nR NEST HiLo 1:1 Roof Prototype

PROJECT DATA

TYPE	RESEARCH, CONSTRUCTION INNOVATION
LOCATION	ETH ZURICH, SWITZERLAND
CLIENT	ETH ZURICH + EMPA
PROJECT AND RESEARCH LEADS	BLOCK RESEARCH GROUP [BRG] A/S ARCHITECTURE AND BUILDING SYSTEMS ETH ZURICH
PROFESSIONAL ENGINEERS	BOLLINGER+GROHMANN
GENERAL CONTRACTOR	MARTI AG BAUUNTERNEHMUNG
CONCRETE SPRAYING	BÜRGIN CREATIONS
CONCRETE	HOLCIM SCHWEIZ AG
CONCRETE STRUCTURAL TESTING	INSTITUTE OF STRUCTURAL CONCRETE RWTH AACHEN
CABLENET COMPONENTS	JAKOB ROPE SYSTEMS LEHMANN TRUBB
SCAFFOLDING	DOKA SCHWEIZ AG
DATE	2016 — 2017
TEAM	DAVE PIGRAM IAIN MAXWELL OLIVER BENNETT
IMAGES	NAIDA ILJAZOVIC MICHAEL LYRENMANN URSULA FRICK DAVE PIGRAM OLIVER BENNETT

NEST HiLo 1:1 Roof Prototype

ETH Zurich, Switzerland

nR

The cutting edge of the possible.

This full-scale experiment investigates the feasibility of spraying a textile reinforced thin concrete shell using a lightweight flexible formwork composed of a tensioned cablenet as falsework and tailored fabric as shuttering. This one-to-one prototype (within a bounding box of 20m x 10m x 7m) was undertaken as a dress rehearsal within a largely controlled environment ahead of the ultimate in-situ construction of the NEST HiLo project itself.

The development of the prototype focused on the first layer of NEST HiLo's thin concrete shell and represents a key milestone for the project, as it demonstrates the viability of the proposed lightweight, flexible formwork system to form a complex concrete structure. The prototype was built with the following objectives:

01 — To develop and test the cable net components at real scale.
02 — To test the feasibility of the system and the on-site logistics.
03 — To test the concrete spraying of a large and doubly-curved surface through the carbon-fibre reinforcement.

SM practice director Dave Pigram was research lead and managed the design, planning and construction of the roof prototype with documentation support from the Sydney office whilst on secondment to the Block Research Group [ETH Zurich].

NEST HiLo Roof Prototype
ETH Zurich, Switzerland

Construction Sequence Drawings

01
Setout Constraints
Minimum headrroom
Possible touchdown zones

02
NEST HiLo Roof in context

03 — 06
Steel Supports for roof touchdowns
Prototype Support Scaffold
Timber edge-beam
Tensile scaffold alternative
(if space had permitted)

07 — 10
Cablenet Geometry
Residual Forces
Cable thickness distribution
Node size distribution

11 — 14
Digital total station scanning
Scan 01 - Initial accuracy
Perimeter retensioning
Scan 02 - Increased accuracy

15 — 17
Fabric shuttering
Edge clamp
Carbon-fibre reinforcement

18 — 20
Spray sequence

21
Final Shell

360° Walkthrough Tour
Virtual tour of roof prototype by Zitronenwolf.

01
Cable Net

02
Fabric Formwork

03
Final Shell

Cablenet
The doubly-curved form of the roof is defined by a network of rods and cables stretched under tension. This system allows for the realisation of complex curvature with far less material and wastage.

Fabric Shuttering from Below
The cablenet is covered with a tailored geotextile fabric shuttering.
It is this surface that supports and gives form to the shotcrete subtly bulging between the cables and revealing the pattern of thier alignents.

Fabric Shuttering from Above
The overall form of the shell is defined by the shape of the timber edge-beam, by the unique length of each cable segment and by the specififc tension applied at the ends of each cable row.
The upperside of the fabric shuttering reveals the seams of the patterned fabric, and the spacers that will support the carbon-fibre reinforcement.

Concrete Spraying
The concrete is applied by two teams of two. Each team has one member to spray the concrete to the approproate thickness and one to use a vibrating trowel to ensure that the concrete flows in and around the carbon fibre mesh reinforcement.
The spraying must follow a specific sequence so that the cablenet sags as planned under the 19 tons of concrete.

Construction Sequence
ETH Zurich

Shell With Flexible Formwork Removed

01
Test installation of the hydronic heating and cooling pipework to the upper side of the shell.

02
The underside of the shell reveals the pillowed imprint of the cablenet and fabric shuttering in turn revealing the flow of forces between touchdowns.

Selected Publications

01
Beyond Bending
Edition Detail, Germany

02
Robust Resilient Resistant
Edition Detail, Germany

03
An Ultra-Thin Double-Curved Concrete Roof
Architect, USA

04
Ultrathin concrete roof to cap a net-positive energy rooftop apartment
Architect’s Newspaper, USA

05
Bauwelt: Digital Fertigan [Digital Fabrication]
German

06
The Structural Engineer
Special Issue: 2024 Vision

07
Azure
The high-tech future of concrete

08
The Economist
UK/International Edition

Final Roof Prototype
The dramatic form and extreme thinness of the roof along with the pillowed imprint of its fabrication method is revealed.