
The Airshell Prototype
This paper by Alessandro Liuti, Sofia Colabella, and Alberto Pugnale, presents the construction of Airshell, a small timber gridshell prototype erected by employing a pneumatic formwork.
UNDULATUS: design and fabrication of a self-interlocking modular shell structure based on curved-line folding
Curved-line folding is the act of folding a flat sheet of material along a curved crease pattern in order to create a three-dimensional shape. It is a creative and innovative way to produce lightweight and geometrically stiff components using only sheet materials.
The pavilion presented in this paper integrates this principle in a kit-of-parts system. After being cut out of flat plates, the components get their 3D shape by folding them along a set of predefined curved lines.
This deformed geometry, variable in its degree of bending, results in a structurally efficient ‘building block’ that can be combined into different structural configurations depending on its mode of assembly. The components form a weave pattern by connecting them ‘flap to leg’ respectively.
As such, adjacent components lock each other into their rigid three-dimensional configuration and a modular shell structure is obtained. When composed of identical components, the obtained structure combines the advantages of rapid fabrication and assembly with an extensive reuse of components.
However, the pavilion demonstrates that more geometrically and aesthetically challenging compositions, consisting of a series of custom-made components, are also possible and manageable when using digital fabrication techniques.
Furthermore, this paper presents and discusses the digital modelling methods used for the design of the pavilion, as well as the lessons learned by real scale fabrication and assembly.
Curved-line folding is the act of folding a sheet of paper along a pattern of curved creases in order to create a three-dimensional shape. It is a transformation process that combines elastic bending of the sheet through folding of the curved creases.
Many artists used this technique to create beautiful and inspiring sculptures out of paper, like the artwork of David Huffman, Ronald Resch, Richard Sweeney or Corneel Cannaerts.
Although these paper sculptures have a very elegant and humble look, the geometric complexity behind it should not be underestimated and many studies have been carried out to get a better understanding of the geometric nature of curved-line folding, Duncan and Duncan, Fuchs and Tabachnikov.
Furthermore, the complexity of the material-dependent transformation process makes the precise digital modelling of objects based on curved-line folding a real challenge. Nevertheless, the authors of this paper saw great potential in this technique and used it as an inspiration for the design of an innovative structural research pavilion.
In order to comply with the requirements of compact transportation, easy and quick assembly and re-use of all structural parts, the pavilion combines the principle of curved-line folding with a kit-of-parts system. Starting from a flat and compact state during transportation, each component is bent and folded into its three-dimensional configuration.
By mutually connecting the components ‘flap to leg’ respectively, the components form a weave pattern and are locked into their 3D shape forming a bending-active shell structure.
The result is a suspended lightweight cloud-like pavilion with a strong resemblance to the Undulatus Asperatus cloud formation, hence the name of the pavilion. This paper discusses the design and fabrication of the Undulatus pavilion with a specific focus on the digital geometric and parametric modelling and the detailing and assembly of the real scale structure.
The Undulatus research pavilion demonstrates how curved-line folding can be used as a technique to design a very mobile and easily demountable bending-active shell structure.
The pavilion consists in its compact state of 99 flat-folded components that all fit in a box of 45x50x40 cm. Due to the easy-tohandle, reversible connections the system has the advantage of high speed of assembly (about 2,5 hours), low weight (less than 30 kg), demountability and reuse of its components.
Although the digital model did not take into account material properties, it proved to be very valuable to explore a wide range of geometrical designs in an efficient and interactive manner. By observing small scale models the input parameters for the digital model were optimized to correspond better to reality.
Since the shape of the final structure corresponds very well with the digital one, it can be concluded that this approach was a success. Of course, in order to gain more insight in the structural behaviour of the shell structure a FEM-analysis should be performed.
This paper by Alessandro Liuti, Sofia Colabella, and Alberto Pugnale, presents the construction of Airshell, a small timber gridshell prototype erected by employing a pneumatic formwork.
In this paper by Gregory Charles Quinn, Chris J K Williams, and Christoph Gengnagel, a detailed comparison is carried out between established as well as novel erection methods for strained grid shells by means of FE simulations and a 3D-scanned scaled physical model in order to evaluate key performance criteria such as bending stresses during erection and the distance between shell nodes and their spatial target geometry.
In this paper by Frederic Tayeb, Olivier Baverel, Jean-François Caron, Lionel du Peloux, ductility aspects of a light-weight composite gridshell are developed.
In this paper by Julian Lienhard, Holger Alpermann, Christoph Gengnagel and Jan Knippers structures that actively use bending as a self forming process are reviewed.
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