University of Twente Student Theses
Comparative life cycle assessment (LCA) and life cycle cost (LCC) analysis of a structural design with new steel elements and a structural design with reused steel elements
Nikolov, G.D. (2023) Comparative life cycle assessment (LCA) and life cycle cost (LCC) analysis of a structural design with new steel elements and a structural design with reused steel elements.
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| Abstract: | Objective The main goal of this research project is to evaluate and compare the environmental and economic sustainability effects of reused steel elements compared to new steel elements for the design of a section through a factory located in the Netherlands by conducting a life cycle assessment (LCA), life cycle cost (LCC) analysis and a structural design analysis. Methodology The present study consists of essentially three main parts that are briefly summarised here. The first one is a structural analysis that investigates the necessary procedures and assumptions for the optimisation of the current design and what additional testing and changes are required when considering reclaimed steel elements as compared to new steel elements. This was done via literature research and with the help of the structural modelling program Technosoft Raamwerken V6. The second main component is the LCA that evaluates the environmental impact and provides a calculation of the shadow prices of the original and optimised designs via the Environmental Cost Indicator. In this part, a scenario analysis is performed for four cases that are based on the Environmental Product Declarations (EPDs) created by the steel research organisation Bouwen met Staal and are the following: • Original design of the structure with 100% new steel in the product stage and 16% reuse of the material in the end-of-life stage based on EPD1 • Optimised design of the structure with 100% new steel in the product stage and 16% reuse of the material in the end-of-life stage based on EPD1 • Optimised design of the structure with 90% reused steel & 10% new steel in the product stage and 16% reuse of the material in the end-of-life stage based on EPD2 • Optimised design of the structure with 100% new steel in the product stage and 80% reuse of the material in the end-of-life stage based on EPD3 Finally, the third part is a parallel and complementary LCC analysis that evaluates the economic performance of the four scenarios over their life span of 50 years including the initial and future costs. Also, a sensitivity analysis of the costs as a function of the discount rate is performed to ensure the robustness of the results. Results From the structural analysis part a few destructive and non-destructive tests were identified which serve to ensure that the mechanical properties of the reclaimed steel elements are up to standard. Examples of the tests include tensile tests, hardness tests, Charpy impact test and instrumented indentation testing. This type of testing is necessary because the modelling program that is used for the optimisation of the structure assumes certain default parameters of the steel elements. If there is a mismatch, the results will be incorrect and might cause critical failure once the structure is built. Also, some of the main identified constraints that are associated with reusing steel elements are that the donor building must not be built prior to 1970, no signs of corrosion are present and the elements have not been exposed to extreme loads. In the end, the optimised design had 15.47% less material than the original design when considering only the beams and the columns. However, when the recommendations for reusing steel elements are applied it was found that extra supports are needed to mainly prevent lateral torsional buckling of the bearing beams. The results from the LCA show that in terms of kgCO2eq when the original design made with new steel elements is compared to the optimised design with reused steel elements there is a reduction of 83% of the global warming potential of the whole structure. If the same comparison is made only for the optimised design with new and reused steel elements, there is 80% decrease in CO2 emissions. Regarding the shadow costs expressed by the environmental cost indicator, there is a 73% reduction in the environmental costs from the original design made with new steel elements to the optimised design iii made with reused steel elements if the potential savings in module D are included – from € 2301 to €618 for the whole structure. If the same comparison is made for the optimised design modelled with EPD1 and EPD2 the reduction is approximately 69%. Finally, the LCC analysis shows a 50% reduction in the LCC value between the original design built with new steel elements and the optimised design with reclaimed steel elements at 5% nominal discount rate and 4.4% inflation. If the same comparison is made for optimised design made with new and reused steel elements the reduction is 40% even though in all cases there are extra costs incurred for testing and reconditioning the reclaimed elements. Conclusion At present, there is an ever-increasing shift towards more environmentally friendly and economically efficient structural designs in the construction industry due to the climate change phenomenon. Therefore, companies are striving for the development of effective solutions that aim to achieve the targets set by the United Nations in the Sustainable Development Goals (SDGs) in 2015 (UN, 2015) and by their national governments (e.g. the Climate Law in the Netherlands (Klimaatwet, 2019)). Therefore, this report clearly shows and evaluates the environmental and economic trade-offs of reusing structural steel elements with the hope that the insights gained from the LCA and LCC analysis of this case study will facilitate the decision-making process within Bilfinger Tebodin. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/95702 |
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