BIM-Based Management System for Off-Site Construction Projects

Abstract

Offsite construction (OSC) is one of the alternative methods for the various challenges that the construction sector faces today. This study developed a management system based on building information modeling (BIM) to execute OSC projects successfully. Because OSC differs from the conventional onsite building method, the authors studied and analyzed several project cases and interviewed the participants and stakeholders. The OSC method has unique characteristics in the aspects of the projects’ location and time, production process, flow, method, facility, and environment. Moreover, before the system development, we analyzed the OSC project management, usability, and system requirements. These requirements were turned into a BIM-based system following a waterfall model, with six management menus: drawing, schedule, production, logistics, installation and progress monitoring, and progress payment. This study implemented each menu’s vital functions within the system more effectively due to the BIM-based technological features, such as object-oriented data processing, visualization, high interoperability, linkage, and integration. The developed system was applied to four projects. The test resulted in a streamlined work process, improved activity, and less input time and workload than in a non-BIM-based management environment. These findings indicated that the proposed BIM-based system enabled OSC project management to perform better.

1. Introduction

Recently, the construction industry has been plagued with various difficulties. The productivity of the construction industry is developing gradually, unlike the rapid development trend of other industries. The stagnation of labor productivity in the construction industry has lasted for a considerable period, and productivity growth has averaged only 1% worldwide for the past 20 years [1]. The shortage of skilled workers in the construction industry has emerged as a significant problem [2]. According to an existing report, a notable risk to the construction industry is the shortage of skilled craftsmen [3], and 64% of regions worldwide announced that they are experiencing difficulties in supplying skilled workers for various reasons, such as COVID-19 [4]. In addition, the construction industries of nearly all countries are under pressure to adopt carbon-neutral practices to address climate change problems such as global warming. The industries are attempting to decrease the environmental load for sustainable development [5]. Considering that the carbon emission of the construction sector in 2020 was 38% of the total [6], the construction industry must respond more actively to climate change [7,8]. Furthermore, occupational accidents are more prevalent in the construction industry compared to other industries worldwide [9]. In particular, 44% of fall accidents—which are most likely to lead to death—in the last three years (from 2019 to 2021) occurred in the construction sector [10]. Accordingly, strategies for preventing safety accidents in the construction industry must be actively identified [9,11].

Offsite construction (OSC) has emerged as a promising alternative to address the abovementioned problems [12]. In the OSC frameworks, the mechanical, electrical, and plumbing (MEP) elements, including the structural and nonstructural elements of a building, are produced offsite and then transported and installed onsite. Compared to the conventional production method, the construction period, cost, and workforce requirements in the OSC frameworks are 30–50% [13], approximately 50% [14], and approximately 5% [15] lower, respectively. OSC can respond more flexibly to changes in the construction industry. By producing the components, approximately 85–90% of the project work, in specialized plants, this method can minimize simple onsite production activities, reducing inefficient energy and material consumption [16]. Moreover, owing to reduced onsite work, the projects are less dependent on human resources [17]. Workers can work safely and more comfortably in indoor spaces [18,19] and standardized production can help to enhance the finishing level of building projects [20]. The effectiveness and flexibility of the OSC approach are driving countries worldwide to adopt it [21]. The UK and Australia have implemented mid- to long-term policies to revitalize OSC projects since the early 2000s [22]. Moreover, the National Institute of Standards and Technology of the US has selected permanent modular construction as one of the innovation factors for the future construction industry [23]. Since the 1970s, Japan has steadily increased the proportion of OSC activities in factory-built housing projects, and the focus areas at present are the marketability and quality [24,25]. China is also concentrating its national capacity on raising the proportion of OSC projects to 30% over the next decade [19]. The global OSC market size was USD 820 billion in 2020 and is expected to reach USD 1.9 trillion in 2025, considering the future growth rate [26].

The implementation of OSC projects requires appropriate management techniques and systems. Supply chain management (SCM) plays a vital role in OSC projects. Because OSC projects are concurrently produced, transported, and installed at different locations, SCM is required to organically connect these processes. Additionally, OSC projects require careful management of the production and logistics stages in addition to the installation stage. As 80–95% of OSC production occurs offsite, stocking, outgoing, transporting (to the site), and loading activities must be appropriately performed [27,28]. To ensure the efficiency of the offsite tasks, OSC projects necessitate the management of each stage of production, logistics, and installation and the integration of SCM in each stage. The success of the OSC project relies on these management activities and appropriate systems [29]. Specifically, the efficiency and productivity of each work process must be improved through the integrated management of the project [30]. Management tools limited to specific goals (e.g., scheduling, costing, monitoring, and establishment) are somewhat challenging to manage as a whole for the OSC projects with highly diversified management elements. Moreover, the existing systems are mainly specialized for the managing of onsite work and thus cannot appropriately optimize OSC projects, in which most of the tasks are performed offsite.

Building information modeling (BIM) technologies are promising for managing OSC projects. Since its introduction in the construction industry in the early 2000s, BIM has been applied to numerous projects and achieved encouraging results [31]. BIM is being actively implemented in design fields such as basic design, visualization, MEP, and interference checks, as it can handle three-dimensional (3D) information [32]. Recently, with the convergence of digitalization and automation technologies, BIM has been used to manage the schedule, cost, safety, and quality in order to enhance the project performance [33]. BIM technologies can facilitate the management of OSC projects [34], especially in terms of the SCM, which is the core of OSC projects, by integrating the vast amount of information generated within the building project [35]. In addition, BIM can facilitate collaboration between the participants in OSC projects [36,37]. The participants can work with high-quality and detailed designs through design for manufacture and assembly (DfMA) techniques at an early stage and collaborate to achieve various objectives, such as time, cost, and progress management in the construction stage [38].

Considering these aspects, this study was aimed at using the BIM technology to establish a management system for OSC projects. The development followed the waterfall model, also known as the linear sequential model, and the paper was also organized according to each stage of the waterfall model—requirements analysis, design and implementation, and testing. First, recent trends in the BIM-based project system development and OSC project management, which differs from that of traditional construction projects, were examined, and the literature relevant to the OSC project management systems was reviewed. Prior to the system development, the authors examined the characteristics of OSC projects through case studies and expert interviews and subsequently derived the management requirements. The system environments and functions were implemented using various BIM components and application programming interfaces (APIs). Finally, the proposed system was applied to ongoing OSC projects for a certain period and evaluated, and the effectiveness of the management system based on BIM was demonstrated.

2. Literature Review

2.1. OSC Project Management

OSC has been assigned different terms over the years: offsite manufacture or production [30], prebuilt construction [39], prefabricated building [40], and pre-assembly [41]. Despite subtle differences among these concepts, they are consistent with the definition of OSC [42,43,44]. In general, OSC is aimed at completing a building by producing the components of a mass or structure in a controlled location offsite, transporting these entities to the site, and completing the assembly onsite [45,46,47]. The following methods are also categorized as OSC because the proportion of offsite production is higher than that of the onsite construction: modular construction [48], precast construction [49], industrialized building [50], modern methods of construction [51], and systems building [41].

Although construction is conducted onsite in OSC projects, the finished products are transported by road from the factory to the site in vehicles. This feature shortens the project period by allowing work that is typically performed sequentially in a single space to be performed simultaneously in multiple areas [52]. In addition, offsite production with specialized systems minimizes the temporary facilities required onsite and the overhead costs. Moreover, the direct costs decrease owing to the standardized production [20]. In addition, uniform production following confirmative drawings and line processes results in improved quality [53]. Finally, in the OSC framework, the resources do not move to the fixed products, and instead, the products move to the fixed resources, which eliminates dangerous activities, especially in terms of scaffolding [23]. Furthermore, simplified onsite work lowers the environmental burden associated with the construction industry by minimizing the waste and maximizing the energy efficiency [19,54].

Considerable research has been performed on OSC. Jang, et al. [55] conducted a holistic review of OSC processes and highlighted the active research being performed in the manufacturing and assembly fields. The researchers have also attempted to apply emerging technologies to OSC projects [56,57]. Notably, OSC projects can be optimized using IoT technologies [58,59]. Studies have also been performed on the three phases of the OSC project: offsite production [29,53,60], transport [40,61,62,63,64,65,66], and onsite installation [67,68,69,70,71,72].

2.2. OSC Project Management Systems

Traditionally, the overall system used for project management has been termed as the project management information system (PMIS). According to the Project Management Body of Knowledge 6th Edition, a PMIS is an information system consisting of the tools and techniques used to gather, integrate, and disseminate the outputs of project management processes. Nitithamyong and Skibniewski [73] proposed a system named the project management systems–application service provider (PM–ASP) to eliminate the inefficiency of traditional communication methods. Initially, PMISs were designed as online programs, software, or systems with information management (e.g., creating, sharing, and distributing) capabilities. However, with the growing importance of real-time monitoring and integrated management, the smart PMIS (SPMIS) was introduced, which involved advanced technologies, such as radio frequency identification (RFID), BIM [74], and simulation [75].

An OSC project ends when a component from the origin reaches its destination. This component goes through its lifecycle along the supply chain with the information on the platform [76]. Several studies have highlighted the significance of the information flow and sharing and have proposed platform-based approaches. Ergen and Akinci [77] highlighted the lack of tools for data creation, access, exchange, and storage during an OSC project and proposed a system to address the information complexity from the SCM perspective. However, this system was a framework-level proposal that was not validated by practical application to an OSC project. Additionally, several case studies have been performed to establish management models to trace the life of precast concrete (PC) components with RFID. In addition to the use of RFID, Wang and Hu [78] developed an information exchange platform through cloud-based BIM. Zhong, et al. [79] verified that the information exchange using BIM in OSC projects could help to enhance the SCM performance. Notably, the authors focused only on information acquisition with IT but did not advance to the automation or optimization of this information flow in terms of SCM. In addition, phase-by-phase focused management may limit communication with the individuals involved in other phases. Overall, none of the existing studies has focused on RFID and BIM-based integrated management systems (IMSs) that can connect the internal and external entities in each phase based on the SCM perspective and enhance the understanding of the OSC project.

2.3. BIM-Based Project Management Systems

BIM has played a vital role in construction project management since its development. BIM is often actively applied from the design stage. The prefabricated building project analyzed by Liu and Zou [80] was designed through BIM, and the quality of both the design and the construction was improved through data visualization and linkage. Moreover, the design collaboration proposed by Tuval and Isaac [81] uses openBIM to enhance online communication among the participants without time and space limitations.

Several researchers [82,83,84,85,86] applied BIM in the construction stage for managing the budget, quality, procurement, and monitoring requirements. Kim, Chin and Kwon [84] calculated the quantity of building interior components based on BIM. He and Liu [83] developed a schema to track the final cost by building a relational database based on BIM. Additionally, Stransky and Matejka [85] showed that BIM can be used to realized digitized quality control in projects. Procurement management is essential as the construction stage involves the logistics of a variety of raw materials. Hamledari, Rezazadeh Azar and McCabe [82] developed a BIM-based automatic quality detection method by comparing as-built and as-is frameworks in the construction stage using International Foundation Classes (IFCs) with excellent compatibility.

BIM enables rapid and real-time management of construction projects and the achievement of data-based performance improvements. Xue, Hou and Zeng [86] used the elements of BIM to track construction progress. By incorporating RFID technology, Qi, et al. [87] proposed a real-time system for managing residential construction projects by tracking prefabricated components. Moreover, several researchers [34,58,88,89,90,91,92,93,94,95,96,97] have developed a management system by applying BIM technology in many areas of construction projects. Other researchers have focused on effectively managing construction projects with BIM by fusing it with other technologies such as geographic information systems [96,97], blockchain [88,95], and the internet of things [34,88,95]. Moreover, many researchers have attempted to develop BIM-based management systems for OSC projects, in which information sharing is highly necessary [58,89,90,93].

3. Requirements Analysis for System Development

In this study, the authors analyzed the characteristics and management requirements of OSC projects prior to system development. After identifying the research trends for OSC project management and system development through a literature analysis, five OSC projects were selected and analyzed. The authors identified the contents for OSC project management, such as roles, work processes, decision-making tools, and formal documents, through field surveys and interviews with each participant in the design company, factory, and construction site. Through this process, six characteristics of the OSC project were derived. In addition, we specified the scope and functions to be included in the system by discussing with the practitioners the concepts to enhance the existing tasks and processes in OSC projects. Subsequently, the concepts were exchanged with the practitioners, optimized, and verified to ensure their efficiency and practical applicability throughout the management system development.

3.1. Characteristics of OSC Projects

3.1.1. Production Location and Time

OSC projects involve concurrent production in multiple distributed locations, including factories, transport modes, and the construction site. Unlike traditional construction approaches, in which most of the production occurs onsite, the elements, parts, pre-assembly parts, units, and modules are produced in factories in OSC projects. The components are produced considering individual and overall schedules at the distributed locations and transported to and installed at the site as scheduled. Because most of the work is performed onsite in the traditional production method, the order and float time management between work types is vital. Conversely, the success of OSC projects depends on the comprehensive coordination of simultaneous production, transportation, and installation inside and outside.

Because most of the work is performed in factories, OSC projects are not subject to constraints such as weather, time, and complaints. In addition, continuous and additional tasks that cannot be performed onsite can be accomplished using the operating facilities and equipment in the factories. In the installation stage, the working time can be reduced by procuring only the target product on time for the finished product. In addition, the working period in the onsite production method depends on the production status and is difficult to adjust. In contrast, in the OSC project, the duration can be shortened by ensuring sufficient production through pre-negotiation with factories.

3.1.2. Production Process

In OSC projects, the supply chain is connected and integrated throughout the production process. The design derived in the design and engineering stage reflects the technical requirements and performance objectives of factory production, transportation, and onsite installation. In traditional building projects, the design and construction processes are isolated, or the construction company temporarily participates in the design stage to perform constructability reviews and VE. In contrast, in OSC projects, all the technical aspects associated with the design, engineering, production, transportation, and installation processes and the performance items, such as the cost, period, and quality, are determined in advance, and the supply chain is tightly coupled. The participants provide the requirements and constraints in the design stage, and the DfMA is performed considering these aspects.

In the production phase, just-in-time (JIT) production is achieved by establishing a production plan linked to the onsite installation schedule. The producer establishes a baseline production plan in consultation with the site, and the production is performed according to this plan. The production plant adjusts the plans, facilities, and equipment considering the production plans, raw material status, inventory status, and lead time for other projects. The finished products are transported to the site by the import request and installed, and the remaining product is managed as the inventory. In the onsite installation stage, the work is performed in connection with the factory production process. In the field, the product is requested to be brought into the factory in advance according to the installation plan, and the brought-in components are installed in order. Through continuous progress monitoring, the site conducts work and coordinates schedules. The adjusted installation plan is shared with the producer and reflected in the production plan and inventory management, and this cycle continues until the installation is complete. The inventory management is optimized even if the delivered products are temporarily stored and installed onsite.

3.1.3. Production Flow

In OSC projects, production is performed by the personnel using the facilities and equipment in the factory. The factories that produce the components, parts, and modules use production lines, as in manufacturing scenarios. Unlike the fixed-position process, in which the workers and equipment move directly to the production site to perform work, the OSC method removes components according to a line process consisting of fixed facilities and equipment in the factory. The line process is efficient for repetitive mass production owing to its dedicated facilities, the operator’s learning effect, and the ease of quality control.

In the OSC project production process, the raw and intermediate products are converted to components, parts, and modules as they move through the production facility, and the final product is transported and installed onsite. Specifically, the raw materials move along a production line involving facilities and equipment to be processed into intermediate products, and the intermediate products are moved and converted into final products. Various products can be produced by adjusting the facilities and equipment installed in the production plant and by training the workers accordingly. The OSC factory line resets facilities and equipment when the products are changed, and the operator training is performed. In this manner, the construction company can respond efficiently to changes in the components, parts, and modules constituting one OSC project.

3.1.4. Production Method

The OSC method uses standardized components, parts, and modules to perform the design and engineering. Unlike the one-off production method based on the design provided by the client in conventional building projects, OSC projects involve the assembly of mass-produced components. In the design stage, the DfMA is performed on the standard components, parts, and modules to satisfy the technical requirements and optimize the cost, period, and quality required in the factory production, transportation, and onsite installation stages. Therefore, the design objectives include the simplification of the production components and parts, procurement in the transportation process, and the assurance of constructability and performance in the installation process.

The repeated mass production of the components, parts, and modules occurs in the production phase. A key advantage of the OSC method is that the efficiency can be enhanced through the mass production of standardized components, parts, and modules. An OSC production plant produces the components and parts required for each type of work and uses them to manufacture pre-assembled parts and modules. In the traditional onsite production methods, project-based production is performed for only one site. In contrast, OSC production plants adopt a product-based production method, in which compatible products for any project can be produced. Repetitive mass production can decrease the lead time and costs and enhance the quality.

3.1.5. Production Facility

Unlike the traditional construction production method, in OSC projects the facilities and equipment are extensively used to manufacture heavy and bulky products at the factory, transport them to the site, and install them. Facilities such as line processes are established in the factory production stage for mass production. In a production line, the workers perform tasks using production facilities and equipment, and the components are moved by heavy equipment. The final product is moved to the site using transportation equipment such as trucks and trailers. In the field, installation is performed using equipment suitable for each product. In general, OSC-type products have a large weight and volume, and thus, equipment planning is a key factor influencing the work efficiency.

3.1.6. Production Environment

The OSC system is relatively immune to climate and weather because the production process is performed inside the factory. In the traditional production method, the materials used and the working period depend on the climate as extensive outdoor production is involved. Working in inclement weather such as rainy and winter conditions is challenging. Not only is the OSC plant not affected by these influences, the environments (e.g., temperature, humidity, and lighting) required for the operation can be created. Continuous work can be performed in an environment that is controlled and isolated from the outside, which helps to reduce the time and enhance the quality, safety, and efficiency.

3.2. Elements of OSC Project Management

To enhance the OSC project performance and maximize the benefits, a management process suited to the characteristics of the OSC production method must be established. To this end, this section presents the project management, usability, and system requirements.

3.2.1. Project Management Requirements

The OSC project supply chain must be systematically and effectively managed. Specifically, the system must be able to facilitate synchronized and timely production along with integrated data-based management. OSC projects in each domain, such as factories, logistics, and construction sites, must be managed through integrated data-based management, by linking the data related to each area. The data can be linked and integrated through BIM-based parametric design technologies. Furthermore, the system must have information sensing and synchronization functions to track the status of the components in real time through the factory–logistics–construction site flow to achieve the JIT production goal of the OSC projects. In OSC projects, information for each management area is continuously generated and exchanged in real time across the areas. Therefore, information related to the components, the basic unit in OSC projects, must be appropriately managed. In conclusion, from the SCM viewpoint, the management system must involve the following functions.

• BIM-based design–production–installation information linkage and integration;
• Zone plan and installation order management;
• Importing and integration of design and engineering models;
• Sensing and synchronization of the product status (production/stocking/shipping/transportation/entry/assembly);
• Product location tracking.

Moreover, the OSC project management system must take into account the characteristics of each stage of production, logistics, and installation. Offsite production distributes the management points of the OSC projects to factories, logistics, and construction sites. Therefore, in addition to the finished products, the overall factory production, including the facilities, equipment, and resources, must be managed. Furthermore, logistics management from production to construction site introduction is required. First, the OSC project management systems must effectively respond to distributed management points by establishing a plan which is suitable for the characteristics of each stage of the OSC project and has the ability to grasp the current status. The production phase requires the visualization of the following points for timely management: production, storage, and the inventory management of the components and their shipping for onsite delivery. Additionally, in the logistics phase, transport information such as that of the delivery products, vehicles, and road conditions must be considered. In the installation stage, the construction status of the components must be monitored. The management system must also be able to manage and support the overall plant production. Production in a factory is typically based on the drawings confirmed at the design stage. Therefore, it is crucial to link and manage the product and mold drawings (if necessary) with design drawings. In addition, offsite manufacturing must be performed according to the onsite installation schedule. Accordingly, the system requires a planning function to satisfy the onsite installation schedule by reflecting variables such as the product design, raw materials, and lead time. Finally, the project management system must track the production status, inventory, shipment, transportation, entry, and installation of components. The manufactured components are stocked until requested for delivery by the site. Because the manufactured products have a higher volume, weight, and lead time compared to those in traditional projects, strict inspection is required at every stage. Additionally, digital-based management must be implemented to ensure accurate and timely procurement. Therefore, an environment in which the product information is transmitted to the system in real time through sensing technologies and the collected data can be linked with an appropriate component is required. Overall, the system must have the following functions for managing the production, logistics, and construction stages:

• Automatic establishment of production plan based on component characteristics, production environment, and resources;
• Automatic vehicle matching based on component characteristics and installation schedule;
• Lift plan simulations considering equipment specifications and site environment;
• Automatic establishment of installation schedule considering master, zone, and equipment planning;
• Resource–intermediate product–end product–inspection chain management;
• Quantity and location management by component;
• Visualization of project process status based on BIM;
• DfMA-based BIM production drawing management;
• Linkage between onsite installation schedule and factory production schedule;
• Device setting for finished product quality check and synchronization between management systems;
• Management of component information (e.g., size, date and time, and location) through sensing.

3.2.2. Usability Requirements

The system functions specific to OSC projects must be intuitive and efficient. The usability requirements constitute information input and output automation, information visualization, and information-based communication. First, the OSC project accompanies considerable information, and the interdependence between the information points is high. Therefore, an input/output automation function must be established to conveniently manage all the information. In most construction projects, people manage the data manually, such as by directly collecting information and creating and printing documents. This management method consumes considerable time and resources, and information update through continuous iteration is inevitable. Manual information management is inefficient, and it is challenging to ensure accuracy owing to human factors. This aspect may limit the success of the OSC projects that rely heavily on information. Therefore, functions capable of automating the information input and output in various ways must be introduced to facilitate efficient information management.

Second, the key indicators of the project must be visualized to enable their monitoring to facilitate decision making. In general, even if a system has the status for each stage (Section 3.2.1), it is challenging to make information-based decisions if the data cannot be effectively delivered. Accordingly, it is necessary to improve the information usability for each subdivided management element, such as the schedule, component, and cost, as well as the project or phase information, from a holistic perspective. The system can support optimal decision making by effectively placing the interconnected variables on one screen.

Third, the participants must be able to share the project plan and status through the system and proceed with the project accordingly. Because OSC projects involve a high interrelationship between the preceding and the following tasks, the system needs a function that allows the parties to evaluate and enhance the performance. Information exchange within the system is also essential to minimize damage by responding immediately to any changes. The requirements from this viewpoint can be summarized as follows.

• Sensing and parametric-design-based data input automation via a mobile reader (e.g., component selection on both two-dimensional (2D) and 3D drawings);
• Visualization for status by project and component;
• Document (i.e., production log, shipment request, invoice, and payment) analysis and templates;
• 2D–3D model linking for DfMA; review of exchange of opinions for each stage of installation–production–transport;
• Sharing of and response capabilities to real-time changes for each stage manager;
• Visualization of progress by management elements (e.g., schedule, component, and cost).

3.2.3. System Requirements

The system implementation involves the following requirements: an environment that supports integrated data management through BIM (necessary for realizing the project management and usability requirements covered in the previous sections) and the overall system function. For data-based project execution, the management system must be able to sense, integrate, process, and analyze the data generated in real time at each stage according to the conditions. Databases (DBs) and DB management systems (DBMSs) that can handle data of various formats and sizes are required, and open source-based servers must be established to supply data to various places and channels. In addition, the elements for expansion, linkage, and system operation are required. The libraries for implementing essential elements and detailed functions for the system operations must be identified. In addition, the tools for interaction between the system and external data or programs are required.

• Model, drawing, component, document, transport vehicle, and equipment DB;
• DBMS for creating, reading, updating, and deleting data;
• Servers for application management and data transmission and reception;
• Development environments (i.e., operating system (OS), integrated development environment (IDE), development language, and framework);
• 3D view interface and user interface (UI) control libraries;
• APIs for IFC format creation and control and non-IFC format input and output.

4. System Implementation

The authors implemented a BIM-based OSC project management system according to the requirements derived in Section 3. The implemented system integrates the various data used during the OSC project in an object-oriented parametric form. This section describes the system development environment, implementation process, and the several functions and details required for the OSC project execution.

4.1. Development Environment

Table 1. Development environment and components.

Name	Role
Microsoft Windows 8/8.1/10	Operation system
Microsoft .NET 4x	Framework
Microsoft Visual Studio 201x	Integrated development environment (IDE)
MariaDB 10.x	Database management system (DBMS)
Microsoft C# 7.x	Programming language
CentOS 8.x	Server for web access authentication and content management, application execution environment and database (DB) connection, DB, and file data management
DevDept Eyeshot 12	Three-dimensional view interface
DevExpress 18.x	Windows user interface (UI) control library
xbim toolkit 5.1.x	Application programming interface (API) for .ifc controls
Microsoft Excel 14.x	Data input/output format API

summarizes the system implementation environment, which consists of the fundamental and functional parts for BIM-based project management.

The proposed system has the following essential environmental elements. Considering the usability, Microsoft Windows, a popular OS, is used, and Microsoft .NET is applied to ensure smooth program development and execution. Moreover, the system involves a program based on Microsoft Visual Studio, an IDE that can develop all desktop and web applications to be run on Windows. The program is implemented in Microsoft C#, a language that works reliably and efficiently in this environment. The MariaDB is used to manage the massive data created, changed, and stored in the system. The MariaDB is an open DBMS with high compatibility and openness with other programs and is widely used for development owing to its stable performance. Each server is established based on CentOS Linux for web access authentication and content management, application execution and DB access, and the management of the DB and file data.

Furthermore, the system has a 3D model view-based interface and API environment to implement BIM technology-based functions to facilitate OSC project execution. The 3D view interface environment is established using DevDept’s Eyeshot, and DevExpress’s UI is used for program input/output and operation control. The system also includes an API for xbim toolkit, openBIM, to ensure that the IFC format, which is a platform-neutral, open data scheme of BIM, can be recognized and edited in this program. In addition to the BIM models and drawings, this system includes APIs for Microsoft Excel to input or output various text and numerical data generated during OSC projects.

4.2. Development Environment

The system implementation is illustrated in Figure 1: the basic requirements of the system are designed and incorporated considering the OSC project management requirements presented in Section 3.

After implementing the detailed functions, the development is performed through repeated testing and improvement processes. The system designs and implements the relational DB and UI to effectively manage the various kinds of information in the OSC project. The data loaded into the DB are divided into information already generated in the design phase and information to be additionally generated in the construction phase (Figure 2).

Tekla Structures, a widely used component design program for OSC projects, can export the model in an IFC format readable by the system. The core information in the IFC file imported into this system is stored in related objects (i.e., project and elements/drawing management) in the DB. According to the defined relationship in this system, the production, logistics, and installation steps are performed, and the information generated during the steps is managed. In addition to the model data, the information that needs to be pre-constructed is imported into the system and used for digital-based OSC project execution using BIM. The system UI is designed such that the users could easily use the information on the screen in an optimized manner to satisfy the requirements of the OSC project. For example, for each information point of the production, logistics, and installation stages, only a single information stage needs to be presented at a highly detailed level. Furthermore, from the overall project and SCM perspective, the abbreviations for all stages must be organically presented on one screen. Consequently, a system interface is built that allows users to efficiently use information in the DB according to the characteristics and requirements of the OSC project.

After establishing the basic entities, the detailed functions are implemented to satisfy the requirements. This system reflects the execution results and the data of the external programs by establishing a plug-in interface to ensure that specialized-skill-required functions can be effectively implemented through dedicated software. Specifically, the central information of the DBMS is the IFC format of the model generated from the structural design tool and is recognized by the system through the xbim toolkit. Microsoft Excel, a spreadsheet program commonly used for quantity calculation and table work, is linked and used for data input/output and document management. These APIs are linked and integrated with the functions implemented to satisfy the project management, usability, and system requirements to establish a BIM-based management program. Finally, the initial system is implemented and tested and improved several times. After checking that each function of the initial system works appropriately, updates such as bug fixes, processing speed improvement, and design enhancements are made through alpha testing. The performance and function of the developed system is enhanced to ensure its applicability to OSC projects.

4.3. System Functions and Implementation Detail

The BIM-based OSC project management system has six management elements: drawing, schedule, production, logistics, installation, and monitoring/payment. This section describes the process of implementing the functions and technologies for each element.

4.3.1. Drawing Management

The proposed system implements functions for managing all the 2D and 3D models required for the construction and production. The drawing management function can import drawings into the management system, and the participants can review/modify the drawings. In the OSC project, the drawings specialized for each design, MEP, production, and installation are derived from the reference drawings. Therefore, this management system has a function to handle vast drawings effectively. BIM, commonly performed in OSC projects, has a large capacity because it includes detailed information, which may decrease the processing speed and prevent the active use of BIM in a working environment which requires prompt and immediate responses. Furthermore, the system has a function to import only the core elements from the IFC file and to filter only the required elements when loading into the system. Additionally, for early production in OSC projects, the system has a function that allows the participants to make design decisions conveniently. Managers can take notes or join live meetings while reviewing drawings in the system. Additionally, the system can print the results of the drawing review as a customized document. For example, the participants can discuss problems with the drawings in the system and automatically print a design defect document containing the following items: overview (i.e., project name, date, and title), diagnosis (i.e., errors) with drawings, probable causes, and suggestions (i.e., modified drawings, solutions, and preventive measures). This system is implemented by retrieving the necessary information from the BIM-based object properties to ensure that users can conveniently create documents.

The management system uses object-based BIM technology to implement the filtering function. For example, in the case of PC entities among the OSC components, a general IFC file includes all the information on, for example, component shapes and structural materials such as reinforcement bars and accessories such as hardware elements. If all this information is fetched, time may be wasted in unnecessary data processing. Therefore, this management system is added on to the BIM design tool to selectively export only the classes related to the OSC component (Figure 3).

For example, when exporting a PC project model from Tekla Structures in the IFC format, this system exports only the concrete modeling corresponding to the component among objects such as concrete, reinforcement bars, and hardware. The remaining objects (i.e., rebar and hardware) are stored as sub-properties of the component. Consequently, only the concrete objects are the output in the 3D view of this system, and the detailed design information is implemented to be viewed in the property window of each object.

Furthermore, a BIM function is implemented to enable the integrated management of the drawings and derived engineering designs. Although commercialized BIM design engines provide various functions for OSC, several functions need further development. For example, a typical mechanical design library does not cover all the special cases, such as dedicated piping for firefighting or hot water heating coils. In contrast, the proposed management system defines rules using xbim, a commercialized openBIM tool capable of object-based modeling for all additional elements in the engineering design of the OSC project. Additionally, a library of visualized elements is established through DevDept Eyeshot, and a DevDept Express-based interface that users can easily recognize and use is implemented.

4.3.2. Schedule Management

The participants can establish a closely connected plan between production, logistics, and installation and manage the project using the schedule management function of the proposed system. The management system enables the establishment of the master plan showing the timeline of each milestone, the zone plan for performing the construction, and the equipment plan for installing the product. The schedule manager can establish the master plan by entering milestones and designating deadlines in the management system. Subsequently, the management system is used to establish zone planning, order, and deadline. As shown in Figure 4, administrators can divide the site into several zones by selecting the space as polygonal or free-form on the space planning screen.

In addition, detailed information of the components belonging to the zone can be examined. The users can designate the order by zone, considering project-specific conditions such as accessibility of equipment and workers. Specific deadlines for each zone can be established, and the participants can review whether these schedules conform to the master plan. Additionally, the equipment planning necessary for product installation to plan the schedule of products belonging to each zone can be performed. When the schedule manager selects equipment on the equipment plan screen of the system, a list of equipment available for the project appears, derived from the equipment DB. After setting the equipment and the number of units, the management system suggests a movement route that conforms to the master and zone plan. When the user decides the movement route, the installation schedule of each component is automatically established, and production, transportation, and installation are performed in order.

BIM-based parametric modeling technology is used to realize automatic equipment planning. When the user selects specific equipment, this system automatically examines the movement line and cross-section, determines the installation possibility of each component, and establishes a specific installation schedule. The information of the equipment selected by the user is connected to the centralized digital model (CDM) from the DB in the system. Therefore, the construction possibility is determined by calculating the lifting loads of all the components applied to specific equipment. Based on these calculation results, the system outputs all available movement lines for all components, and the user can select the most suitable movement line for the project.

4.3.3. Production Management

The system involves a production planning and monitoring function for the streamlined execution of the production stage, which accounts for a large proportion of the OSC project. Production managers can use the system to establish a plan for the lead time and expected installation date of the target component and produce the component accordingly. The users can calculate the appropriate lead time after reviewing the production drawings saved as the attribute information of the component. Moreover, the system can establish a mold plan, such as that of a PC component, when necessary. On the production plan screen, the production schedules of the components with a lead time are automatically calculated and displayed as a matrix. Production managers can not only adjust and customize the plan but also rapidly identify missing components. Additionally, the system can track the production status of the components. Using the production status tracking function, users can perform JIT management of the OSC projects with thousands of components or more. The products undergo sequential positional and situational changes until they are finally integrated into a complete structure onsite. In many OSC projects, the sensors are attached to components to manage them from the final point of production. The proposed system can store the tagged data (i.e., date and location) as attribute information of the component in the DB. The finished product is moved to a yard or warehouse and awaits delivery requests from the site. As soon as the producer tags these components, the information sent to the management system allows other participants in the project to determine the production status.

The production planning system is automated through BIM object-based information management. In establishing a production plan for an OSC project, the key factors are the quantity, lead time, and delivery date of each component. The management system has an object-based environment in which each 3D model has a unique ID and various attribute information. The production quantity is calculated by assigning the same product number to components with the same shape and joint information. In general, the product lead time must be determined after carefully examining the drawings. The proposed C#-based management system reads BIM information through xbim and visualizes it as a 3D view by .NET-based DevDept Eyeshot. In this case, the 2D and 3D information is stored and linked to each component as a CDM. Therefore, when the user right-clicks a component on the 3D view screen, the production drawing appears (Figure 5). Managers can use this multidimensional BIM information to accurately estimate the product lead time.

To track and manage the product status offsite, technologies such as RFID and real-time location systems (RTLS) are fused with the BIM-based attribute information integrated-management technology for each component. RFID is used to identify a component and generate attribute information on the BIM. This RFID framework consists of a tag for identification, a reader for sensing, and an antenna for data transmission and reception. Once the antenna and reader are installed at the appropriate place, the nearby component can be recognized by receiving its information from the tag. Anticipating the occurrence of unintentionally repeated tagging, we process the data in an FTP format with the controller and finally transmit it to the system without duplicate noise. The data required to be transmitted and received through RFID include not only the ID and time but also the exact location of a component (determined using the RTLS). Bluetooth low energy, which has a small error range and low cost, is used to track the factory inventory and installation location in real time.

4.3.4. Logistics Management

The system enables logistics management to ensure that the inventory stored after production in the factory is shipped and delivered to the site on the scheduled date. The shipping process begins when the installation manager requests delivery of the component (Figure 6).

Onsite installers can request the import of products on schedule through the management system. When the user clicks “Add Component” in the import request window and selects the target models in the 3D view, they are added to the request list. The components in the delivery request status are automatically matched with the appropriate vehicle from the system DB, considering the transport schedule and physical characteristics such as the shape, size, weight, and quantity. Subsequently, the management system sends shipping notifications to the driver with the automatically generated invoice. The inventory manager identifies the location and status of the components to be shipped out using the system and completes the final finishing of the product. When the vehicle arrives at the factory, the product is loaded onto it, and the vehicle departs to the site. Installers can share this status in the system in real time. The component delivery is complete when the vehicle arrives at the site and passes through the gate. Product and vehicle information is collected through readers attached to both sides of the gate and then transmitted to the management system. The installer receives the information of the imported products in real time through the system, and the delivery process is completed with the inspection and unloading of the product.

In the logistics stage, in which the location of the products changes dramatically, management from the JIT perspective is vital. Requests and approvals for transporting components (e.g., production log, receipt request, invoice, and receipt confirmation) must be promptly made. A BIM-based system can effectively implement such request-granting procedures. Because all the information related to a component is managed as a CDM, other information related to one of the properties can be retrieved at any time. In addition, a documentation function is included in the management system to maintain continuity with the existing workflow. In practice, document exchange between business partners through e-mail, fax, and postal mail has different document formats. Using DevExpress’s extensive UI control functions optimized for C# and .NET-based environments, a digital form design is established between various customers in the management system. Additionally, the system can retrieve and output only the required information from the model DB, allowing automatic creation of the document. To enable the JIT management of the logistics phase, the proposed management system uses the global positioning system (GPS) technology. Using RFID alone, location tracking can be realized through reception with GPS. Unlike in the factory and onsite environments, in which precise resolution is required because the components are placed close to one another, the positions during transport have a reasonable margin of error. Consequently, the system receives location data from a GPS attached to the vehicle when the component is being transported. These data are stored as sub-attributes for each component.

4.3.5. Installation Management and Progress Monitoring

The BIM-based management system can monitor onsite installation work and OSC project progress. The site manager can manage the status of products from their entry to the site to their assembly. The proposed system can manage onsite construction by integrating multidimensional attribute information for each component using BIM and sensor-based real-time location tracking technologies such as RFID, RTLS, and GPS. The product delivery status is recorded by receiving the recognized product location and time data through a sensor on the gate. The arriving products are moved to the installation location and assembled in order. Moreover, the proposed system can track the installation status of products by receiving data from sensors attached to drones and equipment for moving and lifting products. If the position of the detected component matches the position in the BIM model, the installation process is complete, and the construction is completed through the detection procedure.

The management system integrates all the project statuses, including production, logistics, and onsite installation to enable monitoring according to the set conditions. To this end, the data collected from the various channels are integrated and managed in the system based on BIM. The management system can enable the monitoring of progress from a microlevel, such as a component, to the macrolevel (the entire project). For example, a manager can verify the lifecycle stage of a particular component (production, logistics, or installation). A component is recognized as a model object with a unique ID in the system, and the CDM interconnects the information of all the components through BIM. In this manner, the proposed system can implement the calculation result of the numerical data through the BIM-based interworking. For example, the percentage of components with the same shape and size in production, transport, and installation can be identified. Moreover, the achievements against goals at present or at a given point in a project or phase can be evaluated. This system has a progress monitoring dashboard to effectively visualize the status of all or individual phases. The screen displays important project and stage management indicators (e.g., numerical and 3D models for schedule, cost, and component status). Furthermore, the key indicators are arranged on one screen to allow users to rapidly recognize abnormalities and prevent significant problems.

4.3.6. Progress Payment Management

The proposed system has a progress payment management function that can rapidly and accurately settle costs according to the project progress. The progress payment management consists of three subfunctions: data management for billing, the automatic creation of installed quantities using BIM-based information, and the status of past invoices. The data required for billing consist of the quantity and unit price. The default value of the component quantity is derived from the number of individuals with the same attribute by the CDM. Moreover, the system can handle any quantity calculation formulas or premium conditions included in the project contract. Instead of directly inputting a list of components, quantity, and unit price required for an invoice, users can easily retrieve it from the system through the object-based attribute information. A subfunction is introduced to derive the project progress and performance indicators from past payment details. This function enables the querying of past payment history and can derive performance indicators such as the cumulative amount and quantity of a component or budget execution rate of a project.

The system linked related data through a BIM-based parametric modeling function to manage progress payment rapidly without errors. The contract amount, component model, and past payment details are linked in the DB, and the resulting values are calculated using this information. Figure 7 shows a sequence diagram of the user interaction with the main detailed functions in the progress payment management module.

The diagram illustrates the progress payment management in three main parts: contract amount inquiry, new invoice creation, and past payment history management. The contract amount is used to automatically calculate the unit price information required for billing (Figure 7A). Users can check the unit price in the BIM attribute information of the management system, the raw data of which are the contract amounts. Because these contract amounts often vary during the project, the system can save the change records and retrieve the most recent value when creating an invoice. Moreover, the system links the contract amount and the BIM component model to automate the cost calculation (Figure 7B). Although this system can automatically calculate the billing quantity by the CDM stored as a sub-property of the components, it uses the contract bill-of-materials value instead because the exact quantity and the cost of the materials required for one complete component depend on the contract’s terms and formulas. For example, in certain project contracts, the number of sills for columns or beams is extremely small, and they are not counted independently. In addition, a premium may be applied to the actual quantity in the case of parts that are difficult to manufacture or which require a large amount of materials. Therefore, the proposed system calculates the value closest to the actual cost by integrating the component ID, quantity, and contract through the CDM. Finally, the system can manage indicators such as the completed quantity and cost per entire project or each component (Figure 7C). An inquiry regarding past payment details is also possible, and the detailed information is displayed by clicking on the desired details in the list.

5. System Application and Effects

The BIM-based OSC project management system has been applied to four projects: two warehouse projects, an apartment project, and a large shopping mall project. Each project was in the stage of construction of the PC structure, and the system was tested for approximately six months (March–August 2022). The flow (process) of various management tasks during the project was improved compared to that when a system not based on BIM was applied. Subsequently, the time and workforce required for management tasks decreased, and the accuracy of the tasks was enhanced owing to the BIM-based data management.

5.1. Drawing Management

By applying this BIM-based system to test projects, the participants could more effectively perform the drawing management tasks. In an environment in which BIM was not supported, the project participants could only obtain information provided by the files loaded into the system. For example, even when computer-aided design drawings were imported into the system, the image could not be extended to derive other necessary information (shape, quantity, size, weight, volume, expected installation date of different views, and dimensions). Therefore, the project participants manually processed the information into the required form and produced the document. This process was time- and effort-intensive, and incorrect information was shared owing to human error.

In contrast, the BIM-based system represented the shape of the project in the form of a 3D view. This view was not simply a graphic object with high visibility but acted as a DB containing architectural information. In this manner, the testers could select a component from the 3D view of the system and immediately search the data stored in the DB or the visually processed data. The users could also promptly plot drawings from the system screen to the desired viewpoint and dimension. In addition, intuitive communication was possible by directly marking or leaving notes on the parts that needed discussion, on the system drawing. In fact, during the test period, several project participants actively conducted meetings using the communication tools on the management system. The screens and data of the management system, including drawings, could be easily exported to other media such as a social networking service (SNS). By leveraging these features, the users did not need to transform or update information during decision-making activities such as meetings, contacts, and presentations. In this manner, the time and workforce required for the unit work of the project were reduced, and the errors that occurred during information processing were prevented.

5.2. Schedule Management

The participants in the test projects used the system to establish an accurate plan for schedule management and to implement the project as planned. Before the system application, the participants used other schedule management tools to establish the necessary plans (i.e., master plan, zone plan, equipment plan, and the OSC component installation schedule). However, these interrelated plans were not automatically linked to one another, which made it challenging for the staff to manage the schedule. In one project, before the application of the system, the exact installation date for each component was planned with considerable effort to achieve the milestone of the master plan within the deadline. However, owing to a minor error in the equipment plan, there was a setback in the master and detailed installation schedule, which was eventually resolved by completely revising the zone and floor plans. Although these plans were interrelated, the inconsistencies or conflicts between the plans could not be automatically recognized in a non-BIM-based environment. In addition, although the schedule managers invested considerable time and workload in planning and reviewing, preventing errors at the source was challenging. Therefore, frequent plan revisions and rework during the project were inevitable.

These difficulties could be resolved by the application of the proposed system. The BIM-based component model included not only visual information but also multidimensional information by linking all the data in the DB by the CDM. This interworking of data for each object helped identify errors in the plan through the interconnection of plans. The schedule managers could prevent inconsistencies and conflicts in advance during the planning process. Consequently, the number of revisions to the schedule plan was reduced in the test projects, and the participants effectively managed the schedule based on a reliable plan by minimizing rework.

5.3. Production Management

The project participants efficiently managed the production process for each component, from planning to production, using the BIM-based system. In general, in OSC projects, production and installation are performed in different places and considerable communication arises between agents using various data for the timely procurement of components. In the past, the production managers at the plant periodically recorded the production status in a spreadsheet and shared it with the site managers. After they ordered the components according to the given data, the producers confirmed the order and started production. Again, the production managers shared the production status of the component with the site, and the subsequent processes were repeated. Data in various forms and versions were exchanged via e-mail or cloud storage, and in certain cases, information was exchanged over the phone without documents. In many cases, the person in charge of sending and receiving documents and the person in charge of communication were different. Because of this inconsistency, important data were often not accurately shared with all participants. Moreover, the presence of several versions of the documents led to human errors during production and exchange, and the participants had to spend additional time and labor to reconfirm or change the contents of orders and production. These data were periodically updated, which was inconvenient.

When the proposed management system was implemented, the production and onsite personnel could communicate promptly, conveniently, and accurately without additional data production and contact, and the production was managed accurately based on the data. The site managers could easily place an order by selecting the required component in the 3D view of the system, and the producers could immediately confirm these requests via notifications from the system to initiate production. In this manner, the system enabled faster and more convenient communication and minimized the possibility of the omission of exchanged information by providing a unified channel to the participants. Additionally, the production managers could save the time and human resources required to record production logs for each component by using the RFID technology implemented in this system. The proposed BIM-based system could manage a vast amount of multidimensional information, including the component status acquired by RFID in an integrated manner in the system DB. Using these data, the production managers could replace the production log by tagging the RFID once the component was produced. Consequently, the system application reduced the existing workload in the test projects, increased the reliability of the data, and shortened the time required for overall production management. In addition, the project participants could not only visually check the status of the components on the system in a 3D view but could also print the status in the form of a spreadsheet, if necessary, in parallel with the existing work.

5.4. Logistics Management

By integrating BIM and RTLS, the proposed management system rendered the process of the factory shipment of the components to the onsite import more efficient in the transport phase of the test projects. Because the correct and timely procurement of components is essential in OSC projects, the project participants tried to closely track each component’s shipment status, transportation, and import. Notably, before the proposed BIM-based system was applied, it was challenging to manage each of the thousands of components per project. Before testing, the projects were associated with unique systems, some of which involved advanced technologies. Because the data were not automatically linked, the personnel in charge had to review the data sequentially before proceeding to the next step. Accordingly, the errors in communication between the factories, vehicles, and sites occurred frequently in addition to the human errors that led to incorrect shipment or the omission of components. These errors required the correct components to be reshipped and transported or, in severe cases, to be remanufactured. These additional inputs of resources, such as cost, time, and workforce, resulted in project losses.

After the application of the proposed management system, the errors in the logistics stage were significantly decreased because the BIM environment system matched the data collected from the sensor to the appropriate object using global unique identifiers (GUIDs). Using this technical basis, the logisticians could streamline the shipment, transportation, and import procedures. Figure 8 shows the logistics management performed using this system based on the BIM and RTLS technologies.

Once a tag is attached to an item after production and setting, the system can store the information received from the tag as a sub-property of the component. Consequently, the managers could register the production status of the components in the system through tagging without creating production documents. Even when a component was being transported, the GPS information (from sensors mounted on the vehicle) was transmitted to the system, allowing the users to identify the component location in real time. The system recognized a component arriving at the site through a sensor installed at the gate. The testers did not have to wait at the gate and manually list each vehicle and component entry. In this manner, the proposed system enabled time and human resource savings compared to the traditional system and prevented errors or omissions.

5.5. Installation Management and Progress Monitoring

Using the proposed system, the administrators could more rapidly, accurately, and conveniently manage the installation status of the components onsite. Moreover, the users could effectively monitor the project progress by leveraging the BIM-based visualization data. In the existing project management environment that did not support BIM, the participants printed out 2D drawings for each floor to visualize the installation status, pasted them on the wall, and then colored them manually after checking whether each component was installed (Figure 9A).

This tedious task was highly time-intensive and had to be repeated periodically. Consequently, installation management was error-prone. In several cases, drawings or installation records (logs) were inaccurate, or the staff colored the wrong component. When the progress/cost execution rate or the numerical data were derived based on these inaccurate data, a notable ripple effect was observed on the project. Moreover, when fundamental aspects such as the design were changed, a complete rework had to be performed, resulting in a considerable waste of time and money.

The proposed system could overcome the abovementioned limitations. The users could effectively manage the project status. The site managers could easily examine the installation status of the components through a 3D view of the system implemented based on BIM (Figure 9B). In addition, project performance indicators such as the progress rate could be derived using data linked by the BIM without additional calculations. Therefore, the users could check the installation status of the project at a specific point in time through color-based 3D views and numerical information. Because the GUIDs recognized each component as a unique object, the corresponding information could be managed through the CDM in the system DB. Furthermore, the information to be stored in the sub-properties of the component model was matched only when it matched the model GUID, to ensure the connection accuracy. In this manner, the testers could streamline the cumbersome and repetitive tasks required to be performed in the non-BIM-based environment. Therefore, the time required to determine the progress status was shortened, and more accurate data-based monitoring could be accomplished.

5.6. Progress Payment Management

The managers of all four projects could perform faster and more accurate work using the automated progress payment management function of the proposed BIM-based system. Progress payment billing is a critical process related to the project cost and requires precision. When using the non-BIM-based system, managers requested payment by manually calculating, verifying, and matching the type (i.e., component ID/bill of material), quantity, and contract price of the installed components for a given period (Figure 10A).

The repetitive calculations and review processes were time-intensive, and it was difficult to prevent human errors despite investing considerable attention and effort. As shown in Figure 10B, the BIM-based management system helped alleviate these difficulties by providing an automated progress payment function. The users could not only check the installed components from the 3D view in the system but also immediately obtain the quantity information for each component linked by BIM simply by clicking on a specific item on the screen. In addition, in the BIM-based DB, the contract information was stored as an attribute for each component, and thus, the managers did not have to spend additional time matching and reviewing components, quantities, and unit prices. Additionally, using the data linked by the CDM, the process of manually processing information was eliminated, and errors could be fundamentally prevented. Through these process improvements, the input workforce was reduced compared to that associated with the non-BIM-based environment, enabling the efficient management of human resources.

6. Conclusions

This study was aimed at developing a BIM-based management system to effectively implement OSC projects. According to a literature review, considerable research is being performed for OSC project and system development to facilitate project management, and cutting-edge technologies, including BIM, are being integrated. Despite these efforts, the existing systems could not effectively accomplish the management tasks of the OSC projects, owing to their unique characteristics. Based on OSC project case studies and expert interviews, the authors analyzed the OSC project management characteristics considering six aspects, including the location and time. In this manner, the BIM-based management system requirements were derived from the project, usability, and system perspectives.

These requirements were reflected through several functions. Specifically, the proposed system involved functions for linking and integrating the production–logistics–installation processes and performing each of them efficiently considering six aspects, including drawing management. These functions were implemented through BIM-based parametric modeling, object-based data management, and integrated attribute information management for each element. The proposed system was applied to four OSC projects. Using this BIM-based management system, the users could smoothly manage the drawings and models of the OSC project, which increased the interoperability of the planning and execution. This interoperability facilitated the SCM of the OSC project, which is typically performed separately in factories, vehicles, and construction sites. In addition, because each task in the production, logistics, and installation stages was performed based on data through the management system, the task accuracy increased. Overall, the use of the BIM-based management system helped to improve and automate the existing processes and decrease the time and labor required.

The contributions of this research can be summarized as follows. A BIM-based OSC project management system was developed, thereby highlighting the potential of the application of BIM technologies in the field of OSC management. Although BIM has already been applied to a certain extent in OSC project management, the implementation has been limited to several stages, such as factory production, logistics, and onsite installation, or to a few domains, such as process, cost, management, transportation, and installation management. In contrast, the proposed BIM-based management system can enable the integrated management of the entire supply chain of OSC projects. To enhance the management efficiency, the proposed system uses BIM technologies to develop element technologies for various OSC project management aspects, such as production–logistics–installation integrated monitoring, automatic equipment planning, automatic payment calculation, and real-time communication. In this study, the characteristics of the OSC project management were studied and used to derive the requirements for management system development. Although several researchers have focused on developing a management system for OSC projects, the focus was on implementation and development rather than the analysis and design of the OSC requirements. In contrast, in this study, literature reviews, case studies, and expert interviews were performed to comprehensively derive the requirements. Using this information, the authors developed a BIM-based management system tailored to OSC projects. Most of the existing studies on OSC management or management systems were performed based on the management techniques or management systems of onsite production methods. In contrast, this study was based on the characteristics of OSC project management and the corresponding requirements for system development. Because of the use of targeted information, a system suitable for OSC project execution equipped with the necessary functions was developed. The system was applied and validated in demonstration projects, and the results highlighted that the system could improve the process and accuracy and reduce the time and human resource inputs.

Notably, the proposed BIM-based management system is under continuous testing, and there remains the scope for improvement. Specifically, all the functions required for OSC project execution have not been established. BIM technology is constantly developing and converging with other innovative technologies such as blockchain and artificial intelligence. Therefore, additional functions necessary for OSC project execution, such as DfMA, must be incorporated using these technologies. Moreover, the proposed system has been developed centered on PC structures and does not represent all OSC methods. Therefore, the management system must be verified for other types of OSC projects such as modular constructions and finishing processes.