木造建築の敵「乾燥収縮」により構築するタワー!?

© ICD/ITKE University of Stuttgart

〈ウーアバッハ・タワー（Urbach Tower）〉は自己成形する木材でつくられた、ドイツの町ウーアバッハ（Urbach）のランドマークとなる木造タワーです。

木造建築において一般的に、抑制する必要のある木材の乾燥収縮を、予測・活用する「マテリアル・プログラミング」により、木材が自ら形状を形成する「セルフシェイプ・マニュファクチャリング」建築であり、建築規模での取り組みとしては世界初となります。

シュトゥットガルト大学の計算デザイン・建設研究所（ICD）と建築構造デザイン研究所（ITKE）の建築家・エンジニアのチームによるプロジェクトです。

（以下、ICDから提供されたプレスキットのテキストの抄訳）

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

〈ウーアバッハ・タワー〉は、セルフシェイプ・プロセスにより生成される湾曲した木製部材により構成されている。 自己形成する建築規模の部材からつくられた世界初の木造建築物である。

この取り組みは木材製造において、重機によるエネルギー集約的な「機械成形プロセス」から、材料が自力で成形する「セルフシェイプ・プロセス」へのパラダイムシフトを意味する。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

この形状変化は、木材の特性である含水率の低下による収縮のみで行われる。高さ14mのタワーの各部材は平らな状態で設計・製造され、乾燥プロセスを経ることで、プログラムされた最終的な曲面形状に自律的に変化する。

これにより、持続可能で再生可能な地元産の建材を使用した、高性能であり優美な建築物の新たな可能性が開かれるのである。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

「マテリアルプログラミング」と「形状変化予測」

木造建築では一般的に、水分による割れや変形が問題となるため慎重にコントロールする必要がある。

対してこのプロジェクトでは、自然発生する強力な変形を利用して、あらかじめ設計された自己形成の動作を引き起こすように木材をプログラムし配置する。

機械がさまざまな動きをするようにプログラムできるのと同じように、木材も乾燥させるとあらかじめ決められた形状に変形するようにプログラムすることができるのである。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

木材を曲げて構造や美観を整える方法は何世紀も前から存在しているが、そのほとんどは機械的な力に頼っている。そして、含水率の変化により木材がどのように変形するかについても、実務や学術面ではよく知られている。

デザイン思考への転換と、より正確な予測を可能にするコンピュータによるシミュレーションにより、水分による膨張と収縮を利用して、より大きなスケールで特定の自己形成を設計しプログラムすることが可能となった。

© ICD/ITKE University of Stuttgart

© Empa

© ICD/ITKE University of Stuttgart

建築規模の「セルフシェイプ・マニュファクチャリング」

〈ウーアバッハ・タワー〉は、スイス産のスプルース材による湾曲したCLT部材で構成されている。CLTの各層を構成する木材パネルの乾燥には、建設業界でスタンダードな乾燥技術を使用している。

精密に湾曲した木材パネルを積層し形状を固定することで、安定した形状を持つ大きな曲面CLT部材を形成する。

© ICD/ITKE University of Stuttgart

さまざまな曲率のアールを生み出すために必要な材料配置の設計・予測・最適化のため、使用する材料に特化した計算力学モデルを開発した。

無垢材ボードの「セルフシェイプ・マニュファクチャリング」と、さまざまな曲率への迅速な適応性により、持続可能で再生可能な地産材を使用した、薄型木造シェル建築の新たな可能性が切り拓かれた。

〈ウーアバッハ・タワー〉は、この技術を建築規模の耐荷重木造部材に適用した世界初の事例である。

© ICD/ITKE University of Stuttgart

既存の木材製造プロセスに適合するサステナブルな木造建築

〈ウーアバッハ・タワー〉は最大15m、厚さ90mmのCLT部材で構成され、5軸CNC等により加工され、外側にはラミネートされたラーチ材からなる保護層が追加されている。これには、紫外線や菌類の影響から木材を保護する、透明で耐久性のあるコーティングも施されている。

ラーチ材は屋外の風雨にさらされると、裂けたり灰色に変色することなく、時間の経過とともに均一な白色を帯びてくるのである。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

地域の原木を製材所で切り出すところから、セルフシェイプ・パネルの製造、乾燥、最終加工、事前組み立てまで、すべてのプロセスが同じ企業グループ内の同じ場所で行われる。

これは、持続可能で革新的な生産を可能にするだけでなく、セルフシェイプ・マニュファクチャリングが既存の木材加工や製造のワークフローにいかにシームレスに統合できるかを示している。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

〈ウーアバッハ・タワー〉は、12のCLT部材とそれらをつなぐクロスネジで構成されており、現場に搬送する前に3つの部材グループに分けて接続されている。これにより、大規模な足場や型枠を必要とせず、4人の職人により1日で組み立てることが可能となった。

この建築は、熟練した技能、デジタル技術の革新、科学的研究の交差点で生まれる、効率的で経済的、エコロジカルで表現力豊かな木造建築の可能性を示している。

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

© ICD/ITKE University of Stuttgart

以下、ICDのリリース（英文）です。

URBACH TOWER
A unique Landmark Built from Self-Shaping Wood
Remstal Gartenschau 2019, Urbach, Germany

The Urbach Tower is a unique wood structure. The design of the tower emerges from a new self-shaping process of the curved wood components. This pioneering development constitutes a paradigm shift in timber manufacturing from elaborate and energy-intensive mechanical forming processes that require heavy machinery to a process where the material shapes entirely by itself. This shape change is driven only by the wood’s characteristic shrinking during a decrease of moisture content. Components for the 14 m tall tower are designed and manufactured in a flat state and transform autonomously into the final, programmed curved shapes during industry-standard technical drying. This opens up new and unexpected architectural possibilities for high performance and elegant structures, using a sustainable, renewable, and locally sourced building material.

The Urbach Tower constitutes the very first structure worldwide made from self-shaped, building-scale components. It not only showcases this innovative manufacturing approach and resultant novel timber structure; it also intensifies the visitors’ spatial involvement and landscape experience by providing a striking landmark building for the City of Urbach’s contribution to the Remstal Gartenschau 2019.

Material programming and predictability of shape change

In timber construction, moisture typically causes problems with cracking and deformation; hence, moisture changes and stress development must be carefully controlled. In contrast, in this project wood is programed and arranged in a way to utilize this powerful, naturally occurring deformation to trigger a designed self-shaping behavior. In the same way that machines can be programmed to perform different movements, wood parts can be programmed to transform into predetermined shapes when dried.

While methods of bending wood into different shapes for structure and aesthetics have existed for centuries and have become recognized industrial processes, they still mostly rely on brute mechanical force for the shaping process. Similarly, an understanding of how wood deforms due to changes in moisture content is well known in practice and academics. However, a shift in design thinking, as well as new computational simulations for more accurate prediction, now allow us to use this moisture induced swelling and shrinking to design and program specific self-shaping movements at larger and larger scale.

Self-shaping manufacturing at building-scale

The pioneering development of large-scale self-shaping constitutes a paradigm shift in timber manufacturing from elaborate and energy-intensive mechanical forming processes that require heavy machinery to a process where the material shapes entirely by itself. This shape change is only driven by the wood’s characteristic shrinking during a decrease of moisture content. The curved Cross Laminated Timber (CLT) components for the tower’s structure are designed and produced as flat panels that deform autonomously into predicted curved shapes when dried. The 5.0 m x 1.2 m spruce wood bilayers parts are manufactured with a high wood moisture content and specific layups and dried in an industry standard technical drying process. When removed from the drying chamber the parts are precisely curved. The parts are overlapped and laminated together to lock the geometry in place, forming larger curved CLT components with form stable geometry.

Material specific computational mechanics models have been developed to both design, predict, and optimize the material arrangement required to produce different curvature types and radius. The technology of self-shaping manufacturing for solid timber boards and the rapid adaptability of the process to different curvatures open up new and unexpected architectural possibilities for thin shell wood structures, using a sustainable, renewable, and locally sourced building material. The Urbach Tower is the very first implementation of this technology on building-scale, load-bearing timber parts.

Sustainable wood construction and functional timber cladding

The self-shaping components are made entirely of spruce wood boards sourced regionally from Switzerland. Individual components span up to 15 m with a radius of 2.40 m and a structural thickness of only 90 mm. The components are 5-Axis CNC cut and detailed from half cylinder blanks and pre-assembled into building groups of three components for transport, including water barrier and external wood cladding. With precise curvature and optimal fiber alignment from the manufacturing process, each component is cut in detailed in just 90 minutes of machine time. A custom-made protective cladding layer consisting of glue laminated larch wood is added on the outside. This also includes the application of a transparent and durable inorganic coating, which protects the wood from UV radiation and fungi attack. Instead of ripping and turning silver-grey when exposed to outdoor weathering, the larch wood will take on an even white color over time.

The entire process chain, from cutting regional logs in the sawmill to the production of the self-shaping panels, the drying process and final machining and pre-assembly takes place within the same group of companies and at the same location. This not only allows for sustainable and innovative production, but it also shows, how the self-shaping manufacturing can seamlessly integrate in established industrial wood processing and manufacturing workflows.

Thin-shell high-performance timber structure

The Urbach Tower consists of 12 curved components made from cross-laminated timber. The tower’s load-bearing structure exhibits a thickness of 90mm while cantilevering over 14 meters resulting in a span to thickness ration of approximately 160/1. The inherent curvature enables a highly slender and lightweight tower structure of only 38 kg per square meter surface area. In the assembled state, the tower acts as a surface-active structure through its expressive curved geometry. The lightweight building elements are connected by crossing screws, the arrangement and specific angle of which is optimised throughout the structure in relation to their utilization while preserving a continuous connection along the seam for homogeneous load transfers.

The prefabricated assembly groups of the tower, each consisting of three curved components, were assembled in a single working day by a team of four craftsmen without the requirement of extensive scaffolding or formwork, and topped-off by a transparent roof. The structure showcases the possibilities for efficient, economical, ecological and expressive wood architecture that arises at the intersection of master craft, digital innovation and scientific research.

Unique architectural landmark for the Rems Valley

The Urbach Tower is one of 16 stations designed by some of the most renowned German architects for the Remstal Gartenschau 2019. The stations are small, permanent buildings that evoke the traditional white chapels distributed in the fields and vineyards along the scenic Rems Valley. Located on a prominent hillside in the center of the valley, the 14 m tall tower is a striking landmark that visually connects several stations. It provides a place of shelter, internal reflection and outward view by revealing stunning vistas and framing the landscape. The distinctive form of the tower constitutes a truly contemporary architectural expression of the traditional construction material wood. It celebrates the innate and natural characteristics of self-shaped wood in its upwards spiraling shape.

The concave curvature of the structure on the outside results in sharp lines and crisp surfaces, which is further accentuated by direct day light and whitening of the larch cladding over time. In contrast, on the interior the convex curvature creates an unexpected visual and tactile material experience, with the timber structure appearing to be almost soft and textile-like, highlighted by the light washing the gently undulating surfaces. Opposite the entrance, the thin wood envelope opens like curtain, putting the Rems Valley on center stage.

Project Team:

ICD – Institute for Computational Design and Construction, University of Stuttgart
Prof. Achim Menges, Dylan Wood
Architectural Design
Self-forming Curved Wooden Components Research and Development

ITKE – Institute of Building Structures and Structural Design, University of Stuttgart
Prof. Jan Knippers, Lotte Aldinger, Simon Bechert
Structural Design and Engineering

Scientific collaboration:

Laboratory of Cellulose and Wood Materials, Empa (Swiss Federal Laboratories for Materials Science and Technology), Switzerland & Wood Materials Science, ETH Zurich (Swiss Federal Institute of Technology Zurich)
Dr. Markus Rüggeberg, Philippe Grönquist, Prof. Ingo Burgert
Self-forming Curved Wooden Components Research and Development (PI)

Industry collaboration:

Blumer-Lehmann AG, Gossau, Switzerland
Katharina Lehmann, David Riggenbach
Self-forming Curved Wooden Components Research and Development,
Wood Manufacturing and Construction

Project Support

Gemeinde Urbach

Remstal Gartenschau 2019 GmbH

German Federal Environmental Foundation
Design, Fabrication and Engineering Methods for the application of curved wood elements in high-performance, resource-efficient wood construction: Project Tower Urbach, Remstal Gartenschau 2019

Innosuisse – Swiss Innovation Agency
Smart, Innovative Manufacturing of Curved Wooden Components for Architecture with Complex Geometry

Carlisle Construction Materials GmbH
Scanntronik Mugrauer GmbH

Project Data

Dimensions
・14.20 m tall timber structure
・4.0 m radius bottom, 3.0m radius top, 1.6m radius middle
・Spruce Wood CLT with 10-30-10-30-10 build up
・Larche Wood façade with titanium oxide surface treatment
・5 axis CNC cut components
・12 individual prefabricated components pre-assembled in groups of 3
・Crossing screw connection detail with wood alignment blocks
・8 Sensors to monitor internal WMC of the structure

Construction System
Curved surface active tower structure, self-shaped curved cross laminated spruce timber (CLT) 10 -30-10-30-10 layup, glue laminated Larch façade with titanium oxide UV protection surface treatment, curved polycarbonate roof with steel support structure.

Quotes from Project Partners

Prof. Achim Menges, Dylan Wood
ICD – Institute for Computational Design and Construction

“Computational design and simulation enables us to work with the material and to unfold specific form from it, rather than forcing it into shape.”

“Wood can be programmed to take a specific shape. While making this work is relatively simple, predicting the outcome is the real challenge. Being able to do so opens up many new architectural possibilities.”

“The self-shaping manufacturing technology highlights how advanced understand and computational models of even the most well-known materials can lead to innovative and sustainable building processes.”

Prof. Jan Knippers, Lotte Aldinger, Simon Bechert
ITKE Institute of Building Structures and Structural Design

“The structure is more than 14 m high, only 9 cm thick and with no visible details: What looks simple is difficult to achieve and only possible through an ingenious interplay of form and force.”

Dr. Markus Rüggeberg, Philippe Grönquist, Prof. Ingo Burgert
Laboratory of Cellulose and Wood Materials, Empa (Swiss Federal Laboratories for Materials Science and Technology)

“We are proud to have developed the world’s largest self-shaping elements, by an elaborate use sustainable material wood. The unique tower design highlights the complex shapes enabled by this new manufacturing principle.”

“The ability to predict and even design the shape shifting patterns in large wood bilayers opens entirely new application of wood as building material, ranging from self-shaping entire building components to meter sizes high stiffness passive actuators for building facades, all with a highly sustainable natural material.”

Katharina Lehmann, David Riggenbach
Lehmann Group / Blumer Lehmann AG

“The project is an outstanding example of the interaction between technology, research, architectural ambitions as well as practical skills and of know how. From an industry perspective the self-shaping manufacturing highlights the incredible intelligence of wood as a material. It is always surprising to see there is more to learn from a material we have worked with for generations.”

“The research in shelf-shaping manufacturing adds an entirely new dimension to timber! While we consider ourselves experts in timber construction, taking on innovative projects like this are inspiring and at the same time show us there are endless potentials for wood as building material”.

“While machining and processing are a cornerstone of the wood industry, the self-shaping technology highlights how advanced knowledge and understanding of the material can lead to truly inspiring timber architecture.”

「Urbach Tower」University of Stuttgart ICD 公式サイト

https://www.icd.uni-stuttgart.de/projects/remstal-gartenschau-2019-urbach-turm/