HiLo’s roof is a lightweight, doubly curved, concrete sandwich structure, with two thin layers of reinforced concrete of only 5cm and 3cm thick. Spaced 10cm apart by insulation blocks, the layers are connected by a grid of thin compressive stiffening ribs and vertical tension rods. Combining this lightweight two-layered structure with the strength derived from its highly curved geometry, the roof stands freely on five supports, covering an unobstructed space of 120m2.
Non-standard structures in concrete require custom formworks that typically use massive amounts of cut timber or milled foam as shuttering; the production of these single-use moulds is costly and wasteful. The HiLo roof structure was instead built using a flexible formwork, based on a largely reusable kit-of-parts. The primary structure of the formwork is a cable net consisting of individually cut cable segments connected at custom-designed nodes, tensioned within a wooden boundary frame. A thin fabric membrane is stretched over the cable net and connected to the nodes to form a taut surface onto which the concrete can be cast or sprayed.
All key details of the system were worked out through prototyping in collaboration with experts and partners from industry. The principles of the developed solutions were integrated into a flexible design-to-fabrication workflow implemented with COMPAS, the open-source computational framework for research and collaboration in Architecture Engineering and Construction, which served as a central hub for the computational development, coordination and planning of the key innovations and provided an effective research-to-practice transfer mechanism.
Project by Block Research Group, ETH Zurich
Project partners include ROK - Rippmann Oesterle Knauss GmbH, Dr. Schwartz Consulting, ETHZ Chair for Architecture and Building Systems, Bürgin Creations, Marti Construction SA, Jakob Rope Systems, Bieri Tenta AG, Künzli Holz AG, Pletscher Metallbau AG, Contec AG.
Financial support by ETH Zurich, Dr. Max Rössler, Empa, Holcim Switzerland, NCCR DFAB.