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A tool to compare civil engineering design alternatives on the aspect of circularity

Meijer, Erik (2018) A tool to compare civil engineering design alternatives on the aspect of circularity.

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Abstract:The Dutch government wants to transform the Dutch economy into a circular economy (CE) in 2050. The construction sector has to comply with the concept of CE and is looking how to incorporate circularity into infrastructure objects, such as a bridge. Main aspects of circularity are the material use and energy use for the construction of an infrastructure object and its ‘end of life strategy’. Ideally only renewable energy is used for the processes of construction and breaking down of the infrastructure object. The used materials should be returned to the ecosystem without harm, or should be reused again at their end of life so no materials are lost. The construction sector is searching for a way to incorporate the aspect of circularity in the design of infrastructure objects. During the design of an infrastructure object design decisions have to be made. Various design alternatives are possible as function fulfiller for certain subsystems or elements. In design decision processes, different design alternatives are compared using various assessment criteria, to ultimately choose a design alternative that satisfies the requirements. Examples of assessment criteria are costs and safety. Yet circularity is not an assessment criterion yet, while design alternatives can have impact ‘on the circularity of an infrastructure object’. To incorporate the aspect of circularity in infrastructure objects circularity should become a design assessment criterion. However, currently there is not a systematic method to compare design alternatives on the aspect of circularity. The goal of this research was develop an instrument that allows comparison of civil engineering design alternatives on the aspect of circularity. In the future the developed instrument, an indicator framework with a proposed scoring system, might lead to more circularity in infrastructure objects. During the early design phase design decisions are made that could impact the circularity. In early design phases detailed information is not available and detailed calculations cannot be made. The proposed descriptive scoring system allows designers to score the indicators already during the early design phases since it does not require detailed information or calculations. The framework also takes away the discussions, which currently take place for each distinctive project, on what aspects circularity need to be assessed for one specific project. Application of the indicator framework results in scores for each indicator. The scores of the indicators provide insight in the circularity of a design. This allows comparison of different design alternatives as the scores of the indicators exposes differences and similarities between designs on the aspect of circularity. The research outcome is an indicator framework with a scoring system that allows the comparison of design alternatives on the aspect of circularity. The indicators are divided in three categories: ‘resource use’, ‘design characteristics’, and ‘end of life phase’. The categories comply with the lifecycle phases of an infrastructure object, respectively the production and construction phase, user phase, and end of life phase. The indicators represent different aspects of circularity. Examples of indicators are ‘renewable energy use’, ‘lifespan’ and ‘reuse rate’. A brief explanation for each indicator is provided in the indicator framework. Validation with the experts shows that, altogether, the indicators cover all the relevant aspects of circularity for civil engineering design alternatives. Most of the indicators are scored on a five-point interval scale. The five scores are: ‘poor’, ‘fair’, ‘good’, ‘very good’, and ‘excellent’. The different scores are described for each indicator. If possible the different scores are described with percentage ranges. An example of an indicator and score is given. Indicator Score Scoring description Reuse of existing objects, components and materials Fair A small amount of the object (20-40%) consists of recycled materials or reuse components. The indicator ‘reuse of existing objects, components and materials’ represents how much of the design alternative consists of existing objects, components and materials. Using existing objects, components and materials in a new object contributes to circularity by saving the use of new finite resources and by closing of the material cycle. The score fair indicates that the assessed design alternative consists for 20-40% of existing objects, components and materials, and for the other part of new resources. The research objective is achieved by conducting a literature study and expert interviews. First a literature study was done into circular economy frameworks and indicators. A literature matrix was used to identify the indicators to measure circularity, used in multiple articles. This resulted in an indicator framework. Second, eight experts in the field of circularity were interviewed to find out if the indicator framework was complete and how a measurement instrument could be developed for the indicators. Seven respondents are active in the construction sector and one expert is active in product design. The transcriptions of the interviews were analysed by using the indicators from the literature study as labels that guided coding. If the majority of the experts agreed with an indicator the indicator was included in the final framework, otherwise the indicator was deleted. The literature and experts agree on the set of indicators to measure the categories ‘resource use’ and ‘end of life phase’. This was not the case for the set of indicators for the category ‘design characteristics’. These indicators are not exactly defined in literature and were too complex for the experts, which make the set of indicators difficult to define. Additionally, the indicators consist of different factors (e.g. the fixing method of components) that together influence the score. The indicators can partially overlap each other, which makes it more complex to define them.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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