Physical — ACORN

To reduce the environmental impact of the concrete construction industry, ACORN is investigating the following concepts:

STRUCTURAL SYSTEMS

We see potential in two structural systems.

Non-prismatic beams that follow the moment distribution to optimise the concrete utilisation in the beam, instead of following the rationalisation imposed by a prismatic timber formwork. As opposed to flat slabs working in bending, requiring thickness and reinforcement, compression-dominant shells work mainly in compression and therefore are thinner and require less reinforcement, if at all.

*Non-prismatic beam following the bending moment and formed with a flexible formwork.*

*Segment of a concrete shell prefabricated off-site on a flexible formwork to assemble on-site.*

APPROACH

To build these advanced shapes efficiently and sustainably, we rely on digital fabrication.

Off-site automation and robotics push towards segmented structures that are produced in a factory and assembled on-site. We detail our connections to allow disassembly to be able to recycle/reuse/reassemble/reconfigure the structure at the end-of-life of the project for a circular economy of construction.

*The philosophy of ACORN: designing and planning segmented concrete structures for off-site automated construction, on-site assembly and disassembly for a circular economy of construction.*

*Robot cells on the Strong Floor of the Civil Engineering Building at the University of Cambridge with two ABB IRB 6400R (2.8m reach and 200kg payload).*

TECHNOLOGY

We identified several automation technologies to produce our structures.

Reconfigurable moulds consist of a set of vertical pins holding a flexible formwork and fitting a doubly-curved target surface on which the concrete element is cast.

Concrete spraying projects concrete on a curved formwork, which adheres to the surface thanks to self-compaction. Robotic spraying enhances the quality of the spray by carefully following a path with the appropriate position and orientation from the surface.

Actuated, reconfigurable mould supporting a flexible formwork of rods for casting doubly curved structural elements. Modular modules of 1m x 1m including each nine actuators with a travel height of 400mm.

*Off-site automated shotcrete to spray concrete following a specific robotic trajectory using a PS9000i GRC spray station by Power-Sprays.*

Filament winding breaks the constraint of high rationalisation of steel reinforcement bars thanks to the flexibility of a filament before it sets under the coating of a resin. Robotic winding faithfully produces complex, optimal reinforcement layouts.