interference penalty score per component in the assembly sequence  
\(n\) = the number of components  
nodes, 'x', 'y', and 'z', were connected to extract precise x, y, and z coordinates for each component's centroid.  
After this process was performed for the columns, beams, and slabs, the information for each object comprising the 3D model was extracted. The extracted information was formatted as an Excel file. Additionally, to discern the assembly sequence for the components, the zone information necessary for each assembly was included in Excel to build the component-specific data. An example of the extracted information is presented in Table 1, encompassing the component ID, x, y, and z coordinates, and floor information.  
This research not only aimed to determine the initial sequence for assembling the construction elements but also intended to adapt to changes in the construction site. To achieve this adaptability, a method is required to select elements for which assembly sequences require determination among all the elements constituting the building. Elements marked with an 'Installation' column value of 0 in the information table (Table 1) were identified as not yet installed. Thus, the assembly sequence was generated specifically for these elements with an installation value of 0. By assigning 0 to certain elements, the model represents changes in the construction conditions. It is important to note that in this process, it was assumed that all the necessary elements for the task were already available on site, focusing solely on the assembly stage.