## 1 Introduction  
In recent years, the concept of smart cities has gained significant momentum as a transformative paradigm in urban development. Smart cities integrate a plethora of advanced digital technologies, including the Internet of Things (IoT), big data analytics, artificial intelligence, and cloud computing, with the overarching goal of optimizing urban functionality, enhancing sustainability, and improving the quality of life for residents. This integration enables real-time data collection, analysis, and decision-making, leading to more efficient resource management, improved infrastructure performance, and enhanced public services. In the context of smart cities, the Architecture, Engineering, and Construction (AEC) industry has been undergoing a profound digital transformation, with Building Information Modeling (BIM) emerging as a cornerstone technology. BIM has revolutionized the AEC industry by providing a comprehensive digital representation of the built environment. It allows for the creation of detailed 3D models that encompass not only the geometric and spatial information of buildings but also their functional characteristics, material properties, and construction schedules. Through BIM, architects, engineers, contractors, and other stakeholders can collaborate seamlessly, sharing and updating information in real-time throughout the project lifecycle. This enhanced collaboration has been shown to significantly reduce errors, improve design quality, and increase construction efficiency. For instance, studies by [PERSON] et al. demonstrated that BIM implementation can improve project success by enhancing communication and coordination among stakeholders [1]. Additionally, research by [PERSON] and [PERSON] highlighted the importance of effective BIM/GIS data integration for smart city applications, enabling better spatial analysis and decision-making [2]. However, with the expansion of regional projects, such as large-scale building complexes and urban parks, the AEC industry has faced new challenges. The increasing number of project participants and the exponential growth of project information have led to inefficiencies in data and information exchange. As noted by [PERSON] et al., the lack of integration between different digital construction technologies, including BIM, IoT, and blockchain, has hindered the realization of the full potential of smart buildings and cities [3]. Ineffective information management has resulted in project delays, cost overruns, and compromised quality. For example, in the construction of a large urban development project, the inability to effectively share and update information among multiple contractors and subcontractors can lead to design clashes, rework, and material waste. Given the critical role of the AEC industry in smart city development and the need for efficient information management, establishing an effective protocol for collaborative multi-scale information management through BIM is of paramount importance. While some studies have explored aspects of BIM application in construction projects, a comprehensive approach that addresses the unique requirements of multi-scale projects in the context of smart cities is lacking. This research aims to fill this gap by proposing a novel method for collaborative multi-scale information management using BIM and validating it through a case study of a large-scale urban development project, such as the Xiongan New Area. By integrating BIM with other relevant technologies and developing a robust information management protocol, this study will contribute to the digital transformation of the construction sector and provide practical guidance for future smart city projects. A unit is an economic entity that can own assets, incur liabilities, engage in economic activities and conduct transactions with other entities in its own name. In this paper, the unit refers to the economic entity related to engineering [4].