Circularity in the structural design

Abstract

Politicians, scientific researchers and companies all know; the transition to a Circular Economy [CE] should start now, or actually should have started yesterday. The CE is an economic system that replaces the current take-make-waste linear system and replaces this with the reduction, reuse and recovering of resources. The challenge is to build with limited emissions, depletion and pollution of the living environment. Looking more specifically to a building, the load-bearing structure is responsible for a significant part of the material related environmental impact. In order to reduce the environmental impact of a building, more guidance is needed as the implementation of the CE principles requires a new approach for designing. The principles of the CE are safeguarded in various circular design strategies. Which circular design strategy is most beneficial for the project depends on the requirements and ambition of the project. The resulting difference in environmental impact caused by the design choices should be illustrated. Unfortunately, the current determination methods for the environmental impact do not include the design principles of the circular design strategies. Besides, the environmental impact is assessed at the end of the design process. Once the design is final, adjustment to improve the environmental impact are too difficult or costly.
In this research a design tool is developed that makes the practitioners in the building sector aware of the environmental impact of the design choices. Three circular design strategies are presented in the tool that can be followed to stimulate the development of a circular building project. The design tool can be used in the preliminary design phase to create and explore varying structural design variants in line with the chosen circular design strategy. The structural design variants can be compared on their environmental impact expressed in five indicators: the MPG, the environmental performance value (in Dutch: Milieu Prestatie Gebouwen [MPG]), the produced amount of CO2 emission, material usage, expected service life and building costs.
The research shows that based on literature review, expert judgement and open databases a design tool can be built, which gives insight in the environmental impact and more design parameters to support the implementation of circular solutions in the preliminary design phase. To meet the unique project specifications different solutions are required. Therefore, the design tool supports the design process with a uniform approach. The outcome of this research highlights three main influential aspects for the determination of the environmental impact; (1) the expected lifespan of the design assumed in the calculation method, (2) the quality of the environmental database of materials and (3) the total applied materials in the load-bearing structure. For the practitioners of the design process it is extremely important to be aware of the effect of changing the expected lifespan and thus the determination method for the environmental impact and the quality of the environmental database used.