Tensile structures are widely used as a means of protection against the weather in publicly used spaces. This is because such buildings can span large distances and are esthetically pleasing. Tensile structure is a construction of elements carrying only tension and no compression or bending. Tensile structures are generally supported by some form of compression or bending elements for example the masts in The O2, known as the Millennium Dome.
Why is fabric used in tensile structures?
Fabric can facilitates greater spans than traditional building materials, with a minimal supporting structure. Opaque and dynamic, organic shapes bring the feeling of the outside inside. Such buildings provide shade and protection from negative weather conditions.
Are they cost effective?
If you compare it with concrete and steel construction, there is an economy of cost per square meter, strength and longevity with fabric building. Big cost saving comes with a short installation time. The support structure and fabric membrane is pre-fabricated and assembled on construction site.
What is tension?
Tension is the force which pulls the molecular structure of a material apart. True tensioned fabric structures are those in which every part of the fabric is in tension. It is the best way of using any material because it utilizes the whole cross section at maximum efficiency rather than just the material at the extremes of the cross sectional form. The basic rule for stability is that a tensile structure must curve equally in opposite directions; this gives the canopy its 3D stability.
Is the fabric elastic?
The fabric used in tension structures is not very stretchy or elastic. It will not balloon under wind loads and settle under snow. Fabric, being flexible and normally woven, is stretches across the diagonal plain to a greater extent than in the direction of the weave; this can be most easily seen with a piece of netting. Ordinary structural external fabric has a tensile strength of ten tons per linear meter and will creep no more than a few percent after 20 years in extreme weather conditions. Certain fabrics can also have more stretch in one direction than in the other.
How is a 3D form achieved?
The complex 3D form of a canopy is achieved not by elastic fabric, but by cutting the fabric and bonding it together to make its final 3D shape. The fabric is loaded during the installation process. This is called pre-tension or pre stress. Pre-tension is the most efficient way of resisting live loads such as snow, wind and other extreme conditions.
What types of fabric can be used?
There are many different fabrics with various features and benefits to each one, however there are three basic external fabric types most commonly used in tensile fabric structures. External fabrics such as PVC (polyvinyl chloride) coated polyester; silicon coated glass; and Teflon coated glass P.T.F.E. (polytetrafluoroethylene). They have different benefits in terms of cost and durability. PVC coated polyester is the least expensive and has a design life of ten to twenty years. Silicone coated glass cloth and Teflon coated fabric has a higher tensile strength than PVC coated polyester, but is slightly more brittle.
Can a tensile fabric structure cope with the weight of snow or heavy weather?
A fabric structure, once it is tensioned, can take a large amount of applied weight and the fabric is very tight. Fabric structures even have been built in typhoon and tornado areas.