Building information model (BIM) technology is a digital foundation for collaborative design in AEC (architecture, engineering, and construction) projects as it enables interdisciplinary team members to collaborate through sharing design attributes, changes, and issues. Academia and the AEC industry have increasingly developed methods and platforms supporting collaborative BIM design. One of the significant milestones is developing a common data environment (CDE). The latest ISO 19650 standards [2] recommends a CDE as “the single source of information to collect, manage and disseminate documentation, the graphical model and non-graphical data for the whole project team”. CDE promotes design collaboration efficiency by (1) specifying standard workflows to separate the life cycle of proje...[ Read more ]

Building information model (BIM) technology is a digital foundation for collaborative design in AEC (architecture, engineering, and construction) projects as it enables interdisciplinary team members to collaborate through sharing design attributes, changes, and issues. Academia and the AEC industry have increasingly developed methods and platforms supporting collaborative BIM design. One of the significant milestones is developing a common data environment (CDE). The latest ISO 19650 standards [2] recommends a CDE as “the single source of information to collect, manage and disseminate documentation, the graphical model and non-graphical data for the whole project team”. CDE promotes design collaboration efficiency by (1) specifying standard workflows to separate the life cycle of project data into different stages, (2) offering practical conventions for liability control during data production and delivery, and (3) providing explicit data status definition and a greater version management to improve data reusability. However, existing design collaboration platforms and design CDEs have a centralized system architecture, which suffers cybersecurity risks of design data manipulation, single-point failure, and denial of access, leading to a loss of data traceability, a decline in design productivity, project delays, and even legal disputes.

Blockchain is a promising technology to solve such risks by providing decentralized and immutable data storage. Unlike conventional centralized systems, blockchain employs a decentralized peer-to-peer system architecture, allowing every peer to own a complete, traceable, and irreversibly blockchain ledger. Applications of blockchain have been initially investigated for securing digital collaborations in construction, such as construction quality information management, supply chain management, and interim payments management. However, the implementation of blockchain in CDE and BIM collaborative design is still in its infancy for four research gaps: (1) difficulty in storing or decentralizing large-sized BIM models when using blockchain, (2) lacking access control methods to protect sensitive/confidential BIM data in a transparent blockchain, (3) lacking automated and efficient BIM versioning approach when collaborating in a blockchain, and (4) difficulty in quickly deploying and using blockchain in BIM collaboration scenarios.

Therefore, this research aims to develop a distributed CDE (DCDE) using blockchain to enhance data security in BIM-based collaborative design. Contributions lie in four aspects:

(1) Developed a DCDE framework to solve the problem of large-sized BIM data decentralization (Chapter 3). A distributed common data environment (DCDE) framework is proposed leveraging two distributed technologies: blockchain and Interplanetary File System (IPFS). This novel blockchain-IPFS integrated method stores both BIM models and design changes in a distributed manner. Fundamental problems like what is the workflow when collaborating in a blockchain-IPFS-based CDE and how project members could exchange information in such CDE are explored in this work.

(2) Proposed a confidentiality-minded framework (CMF) for sensitive BIM data protection in DCDE (Chapter 4). Although the DCDE secures data storage, data access control is still a concern due to network transparency. Thus, a confidentiality-minded framework (CMF) is developed on top of the DCDE to prevent unauthorized access to sensitive BIM data in a blockchain ledger. Besides, new design strategies are developed in CMF to facilitate design coordination within the access-controlled blockchain network.

(3) Developed smart contract swarm and multi-branch structure for secure and efficient BIM versioning in DCDE (Chapter 5). Except for the data storage and privacy-preserving problem, automated BIM version management in a distributed network is a challenge. Therefore, a two-layer container common data environment (TLCCDE) model is developed to advance the DCDE by building a separate transition channel in which unapproved data can be segregated, and liabilities during the version approval process can be controlled. Within the TLCCDE, a smart contract swarm (SCS) is developed to automate versioning actions in the blockchain. Furthermore, a novel multi-branch structure (MBS) with efficient algorithms is designed to manage version change continuity, issue attachment, and dependency compliance simultaneously.

(4) Developed a lightweight Blockchain-as-a-service for fast deployment and usage of DCDE (Chapter 6). Although critical technical problems are addressed for blockchain-BIM integration, the complexity of blockchain still baffles its adoption in actual projects. To this end, a DCDE prototype called lightweight blockchain-as-a-service (LBaaS) is established to secure the BIM design collaboration while eliminating the difficulties of deploying and using blockchain. New technical elements, including a Multi-to-One mapping (MtOM) kit for easy blockchain registration, an integrated workflow retaining existing design practices, and smart contracts for secure blockchain interaction, are developed to support LBaaS functionality.

All developed approaches are illustrated and validated in BIM-based design scenarios, whose data are acquired from actual projects in Hong Kong, including two campus buildings and one mobile cabin hospital for COVID-19 treatment. Results show that: (1) All the proposed technical solutions are tested to be feasible. The DECD allows project members to coordinate design issues in a distributed environment. (2) The computing performances of the DCDE, including communication latency, throughput, and security, are in a reasonable range, thus eliminating concerns and difficulties of using blockchain. (3) Compared with existing BIM collaborative platforms, design efficiency has been enhanced in the DCDE by securing data traceability, automating information exchange, and augmenting communication transparency.