Modular Integrated Construction Research Articles

Stability design of cold-formed high and ultra-high strength steel thin-walled box sections using effective stress-strain model

This paper proposes an effective stress-strain model for integrated analysis and design of cold-formed steel structures with thin-walled sections. The study focuses on square and rectangular hollow sections made from high and ultra-high strength steel. Initially, a shell-finite element model (SFEM) was developed and validated using experimental data, specifically for cold-formed members subjected to axial compression. Subsequently, a comprehensive parametric study is conducted to establish the stress-strain relationship model through nonlinear finite element analysis. The proposed model incorporates material nonlinearity, cold-forming effect, local plate imperfection, and residual stresses into a unified stress-strain curve, leading to advanced structural analysis and design of cold-formed structures using simple one-dimensional beam-column element. Subsequently, the proposed method is then implemented in the conventional finite beam-column element analysis, demonstrating consistent agreement with both experimental tests and sophisticated finite shell element results. Finally, the robustness and validation of the proposed method are established, and its application is exemplified through the design of a modular integrated construction (MiC) structure. This study highlights the versatility and reliability of the proposed approach for the analysis and design of cold-formed steel structures.

Deep learning-based automated productivity monitoring for on-site module installation in off-site construction

Effectively monitoring and analyzing on-site module installation for modular integrated construction (MiC) is essential to properly coordinating the MiC process. In this study, the authors propose an automated productivity monitoring framework for on-site module installation operations consisting of three modules: object detection, activity classification, and productivity analysis. The object detection module detects mobile cranes and modules interacting with mobile cranes, and the activity classification module classifies module installation activities into five different activities by considering the spatiotemporal relationship between the detected objects. Finally, the productivity analysis module analyzes the productivity of the module installation process by utilizing the accumulated activity classification results over image frames. The proposed model achieves an average accuracy of 89% (hooking: 85.71%, lifting: 84.44%, positioning: 94.90%, returning: 83.09%, and idling: 96.87%) in classifying the five activities. The developed framework enables practitioners to measure the productivity of the on-site module installation process automatically. In addition, productivity data stored from diverse construction sites contribute to identifying progress-impeding factors and improving the productivity of the entire MiC process.

Experimental study of the static and hysteretic performance of grouted steel beam-column inter-connections for modular integrated construction

Modular Integrated Construction (MiC) has gained prominence as a construction method, and the integrity of its structural connections plays a critical role in ensuring the overall stability and safety of buildings. This paper presents an experimental investigation into the static and hysteretic performance of grouted steel beam-column inter-connections designed for MiC. The study examines eight full-scale specimens subjected to both monotonic and cyclic loading conditions, with a focus on failure characteristics, deformation behavior, loading-displacement curves, loading-strain curves, skeleton curves of hysteretic loops, stiffness degradation, and energy dissipation. Key findings of the study include the observation of weld cracking between beam flanges and columns in all specimens, highlighting the necessity of welding quality control to prevent such issues. Grouted connections exhibited superior integrity, with no gap opening or misalignment between upper and lower columns. Additionally, it was found that grouting could enhance the stiffness of certain connections. Removal of diagonal stiffeners significantly decreased peak bearing capacity, emphasizing their importance. The composite action brought about by bolts connecting ceiling and floor beams also proved influential. According to Eurocode 3, all grouted specimens fall under the classification of semi-rigid connections, with a distinction made for partial and full-strength connections. This research contributes valuable insights into the static behavior and hysteretic performance of grouted steel beam-column inter-connections for MiC, providing essential knowledge for the structural design and safety of buildings utilizing this innovative construction method.

Experimental study on seismic performance of internal cruciform joints of grouting sleeve connection for modular integrated construction

Modular integrated construction (MiC) adopts room units that integrate maintenance structure, decoration and equipment pipelines in the factory-made modules, resulting in a lack of operating space for connecting modules at the construction site. In the previous research, the joints between modules are usually hinged or semi-rigid connections and partial strength joints. In this paper, a new type of joint with the grouting sleeve connection is proposed to connect modules horizontally and vertically, which is more convenient for construction and does not conflict with interior decoration. Six full-scale cruciform joints were tested to study the effect of axial compression ratio and different structural details. The test results presented the failure mode, stiffness, ductility, and energy dissipation of the specimens. The ultimate inter-story drift ratio is between 4.78 % rad and 5.96 % rad, which is larger than the requirement of 4 % rad in the special moment frame (SMF) system. The horizontal connection plate between modules can cooperate the deformation of left and right beams and columns, and significantly improve the lateral resistance of the joint. The vertical connection between modules did not slip or open and the grouting material is not broken. The inner and outer reinforced plates in the beam-to-column connection can transfer the tensile force of the beam flange well so the outer sleeve does not tear, and the wedge-shaped stiffener can inhibit the cracking of the beam-to-column connection. EC3 Part 1–8 was adopted to evaluate the stiffness characteristic of the proposed connection, indicating that the proposed joint can be classified as rigid joint for the non-sway frame. Finally, the theoretical ultimate resistance of the joint under the ideal failure mode is obtained, which is lower than the test results, indicating that the plastic development of the joint is sufficient and can be classified as full-strength joint.

Sound Insulation Study of Modular Integrated Construction

Recently, Modular Integrated Construction (MiC) has been considered as one new trend of construction method for some applications in Hong Kong due to its ease/speed of installations, build efficiency and environmental benefits. The acoustic performances of typical MiC units in Hong Kong have been investigated. The acoustic findings are analyzed and adopted to compare standards in some other cities over the world and other common constriction in order to derive possible new types of constructions in Hong Kong to improve the building neighboring noise complaints by residents.

Study on the Mechanical Properties of MiC Formworks with Different Material Components

Modular integrated construction (MiC) is a new type of assembled building structure system that consists of prefabricated concrete modules connected using post-cast concrete. To reduce material consumption and realize casting without supporting molds, thin and lightweight concrete formworks (MiC formworks) with a thickness of 30 mm are installed as part of the shear wall. Due to the thinness, concrete pouring tends to cause MiC formwork cracking, mold rising, and other problems. Its stress performance and damage mechanism are not clear. For this reason, three groups of MiC formworks with different material composition types are designed. The static load test is carried out in a graded partition loading mode, and parametric analysis is combined with numerical simulation to systematically study the influence of different material components on the mechanical properties of MiC formworks. The results show that the front cracks of the MiC formworks are mainly distributed under the truss tendons, and the back cracks are mainly distributed in the span position of the adjacent truss tendons. These cracks both occur along the span direction of the MiC formworks. Increasing the concrete strength has a significant effect on improving the load-bearing capacity of MiC formworks, while incorporating steel fibers can significantly improve its deformation and crack resistance. Parametric analysis showed that the steel fiber admixture exhibited limited improvements in the cracking resistance of the panels as the concrete matrix grade increased. The research results provide a practical basis for optimizing the production process of MiC formworks.

Environmental comparative case studies on modular integrated construction and cast-in-situ construction methods

This study contributes to the worldwide efforts of adopting innovative low carbon construction methods to reduce net zero embodied carbon of buildings and to minimize local environmental impacts during the construction period. It uses agent-based models (ABM) to simulate multi-threaded and multi-objective construction activities through collecting detailed project data of two case studies (one using the modular integrated construction (MiC) method and the other one using the cast-in-situ method) in Hong Kong. Considering that the construction process is dynamic and site issues are complex in nature, three major environmental impacts of carbon emissions, air pollution and noise are modelled at fine spatial and temporal resolutions. The findings show that the MiC project has significant environmental advantages over the cast-in-situ project in terms of reducing CO2 emissions, harmful emissions (including sulphur dioxide, nitrogen oxides, and organic volatile compounds), PM2.5 and PM10 emissions, and noise pollution levels, consequently reducing health risk associated with people in surrounding communities near construction sites. In terms of per square meter of construction floor area (per m2 CFA), the MiC project produced 17.60% less CO2, 42.54% less harmful gases, 32.15% less PM2.5 and 27.41% less PM10. The duration of noise exceeding 70 dB (minutes) in the neighbourhood of the MiC project was 81.25% shorter than the cast-in-situ project. The total health damage (in DALYs per m2 CFA) of the former was 63.18% lower than the latter. The research concludes that the adoption of low carbon construction methods like MiC can help to foster sustainable buildings and healthy communities in an urban context.

Balancing economical and environmental trade-off in modular construction yard planning: Models and properties

This study investigates an integrated yard planning and module transportation problem in modular integrated construction (MiC). A Stackelberg game model is proposed to characterize the relations between the government and contractors. The government is the leader and decides the locations and areas of temporary storage yards to facilitate the cost-effective and eco-friendly transportation of MiC modules. The contractors are the followers and decide the transport mode (i.e., road transport or intermodal transport) for modules to minimize their total transportation costs. This study provides an in-depth analysis of model properties to derive a number of useful managerial insights. The economical and environmental trade-offs between costs and emissions are observed. Our study further proves that an optimal solution is likely to simultaneously reduce the overall costs and carbon emissions, in comparison to choosing the location with the largest area to construct a temporary storage yard. These insights offer a comprehensive framework for understanding the interactions between government and contractors. Overall, this paper aims to promote the implementation of MiC by achieving the economical and sustainable transportation of MiC modules.

Pushing the boundaries of modular-integrated construction: A symmetric skeleton grammar-based multi-objective optimization of passive design for energy savings and daylight autonomy

Pushing the boundaries of modular-integrated construction: A symmetric skeleton grammar-based multi-objective optimization of passive design for energy savings and daylight autonomy

Modeling stakeholder-associated productivity performance risks in modular integrated construction projects of Hong Kong: A social network analysis

Modular integrated construction (MiC) has received remarkable attention for enhancing the productivity performance of delivering housing projects in densely populated cities such as Hong Kong. MiC projects suffer from unique risk factors compared with traditional construction methods. Previous studies have mainly focused on the direct linear impacts of risk factors and how they may affect project success. However, the MiC supply chain involves many stakeholders with high interdependency. How the risks are interconnected and interact with different stakeholders is a crucial issue to be analyzed and addressed. This paper deploys a social network analysis (SNA) method to identify and decipher stakeholder-associated productivity performance risks (PPRs) and their interrelations in an MiC project in Hong Kong. Fifteen critical PPRs and twelve essential interactions were demonstrated by simulating the complex network of the target project. Research findings show that inadequate project planning and scheduling has the greatest influence on collaborative decision-making support; Delayed assembly schedule and delayed delivery of modules also exert considerable influence on project planning and scheduling; The main contractor plays a leading role as a coordinator in the whole MiC process. The research further identifies several primary challenges, including the inefficient data capture approach, insufficient supply chain planning and progress monitoring, poor communication and information interchange among project stakeholders, and lack of collaborative decision-making support. This is the first study that dynamically examines and demystifies stakeholder-associated PPRs embedded in MiC projects in Hong Kong on a network basis, which could assist researchers and construction professionals in perceiving, investigating, addressing, and mitigating these risks in an effective and efficient approach.

Comparison of the lateral force-resisting mechanisms of steel MiC structures with full-strength and partial-strength inter-module joints: Experimental and numerical analysis

The modular integrated construction (MiC) approach can significantly transform the construction industry owing to its efficiency, quality, and sustainability. It is believed that steel MiC structures with full-strength inter-module joints can provide better structural behavior than those with partial-strength inter-module joints at the expense of construction efficiency. Therefore, the effects of different joint properties on the critical behavior of steel MiC structures must be investigated, particularly the lateral force-resisting mechanisms, such that guidelines for selecting connecting techniques can be established. To this end, two steel MiC frame specimens with upper and lower steel modules connected via welding and bolting, which can be regarded as two frames with full-strength and partial-strength joints, are experimentally tested. Furthermore, extensive numerical analyses are conducted to investigate the lateral behavior. It is found that compared with the welded specimen, the bolted specimen indicates a significantly lower initial stiffness owing to the shear behavior of the bolted joints. The lateral resistance of the welded specimen can be accurately evaluated by a global failure mechanism comprising plastic hinges formed at the ends of beams and columns. By contrast, the failure mechanism of the bolted specimen depends on the strength of the joints.

Study on Global Imperfection of Modular integrated Construction Structures for Second‐order Analysis

AbstractThe global imperfection significantly influences the stability design of the Modular integrated Construction (MiC) buildings. Currently, the initial global imperfection shapes recommended for MiC structures are formulated based on steel frames whose members are continuously connected. In practice, the columns and beams in MiC structures are composed of the members of adjacent module units, which are discontinuously connected through the special joints. Ignorance of such discontinuous features in MiC structures leads to an inappropriate estimation of the structural resistance. This paper introduces a new initial imperfection shape for MiC structures considering out‐of‐verticality of module columns and eccentricity between modules, capturing the discontinuous feature. Random initial imperfection shapes were generated using Monte‐Carlo simulation based on tolerances in regulations. The proposed imperfection shape is adopted in the analysis of a typical MiC structure and the result is compared with results from existing global imperfections in design codes. This research provides a practical global imperfection for the second‐order analysis and design of steel MiC structures. Recommendation for basic value of the proposed imperfection shape is also provided.

Transportation scheduling for modules used in modular integrated construction

ABSTRACT Modular integrated construction (MiC) is an innovative construction method that is widely used in practice, but high transportation cost is an obstacle to its wider implementation. This paper is motivated by the real-world need for a scientific approach for MiC transport scheduling, and addresses the practical problem of how to achieve on-time door-to-door MiC delivery in an economical manner. An innovative integer programming model is formulated with the objective of minimising the total transportation costs, including trailer rental, fuel costs, and worker salaries. A case study based on Hong Kong data validates that the developed model can be efficiently solved for problems of practical size. The results also demonstrate that the derived MiC schedule plan can reduce transportation costs by 58.7% compared with a just-in-time (JIT) strategy, thus bringing great economic benefits to off-site construction practitioners. Useful managerial implications related to on-site MiC storage areas are derived through sensitivity analysis. Overall, this paper sets the ground for the application of mathematical programming methodology to the off-site construction field. Future research may be devoted to MiC transport scheduling under uncertainty.

A hybrid simulation model for modules installation in modular integrated construction projects

Proper management of the installation process in Modular Integrated Construction (MiC) is essential to achieve the time-saving benefit of MiC. The analysis of the installation process should cover its operational and contextual sides to realistically mimic the problem. In this connection, the parameters governing the operational and contextual realms of the MiC installation process were identified and investigated through literature; afterwards, a hybrid model was developed to estimate installation rate, duration, and cost of MiC projects. In this model, discrete event simulation was used to consider the operational aspects of the process, e.g. tasks, durations, and logical sequence, while system dynamics was utilized to capture its contextual factors, e.g. absenteeism, rework, resource utilization, fatigue, and weather conditions. BIM was used to feed the model by modules’ coordinates and visualize the process. Monte Carlo simulation was adopted to tackle uncertainty and sensitivity analysis was performed to measure outputs variation. The study achieved its aim and objects and the model proved high sensitivity against resource variation and weather conditions, where it was concluded that doubling the resources would reduce the project duration by more than 50% and the weather conditions had an impact of 8.5% increase in project duration. Finally, the model was validated using a case study from the literature.

Exploring the adoption of blockchain in modular integrated construction projects: A game theory-based analysis

Efficient information sharing across Modular integrated Construction (MiC) stakeholders (e.g., client, contractor, manufacturer, etc.) is critical for MiC project success. Blockchain, a creative information and communication technology, provides MiC participants with powerful solutions to address the “island of information” and foster mutual trust among inter-organizational collaborations. However, there is a lack of empirical evidence from the construction industry about blockchain deployment, showing that the industry is cautious about, and generally unprepared for, implementing this disruptive technology. Existing studies mainly focused on proposing technological solutions for blockchain-based applications, with little attempt made to demonstrate how MiC stakeholders make decisions about blockchain adoption. Aiming to bridge this gap, this study adopted game theory to examine stakeholders' decision-making processes. The results revealed the best responses of key MiC stakeholders regarding whether or not to implement blockchain under various conditions. Their decisions were largely influenced by diffusion rate value thresholds, which were mainly affected by three factors: the benefits of blockchain adoption; government subsidies; and relevant costs. In addition, two valuable implications (i.e., enhancing stakeholders’ perceived values on blockchain adoption through pilot projects and publishing subsidy or incentive policies) were determined for promoting the adoption of blockchain in MiC projects.

Classification system for inter- and intra-module joints in non-sway steel MiC structures

The lack of guidelines for determining the rigidity of inter- and intra-module joints in corner-supported steel modular integrated construction (MiC) buildings can lead to unsafe or over-conservative designs. To address this issue, this study proposes a classification system for non-sway steel MiC buildings that covers both inter- and intra-module joints. First, the semi-rigidity of the joint regions in steel MiC buildings was clarified and the necessary degrees of freedom for joint classification were determined. Then a minimum substructure including one joint region was extracted from a steel MiC building, and its carrying capacity was determined as a simplified analytical model that considering the stiffnesses of both the inter- and intra-module joints. The simplified model was adopted to derive explicit formulas for the boundary limits of rigid/non-rigid inter- and intra-module joints, based on the criterion that the carrying capacity of the substructure with finite joint stiffnesses is 95% of that with rigid properties. Finally, the feasibility of the proposed classification system was verified by applying it to prototype MiC structures.

Towards a Conceptual Framework of Using Technology to Support Smart Construction: The Case of Modular Integrated Construction (MiC)

Construction is a major source of carbon emissions. Moreover, it faces various other sustainability challenges, such as construction waste, construction noise, vehicular traffic near construction sites, dust and other air and water pollutants, and safety and well-being of construction workers. Poorly designed and constructed buildings will continue to affect the well-being of their occupants and overall energy efficiency throughout the building lifecycle. Hence, accelerating the transformation of the construction industry towards smart construction or Construction 4.0 is an important topic. The ways that technology can help to achieve smart construction, especially with the adoption of construction methods with increasing construction modularity, should be further explored. Focusing on modular integrated construction (MiC), this paper examines the following questions: (1) How has technology been applied to support MiC development and smart construction in Hong Kong? (2) What are the lessons learned? A case study approach of a building information model (BIM)-enabled multifunctional blockchain-based digital platform is adopted to allow us to systematically consider (1) the main objectives and scope, (2) the stakeholders involved, (3) the key outcomes and processes, (4) the applications of blockchain technology, and (5) the integration with other digital software and management platforms in practice. Drawing upon the experience, we propose a generic four-stage approach in understanding and facilitating the adoption of relevant technology towards smart construction. At Stage One, the technologies of BIM, RFID, and blockchain are applied to support the core elements of MiC production: just-in-time transportation and on-site installation. At Stage Two, the digital platform is extended to serve as an interface for third parties, notably government; monitoring, authentication, and certifications for information sharing; visualization; and real-time monitoring and updating of MiC projects. At Stage Three, the system focuses on people in the construction process, aiming to enhance the safety and well-being of workers and drivers throughout the construction process. Different Internet-of-Thing devices and sensors, construction robotics, closed-circuit television, dashboards, and cloud-based monitoring are deployed. At Stage Four, the full construction lifecycle is the focus, whereby a centralized smart command theatre is set up with multiple sources of data in a city information model.

Blockchain-enabled digital twin collaboration platform for fit-out operations in modular integrated construction

Facilitated by the improved prefabrication rate and polymerization degree using Modular Integrated Construction (MiC), fit-out operations are converged with the off-site production and on-site assembly of prefabricated modules. Information technologies are used for MiC fit-out management and heterogeneous digital twins are generated. However, flexible collaboration of digital twins is hard to achieve and synchronized information sharing among transdisciplinary stakeholders is also hindered by “Islands of Information”. Therefore, this paper develops a blockchain-enabled digital twin collaboration platform for MiC fit-out operations. Firstly, Integrated Domain-Driven Design (IDDD) model is proposed for information integration and interoperation in cross-domain construction projects. Secondly, based on IDDD, digital twins in various domains are integrated for seamless and transparent collaboration in MiC fit-out. Thirdly, Petri net-based workflow model is applied for collaboration of multi-domain digital twins under versioning smart contract, where net structure and behavior attributes facilitate the automatic control during off-site and on-site MiC fit-out processes.

Long-term performance of hybrid MiC buildings considering concrete creep and shrinkage

With the completion of several pilot projects in Hong Kong, Modular Integrated Construction (MiC) is being promoted to boost the productivity and cope with the labour shortage in the local construction industry. However, the possible adverse effects of differential axial shortening due to the time-dependent behaviour arising from concrete creep and shrinkage will only become obvious after a long time. In this study, simplified numerical models are established based on typical hybrid MiC buildings in Hong Kong. Time-dependent analyses considering the creep and shrinkage of concrete are carried out. The construction schedules of the pilot MiC projects are used as a reference to model the staged construction. The results for a 20-storey hybrid MiC building indicate, owing to the concrete creep and shrinkage, noticeable stresses at the module-to-wall connections at the corners of core walls 30 years after construction. The compressive stresses at the bottom of the steel MiC modules will increase substantially over time, which could reduce the amount of material strength that can be utilised by other loads. Hence checking of long-term performance should be conducted at the design stage, particularly focusing on the connections.

Data-driven Game-theoretic Model Based on Blockchain for Managing Resource Allocation and Vehicle Routing in Modular Integrated Construction

ABSTRACT In modular integrated construction (MiC), the resource allocation problem (RAP) adopted by construction sites and vehicle routing problem (VRP) adopted by logistics companies are highly interdependent. However, this interdependence has been overlooked in the literature. Thus, the plans determined by each problem cannot be achieved practically. Moreover, there is no existing VRP model suitable for the MiC application. This study aims to propose a VRP model suitable for MiC, investigate the interdependence between the RAP and proposed VRP model, and develop a blockchain system to secure information sharing between the RAP and VRP. The first two objectives are achieved by developing a coordinated system formulated as a leader-follower Stackelberg game model (LFSGM). This model is presented as a bi-level optimisation model and solved using a nested ant colony optimisation-based algorithm. The effectiveness of the LFSGM is validated using a real case study. The results show that using the traditional approach (i.e. a separate RAP and proposed VRP) succeeds in providing a plan for the construction sites but not for the logistics company. In contrast, the LFSGM offers applicable plans for both the construction sites and logistics company. Lastly, some managerial implications are identified and discussed.