Designing Lightweight Structures from Recyclable and Organic Materials: The Rethinking Lightweight Pavilion
Maren ZYWIETZ*, Karsten SCHLESIERa, Annette BÖGLEa
*HafenCity University Hamburg Henning-Voscherau-Platz 1, 20457 Hamburg, Germany [email protected]
a HafenCity University Hamburg
Figure 1: Modul-based concept with bending-active rods and form-active membrane elements
The current development towards bending-active structural design indicates that lightweight structures constantly evolve due to contemporary demands. This paper documents the approach to rethinking lightweight structures to face the growing scarcity of resources.
Since conventional composite materials in lightweight structures have severe limitations in terms of their recyclability, this raises new challenges for designers and engineers in the use of raw materials. In order to reduce the environmental impact, this research investigates the use of fully recyclable materials made from renewable resources in bending-active tensile structures.
Figure 2: Design proposal of the Rethinking Lightweight Pavilion
Based on an experimental approach, this paper presents an innovative pavilion design which will be exhibited as a built prototype at the IASS WG21 competition. The results of the four-step methodology consisting of parametric design, material testing, numerical simulation and the verification of the results using a mock-up structure are presented and discussed.
The Rethinking Lightweight Pavilion demonstrates that the use of materials suitable for the circular economy can make an inspiring contribution to lightweight structures of the future.
Figure 3: Biological Cycle for the biodegradable load-bearing structural elements (ash wood and wool fabric)
The critical state of our world, our climate, and our environment results largely from our irresponsible use of resources. From an ecological perspective, lightweight structures offer solutions to these problems: By making optimum use of material strength, lightweight structures save material and thus resources. In addition, lightweight structures can often be dismantled and reused.
Figure 4: Failure of a sample in three-point bending flexural testing
Historical development shows that lightweight structures can adapt flexibly to social requirements. This is also reflected in the continuation of the traditional principles of lightweight design in the form of the new structural typology of bending-active tensile hybrid structures. Instead of the former avoidance of bending stresses, these become a decisive form-determining structural element.
Figure 5: Uniaxial tensile test of membrane strips
The consequent demand for high strengths with slender cross-sections has led to increasingly advanced building materials in recent decades. However, the multi-layered, complex composite materials that have been developed have severe limitations in terms of their recyclability. This causes difficulties in the current paradigm shift from a linear to a circular economy.
The aim of this research is to investigate the use of fully recyclable materials in bending-active tensile hybrid structures with special focus on renewable resources. The challenges that arise for structures made of such materials from a structural and mechanical point of view will be determined and approaches to solving them will be addressed.
Figure 6: Wool fabric in biaxial test
The new structural typology of bending-active structures developed in the last decade is characterised by the elastic deformation of individual structural elements, which result in the shape and overall stiffness of these structures. By integrating bending-active elements into a form-active structural membrane, a hybrid system is formed, combining the positive characteristics of both structural typologies.
The bending-active elements provide the double curvature and the necessary pre-stress of the membrane, while the membrane in turn maintains the curvature and increases the buckling strength of the rods.
Previous research projects have demonstrated the application of this principle to small-scale and largescale projects. Due to the complex form-finding process of hybrid structures, computer-aided formfinding has also made significant progress. Current research on bending-active tensile hybrid structures focuses on improving the stiffness and robustness of the structures. In addition, the tailoring of material behaviour, e.g. through CNC knitted fabrics, is being explored for smaller installations.
Figure 9: Finished mock-up installation
The quality of lightweight structures can not only be evaluated in terms of the strength of the materials used. The environmental impact of the materials applied is significant in the evaluation of how sustainable a design can be implemented.
The research for the Rethinking Lightweight Pavilion demonstrates that filigree-looking structures based on complex form-finding and structural action can also be achieved with loadbearing components made from renewable, entirely organic resources. Rethinking Lightweight can thus make an inspiring contribution to how lightweight structures can continue to develop in terms of a resource-respectful use of materials in the future.