Tensegrity Tower
Featured
Gustav Fagerstrom
INTRODUCTION
Aside from battling earthquakes, numerous modern metropolises have to face the issue of the urban heat island, a phenomenon that originates in agglomeration of thermal mass and lack of green spaces. Additions to the city’s urban tissue should therefore aim toward minimising the thermal mass added, as well as employ a strategy for dealing with seismic vibration.
Responding to these issues is the principle of tensegrity. Structures of this type are inherently material efficient
and resilient, with tension and compression members sustaining each other in an equilibrated, rather than hierarchal, system.
In this way the tensegrity system is an interdependent force equilibrium. Mechanical stress is absorbed uniformly by every part of the system. While making tensegrity highly interesting as an architectural construct, dealing with its complexity is also what makes it scarcely implemented.
The reciprocal relationships, source of the system’s properties, become manageable through the use of smart computer geometry; specifically parametric/associative 3d-modeling. This technique also facilitates experimenting with alternatives to mere vertical site boundary extrusion, as well as with non-linear trajectories of vertical communications.
TENSEGRITY AS AN ORGANIC SYSTEM
In 1993 in the Journal of Cell Science (Ingber 1993) a simple mechanical model of the cytoskeleton (the biological cell’s internal “scaffolding”) was presented by Donald E. Ingber, professor at the Harvard Medical School. Alongside was a suggestion on how tensegrity architecture can help explain how processes such as cell shape, movement and cytoskeletal mechanics are controlled. As complexity theory and new mathematics gradually have developed and entered in the world of cell biology, this hypothesis has gained more and more credibility.
The same author states in the same publication in 2003:
“The cellular tensegrity model proposes that the whole cell is a pre-stressed tensegrity structure […] tensional forces are borne by cytoskeletal microfilaments and intermediate filaments, and these forces are balanced by interconnected structural elements that resist compression, most notably, internal microtubule struts […]” (Ingber 2003a, p. 1158)
The cytoskeleton is composed of:
- Weave of double helix tensional microfilaments spanning the surface membrane, intertwining geodetically in triangular formations. This tensile ‘skin’ is notionally irregular – structurally differentiated – and shows radical variations in density and thickness.
- Multiple strands of 13-fold-helix compression elements, microtubules, forming an endoskeleton. These ‘rods’ are bundled, follow a non-linear path and measure 25 times the relative thickness of one tension member.
- Criss-crossing structure of intermediate filaments providing a seemingly random network. Tensile cross bracings between outer membrane and endoskeleton, as well as between individual endoskeletal members.
SPECIFIC POINTS OF INTEREST
-MASS/STRENGTH EFFICIENCY
“A considered unique path of structure is often more valid than the unquestioned assumption of a distributed solution, subdivided equally through a cross-section or plan.”
Cecil Balmond
Geometric layout of material is crucial to strength on all scales. This is not a new revelation, yet only a small minority of architectural heritage has deviated from rectilinear principles. Plates, columns, beams and so on have an orthogonal configuration, as is the case with many engineering components. Evidence however suggests that the essential load paths are not necessarily the rectilinear ones of our traditional structures. This would mean that a lot of unnecessary material, hence energy, is required in order for specific stiffness objectives to be upheld orthogonally. It would then be conceivable that a structure relying solely on non-orthogonal members, of whom a large number are tensile, yields a maximum of strength relative to self weight.
-SYSTEMIC BEHAVIOUR
Some of the more promising scientific features of tensegrity structures lie within their systemic behaviour:
- While the global structure deforms under an extrinsic force, i.e. bends, none of the individual members experience bending moments.
- The system expands as a whole and contracts as a whole; local stresses are being uniformly transmitted throughout the structure, and uniformly absorbed by every part of it. As stated by Hugh Kenner in ‘Geodesic Math and How to Use It’, this is the principle known as elasticity multiplication.
- Mass-efficiency is further actuated by the self-similar property of tensegrity; “[…] can be constructed as structural hierarchies in which the tension or compression elements that comprise the structure at one level are themselves tensegrity systems composed of multiple components on a smaller scale”. (Buckminster Fuller, ‘Synergetics’, 1975)
-SYSTEM REDUNDANCY
In ‘Emergence: Morphogenetic Design Strategies’ (Architectural Design, 73:4, 2004), Michael Hensel et. al. state: “All living structures have a very high degree of redundancy, which is what enables them to be adaptive.” By virtue of their interdependent, rather than hierarchical, force flow, both synthetic and organic tensegrities are very resilient. However the synthetic tensegrity in all its efficiency lacks the built-in redundancy that is the safety valve of engineering practice. Organic cytoskeletal tensegrity allows the cell to reinstate itself to equilibrium when deformed or otherwise affected by mechanical extrinsic forces; even when permanently damaged. This can be attributed to the high level of redundancy together with the gradient material connections present. Cell mechanics appear to successfully wed the efficiency of tensegrities with the resilience of biological systems.
In my mind the pivotal points in the conceptual philosophy of organic tensegrity systems are the material aggregations and interconnections - this is where further effort ought to be invested.
Further development of these would result in a system which distances itself from the reductivist force diagram in which all parts are alike. In this way it begins to take on a different systemic behavior in which material redundancies aggregate differently depending on different load paths, and in which a minimum of energy is lost thanks to continuous material connections.
DISCUSSION AND PRELIMINARY CONCLUSION
A functional tensegrous assembly proposes an integrated solution to multi-performative requirements. In doing so it adds a point of interest to the discussion on differentiated - as opposed to different – systems in a building. The polarisation of these two concepts is central in contemporary discourse and source of reoccurring conflict.
One argues the use of specialised single performance building components, projected and manufactured separately, then subsequently combined hierarchically into an efficient built whole. The other advocates solutions that by virtue of built-in intelligence and variability allow for a singular manufacturing and assembly process. The finished construct here relies on interdependency rather than hierarchy all the while performing all the functions necessary in a building in use. The former’s essence was defined by Mies van der Rohe and to our day it has brought building design to high levels of technological advancement. However, embedded deep within its reductive nature lays its insuperable limitation. The latter tries to emancipate from this and is far less implemented, as it pertains to more recent theories.
Two projects of recent years that in some ways illustrate this polarisation are Carbon Tower by Testa Architecture and Design (project, 2004) and 30 St Mary Axe by Foster and Partners (completed 2004). Naturally, one being still a project while the other is already completed I will be careful as to not make anything else than a simple conceptual comparison between the two. Both draw inspiration from Buckminster Fuller’s ideas on a largely tensile, structural building skin relying on non-orthogonal load paths. Both also employ a cylindrical form which accommodates the tensile envelope and better deals with wind loads.
Both are advanced parametric explorations of tensile building mechanics and as such highly interesting architecturally.
However the tectonics of Norman Foster’s project largely rely on known principles of component design, manufacturing and assembly, albeit in a cutting-edge manner. Peter Testa on the other hand attempts to take the manufacturing and assembly logic to a level that actually parallels the complex reciprocal relationships that dictate the design process:
“When the main structural members of the perimeter helix are pultruded, the fibres cross at the point of a floor plate. Some of the carbon strands are diverted from the main vertical member and are grouped to form cables that run to the opposite side of the helix, tying the external structure together. A floor structure is then woven into and layered onto this surface network of cables. The building is literally woven and braided together.” (Matilda McQuaid and Philip Beesley, ‘Extreme Textiles’)
Carbon Tower applies an unparalleled methodology on material connections and integration of systems that according to Peter Testa himself is the way to distance ourselves from traditional construction techniques: ““We’re still largely working with 19th-century methods. We have to find alternatives. We need to reduce the weight and energy consumption of these large buildings.[..]”
(Washington Post, April 17, 2005)
In its brevity I find this statement to capture very well the core issue of my theses. In my mind, true sustainability must come from this type of will to pose the simple question: what is a building? One answer is ‘our most wasteful and polluting agent’. It might continue to be so until we as a matter of habit learn to question the assumption of continuous compression and orthogonality. I believe that my experiments, if successful, will outline a principle that could increase efficiency in building manufacturing, assembly, maintenance as well as system lifespan.
In this way the tensegrity system is an interdependent force equilibrium. Mechanical stress is absorbed uniformly by every part of the system. While making tensegrity highly interesting as an architectural construct, dealing with its complexity is also what makes it scarcely implemented.
The reciprocal relationships, source of the system’s properties, become manageable through the use of smart computer geometry; specifically parametric/associative 3d-modeling. This technique also facilitates experimenting with alternatives to mere vertical site boundary extrusion, as well as with non-linear trajectories of vertical communications.
TENSEGRITY AS AN ORGANIC SYSTEM
In 1993 in the Journal of Cell Science (Ingber 1993) a simple mechanical model of the cytoskeleton (the biological cell’s internal “scaffolding”) was presented by Donald E. Ingber, professor at the Harvard Medical School. Alongside was a suggestion on how tensegrity architecture can help explain how processes such as cell shape, movement and cytoskeletal mechanics are controlled. As complexity theory and new mathematics gradually have developed and entered in the world of cell biology, this hypothesis has gained more and more credibility.
The same author states in the same publication in 2003:
“The cellular tensegrity model proposes that the whole cell is a pre-stressed tensegrity structure […] tensional forces are borne by cytoskeletal microfilaments and intermediate filaments, and these forces are balanced by interconnected structural elements that resist compression, most notably, internal microtubule struts […]” (Ingber 2003a, p. 1158)
The cytoskeleton is composed of:
- Weave of double helix tensional microfilaments spanning the surface membrane, intertwining geodetically in triangular formations. This tensile ‘skin’ is notionally irregular – structurally differentiated – and shows radical variations in density and thickness.
- Multiple strands of 13-fold-helix compression elements, microtubules, forming an endoskeleton. These ‘rods’ are bundled, follow a non-linear path and measure 25 times the relative thickness of one tension member.
- Criss-crossing structure of intermediate filaments providing a seemingly random network. Tensile cross bracings between outer membrane and endoskeleton, as well as between individual endoskeletal members.
SPECIFIC POINTS OF INTEREST
-MASS/STRENGTH EFFICIENCY
“A considered unique path of structure is often more valid than the unquestioned assumption of a distributed solution, subdivided equally through a cross-section or plan.”
Cecil Balmond
Geometric layout of material is crucial to strength on all scales. This is not a new revelation, yet only a small minority of architectural heritage has deviated from rectilinear principles. Plates, columns, beams and so on have an orthogonal configuration, as is the case with many engineering components. Evidence however suggests that the essential load paths are not necessarily the rectilinear ones of our traditional structures. This would mean that a lot of unnecessary material, hence energy, is required in order for specific stiffness objectives to be upheld orthogonally. It would then be conceivable that a structure relying solely on non-orthogonal members, of whom a large number are tensile, yields a maximum of strength relative to self weight.
-SYSTEMIC BEHAVIOUR
Some of the more promising scientific features of tensegrity structures lie within their systemic behaviour:
- While the global structure deforms under an extrinsic force, i.e. bends, none of the individual members experience bending moments.
- The system expands as a whole and contracts as a whole; local stresses are being uniformly transmitted throughout the structure, and uniformly absorbed by every part of it. As stated by Hugh Kenner in ‘Geodesic Math and How to Use It’, this is the principle known as elasticity multiplication.
- Mass-efficiency is further actuated by the self-similar property of tensegrity; “[…] can be constructed as structural hierarchies in which the tension or compression elements that comprise the structure at one level are themselves tensegrity systems composed of multiple components on a smaller scale”. (Buckminster Fuller, ‘Synergetics’, 1975)
-SYSTEM REDUNDANCY
In ‘Emergence: Morphogenetic Design Strategies’ (Architectural Design, 73:4, 2004), Michael Hensel et. al. state: “All living structures have a very high degree of redundancy, which is what enables them to be adaptive.” By virtue of their interdependent, rather than hierarchical, force flow, both synthetic and organic tensegrities are very resilient. However the synthetic tensegrity in all its efficiency lacks the built-in redundancy that is the safety valve of engineering practice. Organic cytoskeletal tensegrity allows the cell to reinstate itself to equilibrium when deformed or otherwise affected by mechanical extrinsic forces; even when permanently damaged. This can be attributed to the high level of redundancy together with the gradient material connections present. Cell mechanics appear to successfully wed the efficiency of tensegrities with the resilience of biological systems.
In my mind the pivotal points in the conceptual philosophy of organic tensegrity systems are the material aggregations and interconnections - this is where further effort ought to be invested.
Further development of these would result in a system which distances itself from the reductivist force diagram in which all parts are alike. In this way it begins to take on a different systemic behavior in which material redundancies aggregate differently depending on different load paths, and in which a minimum of energy is lost thanks to continuous material connections.
DISCUSSION AND PRELIMINARY CONCLUSION
A functional tensegrous assembly proposes an integrated solution to multi-performative requirements. In doing so it adds a point of interest to the discussion on differentiated - as opposed to different – systems in a building. The polarisation of these two concepts is central in contemporary discourse and source of reoccurring conflict.
One argues the use of specialised single performance building components, projected and manufactured separately, then subsequently combined hierarchically into an efficient built whole. The other advocates solutions that by virtue of built-in intelligence and variability allow for a singular manufacturing and assembly process. The finished construct here relies on interdependency rather than hierarchy all the while performing all the functions necessary in a building in use. The former’s essence was defined by Mies van der Rohe and to our day it has brought building design to high levels of technological advancement. However, embedded deep within its reductive nature lays its insuperable limitation. The latter tries to emancipate from this and is far less implemented, as it pertains to more recent theories.
Two projects of recent years that in some ways illustrate this polarisation are Carbon Tower by Testa Architecture and Design (project, 2004) and 30 St Mary Axe by Foster and Partners (completed 2004). Naturally, one being still a project while the other is already completed I will be careful as to not make anything else than a simple conceptual comparison between the two. Both draw inspiration from Buckminster Fuller’s ideas on a largely tensile, structural building skin relying on non-orthogonal load paths. Both also employ a cylindrical form which accommodates the tensile envelope and better deals with wind loads.
Both are advanced parametric explorations of tensile building mechanics and as such highly interesting architecturally.
However the tectonics of Norman Foster’s project largely rely on known principles of component design, manufacturing and assembly, albeit in a cutting-edge manner. Peter Testa on the other hand attempts to take the manufacturing and assembly logic to a level that actually parallels the complex reciprocal relationships that dictate the design process:
“When the main structural members of the perimeter helix are pultruded, the fibres cross at the point of a floor plate. Some of the carbon strands are diverted from the main vertical member and are grouped to form cables that run to the opposite side of the helix, tying the external structure together. A floor structure is then woven into and layered onto this surface network of cables. The building is literally woven and braided together.” (Matilda McQuaid and Philip Beesley, ‘Extreme Textiles’)
Carbon Tower applies an unparalleled methodology on material connections and integration of systems that according to Peter Testa himself is the way to distance ourselves from traditional construction techniques: ““We’re still largely working with 19th-century methods. We have to find alternatives. We need to reduce the weight and energy consumption of these large buildings.[..]”
(Washington Post, April 17, 2005)
In its brevity I find this statement to capture very well the core issue of my theses. In my mind, true sustainability must come from this type of will to pose the simple question: what is a building? One answer is ‘our most wasteful and polluting agent’. It might continue to be so until we as a matter of habit learn to question the assumption of continuous compression and orthogonality. I believe that my experiments, if successful, will outline a principle that could increase efficiency in building manufacturing, assembly, maintenance as well as system lifespan.
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