Tensegrity is in tension and compression between geometers, materials engineers, biologists and therapists

People concerned about tensegrity often ponder the different groups that use the term. I consider this today as I browse the web for random tensegrity links. One way to divide these groups is between animate and inanimate. Another may be teleology vs. mechanics. Teleology is purpose-driven behavior led by a consciousness being. Mechanics is the predictable aggregate behavior of non-self-conscious materials.

Let's ponder a few posts in the teleological category. People in the manual movement and physical therapy schools use the term to refer proper, healthy balance in one's life. Carlos Castenada was a prominent early adopter. Such uses are very common. In my random browsing today, I see Dennis Bartram considers tensegrity a central idea to his approach to human health. The Toronto Pilates Group's blog has a more detailed comment to make today,

Tom Myers Anatomy Trains as a series of maps to look at how stress distributes itself around the body... Myer’s theory surrounds the concept of ‘Tensegrity’ - a word that’s gained recognition in the manual and movement therapy community- and basically states that structures of balance (ie our bodies) require harmony between tension and compression (or for our application again: length, tone, traction). In the case of Myer’s work it is through a balance in the connective tissue – for all of us – the connective tissue houses everything thus being the ‘lines’ that our muscles, bones, nerves, organs are a part of (and the reason that one part of the body can distress or releive another sometimes quite distant part of the same body).

In a similar vein, Stephanie Fish of Holistic Body Work and Structural Alignment considers today how comprehending alignment in all its aspects, including physical gravity and metaphysical love, can be better considered in terms of tensegrity:

What am I aligning with? We each have our own descriptions and unique expression of alignment. Many of my clients use words such as true power, highest potential, optimal blueprint, dream life, ideal vision, creative source, core self, inner being, God, deep knowing, I am that I am - whatever works for their belief system. In structural integration bodywork, we are aligning with gravity. Buckminster Fuller - who coined the term "tensegrity" which is the model of structural alignment - where all the connective tissues (muscles, bones, ligaments, tendons) are balanced and aligned wrote, “Gravity is Love.” Whatever words we use, I know I am in alignment based on how I feel - a warm buzz, as if every cell of my being is singing, “Yes!” and “Thank you.” I am a physical person, and I feel strength, support, balance, vitality, fluid resonance, and a deep connection when I am in alignment and I enjoy being fully and completely present in what I am doing.

Meanwhile, on the inanimate, mechanical front, tensegrity continues to help structural engineers and artists consider new forms. Take for example Landolf Rhode-Barbarigos' work on pedestrian bridges, published with Nizar Bel Hadj Ali, Rene Motro, Ian F. C. Smith. A delightful overview of these types of applications is Oobject.com's list of wonderful tensegrity structures. Their introduction is a good presentation of the mechanical view:

Tensegrity structures are visually stunning and their combination with computer enhanced structures is creating renewed interest for architectural applications.

Buckminster Fuller coined the term tensegrity when he saw sculptures by Kenneth Snelson and realized that rigid component geodesics were a special case of perfectly balanced compression and tension. Tensegrity refers to structures where compression members (rods) are only connected to each other by tension members (cables). The end result is that the structures appear to float in air.

Despite the fact that tensegrity structures are fantastically efficient, few have been built since they tend to have a single point of failure and need adjustment. Recently however, schemes which combine the intelligence of computing and tensegrity structures have lead to proposals of very large scale structures including sky scrapers.

Engineers and roboticists are researching the algorithms and properties that make such structures work. Jon Rigelsford uses the term in his article on Mechanical Systems in Assembly Automation in 2003. Constructing tensegrity structures from one-bar elementary cells by Li, Feng, Cao and Gao is freely available from the Royal Society. Teleological, movement therapy users of the word tensegrity have little patience to wade through this type of detailed structural analysis, such as the text that they present as their conclusion,

We have developed two different schemes to assemble Z-based tensegrity structures. One is the direct enumeration scheme, which systematically searches for all possible topologies for Z-based tensegrity for a given number of cells and then filters out the unwanted structures among the possible solutions. The other, named the polyhedral truncation scheme, provides a more efficient and fast way for the practical design of tensegrity structures. To construct a tensegrity structure with a required configuration, one just selects a polyhedron with a similar shape, truncates all its vertices and then adds the bars in a canonical manner. Both schemes are easily programmable, and have generated a number of novel tensegrity structures. Finally, it is worth mentioning that, among all types of spatial tensegrity structures, the Z-based structures have the smallest ratio between the numbers of strings and bars, and can be utilized to further construct many other types of stable structures by adding additional strings.

Some applications are not tensegrities per se, but apply tensegrity in the use of steel and its application, such as HDA’s new high tension electric pylons. HDA deployed the Turin Olympic Footbridge, and one an award for this design that they call Dancing with Nature. It features a clever harnessing of the tension in the electric cables themselves as part of the pylon's structural integrity.

Inspired by the form of the shoots of a young plant, HDA’s pylons work off the basis of Fuller’s tensegrity, as the “shoots” are stabilized by a system of tension cables at their tips. The tension and compression of the system gives the pylon an elastic strength to resist wind forces and retain an optimal elegance. Their triangular surfaces are inclined to reflect the light to become a singular and elegant plane with minimal shadow.

The new pylons also respond individually to their natural context and forces. The pylons lean into the direction of the forces of the cables they are required to carry, creating the allusion of the pylons “dancing” across the landscape. The “dancing” pylons find structural equilibrium by leaning into the curve of the electric cables as they follow the constraints of the landscape.

Parametric processes carried out design calculations and form determination while a complex construction phase, where the pylons were fabricated from flat steel plates cut to individual shapes using contemporary numerically controlled tools, assembled the pylons together using automatic continuous welding machines.

Both groups using the tensegrity term share a thirst for, and enthusisatic response to, tensegrity images: pictures, virtual renditions, computer models and movies of tensegrity structures. In my random browsing this morning I stumbled across a few inspiring images. Lida Sklirou uploaded her simple and elegant 6 strut creations, part 1 and part 2. It is the images that lead people to apply the word as a title to their artistic creations and work, such as the rock and roll group Kiss and the Tensegrity Software group of user interface specialists.

Last and least, mindless spam robots use the word as well to construct nonsense texts that can fool search engines, such as this nonsense on a gambling site. They remind us that any delineation betwen animate and inanimate is problematic.