The rebuilding process after a disaster is critical for communities affected by disaster events. The time required to rebuild ideally should be as short as possible. However, building permits for new homes and structures must be issued in compliance with county zoning and state codes. This permit process currently takes considerable time, which has a negative impact on communities affected by these disasters. This study explores the employment of Building Information Modeling (BIM) and Blockchain Technology (BCT) to assist in the rebuilding process after disaster events by reducing the time and resources needed to issue building permits.
In post-disaster recovery, the challenges facing the local governments are the need to spend time to reflect on taking well-planned decisions and enacting quick response, to the willingness of the community to rebuild faster [1
]. The federal-wide efforts provided by FEMA to local governments have been limited to the short-term rebuilding level. FEMA assistance is restricted by The Stafford Act and presidential emergency declarations [4
]. Therefore, many areas at risk need a proactive plan and local vision to streamline the efforts of rebuilding after a disaster. One of the areas that requires improvements is building authorities operations.
A study by Gunes and Kovel [5
] defines a disaster as “an action that may pose threat to life, well-being, properties, material goods, and the environment from processes or technology” [6
]. Technological advancements in recent years have presented several new applications that can address the issue of disaster management and relief efforts. While the loss of life has reduced over the past decade, buildings and infrastructure are still subject to considerable damage. Hurricanes Harvey and Irma that struck Texas, Florida, Cuba, and the Caribbean Islands in 2017 are estimated to have inflicted around $
200 billion in damage in the states of Florida and Texas alone, which is comparable to costs incurred in the state of New Orleans after Hurricane Katrina in 2005. Disaster management and loss reduction have gained much traction in recent years, owing to exacerbating environmental issues and global change [7
]. The Federal Emergency Management Agency (FEMA) is the body responsible for coordinating federal natural disaster assistance for state and local governments in carrying out disaster management practices and providing relief aid to citizens.
Even with a system of recovery processes in place, there are many unprecedented factors that can crop up at any stage, which can severely impede disaster response. This is due to the cumbersome logistics planning and coordination between multiple parties [8
] that include contractors, stakeholders, transport companies, government authorities, and other regulatory bodies. The Cato Institute has issued criticism towards the governmental response to Hurricane Katrina in 2005, stating insufficient resource supply and communication breakdown [8
]. A sudden spike in demand for resources can force contractors to seek contractors that may be located at faraway locations, which may ultimately lead to delayed delivery times. Transportation companies must often traverse through perilous or impenetrable routes to reach the delivery destination [8
Apart from delays in transportation, the sanctioning of permits, and communication between various parties in post-disaster recovery; there is also the possibility of outright fraud as malicious entities can take advantage of the urgency and nature of an emergency. The complexity in coordination is further worsened by suppliers often forced to use carrier networks they do not normally use, owing to urgency and situational pressure [8
], as it is unfeasible to verify the qualifications of every contracted company involved in carrying out relief efforts. For example, during the onset of Hurricane Maria in 2017, an entrepreneur based in Atlanta delivered only 50,000 meals out of the 18.5 million meals contracted by FEMA [9
The unsustainable expansion of the human-built environment and climate change as a consequence of increasing urbanization have exacerbated the frequency and impact of natural disasters. Further, urban hazards cannot be addressed by technological fixes alone, but also necessitate a pro-active study and the involvement of urban landscapes and socio-economic characteristics [10
]. It is, therefore, imperative to adapt to the changing climatic patterns, natural and urban landscapes by building resilience and minimizing costs [11
], as noted in the ‘Stern Review’ (Cabinet Office/HM Treasury 2006).
The prevention and avoidance of threats and hazards fall under the umbrella of the ‘Disaster Risk Management’ (DRM) framework [11
], but there has been little research conducted in formulating an effective mainstream framework for implementation in the Architecture, Engineering, and Construction (AEC) industry. One agreement, however, is that resilience should be systematically built-in to each phase of building (design, construction, and operation) [11
], although there is not yet any concrete progress in erecting a framework.
A primary requirement of an effective disaster management system is the maintenance of a high degree of accuracy of vital information communication pertaining to the disaster on site that is to be disseminated to government and relief bodies. The AEC industry has developed a process over the years to deal with the disaster cycle. This process generally involves four stages [12
], namely: prevention and mitigation: risk assessment and planning; preparation: pre-impact activities; response: emergency management and operations; and recovery: rebuilding and restoration of communities, infrastructure, and services.
Evolving technologies like BIM and blockchain have seen significant advances in recent years and have been widely tipped to disrupt existing socio-technological hierarchies and workflows. The transformative potential of these new developments is evident, but they are still in their nascent stages. BIM is at the forefront of digital transformation in the AEC industry, and there is an increasing interest in integrating BIM workflow and BCT, with a view toward streamlining a number of operations, such as collaboration and design review while addressing issues such as speed, cybersecurity, and data exchange integrity.
The blockchain is a digitized, decentralized public ledger of data, assets, and all pertinent transactions that have been executed and shared among participants in the network. While it is most associated with digital cryptocurrencies such as Bitcoin, blockchain is viewed as an emergent technology that could potentially revolutionize and transform the current digital operational landscapes and business practices of finance, computing, government services, and virtually every existent industry [13
]. The chief hypothesis behind blockchain is the creation of a digital distributed consensus, ensuring that data iare decentralized among several nodes that hold identical information and no single actor holds the complete authority of the network. This enables transparency of activity and enhancement of data security. Figure 1
depicts the general schema of blockchain technology. While initially developed solely for financial transactions with an aim to create a system that enables secure data transfer between two parties without the requirement of an intermediary, the tremendous disruptive potential of blockchain was later evident with the exponentially increasing development of various cryptocurrencies in recent years. By placing emphasis on trust and cooperation between participants, blockchain radically reorganizes existing workflow paths in any organization in which it is implemented, bringing with it a plethora of benefits that include shared learning, instantaneous data exchange, automated contract execution, network security, and improved collaboration.
In general, three generations of BCT can be distinguished: blockchain 1.0, which covers applications enabling digital cryptocurrency transactions; blockchain 2.0, which expands blockchain 1.0 by introduction Smart contracts and a set of applications beyond cryptocurrency transactions; blockchain 3.0, which enhances the capabilities of blockchain 2.0 in terms of transaction time, scalability, and ease of implementation using DApp;
This research contributes to a thorough understanding of the BCT and its current state-of-the-art applications, particularly its relationship to the rebuilding process after disaster. Moreover, this paper provides new approaches for integrating BCT with the BIM workflow, such as improving the framework for automating building code compliance checks and the permitting processes.
The rest of the paper is structured as follows. In Section 2
, the purpose of the study and research questions are described. The objectives of this work are given in Section 3
. The methodology employed to conduct a systematic literature review is introduced in Section 4
. The findings and evaluation of the retrieved literature about BCT are presented in Section 5
, while Section 6
addresses the applications of BCT in different industries. Section 7
discusses the relationships between the BCT and BIM processes. In Section 8
, the paper introduces a new approach for enhancing the framework for building permitting process using BCT and BIM workflow. Conclusions and future research areas are presented in Section 8
The research is designed as a non-experimental, retrospective–prospective study, which examines and curates blockchain technology and BIM integration to improve the post-disaster rebuilding process. The research approach is based on a systematized review of the current development of Blockchain Technology (BCT), and its applications in the AEC to enable the development of an integrative framework for enhancing the rebuilding process after disasters. The procedure comprises two phases. Phase 1 includes identifying the research’s key aspects, selecting the relevant studies, assessing the quality of the content, extracting data, and synthesizing the information. The second phase deals with the development of an integrative BCT + BIM framework, using the information from phase 1 to improve the post-disaster rebuilding efforts.
A comprehensive investigation of the current literature is essential to further the knowledge base of significant topics, enable the formulation of a viable narrative, and justify the research goals and future studies. Figure 1
illustrates the overall method employed in this study. The first phase of the research protocol focuses on the scope identification and the survey background on the current state of BCT and its applications. This phase covers the existing knowledge base, to provide background on the historical developments of prominent BCTG, the significant development of key features, market impact, and uptake. The knowledge of ongoing research efforts could provide a fair prediction of future developments. This phase ascertains the upper and lower limits of relevant fields with respect to the current capabilities and limitations of BCT and BIM. This includes classifying the publications according to the main categories: BCT related only, BCT and the AEC, BCT and BIM, and the post-disaster rebuilding and BIM. Since there has been minimal overlap between the fields of BCT and BIM (or between post-disaster reconstruction and BCT), it was necessary to develop a cache of descriptive data and conceptual underpinnings pertaining to both fields. This review helped to strengthen the research question, clarify the scope and objectives, and validate the direction of the paper. Finally, conclusions about the potential applications of the emerging BCT in the post-disaster rebuilding are presented, as well as a proposal for a new integrative framework resulting from incorporating BCT in the BIM workflow, which could simplify the rebuilding process after a disaster.
Phase 1 of the study centers around assembling evidence through an extensive literature review. The literature review provides definitions, background, historic development, current knowledge areas, and ongoing research efforts on each relevant area. The prevalent aspects currently discussed and researched are used to identify the keywords, which have served to widen the search process in search tools, such as Google Scholar, Mendeley, Microsoft Academic, Bielfeld Academic Search Engine (BASE), arXiv, WorldWideScience, RefSeek, Science.gov, ResearchGate, and Virtual Learning Resources Center. The first set of articles collected was examined for relevancy by reading the abstracts. A closer examination of the papers determined the relevancy of the papers to the post-disaster rebuilding investigation. A preliminary study of literature articles suggests that BIM interoperability, BIM collaboration, data integrity and cybersecurity, Smart Contract (SC), and Hyperledger Fabric (HLF) are the primary aspects of the scope of this research. Figure 2
depicts a summary of the literature review papers that have been studied.
While many publications exist that tackle the fundamentals, operational mechanisms, and research directions of BCT, limited research papers address areas of BCT that overlap with application in the AEC industry and post-disaster recovery. Even fewer publications are available that focus specifically on the use of BCT in BIM processes in connection with rebuilding after a disaster. However, the current number of papers tackling these subjects are reassuring, as many research results published in recent years propose the employment of BCT, precisely its Smart Contract (SC) concept, to achieve different solutions in a BIM environment.
4. Blockchain Technology (BCT)
4.1. BCT Basics
Blockchain concepts, functionality, present implementation, mining, cybersecurity, and transaction protocols are discussed by many studies, such as [13
]. The advantages of using different types of BCT are studied by [21
]. In a blockchain network, the ledger consists of a chain of sequentially arranged blocks of discretized, encrypted data, which is created and stored with cryptographic hashes upon validating a transaction. The two main parts that constitute an individual block are:
Block header, consisting of the block version, a timestamp, Merkle tree root hash equivalent of the transactions, nBits, Nonce, and a parent block. A Block version indicates the set of the block validation. Timestamp displays the current universal time. Nonce is a 4 byte field that generally starts from zero, and increases by one for every hash calculation, thus acting somewhat as a transaction counter. The parent block hash is the 256 bit hash value that references the parent block, i.e., the sequentially preceding block to the one in the discussion. The first block in the chain that does not have a precursor is called the genesis block.
Block body, which contains the actual transaction data. This is the part of the block that effectively dictates the upper limit of the possible transactions, as well as the transaction time [18
The digital infrastructure of the blockchain network can be divided into two layers of code [38
Fabric layer: consists of the actual blockchain code base, communication protocols, public key infrastructure, data structures for database maintenance, and smart contract capabilities. Since the blockchain network is owned and controlled by the developers, the fabric layer cannot be tampered with.
Application layer: contains the application logic of smart contracts. It is collectively controlled by the participants who deploy the code onto the blockchain network when it is operational. Any participant that holds access and control of the deployed code can write the application layer.
The blockchain networks can be generated in several ways. These are typically organized according to the network’s management and permissions, such as public (permissionless), private (permissioned), and federated [18
]. It is worth mentioning that in a public blockchain network, any entity can join as a new user and perform operations, such as transactions or authentications.
4.2. Decentralized Systems
A centralized network is one that tasks a single central node with monitoring, controlling the flow of information between the other nodes, and dictating operational controls. From a personal standpoint, one decision-maker could reduce the likelihood of conflicts and disagreement, but on the other hand, several other factors could affect coherent interoperability and collaborative decision-making, such as if even one of the two parties is acting with malicious intent, or is negligent or incompetent.
A decentralized database structure, which is known as Decentralized Ledger Technology (DLT), is a peer-to-peer network that typically integrates a decentralized agreement mechanism, distributing the computational workload across multiple nodes present throughout the network, facilitating the nodes to create connections, and ensuring the links stay alive, while also ensuring every node in the network receives and transfers out data [18
]. This mechanism excludes the likelihood of a system failure or a complete network blackout. DLTs usually achieve this by integrating a decentralized consensus structure before the blockchain initiating transaction operation. The network participants agree in advance and decide on a consensus mechanism appropriate to their requirements. Every endorsing node in the network runs the same consensus algorithm. Thus, the system does not need any third-party administrator to oversee the data exchange operations [43
4.3. Trust Systems
Members of the network must prove themselves as legitimate members. Thus, reaching a consensus agreement is one of the key features of a distributed technology [43
]. A consensus between all participants in the blockchain network is agreed on prior to the implementation of the BCT, and this agreement ensures that the ledger is shared, unchangeable, and immutable throughout its life.
After agreement on the consensus mechanism, the peers execute the consensus protocol to validate transactions, create blocks and hash chains. The ledger is updated and appended in the event of the occurrence of errors, instead of overwriting them. New transactions recorded on the ledger are validated by miners. A block is mined every few minutes. The Byzantine Generals (BG) problem is central to determining consensus in a BCT, and all consensus mechanisms are developed with the aim to overcome this issue. The Byzantine General Problem was a security flaw in distributed systems developed prior to Bitcoin, in which the nodes aim to reach a consensus despite having a faulty component [44
]. This increases the possibility of malicious intent or network irregularities. The different mechanisms through which consensus is reached are:
Proof of Work: ‘Mining’ or the Proof of Work (PoW) mechanism works by determining the node that writes a block on ledgers using a combination of game theory, cryptography, and incentive engineering [18
]. The nodes in the network compete to solve a mathematical puzzle (generally a computationally difficult but easily verifiable pattern) to record a transaction. Upon resolving the puzzle, a consensus is reached by broadcasting the resolved solution to other nodes in the network, thereby ensuring transparency, robustness, and incorruptibility of the network. Consequently, the group with larger total computing power dictates the decision-making and reaching consensus. The two most popular BCT systems, Bitcoin and Ethereum, operate on a PoW mechanism. However, this involves expensive transaction fees, extensive computing tower, and cumbersome mining processes to create new blocks.
Proof of Stake: The creator of the block is chosen in a deterministic method, depending on the stake held by the participant. An algorithm is employed to determine collective decision-making and the level of privacy between participants. This mechanism requires the credibility of data, which is denoted by proof of ownership of cryptocurrency coins. If a created block can be validated, the cryptocurrency will be returned to the original node as a bonus. This method involves no block rewards but operates solely on transaction fees. It is thus an energy-saving alternative to PoW and presents several economic benefits. Ethereum aims to shift the paradigm by transitioning to a PoS mechanism.
Practical Byzantine Fault Tolerance (PBFT): This is a Byzantine agreement consensus method that can tolerate a maximum of 1/3 malicious byzantine replicas. A primary is selected in each round and is responsible for ordering the transaction. A node enters the next phase if it receives 2/3 of votes from the remaining nodes in the network [18
]. Thus, PBFT requires each node to query other nodes. Hyperledger fabric uses the PBFT algorithm;
Delegated Proof of Stake (DPOS): Stakeholders elect representatives to validate blocks. Since this mechanism features a relatively small number of nodes, the processing of transactions is quicker [18
]. The delegates are authorized to modify the network parameters.
Mining is the mandatory process of recording transactions on the blockchain network using the computer’s processing power. The subset of nodes in the network that are equipped with special software that validate the transactions to be added on the blockchain is called miners [28
A blockchain can address the accessibility and visibility of the data in a secure and efficient manner, since the ledger is distributed [43
]. This ledger facilitates setting different levels of privacy, as every participant is essentially a stakeholder and no single participant has full administrative privileges. Thus, formulating and enforcing consensus is crucial to the blockchain operation, with respect to data updates, error-checking, and collective decision-making. The selection of which BCT to use depends much on the method of the agreement to reach consensus.
Based on the privacy, blockchains can be classified as:
Permissioned blockchains: Permissioned Blockchains restrict the actors that can contribute to the consensus of the system state. Only a restricted set of users have the rights to validate transactions and may also restrict access to approved actors who can create smart contracts. HLF is an example of this permission type.
Permission-less or public blockchains: Blockchain networks that are permission-less allow any participant to create consensus, as well as smart contracts, and uses the PoW mechanism to reach a consensus. They typically use a native cryptocurrency or none to validate transactions. Bitcoin and Ethereum blockchains are good examples of this type of permission.
4.6. Smart Contracts
Smart contracts are contracts programmed with the blockchain that automatically execute upon the fulfilment of certain conditions. This removes the requirement of a third-party intermediary for overseeing the transaction in real-time [45
]. They are an extension of the blockchain that can independently enforce rules without requiring manual intervention. Figure 3
illustrates the concept of a smart contract in a blockchain network.
The following is a definition for the concept of smart contracts [28
]: “Smart contracts are digital contracts allowing terms contingent on the decentralized consensus that is self-enforcing and tamper-proof through automated execution.” The introduction of smart contracts in blockchains has opened many new possibilities, such as complete lifecycle management of legal contracts, automated execution of contracts, and personalization of customizable contracts.
In the context of the BCT taxonomy, two different definitions for the term ‘smart contracts’ are given, since the term is used interchangeably for the written code and the binding contracts [45
]. Smart contracts codes: They are software agents fulfilling pre-set obligations and exercising certain rights and may take control of certain assets within a shared leger.
A high-level definition that combines both aspects of the smart contract and is based on automation and enforceability is given in [46
“A smart contract is an automatable and enforceable agreement, automatable by a computer, although some parts may require human input and control, enforceable either by the legal enforcement of rights and obligations or via tamper-proof execution of computer code.”
Two widely used programming languages for writing Ethereum Smart Contract (SC) are Solidity and Serpent. Further, there are a number of emerging contract-oriented high-level languages under development, such as Viper, Lisk, and chain.
In a Hyperledger Fabric (HLF), SC is known as chaincode, which is executable code, deployed on the network, where it is invoked and validated by peers during the consensus process. The common programming languages used in developing chaincode are Go, Ruby, Java, and NodeJS [51
In summary, the main characteristics of a smart contract generally include [46
Automation: Automation is accomplished by linking the legal prose to the smart contract code via parameters that generate instructions regarding the final operational details.
Enforceability: The smart contract code must execute successfully, accurately, and within a reasonable timeframe. A smart legal contract must include legally enforceable obligations and rights that are expressed in complex, time-dependent, sequential, context-sensitive prose. These may also include overriding obligations based on the fulfilment of certain conditions.
4.7. Hyperledger Fabric (HLF)
Hyperledger Fabric is a platform for generating distributed ledger blockchain systems, supported by a modular design, offering an elastic and extensible digital framework that delivers high levels of confidentiality and scalability. The Hyperledger Fabric is designed to support pluggable implementations of different components and accommodate the complexity and details that exist across the economic ecosystem. The Hyperledger blockchain aims to be a general purpose, enterprise-grade, open-source DLT that features permission management, pluggability, enhanced confidentiality, and a consensus mechanism, and is developed through a collaborative effort. HLF is one of the blockchain projects within Hyperledger. Like other BCT, it has a ledger, uses smart contracts, and is a system by which participants manage their transactions.
Hyperledger was founded by the Linux Foundation in 2015 to advance cross-industry BCT. It was the first blockchain developed that enabled the development of distributed applications written in standard general-purpose programming languages [52
]. Presently, the Hyperledger consortium involves IBM, the Linux Foundation, and other organizations that contribute to the BCT development and related apps [48
]. The open source nature of the BCT is augmented by the lack of necessity in mining cryptocurrency or expensive computations to validate transactions. The HLF was the first blockchain developed that enabled the development of distributed applications written in standard, general-purpose programming languages [52
]. HLF was founded by IBM and aims to be a platform for developing applications with a modular architecture. It permits plug-and-play components and leverages containers to host smart contracts called chaincodes, which comprise the business logic of the application.
The fundamental difference between HLF and other blockchain systems is that it is private and requires permissions. In contrast to an open permission-less system that allows unknown identities to participate in the network (necessitating rules like PoW to authenticate transactions and secure the network), the nodes (members) of an HLF network join through a trusted Membership Service Provider (MSP). Furthermore, HLF offers several pluggable options, such as ledger data, which can be stored in multiple formats, and consensus mechanisms, which can be exchanged in and out; diverse MSPs are also supported.
Moreover, Hyperledger Fabric has the ability to create channels, allowing a subgroup of participants in the network to establish a separate ledger of transactions. This is an especially important option for BIM workflow where subcontractors can exchange data within the only subgroup of the network. For example, the structural engineer of record of the project can exchange information with steel connection subcontractors only while still being part of the HLF network and sharing those transactions with the rest of the nodes.
The HLF has several design components that provide a comprehensive yet customizable, enterprise blockchain [44
Assets: Assets can range from physical objects (real estate and hardware) to the intangible (BIM models, contracts, and intellectual property). Hyperledger Fabric provides the ability to modify assets using chaincode transactions.
Ledger: It is comprised of a blockchain to save the immutable, sequenced records in blocks, as well as a state database to preserve the fabric state. There is generally one ledger per channel. Each node sustains a copy of the ledger for each channel of which a node is a member. The shared ledger encodes the entire transaction history for each channel and includes SQL-like query capabilities for efficient processing.
Privacy: Channels enable multi-lateral data exchanges with the high degrees of privacy and confidentiality required by the AEC specialized and other regulated industries that exchange data on a shared network. A ledger exists in the scope of a channel and it can be shared across the entire network (assuming every participant is operating on one common channel), or it can be constrained to only contain a specific set of participants.
Security and Membership Services: Permissioned membership provides a trusted blockchain network, where participants know that all transactions can be detected and traced by authorized regulators and auditors.
Consensus: It is defined as the full cycle of verification of the correctness of a set of transactions comprising a block in a distributed ledger system. HLF consensus covers the entire transaction flow, from proposal and endorsement to ordering, validation, and commitment. Hyperledger Fabric has been designed to allow a new application to select a consensus mechanism that best characterizes the relationships that exist between participants in the network.
Smart Contracts: Hyperledger Fabric smart contracts are written in chaincode and are invoked by an application external to the BCT when that application needs to interact with the ledger. In most cases, chaincode interacts only with the database component of the ledger, the world state (querying it, for example), and not the transaction log. Chaincode can be implemented in several programming languages. The currently supported chaincode language is Go, with support for Java and other languages coming in future releases.
On one hand, there are notable advantages of BCT that include: the trust system (consensus, mining and the public ledger), secure communication on open networks using cryptography, and encryption; transparency; removal of Intermediaries; decentralization; reduced costs; and increased transaction speed. On the other hand, there are also downsides and risks associated with the standard BCT that can be ignored at this time. These limitations may involve [13
Lack of Privacy: Decentralized public blockchains lack privacy, which will make full acceptance difficult. Not only is the information not private, but it is also readily accessible at any given moment to anyone using the system This is also concerning considering that the computers running a large amount of the blockchain networks are in countries like Russia and China, where computer crime rates are high and personal information may be used against people living in or traveling to those countries. This is particularly an issue for Bitcoin and Ethereum systems.
Security concerns: Blockchain-based assets are like cash. If the cash in your wallet is stolen or lost, then it is gone. Blockchain-based systems use advanced cryptography and encryption that are more secure than standard internet passwords or number access codes. However, more security can sometimes result in a system being less secure. There are countless examples of cryptocurrencies where someone has forgotten their private key and cannot access their money. With blockchain-based systems, transactions cannot be altered or reversed, and there is no intermediary to assist you if fraud occurs on your account. If you sent funds to the wrong account number (wallet) on the blockchain, then those funds are gone. If someone gains access to your private key, they can access other members’ data easily.
Lack of a centralized management entity: The control is placed with most members of the network, creating issues with regards to control of the blockchain network. The decentralized nature of many blockchains means that the system must agree and decide the future direction of the blockchain system. With a traditional network and software, if an organization wants to make a change, they can make that change after approval from relevant departments within the organization. With a decentralized public blockchain system like Bitcoin, changes must be agreed to by a certain majority of the networks’ participants. This may be over 50% but could be as high as 70% to 80% of the nodes of the network. No single entity has control over the changes or direction of a decentralized blockchain system, making them risky for businesses to use as they cannot manage any changes to the system.
Risk of a 51% attack: If someone were able to control over 50% of the computers on a blockchain network, that person would control the transactions on the blockchain network. A malicious user controlling over 50% of the computers on a blockchain network is known as a 51% attack. Leveraging this control over a cryptocurrency network, they would theoretically be able to block new transactions from confirming, reverse transactions, and allow for moving assets freely in a Bitcoin network.
Cost: The Proof-of-Work (PoW) algorithm that many blockchain networks use requires proof that computing power and resources contributed to the network before a block is added to the network. This proof is in the form of an answer to a puzzle that is attached to the block for the network to confirm it is correct. Solving this puzzle requires an enormous amount of computing power and electricity.
Lack of scalability: At the current rate of energy consumption, the electricity costs of running certain public blockchain system, such as Bitcoin, and using the PoW algorithm make it unfeasible to handle the number of transactions (for example, by credit card companies like Visa and MasterCard). This is one of the factors that is presently affecting the scalability of blockchain networks.
4.9. Summary of BCT
Blockchain systems are generally comprised of four building blocks: (1) a shared ledger, (2) privacy, (3) trust, and (4) smart contracts (see Figure 4
). These main blocks are briefly explained below:
Shared ledger: Shared ledger refers to the distributed transaction records in the network. With the bitcoin blockchain system, the intent was to publicize the visibility and transparency of data exchanges. However, enterprise blockchain systems requires a different approach due to the regulation of consumer data.
Privacy: Privacy is achieved through cryptographic encryption of data and ensures that transactions are authenticated and verified. Privacy is a crucial part of the BCT to strengthen security and make the distributed system on the network more difficult to breach.
Trust (consensus): Trust means using the power of the network to verify data transaction. The trust model (consensus) is truly the heart of blockchain applications. Trust is what delivers the tenets of trust, exchanges, and ownership. Trust is what enables the blockchain to displace the transaction system, but this can only happen when trade and ownership are addressed by distributed/shared ledgers. The trust system is modified whenever new participants join the blockchain network and apply BCT to a new use case or change. There is still much work needed to define an optimized trust system for various use cases.
Smart contracts: Smart contracts are business agreements embedded into the transaction database and executed automatically with transactions. Contracts consist of rules that are required in any commerce activities to define the flow of values and the state of transactions. A contract is smart because it uses a computerized protocol to execute the terms of the contract. Various contractual clauses (such as collateral, bonding, delineation of property rights, and so forth) can be transformed into machine language to enforce compliance with the terms of the contract and ensure a successful transaction. Smart contracts are intended to guarantee one party that the other will satisfy their promise. Part of the objective of such contracts is to reduce the costs of verification and enforcement due to the lack of an intermediary party to oversee transactions.
Smart contracts must be transparent (indicating that participants can see or prove each other's actions pertaining to the contract), confirmable (meaning that members can prove to other nodes in the network that a contract has been completed or breached), and private (implying that knowledge of the contents/performance of the contract should involve only the necessary members required to execute it). These advances made it possible for complex business contracts to be codified in a blockchain system.
6. Blockchain and BIM
This section addresses issues related to the potential capabilities of BCT in scaling and enriching the BIM process. It explores various aspects of existing BIM workflow that could benefit from the integration of blockchain technologies.
BIM is at the forefront of digital transformation in the AEC industry, encouraging collaboration and trust and simplifying data exchange. McGraw-Hill reports that BIM adoption increased to 71% in 2012 from 49% in 2009 [17
]. BIM models present a comprehensive design model of the building that can include all aspects of the structure, like architecture, structural elements, and MEP design areas. Further, several built-in plug-ins in BIM platforms, like Autodesk Revit, enable the simulation of external site conditions, geography, weather, as well as carry out energy analysis, building energy modeling, structural analysis, etc. In the future, BIM development will eventually aim to unify all design and analysis tools in one platform.
In terms of the benefits incurred from the adoption of BIM in the AEC industry, Cannistrato [65
] studied data from 408 projects over 6 years, totaling $
558,858,574, to quantify how much BIM contributed to saving money. The report indicated that BIM saved more money and the project team became more collaborative in the process. Another example is the study by [66
], which indicated similar results. Their investigation covered a set of 35 case studies between 2008–2010, which all indicate cost savings due to BIM usage. The study has also noted reduced times in project schedules, improved communication, greater information exchange, and higher levels of coordination. The data clearly implies that initial costs, such as hardware upgrades, software implementation, and training of personnel, are offset on the long term upon BIM implementation. However, the BIM process still bears a number of shortcomings. These include some limitations in the schema, technical toolset, and managerial aspects of the current BIM process. More specifically, these deficiencies involve:
an insufficient toolset or methods that can efficiently comment or mark upon Requests For Information (RFIs) [67
no archive of BIM model changes and modification history,
impracticality in the generated list of design errors [68
inapplicability of the integrated model for co-designing in real-time [68
a clear generation of comparative deviation reports contrast design changes between different file versions,
detailed open model templates [70
insufficient communication standards and BIM model sharing that can lead to interoperability issues between different BIM tools [71
a lack of tools to map complex collaborative workflows and insufficient levels of interoperability [74
difficulties in assigning responsibilities and liabilities due to the overlap of roles and responsibilities, ensuring intellectual property protection, risk allocation, privacy, and third-party reliance and software agents [22
insufficient cyber-resilience of the software platform and consequent risks and liability to data theft, tampering, and other cyber-attacks,
time-consuming re-modeling, conversions, and other repetitive tasks that could be automated during the project phases [74
the lack of a legal framework detailing model data ownership and legal/contractual issues [74
6.1. Data Ownership
BIM can address the issue of converting intrinsic value to digital values by creating added value, coupled with BCT’s ability to provide reward mechanisms in the form of virtual currencies that hold validity long after the project’s completion. BIM authoring tools can expand their potentials by adding budget control objects to assist in tracking costs and savings. #AECoin is a recently developed cryptocurrency specifically created for design and engineering transactions. This currency could help address the difficulties in assigning responsibilities and liabilities due to an overlap of roles and responsibilities, ensuring intellectual property protection, risk allocation, and privacy in the current BIM workflow [22
]. Connecting the budget control objects with #AECoin will add many benefits to the BIM process. For instance, #AECoin and the proposed budget control objects can be used to measure the added intrinsic and intangible value of a physical artifact and accurately calculate the rewards earned by the participant by assessing the individual/collaborative project contribution over the product’s lifecycle. This concept of monetizing designs throughout the lifecycle would ensure a superior outcome and more effectively motivate engineers and architects to deliver their best efforts by providing proportionate incentives.
6.2.1. BIM workflow and Security
Most industries currently rely on the “security through obscurity” approach to secure engineering, which emphasizes the confidentiality of the implementation and mechanisms of the cybersecurity system. Thus, a small leak of information could potentially endanger the entire network [55
]. BIM offers a diverse multifunctional workspace that addresses asset management, performance monitoring, and changes management through the lifecycle, apart from overlooking the planning, design, and construction phases of the structure. To facilitate continuous collaboration among all parties, BIM makes use of Common Data Environment (CDE), which provides a single repository for project information. This repository is used to collect, manage, and distribute data for multi-disciplinary teams [24
]. It requires the auditing, monitoring, and tracking of data through the CDE, which will develop throughout the project’s lifecycle. Hence, it is vital to provide suitable governance and curation to address information management and uphold data security, quality, and integrity. Since BIM involves complex interactions involving collaborative actions and information exchange between actors, technology and processes, and inter-relationships, it is crucial to consider cyber-security implications, assess current levels of reliability, address current drawbacks, and reinforce security. In current usage, all BIM data are electronically shared across a common data environment. It is essential for all project members to understand and abide by cybersecurity rules [37
]. There are fewer trust issues among BIM actors compared to those in traditional information sharing. However, BIM’s complicated collaborative framework creates security issues of data leakage, information theft, and information protection while dealing.
Both permissioned and permission-less BCTs have their respective advantages and drawbacks, and the BCT for use must be chosen appropriately based on the desired functionality and level of privacy needed. Concerning BIM workflow, there are generally several different parties working simultaneously on one model. In such cases, implementing a permission-less blockchain could produce positive effects, such as improved communication, transparency of work, and opportunities for collaborative design processes. However, the current socio-economic environment of the AEC industry may necessitate tighter management of permissions due to concerns like data theft, conflicting interests, misuse of information, and others concerns arising from the number of third-parties involved in a typical construction project, which usually entails high levels of copyright, budget, and accountability to government bodies and regulatory entities. Hence, employing a permissioned blockchain is a far more realistic option for most BIM projects.
Cybersecurity can be defined as “the collection of tools, policies, security concepts, security safeguards, guidelines, risk management approaches, actions, training, best practices, assurance and technologies that can be used to protect the cyber environment and organization and user’s assets” [24
]. The cyber environment includes the Internet, telecommunication networks, embedded processors, controllers, sensors, data storage and control devices, as well as the information, services, and collaborative and business functions that only exist in cyberspace.
Cybersecurity threats that can potentially affect BIM workflow. Its connected systems can be classified into three categories:
External threat agents: unconnected malicious outsiders, criminal entities attempting to access data for reconnaissance, hackers, intellectual property theft, the leak of sensitive or confidential information, and malware that can attack the BIM database;
Internal threat agents: involved participants who may bear malicious intent, the abuse of authorized access to steal, leak, or corrupt information to disrupt BIM operations, as well as human errors like omissions, ignorance, or negligence of work;
Systems and business failures: natural causes by extreme weather, interference from animals, storage device failures, poor maintenance of the centralized IT infrastructure, bankruptcies, and business failures.
6.2.2. Advantages of using BCT for Improving Cybersecurity
The elimination of the requirement of a designated intermediary party to oversee data transactions in the network offers several improvements over existent systems in terms of cybersecurity levels. Blockchain networks ensure that no single node in the network has complete access to all the information. Multi-signature (multisig) protection can add another layer of security in authorizing transactions by accepting more than one key. Hackers can gain complete access in the network only if more than 50% of the nodes are compromised [55
Effective interoperability can be achieved by ensuring the identifiability and authentication of participants and establishing a ubiquitous and secure infrastructure that serves as a repository for data storage, as well as a reliable platform that facilitates data exchange, subject to required permissibility levels. Key features of a blockchain, such as utilizing secure cryptography, asset sharing, auditing trails of data access, and a resilient peer-to-peer network, present a novel and promising emergent method of addressing cybersecurity and collaborative issues. However, it should be noted that the implementation of BCT does not directly ensure infallibility. Further, blockchain can enable a secure and transparent method of Proof of Delivery (PoD) for the transport and delivery of physical assets [33
The immutable, instantaneous, and transparent nature of DLT emphasizes compliance and trust between all involved parties on the network. The current economy, which is inherently adversarial, incentivizes the minimal exchange of information between parties involved in the completion of a project with the intention of protecting one’s interests. The advent of BCT is increasingly disruptive to the existing paradigm and will shift work culture in a direction that rewards collaboration and proves advantageous in the design process by facilitating better-informed decision making, collaborative learning, and easier debugging of errors. This change can be accelerated by the ability of BCT to reward the intrinsic value of any data through an #AECoin cryptocurrency [21
]. Blockchain can facilitate the creation of a registry comprised of past achievements and the qualifications of individuals, with a view toward enabling a comparison of team constellations and thus aiding in the decision-making processes for clients and project managers to select a versatile and well-balanced team with diverse skill sets and experience. The BCT platforms can primarily serve as recordkeeping tools to record changes in the BIM model throughout the design and construction phases of the structure.
Moreover, smart contracts can be programmed to automate awarding or revoking privileges based on the satisfaction of certain terms, as well as store an immutable record of all modifications in the BIM model data, along with other associated information [27
]. The tamper-proof append-only nature of the records in a DLT also help to enforce compliance among workers. The transparency of the DLT coupled with the database properties of BIM [27
] can introduce an ‘evidence of trust’ [21
], which would create a new value proposition for the AEC industry.
This paper presents a comprehensive survey of BCT and its applications in the built environment and examines BCT’s potential integration with Building Information Modeling (BIM) workflow. This study examines how commissioning distributed ledger technology (DLT), such as the Hyperledger Fabric (HLF), could be advantageous in the BIM working processes by reinforcing network security, providing more reliable data storage and management of permissions, and ensuring change tracing and data ownership.
The building permitting process is more complicated during post-disaster redevelopment than pre-disaster development, due to the additional responsibilities imposed on the building officials to assess damages and uphold federal and state government requirements. The process is often characterized by a longer duration, which adversely affects the rebuilding efforts. The proposed BCT+BIM framework has the potential to enchance the permitting process and positively impact post-disaster recovery efforts.
The present example indicates that the application of BCT in a BIM workflow creates a system that is built on the principles of decentralization, open governance (or self-governance), and transparency, a system that rewards innovation and eradicates disintermediation. Moreover, such systems provide the secure execution of BIM data exchanges and validation through privacy and trust mechanisms, in a secure process that facilities speedy, robust transactions. The cryptographically enforced interconnectivity in the blockchain applications fosters the stability and security of distributed ledgers.
HLF is a BCT that is particularly suited for developing the automation of code-checking compliances (ACCC) in BIM workflows, due to its ease of programming (using SDK), flexibility, user-defined smart contract (chaincode), robust security, identity features, and modular architecture with pluggable consensus protocols. The example presented depicts that the smart contract technologies (also known as chaincodes) available in HLFs are promising technologies for advancing the security and efficiency in the AEC industry, particularly for post-disaster recovery. The removal of an overseeing third-party in the proposed BCT+BIM as an essential actor in any transaction related to post-disaster rebuilding could lead to significant savings by negating processing fees, paperwork, and the time needed to issue building permits. Moreover, the proposed integrative BCT+BIM framework aims to provide transparency and secure network services without interruption during the process of rebuilding after a disaster. In this framework, the HLF can address many of the current concerns, such as data security, privacy, the speed of transactions, and change tracing and permission management that arise from using centralized BIM work processes. Future research will focus on expanding the integrative framework to include other issues related to post-disaster recovery efforts, such as infrastructures and services.