The BIC Structure
Exhibited during the IASS 2015 symposium at the Muziekgebouw in Amsterdam, the BIC structure is a continuous hybrid form-found structure made out of 10 000 BIC Cristal pens.
The BIC structure has been presented as a structural installation for the IASS (International Association for Shell and Spatial Structures) 2015 symposium. It is made out of 10 000 BIC Cristal pens that are a living symbol of the 1950’ industrial era of consumable engineering. 100 billion pens have been sold since then and half a century later, it is still a mythical pen, affordable, practical and durable. Its tungsten ball point is worth 2km of writing. It is pointless to precise the pen is often lost before anyone can see its ink empty.
The BIC Cristal pen was used in this structurally hybrid project as a structural element. The hexagonal section of the pen, ergonomically designed, reflects light in a particular way that gives to the entire structure an unprecedented texture. The project questions, on a wider viewpoint, the capacity of architecture and engineering to use elements for purposes that were not initially foreseen. It explores the ability of architects and engineers to adapt their process of thinking to use unexpected materials to create, in this case, a hybrid continuous form-found suspended structure.
FORM-FINDING AND STRUCTURAL BEHAVIOR OF A HYBRID STRUCTURE
The goal of form-finding is to identify a geometry in static equilibrium with a given set of design loads [1]. The particle-spring method allows rapid and parameter-depending form explorations [2] [3]. It also gives a qualitative understanding of structural behavior [4]. This objective is achieved by defining particles, with masses, on which loads are applied, and strings with specified stiffnesses and lengths [3] [1] [5]. The overall procedure attempts to equalize the sum of all forces in the system [3].
The structure includes three parts that are defined differently in a single particle-spring model . The initial model includes a rectangular mesh supported on a number of points near its four corners. The central part and the hanging part are defined similarly. The only difference is the direction of applied design loads. With applied loads upwards, the central part takes the shape of a “perfect” compression vault. On the other hand, with applied loads downwards, the hanging part is a cable net working in tension. Elements in these parts sustain thus only axial loads. In contrary, the intermediate part is designed considering the bending stiffness of the elements through the definition of splines [6] [7]. In this study, bending is introduced by trying to keep each three consecutive particles in a straight line.
During the form finding process, the values of numerical quantities (e.g. axial and bending stiffness) are arbitrary since it is only their ratios that affect the equilibrium shape. However, for analysis purposes material properties and element dimensions were defined with collaboration with BIC and are given in the table below.
The BIC pavilion is thus a suspended pavilion designed as a crossing between a hanging model and a vault with the introduction of an intermediate spline network. The outer part of the structure works only in tension while the central part works only in compression. As a result the intermediate part is designed to sustain bending as transition between these two pure structural systems.
GEOMETRY
The mesh geometry of the form-found shape is modified, generating a triangular mesh made of equal BIC-Cristal-length segments. Two algorithms are implemented. The first is a customized compass method [8] [9] [10] [11] [12] [13] . The second uses a spring relaxation method to optimize the segment lengths in the generated mesh [5] [14] [15] [16] .
Compass method
The compass method, first proposed by Frei Otto [12] is a geometric method consisting of tracing a grid with equilateral meshes on a target surface. Two arbitrary curves on the surface are chosen having a common intersection point. These two main curves are then divided. The division points are centers of circles that intersect each other. The resulting rose pattern generates an equilateral mesh.
In the proposed case, the final mesh geometry is the result of an iterative looping algorithm. To simplify fabrication and construction, the implemented algorithm attempts to approximate the initial surface with a new grid composed of identical equilateral triangular modules.
As the algorithm loops, a rose geometric pattern is created on the whole initial surface, creating a network of equidistant points.
By linking resulting intersection points a new mesh is generated.
STRUCTURAL ANALYSIS
Elements in the outer and central part sustain only tensile and compressive stresses, respectively. Due to the overall bending action on the middle part elements sustain either tensile or compressive axial stresses depending on their topology. As expected, and due to its extremely light weight, forces in the structure remain always lower than the estimated element yield strength (70 N/mm2). The maximal compression stress value reaches 1% of the yield strength while the maximal tension value reaches 0.7% of the yield strength.
Project by:
AAU ANASTAS
Landolf Rhode-Barbarigos, The University of Miami.
Yann Santerre.
Design team:
Yousef Anastas, Elias Anastas,
Yann Santerre, Landolf Rhode Barbarigos,
Tim Michiels, Victor Charpentier.
Fabrication team:
Margaux Gillet, Yousef Anastas,
Elias Anastas, Yann Santerre.
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