Exo McCloskey, Ochando, Santelli. 12 January, 2015
Natural Systems and Biomimetics Emergent Technologies and Design, Architectural Association
Exo / Introduction
The arthropod exoskeleton is of interest to architecture as a spatial structure: It is lightweight while protecting the arthropod from the surrounding environment and defining its volume. Most importantly, as it covers an entire body, the material and distribution logic requires the formation of both solid and mobile elements within a contiguous surface.
RESEARCH In order to exploit the variable stiffness logic and capacity of arthropod exoskeletons, the basic construction principles and low-level components are defined. More specifically, lobster cuticles differ from other arthropods’ in that within the characteristic structures of interconnected fibers, their pores create planar honeycomb-like structures that add additional stiffness displayed as thinner shells. ANALYSIS The ‘twisted plywood’ principle or Bouligand pattern principle is abstracted as a linear series of interconnected fibers. The exploration is carried out computationally and fabricated with interlocking strips of polypropylene material. By varying the distribution density of material and angles of intersection, it is possible to create an array of different components with the same overall geometry, but with varying degrees of stiffness and deformation behaviors. SYSTEM DEVELOPMENT Having established local relationships between material distribution and deformation capacity, it is possible to apply the system logic to a substrate geometry. The host surface chosen was modeled after the 1960s Panton chair, as the applied forces are easily calibrated in a computational model at this manageable scale. Learning from the observable differences in behavior with local variation, it is then possible to move towards the scale of a habitable surface/volume.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
Contents Introduction �������������������������������������������������������������������������������������������������������������������������������������� 2 Bouligand Structures ���������������������������������������������������������������������������������������������������������������������4 Cellular Structures �������������������������������������������������������������������������������������������������������������������������� 6 Calibration ����������������������������������������������������������������������������������������������������������������������������������������� 8 Computational Analysis / Setup �������������������������������������������������������������������������������������������� 10 Computational Analysis / Point Loads Parallel to X �������������������������������������������������������� 12 Computational Analysis / Point Loads Parallel to Y �������������������������������������������������������� 16 Computational Analysis / Point Loads Parallel to Z �������������������������������������������������������� 20 Computational Analysis / Bending Moments About Y �������������������������������������������������� 24 Iterative Work Flow ��������������������������������������������������������������������������������������������������������������������� 28 Performance by Differentiation ���������������������������������������������������������������������������������������������� 30 Topological Differentiation / Test Controls ������������������������������������������������������������������������ 32 Topological Differentiation / Minimal Structure ��������������������������������������������������������������� 34 Topological Differentiation / Variable Stiffness ���������������������������������������������������������������� 36 Potential Applications ���������������������������������������������������������������������������������������������������������������� 38 Opportunities and Further Development ���������������������������������������������������������������������������� 40
Natural Systems and Biomimetics Emergent Technologies and Design, Architectural Association
2|3
Exo / Bouligand Structures
EPICUTICLE
EXOCUTICLE
ENDOCUTICLE
Lobster shell photograph.
MATERIAL VARIATION
As a large arthropod, or “jointlimb animal,” the exoskeleton consists of a single material, which allows a large variety of local behaviors along the body of the animal. In this image, the shell structure varies from a rigid shell, to a soft joinery, to another shell.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
Cross section of the lobster cuticle.1
Exocuticle view. 2.
CELLULAR BEHAVIOR
STRUCTURE BY LAYERING
The shell microstructure is differentiated into an epicuticle, exocuticle, and endocuticleeach with observably different densities.1As in other biological applications, their fibers form stacked layers. A high stacking density is encountered in the exocuticle, making this layer rigid as compared to the endocuticle.
Image adapted from P. Romano, H. Fabritius, D. Raabe. ‘The exoskeleton of the lobster Homarus americanus as an example of a smart anisotropic biological material’. Max Planck Institute.
The lobster shell is of interest because its chitin fibers are not aligned in a parallel fashion, but in a seemingly hexagonal pattern. It can be considered a cellular solid based on regular microstructures, forming flat honeycomb arrays. The ratio of segment wall thickness, t, and the segment length, l, changes between the endocuticle and exocuticle layers.1
D. Raabe, C. Sachs. ‘Mechanical Properties of the Lobster Cuticle’. Max Planck Institute.
1
BOULIGAND STRUCTURE
A stack of layers that has rotated 180 degrees is referred to as a Bouligand structure. Assuming chitin fibers as the unit of construction of the Lobster shell, layers of these fibers are arranged within a Bouligand structure. As chitin fibers are gradually rotated in layers, the shell structure acquires its overall rigidity. An exocuticle (see previous page) has observably shorter and longer Bouligand structures. As in exocuticles, the finer the arrangement and the more perpendicular is a layer to the next one (i.e., the shorter the Bouligand), the more rigid the structure. Conversely, the coarser Bouligand structure, as the encountered in the endocuticle, the less stiff the structure is.
Natural Systems and Biomimetics Emergent Technologies and Design, Architectural Association
4|5
Exo / Cellular Structures
LINEAR INTERPRETATION
Bearing in mind the implied hexagonal cellular structures, the lobster’s shell can be abstracted as layers of strips with mirrored curvature patterns. A defined surface is subdivided into points. A weaving pattern allows the interconnection of fiber elements. Two opposing curvatures are distributed along the same direction. These fibers, or material strips, are then layered and rotated above each other for structural redundancy and fixing geometry into shape. Rather than building a planar hexagonal grid, the capacity for layering was introduced by a linear interlocking.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
INDUCED FLEXIBILITY
INDUCED RIGIDITY
0° Layer Rotation
90° Layer Rotation
Additionally, in order to develop the system as a calibratable design tool, it was decided that the aim was to modulate ‘fiber’ intersections for control as opposed to merely adding more layers for rigidity. The material system is then an idea about fabrication according to predetermined intersections. By increasing the angle of rotation between layers, flexibility and rigidity can be locally incorporated. As in exocuticles, the shorter the Bouligand, the more perpendicular fibers are to each other, and therefore the more rigid the structure.
Natural Systems and Biomimetics Emergent Technologies and Design, Architectural Association
6|7
Exo / Calibration
Physical models were used to understand the behavior of the mirrored curvature assembly. These outcomes were essential to calibrating the digital models accordingly. In a series of experiments, it was anchored on one edge as a cantilever. By applying moments about the longidtudinal axis of the sample, the out-of-plane deformation was proven. For in-plane deformation, the piece was loaded either longidtudinally or transversally from the free edge. It was discovered that the strips behave as beams, which acquire stability and stiffness due to the wavy shape. The points of intersection act as constraints.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
PHYSICAL MODEL
DIGITAL MODEL
To model this behavior digitally, the strips are defined as beams. The connection between strips is a significant difference between the physical and the digital models. In the physical model two strips were connected by inserting the slots on the edges. In computational models it is converted into a constrain point which locks the displacement (i.e. no rotation and no translation) between these two strips in that point. This exploration on connections will be one of the further developments to be carried out in this project.
Natural Systems and Biomimetics Emergent Technologies and Design, Architectural Association
8|9
Exo / Computational Analysis / Setup DENSITY OF STRIPS
as modeled on a 30cm x 30cm panel
4 Strips 5 Subdivisions
4 Strips 10 Subdivisions
4 Strips 15 Subdivisions
8 Strips 5 Subdivisions
8 Strips 10 Subdivisions
8 Strips 15 Subdivisions
12 Strips 5 Subdivisions
12 Strips 10 Subdivisions
12 Strips 15 Subdivisions
By varying the distribution density of material and angles of intersection, it is possible to create an array of different components with the same overall geometry (30 cm x 30 cm square), but with varying degrees of stiffness and deformation behaviors. The density of strips can be predetermined by (1) the amount of strips in one direction, as much as (2) the amount of subdivisions, or intersections in a given area.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
LAYER ROTATIONS
REDISTRIBUTION OF INTERSECTIONS as modeled on a 30 cm x 30 cm panel
0°
15°
Rotation of intersection angles by incrementation of distance between ‘fibers’
30°
45°
Shortening segment length away from point loads
60°
75°
90°
Increasing segment length for flexibility away from p loads
One particular sample is then selected from the group to study the effects of layer rotation. The selected sample is defined by 12 strips at 10 subdivisions within a 30 cm x 30 cm square. As this ‘exoskeleton’ is defined as a contiguous surface, another effect to study is the redistribution of intersections that creates regional differentiation of rigid and mobile zones along the global ‘shell’ form: relative variation in intersection angle and segment lengths.
Natural Systems and Biomimetics 10 | 11 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to x SETTINGS OF THE DIGITAL TESTS
Tx, Ty, Tz = 0
Px
Rx, Ry, Rz = 0
Px
Px
1m
1m
y
z x
AIM OF THE TEST Analysis of the properties of the material system in the direction parallel to x and comparison among the different kinds of patterns. MATERIAL PROPERTIES Material: Polypropylene1 Specific weight: 9 kN/m3 Elastic modulus: 1,5 GPa Poisson’s ratio: 0,3 Height of the strips: 10 cm Thickness of the strips: 1 mm LOADS AND RESTRAINTS Loads: Px= 10 N2 Restraints: translations and rotations locked. DIGITAL TESTS Software: CSI Sap2000®
1. www.ing.unipi.it/materiali/caratteritiche (8 December 2014, 10.30 am). 2. The value of loads is chosen in according to the dimension of the patterns and to have the possibility to compare them.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Ux max1 = 37 mm Deformation capacity2 parallel to x Rotation: 0°
0
37 mm
Maximum displacement Ux max = 45 mm Deformation capacity parallel to x Rotation: 15°
0
45 mm
Maximum displacement Ux max = 60 mm Deformation capacity parallel to x Rotation: 30°
0
60 mm
Maximum displacement Ux max = 64 mm Deformation capacity parallel to x Rotation: 45°
0
64 mm
Maximum displacement Ux max = 27 mm Deformation capacity parallel to x Rotation: 90°
0
27 mm
1. U max: maximum displacement observed. 2. Measure of the deformation capacity in a scale from 1 to 7 (1 equal to 0 mm and 7 more than 350 mm).
Natural Systems and Biomimetics 12 | 13 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to x DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Ux max = 8 mm Deformation capacity parallel to x Rotation: 0°
0
8 mm
Maximum displacement Ux max = 20 mm Deformation capacity parallel to x Rotation: 15°
0
20 mm
Maximum displacement Ux max = 52 mm Deformation capacity parallel to x Rotation: 30°
0
52 mm
Maximum displacement Ux max = 52 mm Deformation capacity parallel to x Rotation: 45°
0
52 mm
Maximum displacement Ux max = 48 mm Deformation capacity parallel to x Rotation: 90°
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
0
48 mm
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Ux max = 29 mm Deformation capacity parallel to x Gradient: direction parallel to y
0
29 mm
Maximum displacement Ux max = 91 mm Deformation capacity parallel to x Gradient: direction parallel to x
0
91 mm
Maximum displacement Ux max = 46 mm Deformation capacity parallel to x Gradient: directions parallel to x and y
0
46 mm
Maximum displacement Ux max = 22 mm Deformation capacity parallel to x Mixed pattern 1
0
22 mm
Maximum displacement Ux max = 50 mm Deformation capacity parallel to x Mixed pattern 2
0
50 mm
Natural Systems and Biomimetics 14 | 15 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to y SETTINGS OF THE DIGITAL TESTS
Tx, Ty, Tz = 0
Py
Rx, Ry, Rz = 0
Py
Py
1m
1m
y
z x
AIM OF THE TEST Study of the properties of the material system in the direction parallel to y and comparison among the different kinds of patterns; in order to understand its deformation capacity. MATERIAL PROPERTIES Material: Polypropylene1 Specific weight: 9 kN/m3 Elastic modulus: 1,5 GPa Poisson’s ratio: 0,3 Height of the strips: 10 cm Thickness of the strips: 1 mm LOADS AND RESTRAINTS Loads: Py= 10 N Restraints: translations and rotations locked. DIGITAL TESTS Software: CSI Sap2000® 1. www.ing.unipi.it/materiali/caratteritiche (8 December 2014, 10.30 am). 2. The value of loads is chosen in according to the dimension of the patterns and to have the possibility to compare them.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uy max1 = 117 mm Deformation capacity2 parallel to y Rotation: 0°
0
87 mm
Maximum displacement Uy max = 65 mm Deformation capacity parallel to y Rotation: 15°
0
65 mm
Maximum displacement Uy max = 364 mm Deformation capacity parallel to y Rotation: 30°
0
364 mm
Maximum displacement Uy max = 338 mm Deformation capacity parallel to y Rotation: 45°
0
338 mm
Maximum displacement Uy max = 154 mm Deformation capacity parallel to y Rotation: 90°
0
154 mm
1. U max: maximum displacement observed. 2. Measure of the deformation capacity in a scale from 1 to 7 (1 equal to 0 mm and 7 more than 350 mm).
Natural Systems and Biomimetics 16 | 17 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to y DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uy max = 37 mm Deformation capacity parallel to y Rotation: 0°
0
37 mm
Maximum displacement Uy max = 78 mm Deformation capacity parallel to y Rotation: 15°
0
78 mm
Maximum displacement Uy max = 130 mm Deformation capacity parallel to y Rotation: 30°
0
130 mm
Maximum displacement Uy max = 160 mm Deformation capacity parallel to y Rotation: 45°
0
160 mm
Maximum displacement Uy max = 336 mm Deformation capacity parallel to y Rotation: 90°
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
0
336 mm
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uy max = 46 mm Deformation capacity parallel to y Gradient: direction parallel to y
0
46 mm
Maximum displacement Uy max = 360 mm Deformation capacity parallel to y Gradient: direction parallel to x
0
360 mm
Maximum displacement Uy max = 52 mm Deformation capacity parallel to y Gradient: directions parallel to x and y
0
52 mm
Maximum displacement Uy max = 65 mm Deformation capacity parallel to y Mixed pattern 1
0
65 mm
Maximum displacement Uy max = 143 mm Deformation capacity parallel to y Mixed pattern 2
0
143 mm
Natural Systems and Biomimetics 18 | 19 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to z SETTINGS OF THE DIGITAL TESTS
Tx, Ty, Tz = 0 Rx, Ry, Rz = 0
Pz
Pz
Pz
1m
1m
y
z x
AIM OF THE TEST Analysis of the properties of the material system in the direction parallel to z in order to study its flexible properties and comparison among the different kinds of patterns. MATERIAL PROPERTIES Material: Polypropylene1 Specific weight: 9 kN/m3 Elastic modulus: 1,5 GPa Poisson’s ratio: 0,3 Height of the strips: 10 cm Thickness of the strips: 1 mm LOADS AND RESTRAINTS Loads: Pz= -1 N Restraints: translations and rotations locked. DIGITAL TESTS Software: CSI Sap2000®
1. www.ing.unipi.it/materiali/caratteritiche (8 December 2014, 10.30 am). 2. The value of loads is chosen in according to the dimension of the patterns and to have the possibility to compare them.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max1 = - 221 mm Flexibility2 direction parallel to z Rotation: 0°
-221
0 mm
Maximum displacement Uz max = - 86 mm Flexibility direction parallel to z Rotation: 15°
-86
0 mm
Maximum displacement Uz max = - 66 mm Flexibility direction parallel to z Rotation: 30°
-66
0 mm
Maximum displacement Uz max = - 65 mm Flexibility direction parallel to z Rotation: 45°
-65
0 mm
Maximum displacement Uz max = - 42 mm Flexibility direction parallel to z Rotation: 90°
-42
0 mm
1. U max: maximum displacement observed. 2. Measure of the flexibility in a scale from 1 to 7 (1 equal to 0 mm and 7 more than 700 mm).
Natural Systems and Biomimetics 20 | 21 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads parallel to z DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max = - 59 mm Flexibility direction parallel to z Rotation: 0°
-59
0 mm
Maximum displacement Uz max = - 91 mm Flexibility direction parallel to z Rotation: 15°
-91
0 mm
Maximum displacement Uz max = - 111 mm Flexibility direction parallel to z Rotation: 30°
-111
0 mm
Maximum displacement Uz max = - 205 mm Flexibility direction parallel to z Rotation: 45°
-205
0 mm
Maximum displacement Uz max = - 132 mm Flexibility direction parallel to z Rotation: 90°
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
-132
0 mm
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max = - 31 mm Flexibility direction parallel to z Gradient: direction parallel to y
-31
0 mm
Maximum displacement Uz max = - 884 mm Flexibility direction parallel to z Gradient: direction parallel to x
-884
0 mm
Maximum displacement Uz max = - 650 mm Flexibility direction parallel to z Gradient: directions parallel to x and y
-650
0 mm
Maximum displacement Uz max = - 34 mm Flexibility direction parallel to z Mixed pattern 1
-34
0 mm
Maximum displacement Uz max = - 221 mm Flexibility direction parallel to z Mixed pattern 2
-221
0 mm
Natural Systems and Biomimetics 22 | 23 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads: bending moments about y SETTINGS OF THE DIGITAL TESTS
Tx, Ty, Tz = 0
My
Rx, Ry, Rz = 0
My
My
1m
1m
y
z x
AIM OF THE TEST Analysis of the properties of the material system in the direction parallel to z and comparison among the different kinds of patterns. MATERIAL PROPERTIES Material: Polypropylene1 Specific weight: 9 kN/m3 Elastic modulus: 1,5 GPa Poisson’s ratio: 0,3 Height of the strips: 10 cm Thickness of the strips: 1 mm LOADS AND RESTRAINTS Loads: My= 1 N·m Restraints: translations and rotations locked. DIGITAL TESTS Software: CSI Sap2000®
1. www.ing.unipi.it/materiali/caratteritiche (8 December 2014, 10.30 am). 2. The value of loads is chosen in according to the dimension of the patterns and to have the possibility to compare them.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max1 = - 445 mm Flexibility2 direction parallel to z Rotation: 0°
-455
0 mm
Maximum displacement Uz max = - 180 mm Flexibility direction parallel to z Rotation: 15°
-180
0 mm
Maximum displacement Uz max = - 168 mm Flexibility direction parallel to z Rotation: 30°
-168
0 mm
Maximum displacement Uz max = - 143 mm Flexibility direction parallel to z Rotation: 45°
-143
0 mm
Maximum displacement Uz max = - 84 mm Flexibility direction parallel to z Rotation: 90°
-84
0 mm
1. U max: maximum displacement observed. 2. Measure of the flexibility in a scale from 1 to 7 (1 equal to 0 mm and 7 more than 700 mm).
Natural Systems and Biomimetics 24 | 25 Emergent Technologies and Design, Architectural Association
Exo / Computational Analysis / Point loads: bending moments about y DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max = - 117 mm Flexibility direction parallel to z x Rotation: 0°
-117
0 mm
Maximum displacement Uz max = - 156 mm Flexibility direction parallel to z Rotation: 15°
-156
0 mm
Maximum displacement Uz max = - 157 mm Flexibility direction parallel to z Rotation: 30°
-157
0 mm
Maximum displacement Uz max = - 390 mm Flexibility direction parallel to z Rotation: 45°
-390
0 mm
Maximum displacement Uz max = - 221 mm Flexibility direction parallel to z Rotation: 90°
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
-221
0 mm
DIGITAL TESTS Plans of Patterns
Displacement Analysis
Evaluations
Maximum displacement Uz max = - 52 mm Flexibility direction parallel to z Gradient: direction parallel to y
- 52
0 mm
Maximum displacement Uz max = - 1091 mm Flexibility direction parallel to z Gradient: direction parallel to x
-1091
0 mm
Maximum displacement Uz max = - 975 mm Flexibility direction parallel to z Gradient: directions parallel to x and y
-975
0 mm
Maximum displacement Uz max = - 42 mm Flexibility direction parallel to z Mixed pattern 1
-42
0 mm
Maximum displacement Uz max = - 390 mm Flexibility direction parallel to z Mixed pattern 2
-390
0 mm
Natural Systems and Biomimetics 26 | 27 Emergent Technologies and Design, Architectural Association
Exo / Iterative Work Flow
SURFACE VARIABLES
COMPUTATION
mesh subdivisions
variable surface
force flow
force reactions
host surface
loads
rigidity requirement
DESIGN INPUTS
INPUT SURFACE
3D MESH
APPLICATION OF LOADING
DISPLACEMENT ANALYSIS
In its current state, the interlocking system has been developed as a scaleable system, in which a predetermined surface is an input. This surface is turned into a digital mesh, that can then be loaded with forces. Its displacement is measured and the grid points on the mesh are manipulated accordingly. This structure is then interwoven and populated. The structural model as an output can then be an input for a fabrication process by laser cutting linear components or computer analysis as a feedback mechanism for the system.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
STRUCTURAL MODEL density differentiation
populated frame
DIGITAL MODEL
OUTPUT
digital export
computer analysis fabrication
GRID PINCH TOWARDS HIGH DISPLACEMENTS
WEAVING OF DIRECTIONAL FIBERS
EXTRUSION OF BEAM MEMBERS
THICKNESSES AND TOLERANCES
Initially, in order to test these ideas, the project used the 1960s Panton chair as a substrate surface at a manageable scale in which a single surface is differentated and has identifiable loads. As the property this project seeks to exploit is variable stiffness, this workflow is introduced as a way to better understand different density variation patterns in reaction to high displacement and to iterate accordingly.
Natural Systems and Biomimetics 28 | 29 Emergent Technologies and Design, Architectural Association
Exo / Performance by Differentiation
Notably, the regular grid demonstrated the least and homogenenous deformation upon loading. By densifying away from high displacement areas, most deformation occurs parallel to the orientation of the SAP2000areas, grain. By densifying near high displacement the surface deforms perpendicular to the grain.
REGULAR GRID
When tested against the Panton chair as a host surface, the same principle held true. Densification of the fiber pattern away from points of high displacement meant that the chair was largely deformed in such a way where its seat would lower and its back would push against the user. Conversely, adding material near areas of high displacement increased the capacity for the overall surface to deform where its sides would push into each other, i.e., folding onto the body of the user.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
DENSIFICATION AWAY FROM HIGH DISP.
DENSIFICATION NEAR HIGH DISPLACEMENT
Natural Systems and Biomimetics 30 | 31 Emergent Technologies and Design, Architectural Association
Exo / Topological Differentiation / Test Controls
UNDEFORMED GEOMETRY
With the ambition of creating habitable surface/ volume, the hemisphere is an appropriate substrate surface to study a differentiated contiguous surface. The surface can then be subjected to structural analysis [Karamba 3d] where it is supported on the XY and XZ planes and deformed by gravity. The test results on the right are displayed for a regular weaving pattern, as an experimental control. At this point, there are two ways in which one could approach surface articulation. (1) optimization for the support of self-weight with minimum material effort or (2) the designed articulation of rigid parts and mobile parts as in the lobster shell.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
ANCHORING STRUCTURE ON XY PLANE
ANCHORING STRUCTURE ON XZ PLANE
Isometric
Top
Front
Natural Systems and Biomimetics 32 | 33 Emergent Technologies and Design, Architectural Association
Exo / Topological Differentiation / Minimal Structure
UNDEFORMED GEOMETRY When material distribution is optimized for a load case in which the applied force is an equally distributed load in the -Z direction and anchored in the XY plane, one can attain a minimal deformation. When anchored in an XZ plane, however, the deformation is markedly larger than that of the regular distribution, due to insufficient structural capacity at the supports.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
ANCHORING STRUCTURE ON XY PLANE
ANCHORING STRUCTURE ON XZ PLANE
Isometric
Top
Front
Natural Systems and Biomimetics 34 | 35 Emergent Technologies and Design, Architectural Association
Exo / Topological Differentiation / Variable Stiffness
UNDEFORMED GEOMETRY
When the weaving grid is ‘pinched’ at certain points, one differentiates density and structural redundancy into areas that are analogous to the lobster shell’s hard vs mobile parts where dense areas are less deformed.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
ANCHORING STRUCTURE ON XY PLANE
ANCHORING STRUCTURE ON XZ PLANE
Isometric
Top
Front
Natural Systems and Biomimetics 36 | 37 Emergent Technologies and Design, Architectural Association
Exo / Potential Application
As a lightweight enclosure with variable stiffness, one potential application of this structure is as a subdivided canopy structure. This geometry the mobile portions of the structure behave similar to roof expansion joint systems with multi-directional movement capability. As the current exploration does not take into account weatherproofing, the system can be utilized either as a primary protection barrier (shading device) or as a secondary system above or below a variety of construction materials.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
Natural Systems and Biomimetics 38 | 39 Emergent Technologies and Design, Architectural Association
Exo / Opportunities and Further Development
As further developments for this system, three different scales may be considered. Regarding to a local scale, an exploration on the connections between two strips could be carried out. These connections will be designed according to thickness and properties of the strips material. The addition of a complementary connection element may be necessary in a large scale. When it comes to a wider view, in order to have a single layered waterproof envelope, the addition of elastic material (i.e. silicone), between strips may be considered and developed. Additionally, this elastic material may work as bracing. In a more global scale and under wind or seismic efforts, the roof tends to move horizontally. Were the EXO system supported by columns, the ductility of the system would absorb relative displacements.
Another option is to extend portions of the EXO system to anchor directly into the ground, thereby resisting lateral loads by the own strength of this system.
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
REFERENCES. -P. Romano, H. Fabritius, D. Raabe. ‘The exoskeleton of the lobster Homarus americanus as an example of a smart anisotropic biological material’. Max Planck Institute. 2006. -Lorna J. Gibson, Michael F. Ashby. ‘Cellular Solids: Structure and properties’. Cambridge Solid State
Science. 1999.
-D. Raabe, C. Sachs. ‘Mechanical Properties of the Lobster Cuticle’. Max Planck Institute. -D. Raabe, P. Romano, A. Al-Sawamih, C. Sachs. ‘Mesostructure of the exoskeleton of the lobster Homarus americanus’. Max Planck Institute. -D. Raabe, S. Nikolov, C. Sachs. ‘Structural building principles and mechanics of chitin-based biological composite material with hierarchical organization: example of the lobster Homarus americanus’. Max
Planck Institute.
-D. Raabe, P. Romano, C. Sachs. ‘Acta Materialia’. 2005
- Alexander Stirn. ‘The formula for lobster shell’. MaxPlanck Research 1/12. Pages 72-79. Max Planck Institute. 2012.
Natural Systems and Biomimetics 40 | 41 Emergent Technologies and Design, Architectural Association
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Architectural Association. School of Architecture. Emergent Technologies and Design. Term 1. 20142015 Natural systems and biomimetics workshop. Documentation.
Declaration:
‘We certify that this piece of work is entirely our own and that any quotation or paraphrase from published or unpublished work of others is duly acknowledged.’
Francis McCloskey
Carlos Ochando
Lorenzo Santelli
Group 4 _ McCloskey, Ochando, Santelli. 12 January, 2015
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