Last edited 21 Aug 2017

Tensile structures


A tensile structure is a structure that carries only tension in the fabric system, and no bending or compression. In simple terms, it is a piece of fabric pulled in opposite directions until it is rigid through tension.

Tensioning, usually with wire or cable, provides the structure with its critical support. Tensile structures are a common type of thin-shell roof structure, and can be used to span large unsupported distances economically.

Tensile structures differ from tensegrity, which is a structural form that comprises both tension and compression elements. Although it is usual for tensile structures to be supported by some form of compression or bending elements, for example masts, compression rings or beams, that help to distribute forces.

Temporary buildings that are erected and dismantled will frequently use membranes in tension, as will designers of lightweight additions to existing buildings, such as canopies, covered walkways, shading systems, and so on.

The standard forms and principles on which tensile structures tend to be based are The Saddle and The Cone. The Saddle form is a hyperbolic paraboloid, made by two high and two low points. For more information, see Hyperbolic paraboloid. The Cone form is created by radians and hoops to create a volcano-shape. Although in general, tensile structures have very versatile qualities and can be used to create a wide range of different geometrical shapes.

For more on the structural behaviour, see The structural behaviour of architectural fabric structures.

An advantage of tensile structures is that they use less material than traditional structures and, as a result, are lighter. The tensioning provides the weather- and damage-resistant properties, as creases in the fabric are eliminated.

There are four types of fabric that are commonly used for tensile structures.

  • PVC-coated polyester fabric: This is cost-effective, with a 10-20 year lifespan and is a good solution for temporary building applications.
  • PTFE-coated glass fabric: This is an inert fabric, so it can only be used for permanent structures. It has high strength and is considered non-combustible.
  • ETFE foil: This is often used where thermal properties are critical, and it can also be transparent or fritted according to the level of translucency required.
  • PVC glass fabric: This is often used for internal elements such as in atriums, where minimal maintenance is required.

There are also uncoated fabrics such as simple woven or high-strength woven fibres, canvas and nylon that can be used.

At the edges, a material can be fitted in one of two main ways. It can be rope edged, where a cable runs in a sleeve and is connected at both ends to a rigid structure. Or, it can be hard edged, with a continuous connection to a rigid structure through clamping plates, with or without prestressing devices.

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