Discussion of design for disassembly principles under the guidance of design for manufacture and assembly strategies in the construction industry

Abstract

Today, when the life of a building is complete, the general practice is to take the valuable parts and send the remaining ones to landfills. This practice; cannot be sustained in any respect since the wastes related to the construction industry have one of the highest percentages of the earth's waste amount. Besides, the construction industry is responsible for more than one-third of overall carbon emissions. At this point, Design for Disassembly (DfD) in buildings is a promising concept that targets the non-destructive separation of components and materials to recycle, reuse, or relocate at the end of initial use. Even though DfD has been studied in product design areas for a couple of decades and construction since the late 90s, with the urging need to create a more sustainable environment, it recently started to be discussed more as a solution to fight building obsolescence. However, However, the application of DfD is based on design guides and principles, and there is no systematic quantitative method for the construction industry. Another design methodology with similar concerns is Design for Manufacture and Assembly (DMfA), which is based on the principles of optimization of materials and coordination and aims to reduce part counts, assembly time, and overall costs ultimately. Early DfMA studies date back to the 70s in product design to respond to the competitiveness of the production industry. However, it received attention in the construction industry mainly in recent years. In reviewing the literature associated with DfD and DfMA, one finds that both methodologies have common approaches as reducing part counts, adopting modular and standard design principles, considering orientation and handling for the process, etc. In addition, it has been spotted that DfMA, which is a former and more settled methodology, has been examined more systematically than DfD. At this point, it is questioned if there is a possibility of enabling DfD principles and establishing a framework for a systematic methodology under the guidance of DfMA applications in the construction industry. The main goal of this thesis is to search for the above-stated possibility and whether one can find a set of practical solutions to identify the missing points of the DfD and approach for increasing the reuse possibilities of building elements and components and to provide data that can develop the necessary methodologies to extend its application. The remainder of this thesis has organized as follows. In the first chapter, the thesis's objective, scope, and method are presented, and the flowchart of the study is given. In brief, this thesis aims to examine the DfD methodology and determine its most comprehensive current principles, identify barriers to its implementation, and examine the DfMA methodology by identifying strategies via literature review and then discuss these strategies in line with DfD principles. The concept of DfD is defined in the second chapter, and its study area is explored. Its relationship with the building life cycle and possible end-of-life scenarios are explained. The aims, benefits, and advantages of DfD are expressed, and then the state of DfD in the product and the construction industry is investigated. In the end, limitations and challenges for DfD implementation are discussed. The chapter concludes by questioning the possibilities of DfMA as another DfX methodology as an exemplary field for DfD. In the third chapter, comprehensive research on the DfMA field explores the possibility of creating a more detailed and comprehensive framework for implementing DfD. In this context, the DfMA methodology has been explored in all its possibilities in the product and construction industries. First, the origin of this concept is searched in the manufacturing industry. Its qualitative and quantitative assessment methodologies were listed. Then, a systematic database search is conducted to fully understand how DfMA is used in the manufacturing and construction industries. From this literature search, studies related to the architecture, engineering, and construction (AEC) field were refined and examined in more detail to understand the scope of DfMA applications in this field and to evaluate whether they can serve as an example for DfD. AEC-related search results were analyzed with context-specific research questions. The systematic literature review in this chapter showed that DfMA applications are quite different in the manufacturing and construction industries. That can be attributed partly to the fact that construction outputs like buildings and bridges are more than mass-manufactured products. Because they are all custom-made and created in their unique environments, each must fulfill a particular composition of functional requirements. Besides, the main difference between these two industries is found in how DfMA is applied. More systematic tools are developed in manufacturing, and the study area boundaries are much more distinct than in construction. The efforts to implement DfMA in the AEC sector were found to be worthwhile and gave researchers and practitioners a starting point even though a thorough strategy has yet to be created. However, the DfMA characteristics and approaches used in this research can offer a common framework for the DfD roadmap. DfMA characteristics and approaches used in this research were found promising to guide DfD implementation. In the fourth chapter, a series of discussions were held on the results of the DfMA study in the scope of enabling DfD use in AEC. Those discussions demonstrated that learning from DfMA has a significant potential to establish a systematic DfD approach and, thus, increase the implementation of DfD in the AEC sector. Before the discussions, the results of research questions regarding DfMA enablers/strategies and parameters are organized to set a comparable context. The DfMA strategies are grouped under five categories, of which four are found relevant to building cycle stages, which are (i) planning and programming, (ii) conceptual design, (iii) detailed design, and (iv) construction stage. The fifth category involves technology-related enablers. Regarding the discussion of DfMA parameters for DfD, parameters are refined first, and input parameters are considered for discussion. Then, their use possibility is discussed, considering different end-of-life scenarios. It has been found that the importance of an input parameter may differ in different DfD end-of-life scenarios. For example, one parameter may be highly relevant for one scenario while it may not be considered essential for another. That also varies when considering different parts, such as materials and components. Comparative evaluation of input parameters showed that parameters considered in DfD are currently in a limited variety and need to be enriched to a broader application. This study presents the first attempts in this way and shows there is potential to improve. Altogether, the research and discussions showed that DfD could benefit from DfMA, and in-depth studies of DfMA applications serve as a suitable foundation for creating a more comprehensive DfD approach. For future studies, a research framework is also proposed. In the fifth chapter, this thesis is concluded with a general evaluation of the overall study. Also, the limitation of this study is identified, and suggestions are made for future research.