Mass Imperfections

Palestinian architects Elias and Yousef Anastas of AAU Anastas have recently completed a structure composed of hand-made olive wood modules. The piece draws inspiration from traditional embroidery techniques and is a reaction to the mass production of “holy” sculptures within the Palestinian souvenir industry. The structure was presented at the Dubai Design Week 2016 in October. Karamba was implemented as a tool to analyze the structural performance of the piece.

Text from Architects:

The process of fabrication of olive-wood objects in Bethlehem calls high-tech mass customization into question. Mass imperfections is a project that experiments the potential of artisanal fabrication for the construction of large-scale structures. The project experiments the ability of craftsmanship of stepping back into the forefront of the fabrication processes.Mass imperfections challenges high tech fabrication processes by monitoring and anticipating imperfections of highly skilled artisans.

The structure’s global shape is a 3m high arch made out of olive-wood pieces that are 1cm thick. The structure is made out of 552 mutually supported olive wood pieces that are small with respect to the entire structure. Each olive-wood panel has six vertices, three of which are supported by three neighboring panels while the remaining three support three other neighboring panels. In that sense, the structure is reciprocal; each panel plays an equivalent structural and topological role in the overall stability of the structure.

The global shape of the structure has been determined according to a process of design at the opposite end of the planning spectrum, from the bottom up. After several experimentations of faithfulness of an artisanal fabrication to a designed complex-shaped geometry, the level of imperfections has determined the family of possible panels and consequently potential global forms. The understanding and monitoring of imperfections helped merge into the deep understanding of local know-hows, and capacities of widening or subverting the initial end result to new uses.

Olive wood has the particularity of being issued of branches thus avoiding the uprooting of the entire tree. The collected wood is of relatively small dimensions initially soaked with oil and water. Before it is ready for use, the wood is dried in hangars protected from exterior climatic conditions for several years. Once the wood is dry, it usually has a volumetric mass varying between 800 kg/m3 and 990 kg/m3. For the purpose of this project physical tests were held on dry olive wood in order to input our Finite Element Analysis (FEA) with the correct material properties:

density = 0.92
modulus of rupture (Mpa) = 120
Compressive strength (MPa) = 90
Tensile strength (MPa) = 77

The first concern of the structural analysis was to ensure the stresses in the panels were not exceeding the strength of the material, while our second concern involved the global buckling of the arch given itsslenderness. The panels were defined as shell elements while their connections were free to rotate along the axis of connection.
The following diagrams show the values of axial stress in the structure and the displacement values. Although the thickness of panels is 1cm, their curved shape and the interlocking arrangement of the structure’s modules gives a 2cm structural thickness.