## 3 Results
### Phase I: Defining PC On-site Assembly Optimization Principles via BIM-GA Hybrid System
#### 3.2.2 Application of Genetic Algorithm
Following the procedure outlined in Image 5 of Figure 14, where the adjacency criteria of the work radius are satisfied, nearby column components take precedence in installation. The remaining components were installed at nonconflicting points on subsequent dates, as shown in Figure 6. This outcome demonstrates that by applying the conditions of task complexity, work radius adjacency, and component feasibility, an assembly sequence can be generated to meet the specified constraints. That sequence prioritizes component installation based on feasibility, starting with those in close proximity, while ensuring consecutive installations of the same type of work in nonconflicted situations. As mentioned in Section 3.2.3, users must verify their structural satisfaction after understanding the assembly sequence through simulation. Most assembly sequences have structural stability. Image 3 in Figure 14 shows an instance in which two slabs were installed before all four beams. In such cases, users can actively modify the assembly sequence by adjusting the timing of slab installations to validate and finalize the assembly order. Figure 13: Result of the case study. (**a**) Starting component ID and location. (**b**) Converged fitness value. (Source: own elaboration). The analysis of converging results from the graph identified four distinct assembly plan tendencies:

1. Commencing on 23 June, the first strategy involved prioritizing the installation of components in areas expected to face interference, aiming to prevent clashes. However, while emphasizing installation in interference-prone zones without violating the component installation feasibility (Constraint 3), additional penalties for adjacency were incurred. 2. Another strategy commenced by placing the column components in the upper-left corner and postponing the areas susceptible to interference. This sequence aligned with the component installation feasibility but resulted in higher penalties (Constraint 3), primarily because the initial component placement did not meet specific conditions. 3. The third strategy begins with the installation of the upper-left column component, followed by the immediate installation of interference-related components post-overlapping dates. Although this approach prioritizes component feasibility (constraint 3), it incurs penalties for task complexity and adjacency. 4. The fourth approach outlined an assembly plan that deviated from the feasibility of component installation (Constraint 3). In real-world scenarios, construction cannot proceed without timely delivery of PC components. Moreover, in instances where interference with other construction activities occurs, prioritizing PC installations is imperative. Consequently, this assembly plan was excluded because of its impracticality in meeting essential construction requirements. During the interviews, it was noted that, generally, when on-site situations similar to the one described above occur, the usual practice involves temporarily deferring the conflicting area and proceeding with the initial cycle work on the next floor. However, this study leveraged the developed system to effectively manage on-site conditions, enabling a broader exploration of assembly plan alternatives. Upon comparison with experience-based plans, it was noted that the penalty values for the alternatives did not differ significantly. This suggests the potential for considering a more varied range of on-site plans. Although this study focused on three constraints, future studies could encompass a wider range of constraints, fostering a more systematic and diversified exploration of assembly plans. ## 4 Validation and Discussion

To validate the practicality and assess the effectiveness of the proposed assembly sequences derived from the defined constraints, thorough interviews were conducted with the site manager who oversaw the PC construction site.