Off-site Construction Research Articles

The merits of varying forms of mass timber products for offsite and modular construction

Mass timber is a family of Solid Laminate Timber Systems (SLTS) formed from smaller sections of timber connected by glue, mechanical fixings, moisture movement or a combination of methods. These products, which include Structural Composite Lumber, GluLam, Cross Lam, Nail Lam and Dowel Lam (or Brettstapel), have over the past two decades seen an extraordinary upsurge in use internationally. This global phenomenon has been driven by a greater emphasis on the sustainable use of renewable resources and by significant technological developments in the manufacture of SLTS. This research paper considers the merits of each of these products, their manufacturing processes and the corresponding quality assurance requirements necessary for successful project delivery. The paper describes the advantages and barriers to the use of the mass timber and provides an overview of the various aspects to be considered during design for offsite and modular construction. The work presented also provides case studies of how these products have been researched and utilised into live projects in the UK utilising local resource resulting in the formation of new supply chain arrangements. The work further explains the advantages of the respective systems for the given application including information on species selection, connection systems employed and the necessary onsite and offsite management approaches deployed.

Investigating the effects of reduced technological constraints on cycle time through simulation modelling for automated steel wall framing

Off-site construction constitutes a paradigm shift in construction promoting improved sustainability. At present, North Americaäó»s building construction sector is still dominated by conventional stick-built construction, which is prone to excessive material waste, longer cycle times, high labour costs, and lower quality. In contrast, inspired by the manufacturing industry, off-site construction is an approach in which building components are prefabricated in factories and transported to the construction site for on-site assembly. As the concept of off-site prefabrication gains momentum within the domain of construction, some home builders are bringing the traditional industry practice into a factory setting, thus resulting in stick-building- under-a-roof. This paper describes the development of simulation models for the automated light gauge steel framing process using discrete-event simulation mimicking real-time machine production capacity and cycle time. At present, the literature on the development of such models for automated construction machinery is lacking; in this context, this paper aims to showcase the advantages of simulation as a decision-making support tool. Construction of such models provides a useful tool for understanding bottlenecks in machine operations that can be addressed to meet local demands. Since the steel framing process primarily consists of manual assembly and fastening of cold-formed steel (CFS) frames, these models showcase the potential to increase the level of automation through the addition of various mechanical and control modifications to an existing prototype steel framing machine. The results show that cycle time reductions of 13 percent or greater are possible by applying the proposed modifications.

Predictive Model for Siding Practice in Panelized Construction

Offsite construction offers an opportunity to standardize processes and better predict schedule requirements when compared with onsite construction. This predictability allows for balanced labor distribution and accurate time estimation. This research investigates the exterior wall siding practice at a panelized home manufacturing facility in order to predict future productivity of this operation based on a time study and known panel design characteristics such as wall length, wall height, and number and size of openings in the wall. The siding workstation is currently a bottleneck in the wall production line. In this area vinyl siding, window and door trim, and other exterior finishes are added to the panels. The case study plant uses a radio frequency identification (RFID) system to track panel locations and the amount of time spent at each station. This system tracks the time the panels spend in the siding area, but not the amount of time that is necessary to complete the work required. This discrepancy results in difficulties identifying the idle time and the working time within the total duration. By applying data science procedures of classification and association applied to lean manufacturing concepts, such as value-added activities and waste minimization, the research in this paper establishes a model to predict the labor requirement for each panel at early design stages. Using the developed model, the case study factory is able to quantify the idle versus working time that panels are subject to at the exterior wall siding workstation, as well as the ratio of value-added activities to non-value- added activities.

Mass Customisable Roofing Solutions for the New Build and Retrofit Markets in the UK

Major house builders and contractors in the UK are seeking alternative solutions to form the structural frame of pitched roofs for various reasons; speed, health and safety, quality ease of use. They are exploring the use of offsite systems, which arguably provide all of the above benefits. However, these systems are typically considerably more expensive, often difficult to scale-up and limited in their design scope compared to traditional roof truss solutions. The strategic aim of the research reported on in this paper was therefore to develop a mass customisable roofing solution to allow the UKäó»s largest roof truss manufacturer to enter into the off-site construction sector without reinventing their business architecture. The research considered both the new build and retrofit market. The first roof solution for the new build market is a äóÖsliding roofäó», a roof truss installation method which includes a pre-prepared system created under factory conditions. The system is delivered to the construction site where it is lifted onto one end of the structure. After the system is in placed it is opened the length of the roof. The second system investigated, to be used for the retrofit market, is a self-supporting and thermally insulated roof panel, designed and developed for a multitude of pitched roofs. Working with the industry partner the suitability of the roof systems as effective off-site solutions has been trialled. The full process was monitored from a design, manufacture and construction perspective with a critical appraisal undertaken for evaluation purposes. These finding are reported.

A BIM-based Supply Chain Integration for Prefabrication and Modularization

Prefabrication and modularization helps to reduce cost and schedule time for on-site activities. The use of Building Information Modeling (BIM) helps to improve collaboration and improve the construction process. The improved installation precision provided by BIM Model-Driven Prefabrication can decrease on-site labor time and increase productivity. Prefabrication, Modularization, and off-site construction transfers activities that would have been performed on site to earlier stages of the supply chain. The implementation of Just-In-Time (JIT) delivery transfers the costs and risks associated with inventory to the supplier. Construction Supply Chain Integration can help reduce cost and waste across the supply chain particularly for large and complex buildings. This paper presents a methodology that utilizes a BIM based construction supply chain integration to reduce cost and waste in the construction and offsite manufacturing processes. It utilizes the integration of BIM with the on-site schedule and the manufacturing or fabrication schedule of the different supply chain members. The methodology utilizes the onsite schedule, lead times of prefabricated elements or modules and the transportation logistics to help reduce cost across the supply chain. The information, material and cash flows as well as the transportation logistics is utilized in generating an optimized just-in-time delivery schedule for large and complex buildings. The optimized delivery schedule takes into account the variations in the on-site and off-site schedules to forecast delivery dates of precast elements or fabricated modules.

Front Matter, 2018 MOC Summit proceedings

Proceedings of the 2018 Modular and Offsite Construction (MOC) Summit held in Hollywood, Florida, USA, March 22 - 25, 2018.

Effect of stakeholder collaborative management on off-site construction cost performance

Off-site construction (OSC) has been a hot issue in the construction industry. However, high cost was an important factor that hinders the OSC development. This study attempts to explore how stakeholder collaborative management and OSC cost performance relate to each other. Semi-structured interviews were conducted to explore and verify the quantitative indicators that measure stakeholder collaborative management and cost performance. Interaction frequency, emotional intensity, familiarity, and reciprocity were selected as the metrics to measure stakeholder collaborative management. Unilateral cost and production cost of precast components were used to depict OSC cost performance. Meanwhile, social network analysis (SNA) was adopted to obtain density, network centralization and centrality to estimate the network relationship. This study attained the adjacency matrix by a survey, and then developed an OSC collaborative project management primary framework (OSCCPMPF) through SNA to explore the evolution process of collaboration among stakeholders. Hypotheses were developed. Then, multiple case studies were conducted. This study found that stakeholder collaborative management positively affects cost performance. Meanwhile, cost performance was the most important driver for stakeholder collaborative management. Network relationship had a positive impact on cost performance. Additionally, differential strategies can be adopted to promote the OSC development. The findings are useful for setting up a benchmark framework for cost management and project management mode in OSC.

Developing Timber Volume Calculators Through a Comparative Case Study Analysis of Wood Utilization in On-Site and Off-Site Construction Methods

The research and development of Timber Volume Calculators (TVCs) was conducted to determine the amount of wood used in off-site light-frame construction compared to traditional on-site stick-built construction. A four-story mixed rate housing project in the fastest growing region in the US was used to: 1) quantify the total wood volume of the project as-built stick framed onsite, and 2) compare it to simulated factory built panelized and modular construction methods for the same housing configuration. Panelized construction used 6.7% more total wood and modular construction 69.4% more than the as-built scenario. A life cycle assessment found that panelized and modular construction store 4.5% and 32% more CO2 equivalent than on-site stick built construction. Next steps for evaluating economic costs of off-site constructed systems are presented.

Critical evaluation of off-site construction research: A Scientometric analysis

Abstract Practical interest in ‘off-site construction’ has risen remarkably over the last decade, and with it there has been a burgeoning of academic research in the field. Complementing this research, a number of literature reviews have been conducted. None, however, are systematic. This study addresses this lack, offering the first bibliometric study to explore the state of off-site construction research (OCR). A quantitative approach using ‘science mapping’ techniques is employed to examine 501 top-ranked construction journal articles. Longitudinal trends in publishing are identified, as are dominant research sub-fields, their connectedness with other areas of study, as well as citation patterns, publication journal areas of focus, key research institutions, key research persons, along with the extent to which these interact with each other in research networks. The findings are instructive in identifying the deficiencies in current research. Among these is a bias towards product research over operations and management, and a sharp compartmentalization of sub-fields, with little or no cross-fertilization between researcher areas, the researchers themselves, nor the research institutions. Clearly, this awareness will inform industry, journal editors and researchers of the need for a deeper exchange of ideas in any future research efforts.

Design automation of control panels for automated modular construction machines

Modern modular construction demands high quality, cost-effective, and efficient production of components. These requirements have led to the emergence of offsite construction manufacturing, which necessitates the use of automated machines. Compared to traditional onsite methods, offsite modular construction has a positive impact on quality, safety, cost, and productivity. Methodologies exist in the design of automated modular construction machines. This automation consists of not only the machines but also the supportive electrical and pneumatic systems, which, regardless of the design approaches used for automated machines, can be applied to the design of their associated systems. To avoid costly design changes, there is a clear need for a systematic and iterative design methodology at the conceptual design stage. For the control panel, the conceptual design method introduced in this paper facilitates the subsequent computer-aided design to be performed at the detailed design stage. Integrated function modeling, combined with axiomatic design and design structure matrix, constitutes the conceptual design approach for the control panel. In this work, linear time complex algorithm is developed for automating the layout of the electrical devices and wiring connections in order to facilitate computer-aided design implementation in the detailed design phase. Furthermore, the control panel guidelines and standards that constitute the prior knowledge of the design process are embedded in the algorithm.

Off-site Modular Construction as a Method of Improving Construction Quality and Safety

Off-site Modular Construction as a Method of Improving Construction Quality and Safety

Structural Equation Modeling to Analyze the Critical Driving Factors and Paths for Off-site Construction in China

Off-site Construction (OSC) is an alternative to conventional construction. However, China lags behind developed countries in terms of its OSC development. The chief goal of this study is to demonstrate the critical driving forces and solutions that promote OSC development. A total of 21 hypotheses are established to present the interrelations among eight driving forces. Based on 176 valid responses from developers in mainland China, a structural equation model is built to explore the key solutions and the critical driving forces. Most driving forces, such as Pursuit of Sustainable Competitiveness (PSC), Governmental Policies and Regulations (GPR), Technological Innovation (TI), Corporate Social Responsibility (CSR), and Construction Market Demand (CMD), can affect a Corporation’s Willingness and Behavior (CWB) in adopting OSC through two mediating factors, namely, Economic Benefits (EB) and social and environmental benefits. The findings highlight five main driving solutions to promote OSC, namely, “PSC → EB → CWB,” “PSC → TI → EB → CWB,” “GPR → TI → EB → CWB,” “GPR → CSR → CWB,” and “GPR → CMD → CWB.” Governments and project clients are also identified as important players in the development of OSC in China. These results provide a valuable reference for the government to understand the underlying interrelationships among the driving forces and key solutions to the development of OSC in China.

Using noisy RFID for accurately monitoring the assembly line of panel fabrication

Over the past few years, the interest towards off-site construction as part of project delivery for residential and commercial buildings has increased dramatically. In this regard, buildings are decomposed into panels that are manufactured using assembly lines smilar to what was developped to the automotive industry. However, because these serial production systems do not have buffers that could store intermediate products when a bottleneck occurs downstream, it often happens that these products are required to wait at the current workstation before production can resume. In this contribution, we develop algorithms allowing the waiting times to be extracted from timestamps that are collected from an RFID system reading the tags on panels as they enter each workstation.

Front matter, 2017 MOC Summit proceedings

Proceedings of the 2017 Modular and Offsite Construction (MOC) Summit held in Shanghai, China, November 10 - 12, 2017.

Energy optimization in modular buildings made from 3d printing

Off-site construction involves the process of designing, fabricating, transporting and installing building elements for rapid site assembly to a greater degree of finish than in other types of on-site construction methods. However, some pieces of the building depending on the geometry, materials and weight can be produced using 3D printing on-site. Energy consumption can be modified based on the available resources on construction site such as labours, factories, and materials. This study focuses on energy optimisation based on simulating site available resources when 3D printing technology is available. The paper compares three proposed different cases including balconies are entirely concrete, balcony Containers are replaced with soil and a shade factor was applied as well as case 2 with the added effect of evapotranspiration.

Integrated production planning and control system for a panelized home prefabrication facility using simulation and RFID

The construction industry is adopting off-site construction for its superior quality, short cycle time, and minimal environmental impact. Among the different off-site construction methods, panelized construction follows a manufacturing approach where houses are built in smaller panels in an assembly line. Due to the complex and unique nature of the home building process, existing manufacturing concepts such as automated production planning and control system are not applicable to the panelized home production facility. This paper utilizes radio frequency identification (RFID) technology, data mining, and simulation-based optimization to develop a production planning and control system for a panelized home production facility. The RFID system is used to automatically collect the production data; however, the RFID data in this study contains considerable noise. Thus, it is crucial to extract the relevant data from the raw data. A RANSAC model is developed for this purpose to automatically clean the RFID data and then use it to build the simulation model, which is then integrated with an optimization algorithm to generate the production schedule and real-time performance monitoring. The proposed framework cleans the noisy RFID data to extract records that represent a steady flow of assembly line. These clean records are then used to build PDFs that are required to develop discrete event simulation model that can help managers to capture an almost real-time snapshot of the production of the assembly line as well as automatically optimize the production schedule. The proposed system is implemented and validated in a panelized wall production facility operated by ACQBUILT Inc., a prefabricated home builder in Edmonton, Canada.

Heathrow’s £16bn expansion and offsite construction: Probing its industry-transforming claims

Heathrow Airport is now taxying toward its long-awaited multi-billion-pound expansion, of which a third runway is just a part. As a capital project it will be one of the UK’s biggest, in a league w...

Optimizing decisions in advanced manufacturing of prefabricated products: Theorizing supply chain configurations in off-site construction

Abstract Robust supply decision making is critical to the advanced manufacturing of prefabricated products. Previous related research focused on minimizing cost overruns in off-site construction supply networks by optimizing purchasing decisions. However, decision parameters such as strategic preferences to include or exclude certain suppliers and utilization of multi-supplier configurations are yet to be formulated and analytically solved. The proposed optimization models aim to enhance supply network performance with a smaller overall investment. Toward this aim, three research hypotheses on optimization of supply decisions and configurations are developed and tested. A real-world precast panel production project serves as the test bed to demonstrate the effectiveness of the mathematical programming and analyze cost implications of supply related decisions. The modeling method and results contribute to optimal decision making in advanced manufacturing of prefabricated products.

IMPROVING PRODUCTIVITY, WORKFLOW MANAGEMENT, AND RESOURCE UTILIZATION IN PRECAST CONSTRUCTION

Construction industry has long dealt with problems such as low productivity, unstable workflow in projects and low utilization rate of resources. Off-site construction, which is a hybrid of mass manufacturing and construction, has significant potential to address aforementioned problems. In order to realize this potential, off-site construction needs to avoid replicating the traditional subcontracting approach and therefore fragmented practice in the construction industry. The current research focuses on restructuring the interaction of resources by using cross-training. Findings show that cross-training resources results in transferring excess capacity from underutilized to over utilized resources in direct or indirect pathways. Such initiatives can significantly improve productivity, workflow management and resource utilization in precast construction that highly specialized resources are not required. The study contributes to the construction management literature by providing insight into dynamics of using multiskilled resources in off-site construction.

OPTIMIZING MULTI-WALL PANEL CONFIGURATION FOR PANELIZED CONSTRUCTION USING BIM

With the rise of Building Information Modeling (BIM), off-site construction is gaining momentum in the construction industry. This construction method can benefit the industry through improved productivity and reduced waste. However, it also poses new challenges to building designers and construction practitioners with respect to building design and construction planning. For example, when designing building products and BIM models, designers needs to consider manufacturing process constraints in order to harness the benefits of manufacturing technology. This is in part due to the fact that, in the offsite construction paradigm, building design must be transformed from product-focused to manufacturing process-driven. At present, considerable human involvement and off-site construction knowledge are required to adapt building design (e.g., panelize building objects) for manufacturing processes within BIM environments. In this regard, this research contributes a BIM-based algorithm for panelizing building components. The proposed algorithm is capable of determining the granularity of wall panels and optimizing the configuration of multi-wall panels under engineering constraints, thereby improving productivity. The proposed approach is implemented within an Autodesk Revit environment through application programming interface. A case study of a residential building is used to demonstrate the proposed approach.