sustainability Article Framework for Designing Sustainable Structures through Steel Beam Reuse Seongjun Kim 1 and Sung-Ah Kim 2,* 1 Department of Convergence Engineering for Future City, Sungkyunkwan University, Suwon 16419, Korea; [email protected] 2 Department of Architecture, Sungkyunkwan University, Suwon 16419, Korea * Correspondence: [email protected] Received: 9 October 2020; Accepted: 12 November 2020; Published: 15 November 2020 Abstract: The architecture, engineering, and construction sector requires carbon-intensive materials, such as steel, in the construction process and generates a large amount of waste in the life cycle. This causes global warming and waste problems. The demand for the reuse of construction materials is increasing, although it is not the convention, to reduce the environmental impact. Although the sustainable effect of the reuse of materials has been proven in several studies, materials are not always reused in practice, owing to the lack of an information system for reusable materials and the economic uncertainty. In this study, we propose a framework for designing structures using reusable steel beams. The design framework consists of a material bank and a design support tool. The material bank provides information on reusable materials based on the building information modeling. The design support tool generates efficient material procurement plans and provides information about the environmental and economic impact of the project. In a case study used to verify the framework, CO2 emissions were reduced by up to 77% through material reuse, which was consistent with the results of previous studies. However, owing to the cost of processing reusable materials, the overall cost was found to increase by up to about 40%. Therefore, an economic analysis over the entire life cycle when using reusable materials needs to be done. Keywords: reuse; design for reuse; material bank; life cycle assessment; life cycle cost; building information modeling 1. Introduction The demand for greenhouse gas (GHG) reduction has increased due to rapid climate change caused by global warming. In particular, the architecture, engineering, and construction (AEC) sector is a resource-intensive industry sector accounting for about 40% of the energy consumption and over 32% of the CO2 generation in the U.S. and Europe [1,2]. There is, therefore, a great need for the AEC sector to reduce its generation of GHGs. In addition, the AEC accounts for 51% of the total steel resource consumption [3] and up to 30% of the global waste generation [4–6], including Europe and most developed countries. The material-related energy consumption accounts for 10–20% of the AEC’s total energy consumption [7], and this proportion increases with the type and life span of the structure. As such, resource consumption in the AEC sector poses a serious threat to the environment, and according to the Organization for Economic Co-operation and Development (OECD), the use of construction materials is expected to increase further in the future [8]. Accordingly, calls for the reduction of both waste and production of construction materials are increasing worldwide. In Korea, the AEC sector accounts for about 40% [9] of the energy consumption, which is two times greater than that of the transportation section [10], and most of the generated waste and GHGs owing to the use of carbon-intensive materials. In 2020, the annual steel consumption of the AEC sector in Korea was Sustainability 2020, 12, 9494; doi:10.3390/su12229494 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 9494 2 of 20 estimated to be over 20.7 million tons [11]. In response to this situation, the Korean government is attempting to reduce GHG emissions by 50% [12] and CO2 emissions from AEC by approximately 60% [13] by 2050. Countries around the world have introduced the concept of a circular economy (CE) to reduce the environmental impact caused by the production of construction materials and the discharge of waste, with waste management being a key strategy for a CE [14–16]. The CE concept is used not only for construction but also for responding to resource depletion and environmental issues and other sustainability issues across all fields. This concept is particularly important in the AEC sector, which has a significant influence on the environment, owing to its large resource consumption and waste generation. The European Union action plan for CE actively encourages the recycling and reuse of construction materials and provides guidelines [17,18]. Reduce, recycle, and reuse are recommended as major strategies for waste management [19]. In particular, the reuse of materials extracted from structures has proven to have a high potential to improve resource efficiency, energy use, and carbon emissions of the AEC sector [20]. When steel scrap is processed using an electric arc furnace for recycling, which is considered an eco-friendly strategy, 0.15–1.03 tons of CO2 are generated in the process of producing 1 ton of steel [21]. In Korea, the electric arc furnace method generates only about a quarter of the CO2 generated by the basic oxygen steelmaking method, in which iron ore is processed using a blast furnace [22,23]; the amount of CO2 generated can be further reduced by the reuse of materials. In addition, the reuse of construction materials reduces material production costs. Reuse is attracting attention as the most promising alternative for enhancing the sustainability of the AEC sector by replacing the resource and energy-intensive material production process and reducing waste. Research has been conducted on design methods for efficiently extracting materials from structures for reuse, or using materials already extracted to apply reuse in the AEC sector. Research on design for deconstruction has developed strategies for both deconstructing structures from the design process, and evaluating tools for ease of disassembly [24,25]. Research related to design for reuse (DfR) has investigated the environmental effects and design strategies of new structures using reusable materials [26,27]. Nevertheless, materials are rarely reused in the AEC sector, and there is a lack of information on reusable materials and their properties. There is no official service that provides a list or status of reusable materials, and even if reusable materials are sought, it is difficult for designers to grasp information on their properties [28–30]. Therefore, the case for construction using reusable materials and the process of design are not well-defined. In addition, project stakeholders, including the owner, are concerned about the economic uncertainty of using reusable materials [28,29,31]. Designers, in particular, are reluctant to reuse because they are concerned that their designs and material procurement strategies may be compromised by limitations in the shape and quantity of available reusable materials [28,29,31,32]. The opportunity to enhance the sustainability of the AEC sector is therefore lost because reusable materials are not used in practice, despite the environmental benefits and existence of policy incentives for reuse. In this study, we propose a framework for designing structures with reusable steel beams to reduce CO2 emissions. The framework consists of a material bank for managing reusable material information and a design support tool to increase the efficiency of reusable material use. The framework supports the design process by providing information on reusable materials, efficient material usage plans, and information on the environmental and economic impact of the project for designers and stakeholders. In this way, it facilitates the process for stakeholders to use reusable materials to improve the sustainability of the AEC sector. Sustainability is a broad term that comprehensively considers the economic and social performance and environmental resilience to balance the interests of current and future generations [14,33]. In this study, we focused on the environmental aspect of the various elements of sustainability. The subject of the proposed framework is a steel beam structure. This is because the demand for steel beams in the AEC sector is very high; 60 million tons of sections are used worldwide every year [34]. In Korea, about 7.9 million tons of steel sections and I beams (or H beams) are produced every Sustainability 2020, 12, 9494 3 of 20 year [35]. Not all the steel components produced in Korea are used in the AEC sectors. Nevertheless, the proposed framework is expected to allow an amount of steel sufficient to cover a significant portion of the Korean and global demand for steel beams. Steel beams are easy to reuse [36,37], and although reuse is not a common practice at present, the steel beam recovery rate in the AEC sector is about 85% [3], making it easy to secure inventory. The environmental benefit that can be obtained through reuse is significant because steel beams require a lot of energy in the production process. In Korea, 67% of the total steel is produced through the basic oxygen steelmaking method using a blast furnace [38]. With this method, about 2 tons of CO2 are generated for every 1 ton of iron produced [39]. In this study, the amount of CO2, which accounts for over 60% of the GHG emissions [40], was calculated to measure the environmental impact of construction projects. The framework of this study focuses on the process of creating design and material procurement plans using reusable materials. Therefore, this study does not include a method of extracting materials from a structure to be deconstructed, or a design method to facilitate extraction. The rest of this paper is organized as follows: Section2 explores previous studies on DfR, material banks for managing reusable materials, and methods for assessing the environmental and economic costs of construction projects; Section3 proposes a design framework for promoting steel beam reuse based on previous research considerations; Section4 describes a case study to verify the e ffectiveness of the proposed framework; Section5 analyzes the results of the case study.