Component-Based Adaptive Shell Structure Haruna Okawa, Keio University http://harunaokawa.com/
Abstract Shell structures have a long lineage. At the beginning of architectural history shell structures were made from bricks that interlocked with their own weight. Later, structures made from concrete and lattices were explored, as can be seen in the work of Félix Candela and Frei Otto. These were created through a process that is time-consuming and labor-intensive with many waste materials left over at the end. Searching for an alternative method, this research aims to connect shell design with non-linear construction techniques, making use of a rapid prototyping process based on computational design and digital fabrication. It uses components whose movement is restrained to a certain range and attempts to simulate the structural state in order to confirm the forms will not collapse, partially, or as a whole. The resulting work is shown here. The self-standing shell was assembled using composite boards created from aluminum sheets attached to urethane boards. 34 individual components interact with each other to create a three-dimensional shell when force was applied to the system. In future development of the model, more accurate collision detection system between each of the individual parts and their adjacent members will be implemented and new fabrication process will be explored. Keywords: shell structure, non-linear construction, aggregate architecture, collision simulation Fig.1 Closeup view of the pavilion
1. Introduction-The Scaffold Problem and Non-Linear Assembly Shell-structured buildings have been explored by many architects and structural engineers, each of them constructed in a different way. For example, L’ Oceanogràfic (2003), designed by Félix Candela used a wooden mould to cast its concrete shell. Although this method is popular for concrete shell construction it leaves a lot of waste once the concrete is cured and the formwork is removed. Another example, Mannheim Multihalle(1974) by Frei Otto is more efficient because it does not require a formwork. Instead a wooden lattice was built on the ground and the application of specific pressure to the total form created a complex three-dimensional curve. However, its formal transformation depended on the application of stress on the structure, making the material structurally weaker. These works are traditional examples of static shell structures. By looking at the relationship between the shell design and its construction method, a critical point is noticed in the transformation strategy that turns a 2D shape to one that is three dimensional. Thus, this research explores the development of an adaptable non-static shell structure utilizing advances in computational design and digital fabrication technology. The goal is to overcome the issues inherent in the traditional examples,
Fig.2 Construction Process of L’ Oceanogràfic
Fig.3 Construction Process of Mannheim Multihalle
namely that the creation process weakens the materials, and that the need for an intermediate support structure can be wasteful.
(Garlock and Billington 2008, 149)
(Nerdinger 2005, 287)
2. Concept-A Pop-up Shell, Self-Optimized Shape
5. Results and Feedbacks-Lightness vs Hardness
The idea is to create a Pop-up Shell that can appear and disappear in a relatively short time. The pop-up process consists of three steps:
The self-supported shell is composed of 34 individual pieces. The simulation was
(1) Transport, (2) Placement, and (3) Stressing. Firstly, the units are stacked and transported to the site. There, they are placed to form a
useful as a tool during the design process, giving an indication of the final shape of
hexagonal grid. By adding pressure, it will eventually pop-up and form a self-optimized shell structure. The significance of this outcome is
the shell structure. As a responsive system, changes made to the surface and the
in the non-linear shell-forming process that takes place in the final stage. Components can go through three different structural modes:
components revealed different shapes. Criteria that had significant impact included the
flat, tensioned, and pressured. The method is non-linear in that the shape does not form slowly as forces are applied, but rather takes
placement of the components, changes in the shape of the initial surface, as well as
place suddenly after a threshold is reached. When combined together, it behaves like a cloth.Yet, thanks to the component system, the
the direction and amount of anchor points. In scaling up the shape, the lightness and
number of components can be incremental and literally infinite variations in shape is available.
hardness of the material were crucial elements and the urethane sheet was found to perform best in terms of rigidity and strength. The precision of fabrication and gap
(1)Transportation of the Units
(3)Stressing
(2)Hexagonal-Grid-Based Placement
between the individual components were key factors to take note of in the built model as they defined how smoothly the components moved and how strongly the friction
>>
connection worked to maintain the final shape under real-world conditions.
>> Fig.4 Workflow of Pop-up Shell
(a) Flat
(b) Tensioned
(c) Pressured Fig.5 Three Types of Structural State
3. Component Design and Simulation -Surface Morphology, Hex Block with Three Legs The component is a hexagon with three legs attached. Each component can be connected to six adjacent parts with ribs that prevent them from separating. As an
Fig.11 Completed Work
aggregate it can move as a cloth, and under the right conditions it becomes a shell
6. Future Development-Accurate Simulation, Integrated Fabrication
structure. In the pseudo-simulation, the aggregate of hexagonal units is replaced by
The simulation process be improved in the next stage of this research. Instead of
a single surface (and in this way is not a full simulation). The surface is transformed
regarding the body as a single surface, collisions between multiple three dimensional
to simulate the physical form making process. Its four corners are set as anchor
objects will be detected as force is applied. In this way the structural transition process
points which give the surface a three dimensional form when moved. The centroids
and stress lines can be simulated more precisely. This will also enable structural
of each unit are located on this surface and move as the surface is transformed.
sophistication of the component. Also, better fabbication methodology should be explored
The height and overall shape correspond with the distance the anchor points have
as there is inevitable inefficiencies of nesting irregular shapes on flat sheets for CNC
moved. Finally, the surface is evaluated at each point and normal vectors are
cutting. Possible solutions include but not limited to create frames, inflatable baloons, and
acquired. Following the position of the points and direction of the vectors, the
so on by hand, 3d printer, moulding, et cetera.
components are placed, creating a shell shape based on the simulation. Depending on the length of the legs, the stretch of the surface is ditermined.
Fig.6 Pseudo Simulation
Fig.7 Interaction between the Components Fig.12 Possible Form of the Component
7. Conclusion-Adaptive Shell
4. Materialization-CNC-milling, Folded Urethane Sheet Several scale models were made before the full-scale shell was built in order to test fabrication methods and to explore the effect of changed
The chained block structural system enabled the creation of an adaptive shell that moves
parameters of the individual components, including materiality and connecting details. The final material used to build the 1:1 scale model is a
between different structural state. The range of each component’ s movement is controlled
hard urethane sheet (Achilles Board ALN/PE Non-CFC), with an aluminum sheet bonded to its top surface and waterproof paper on its bottom.
by multiple parameters such as length of the legs and height of the component. The
A sheet is 910mm by 1820 mm and 15mm thick. In this case 10 sheets were used to make the model. In terms of fabrication, the shapes were
allowance of this movement resulted in flexibility in form. By increasing the accuracy of the
cut with Shopbot and each piece then folded manually. Usually, hard urethane cannot be folded because it will easily crack, however the
simulation and exploring new ways of fabrication, further development in the shape is
addition of aluminum to the front face resolves this issue, so that a folded structure could be produced.
expected. This will allow to get feedbacks and reflect them in deisign more frequently.
(1) Cutting
(2) Folding
(3) Glueing
(3) Combining Component Design
Components Formation
Simulation
Fabrication
Fig.13 Ideal Process of Design and Fabrication References Garlock, Maria E. Moreyra., and Billington, David P. 2008. Félix Candela : engineer, builder, structural artist. Princeton, N.J. : Princeton University Art Museum ; New Haven : Yale University Press Fig.8 Scale Model Printed by Projet4500
Fig.9 Achilles Board Processed by Shopbot
Fig.10 Fabrication Process of the Component
Nerdinger, Winfried. 2005. Frei Otto : complete works : lightweight construction natural design. Basel : Birkhäuser