# Integrated Digital-Twin-Based Decision Support System for
## 3 Methodology  
The objective of this research is to propose an integrated DT-based system to support facility managers in managing clusters of various types of RMB units. The proposed system is designed to enhance decision-making processes related to module allocation plans for new project sites, addressing the challenges of efficient reuse and relocation. While lifecycle management is an integral aspect of RMB operations, this study does not evaluate energy efficiency or end-of-life recyclability. Instead, the focus remains on maximizing the reuse potential of modular units, reducing idle periods, and optimizing logistical coordination across lifecycle phases. To achieve this objective, a case study methodology is adopted, which is particularly suitable for examining contemporary phenomena in real-world contexts and answering explanatory questions [40]. The RMS system in South Korea is selected as the case study, providing a practical context to validate and refine the proposed system. The RMS projects feature various types of modular units, including classrooms, staircases, restrooms, offices, and halls, which have been previously constructed and relocated across multiple sites. These projects highlight the complexities and dynamics of managing RMBs, making them an ideal testbed for demonstrating the effectiveness of the proposed system. As depicted in Figure 2, the research methodology unfolds in three sequential steps: the development of a DT platform, the creation of a DT-based module allocation system, and the implementation of the system in an RMS case study. The first step focuses on the development of a DT platform that integrates three core components: BIM, IoT, and GIS. This platform provides a comprehensive digital representation of RMB units, enabling real-time monitoring, data visualization, and spatial analysis. BIM is utilized to model the physical and functional characteristics of the modular units, including design specifications and condition details. IoT sensors embedded in the  
Figure 2: Research approach. modules facilitate real-time data collection, offering insights into usage history, transportation records, and maintenance needs. GIS capabilities support spatial visualization and analysis, allowing facility managers to optimize allocation plans based on geographical considerations. Together, these components create an accurate and up-to-date DT of the RMB units, forming the foundation for advanced analysis and decision making. Building on the DT platform, the second step involves the development of a DT-based module allocation system. This system is designed to optimize the reuse and allocation of RMS modular units through three key components: data structure and acquisition, a module selection algorithm, and a web-based user interface. A relational data structure is established to handle diverse types of information, including module specifications, conditions, and usage histories, ensuring seamless integration with the DT platform. The module selection algorithm is a pivotal feature of the system, prioritizing suitable modules for reuse based on multiple criteria such as module condition assessments, proximity to project sites, schedule compatibility, and transportation logistics. This algorithm ensures the efficient use of resources while minimizing waste and environmental impacts. To enhance accessibility and usability, a web-based interface is developed, offering a user-friendly dashboard for data visualization, input forms to capture project requirements, and output displays showing recommended modules and optimized allocation plans. The third step involves implementing the proposed system in a simulated RMS case study to demonstrate its practical applicability and effectiveness. The RMS system is chosen for its significant share in the RMB market and its potential for growth in the educational sector. In South Korea, relocatable schools are increasingly utilized as temporary infrastructure to address dynamic educational needs during school expansions and remodeling projects.