## Tensegrity Structures

Tensegrity structures are 3-D trusses where members are assigned specific functions. Some members remain in tension while others are always in compression. Usually for compressive members, solid sections or bars are used; and string or cable type elements can be used as the tensile members.

Most bar–string configurations will not be in equilibrium. Hence, if constructed they will collapse to a different shape. Only bar–string configurations which are pre-stressed and in a stable equilibrium will be called Tensegrity structures. If well designed, the application of forces to a Tensegrity structure will deform it into a slightly different shape in a way that supports the applied forces.

The word “Tensegrity” is a contraction of the phrase “tensional integrity”. It can be traced back to Buckminster Fuller who first coined the phrase in his 1962 patent application. The construction of the first true Tensegrity structure is however attributed to the artist Kenneth Snelson who created his X- piece sculpture in 1948.

To summarise, the above descriptions cover most of the aspects of the Tensegrity concept which are listed as follows:

1. Pin-jointed bar frameworks: Tensegrity structures belong to the structural group of pin- jointed three-dimensional trusses.

2. Pure compressive/tensile members: Tensegrity structures contain only pure compression and tension members. And tension elements used are cables which can sustain only tension.

3. Localisation of compression: In classic Tensegrity structures the compressive elements are discontinuous. They seem to be floating in a continuous network of tension elements.

4. Pre-stressed structures: A state of pre-stress or self-stress is required for the stability of the structure since it stabilizes internal mechanism.

CONCEPT OF TENSEGRITY STRUCTURES

Tensegrity structures are structures based on the combination of a few simple but subtle and deep design patterns:

1. Loading members only in pure compression or pure tension, meaning the structure will only fail if the cables yield or the rods buckle.

2. Preload or tensional pre-stress, which allows cables to be rigid in tension.

3. Mechanical stability, which allows the members to remain in tension/compression as stress on the structure increases.

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