A tensile structure is held together by strong fabric or a network of wire or cable. The tension that these elements are under supports the entire structure. Heavy frames are not necessary and the materials are relatively lightweight, so they are easier to get to construction sites. With fewer materials required compared to other forms of construction, a large indoor space can be built without the need for intrusive support beams and frames. Such a structure can take on a dome, modeled on geodesics, or be cone or saddle shaped.
This principle is used to build many types of permanent or temporary structures. Buildings as large as stadiums and airport terminals have been built using tension-based structural systems. Shopping malls have incorporated them as well, and a tensile structure can also be used for large tents, to build protective covers and shelters, and to cover stages. Fabric structures can covers spaces up to 150 feet (45.72 m) across without support, and structures supported by tension cables can cover even more space.
The type of fabric used depends on the applications, but several types are suitable for use in a tension structure. Some include polyvinyl chloride (PVC) polyester, polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene plastic, and PVC glass fabric. Each is suitable for certain applications and meets specific fire and durability requirements. Many of these materials are also recyclable, adding to the environmentally sustainable characteristics of structures supported by tension.
In addition to a dome, the tensile structure can be cone or saddle shaped. Several mathematical principles are used in the structural design, including Gaussian curvature. The curvature itself can be specifically measured, and a negative value refers to a saddle shape, while a positive number indicates there is a curve with a peak. In terms of physical properties, a tensile structure is being pulled, and all of its elements are in constant equilibrium with gravity. Failure of any small part, such as a cable or fabric sheet, will result in a chain reaction leading to the collapse of the structure.
A tensile structure can comprise the bulk of a building or be added to existing buildings as roof sections, atriums, or outdoor canopies. The structure can last for decades without maintenance. Design principles related to tension construction have been around since prehistoric times. Famous architectural engineers have revolutionized the concept by creating well-recognized structures at major airports and stadiums around the world.