Hybrid Flax Pavilion

Landesgartenschau Wangen im Allgäu, 2024, Germany

The Hybrid Flax Pavilion constitutes a central exhibition building on the grounds of the Landesgartenschau, located on the winding banks of the recently revitalised Argen River. The pavilion showcases a novel wood-natural-fibre hybrid construction system developed by the Cluster of Excellence "Integrative Computational Design and Construction for Architecture" (IntCDC) at the University of Stuttgart, as an alternative to conventional building methods. The unique hybrid system combines thin cross-laminated timber with robotically wound flax fibre bodies to create a novel, resource-efficient building structure made from regional, bio-based materials with a distinct local connection. Flax was historically processed in the local textile industry, whose old spinning mill was renovated as part of the Landesgartenschau. The pavilion's gently undulating roof, together with its circular floor plan and centrally located climate garden, creates an exhibition space that seamlessly integrates into the surrounding landscape. The geothermally activatable floor slab made of recycled concrete provides year-round comfortable use of the permanent building.

A permanent exhibition building demonstrating novel bio-based construction methods

Situated on the lush grounds of the Landesgartenschau, the Hybrid Flax Pavilion provides a central exhibition space. Its design features an undulating roof and a circular glass facade that invites visitors to the striking indoor space from all directions. The fully transparent envelope provides panoramic views which seamlessly blend the interior of the building with the exterior landscape. Echoing the rhythm of the adjacent Argen River, the undulating roof creates continuous yet distinct spatial zones, providing a sense of depth that connects the inner and outer facades. At its core lies a climate garden, serving as an inner courtyard and facilitating natural cross-ventilation and cooling. Together with a geothermally activated floor slab made from recycled concrete and CO2-reduced cement, this ensures year-round indoor comfort with minimal building services.

The pavilion’s roof constitutes the first-ever hybrid structure of cross-laminated timber plates and natural fibre bodies produced through coreless flax filament winding. The 20 hybrid components alternate with regular timber plates to form the distinctive wave-like structure of the roof, which covers the 380m² exhibition space. The goal of this novel hybrid building system is to achieve expansive column-free space while minimising material usage, thus leveraging the synergy between wood and natural fibre composites. The onsite assembly of all 44 ceiling elements was completed in 8 days owing to the integrative computational design process and high-precision pre-fabrication.

The building's design makes use of integrative computational methods to seamlessly incorporate input from various specialists across different fields, bridging the gap between research and industry. This approach encompasses not only the design of hybrid fibre-timber components but also considers interfaces to conventional building elements like the facade and roof, taking into account their interconnected geometric and constructional requirements. This methodology facilitated a flexible, iterative design process, allowing for adjustments and optimisations at every stage of development across all involved disciplines. As a result, the design, manufacturing, and construction process took only 12 months, demonstrating the effectiveness of this integrative Co-Design approach. In the spirit of two-way knowledge transfer between cutting-edge research and construction companies, the building also shows how highly innovative architecture can be built by regional, small enterprises and skilled craftspeople.

Novel hybrid building system using natural fibres

The fibre-timber hybrid system leverages the distinctive qualities of timber and natural fibres, resulting in lightweight, effective building components with superior performance. Incorporating flax fibre components to reinforce the thin wooden elements facilitates the use of fast-growing resources for the construction industry, allowing the significant demand for wood to be met more effectively from locally available timber reserves. The construction system is being developed to enable future material reuse or recycling through the sorted separation of components, following principles of circular construction. The hybrid components aim to achieve a simply supported, beam-like structure with a variable structural height. The fibre body forms a bottom surface that primarily bears tension loads, while the timber panel manages compression forces and constitutes the surface for the roof enclosure. Together they provide the strength and stiffness necessary to carry the high snow loads at the foothills of the Alps. 

Throughout the research and development process, the design of the fibre body was continuously informed by feedback from architectural requirements, structural analysis, fabrication constraints, and material properties. It consists of multiple, sequentially wound flax fibre layers. The primary spine layer aligns with the beam direction, acting as a bottom cord at the centre of the span. The fan layer gradually disperses loads to the edge supports, while the visually dominant lattice layers create a uniform fibre mesh to achieve the required structural integrity. Two additional corner reinforcement layers enhance fibre interaction and provide additional reinforcement in structurally critical areas.

The simply supported, fibre-timber hybrid components cover an 8.6-meter span between linear supports. The radially arranged 120mm thick cross-laminated timber (CLT) plates constitute the primary framework and create the undulating roof profile. The timber plates were manufactured using a 5-axis milling machine and include a series of thru-holes for the timber-fibre-facade connections as well as chamfered edges that continuously change their angle to match the varying orientations of the fibre connections. Flax fibre bodies are affixed by screws beneath every second CLT plate, establishing the hybrid components. Full-scale load tests allowed for the calibration of finite element models and confirmation of the material systems' structural integrity.

From robotic prototyping to industrial filament winding

The coreless filament winding process utilised in the development and production of the fibre elements allows for the selective local deposition of material driven by specific structural, architectural, and material requirements. In contrast to conventional fibre composite fabrication processes, this is achieved without the need for a surface mould, as the winding frame is co-designed with the fibre element so that the element’s final fibre body emerges in the winding process as the equilibrium state of all fibre segments interacting. This project required further adaptation of the coreless filament winding process to accommodate the natural flax fibre material system and unique geometric form of the fibre body of the hybrid component.

This fibre geometry represents a departure from previous geometries because of its use of positive surface curvatures. Typically, positive curvatures are only achievable by a mould, yet this component employs areas of both positive and negative Gaussian curvature. To achieve this, the winding frame includes a “spine” that allows for the positive curvature of the component in its longitudinal direction as well as negative curvature, structural depth, and radius of curvature in its cross-section, all while providing the necessary structure to make the frame self-supporting. Anchor points around the perimeter of the frame were specifically oriented based on the normal of the geometric surface to maintain consistent fibre direction and properly transmit forces from the timber into the fibre bundles, a requirement paramount to the effectiveness of the hybrid component. 

Using this custom frame, the geometry, fibre patterns, and fabrication processes were tested and refined at University of Stuttgart through a series of prototypes wound by a 6-axis robotic arm equipped with a custom end effector. After the prototypes were completed and structurally evaluated, the finalised design was handed over to the industrial partner for serial production using a 5-axis industrial filament winding machine. The fabrication planning was directly integrated into the computational design process and a custom tool converted the geometric data of the fibre component into executable machine code, streamlining the design-to-fabrication workflow and successfully bridging the gap between research and industry.

Research into computationally enabled, bio-based hybrid building systems is being continued at the University of Stuttgart as part of the Cluster of Excellence "Integrative Computational Design and Construction for Architecture".

Cluster of Excellence IntCDC - Integrative Computational Design and Construction for Architecture, University of Stuttgart

ICD Institute for Computational Design and Construction
Prof. Achim Menges, Rebeca Duque Estrada, Monika Göbel, Harrison Hildebrandt, Fabian Kannenberg, Christoph Schlopschnat, Christoph Zechmeister

ITKE Institute for Building Structures and Structural Design
Prof. Dr. Jan Knippers, Tzu-Ying Chen, Gregor Neubauer, Marta Gil Pérez, Valentin Wagner

with support of: Daniel Bozo, Minghui Chen, Peter Ehvert, Alan Eskildsen, Alice Fleury, Sebastian Hügle, Niki Kentroti, Timo König, Laura Marsillo, Pascal Mindermann, Ivana Trifunovic, Weiqi Xie

Landesgartenschau Wangen im Allgäu 2024
Karl-Eugen Ebertshäuser, Hubert Meßmer

Stadt Wangen im Allgäu

HA-CO Carbon GmbH
Siegbert Pachner, Dr. Oliver Fischer, Danny Hummel

STERK abbundzentrum GmbH
Klaus Sterk, Franz Zodel, Simon Sterk

FoWaTec GmbH
Sebastian Forster

Biedenkapp Stahlbau GmbH
Stefan Weidle, Markus Reischmann, Frank Jahr

Harald Klein Erdbewegungen GmbH

PROJECT COLLABORATIONS

Scientific Collaboration:
IntCDC Large Scale Construction Laboratory
Sebastian Esser, Sven Hänzka, Hendrik Köhler, Sergej Klassen

Further Consulting Engineers:
Belzner Holmes und Partner Light-Design
Dipl.-Ing. (FH) Thomas Hollubarsch, Victoria Coval

BiB Concept
Dipl.-Ing. Mathias Langhoff

Collins+Knieps Vermessungsingenieure
Frank Collins, Edgar Knieps

Moräne GmbH - Geotechnik Bohrtechnik
Luis Ulrich M.Sc.

Spektrum Bauphysik & Bauökologie
Dipl.-Ing. (FH) Markus Götzelmann

wbm Beratende Ingenieure
Dipl.-Ing. Dietmar Weber, Dipl.-Ing. (FH) Daniel Boneberg

lohrer.hochrein Landschaftsarchitekten DBLA

Building Approval:
Landesstelle für Bautechnik
Dr. Stefan Brendler, Dipl.-Ing. Steffen Schneider

Proof Engineer
Prof. Dr.-Ing. Hans Joachim Blaß, Dr.-Ing. Marcus Flaig

Versuchsanstalt für Stahl, Holz und Steine, Karlsruhe Institute of Technology (KIT)
Prof. Dr.-Ing. Thomas Ummenhofer, Dipl.-Ing. Jörg Schmied

MPA Materials Testing Institute, University of Stuttgart
Melissa Lücking M.Sc., Dipl.-Ing (FH) Frank Waibel

Construction Collaboration
ARGE- Leistungsbereich Wärmeversorgungs- und Mittelspannanlagen
Franz Miller OHG
Stauber + Steib GmbH

PROJECT SUPPORT:

DFG German Research Foundation

Dieses Projekt wurde durch das Ministerium für Ernährung, Ländlichen Raum und Verbraucherschutz Baden-Württemberg unterstützt.

Bioökonomie Baden-Württemberg: Forschung- und Entwicklung (FuE) Förderprogramm “Nachhaltige Bioökonomie als Innovationsmotor für den Ländlichen Raum”

Holz Innovativ Programm (HIP), Ministerium für Ernährung, Ländlichen Raum und Verbraucherschutz Baden-Württemberg

IFB Institute of Aircraft Design, University of Stuttgart

ISW Institute for Control Engineering of Machine Tools and Manufacturing Units, University of Stuttgart