Integrating Reused Steel Elements in Structural Design

Abstract

The building industry is one of the world’s largest CO2 emitters, the need to transition into a circular economy is becoming increasingly pressing. Steel is a long-lasting and dimensionally stable material and therefore suitable for reuse. However, reuse of steel is not yet implemented on a large scale in the building industry and inventories of available elements are still limited. This thesis showcase how structural engineers can work with reused steel, by the mapping of workflows and suggesting of an semi-automated design process. The thesis is divided into four parts. In Part 1, a mapping of possible workflows is done through literature studies and informal interviews. In Part II, a digital workflow for integrating an inventory of reused elements into a structure is developed. This includes a parametric 3D model in Rhino/Grasshopper, structural analysis using FEM-Design, and a self-scripted tool in C# that performs Eurocode verification and matches reused elements to a structure using an A* optimization algorithm. The optimization objective is to minimise the embedded CO2 equivalents (CO2e) in the structure. In Part III, an iterative design process is carried out to test the digital workflow. Finally, Part IV presents reflections and discussions concerning the project. For the design process, a fictitious office building is designed and matched with two different inventories of reused elements using the developed workflow. One inventory is based on the available elements from the steel supplier Stena Stål, the other is based on a building to be dismantled. For the design process, an iterative approach is implemented. Initially, several rough sketches are created followed by continuous evaluation, selection and developments leading to an increasingly refined design. The developments include defining and applying design principles to reduce the vulnerability to changes of the inventory. They also include smaller design changes, guided by the tool, to further decrease the environmental impact. The result is a design proposal that exemplifies the potential of reused steel elements. The conclusion from the study is that structural engineers benefit from using automated workflows when designing with reused steel because the process is repetitive. Also, allowing reuse to influence design decisions can significantly increase the carbon savings of a project, as small design modifications can increase the reuse rate.