Demonstrating research advances at the ETH Zurich in complex timber structures and digital concrete, the Future Tree is an eye-catching pavilion, spanning over the courtyard of the office building extension of Basler & Hofmann in Esslingen, Switzerland.
The crown of the Future Tree is a timber structure made of 380 timber elements forming a reciprocal frame, supported by the concrete column, anchored to the building on two sides and cantilevering on the opposite corner. The frame’s geometry is informed by its structural behaviour, differentiating its flexural rigidity by playing with the opening of the reciprocal knots to achieve a higher stiffness in the cantilevering part. To integrate geometric, structural and fabrication concerns we developed a custom computational model of the design. The structure is made of acetylated pine wood, full threaded screws and tension cables. The timber elements have been fabricated and assembled using an industrial robot.
The Future Tree’s stem is a reinforced concrete column, made using an ultra-thin robotically 3D printed formwork which is combined with a fast-hardening concrete. This novel fabrication process, known as “Eggshell”, allows for the fabrication of non-standard, structurally optimized concrete structures, whilst being able to integrate standard reinforcement and minimize formwork waste. In the Eggshell process a formwork with a thickness of 1.5mm is 3D printed using a robotic arm. The reinforcement is then placed and the formwork is filled with a fast-hardening concrete in a layer-by-layer casting process. This assures that hydrostatic pressure exerted onto the formwork is kept to a minimum. After hydration of the concrete, the thin formwork is removed and can be recycled. As a first built example using this fabrication method, it shows that non-standard concrete structures can be fabricated efficiently, economically and sustainably.
Gramazio Kohler Research, ETH Zurich
In cooperation with: Physical Chemistry of Building Materials group (ETH Zurich, Prof. Dr. Robert J. Flatt, Dr. Thibault Demoulin, Bruno Pinto Aranda)
Client: Basler & Hofmann AG
Collaborators: Dr. Aleksandra Anna Apolinarska, Dr. Ena Lloret-Fritschi, Joris Burger, Nizar Taha, Fabio Scotto
Selected experts: Basler & Hofmann AG, ERNE AG Holzbau, SJB Kempter Fitze AG, Concrete Structures & Bridge Design (ETH Zurich, Prof. Walter Kaufmann, Dr. Jaimé Mata-Falcon)
Selected contractors: ERNE AG Holzbau (Fabrication timber structure)
Esslingen, ZH, Switzerland, 2019