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Tensile structures

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Tensile structures

  1. 1. TENSILE STRUCTURE
  2. 2. TENSILE IS A TYPE OF FORCE APPLIED ON A MATERIAL. IT IS A CAPABILITY OF MATERIAL OF BEING STRETCH OUT A tensile structure is a construction of elements carrying only tension and no compression or bending.
  3. 3. Definition •The term tensile structures describes the category of buildings in which the load bearing capacity is achieved through tension stress in the majority of the components, such as cables, technical fabrics or foils. •It can also be defined as a structure where the exterior shell is a fabric material spread over a framework. The fabric is maintained in tension in all directions to provide stability. •The only exception is represented by rigid boundaries and structural members which are generally subjected to compression and bending. •Tension structures are commonly subdivided in boundary tensioned membranes, pneumatic structures and pre-stressed cable nets and beams (Lewis 2003).
  4. 4. A tensile membrane structure is most often used as a roof, as they can economically and attractively span large distances. Tension roofs or canopies are those in which every part of the structure is loaded only in tension, with no requirement to resist compression or bending forces. TENSILE STRUCTURE
  5. 5. History Common Misconceptions •FABRIC STRUCTURES CANNOT TAKE HEAVY WEATHER CONDITIONS IS AN INCORRECT STATEMENT. FABRIC IS ELASTIC AND STRETCHES. Fabric has a strong tensile strength and will creep (stretch very slightly) only a few percent over 20 years of use. •Tensile fabric structures have been with us since the Mongolians swept down from the plains, with their yurts as their transpo •And there’s evidence that the Romans even covered the Colosseum with massive canopies, hoisted by an intricate system of p
  6. 6. •But they really came into their own in the last half of the 20th century, when designs like this by Germany’s Frei Otto. Frei Otto Olympic Stadium Colosseum roof Why tensile are the shape they are? •Large flat pieces of fabric are very poor at resisting loads. •Imagine four of you each pulling on the strings laced through a tennis ball. Fig 1. A fifth person pushing down on the ball can
  7. 7. •Imagine a flappy marquee roof. Try lifting two opposite strings and lowering the other two. Fig 2. The ball is now locked in space. Apply this principle to fabric and you have created ‘anticlastic’ double curvature Fig. 1 Fig. 2
  8. 8. • Saddle roof • Mast supported • Arch supported •Combinations Types of Fabric Structures `
  9. 9. Saddle Roof Four or more point system when the fabric is stretched between a set of alternating high and low points The roof plan, taken directly from the structural engineering working drawings, illustrates the roof configuration and its components.
  10. 10. Section through the project showing the stage roof tucked under the auditorium roof. The saddle-shaped roof of the stage cover nestles under the auditorium roof of the project. The leaning A-frames and the stay cables which hold them back are clearly visible, along with the radial cables which shape the tent units. The corner tripods, each consisting of a vertical mast and two sloping cables, are connected to concrete anchors rising from the water. Mast Supported •Tent-like in appearance, mast supported structures typically have one or sometimes several peaks that are supported by either interior or perimeter masts.
  11. 11. •The fabric is attached to the interior mast by special connections, usually a bale ring or cable loop. •Mast-supported structures can also be supported by adjacent buildings. The peaks of a mast supported structure are determined by the design and how the fabric is attached. •Openings are typically ovoid or elliptical. The fabric that extends from the top of the opening is seamed and can necessitate patterning. •Mast supported systems are suitable for long span roofs. `
  12. 12. Tensile Structures In India
  13. 13. Bale rings are a good way to contro l stresses in fabric ro of at high or low po ints. Used at high po ints they must be covered to make the struc ture watertight. If used at low po ints, they can be used to gather rainwater and sno w for redistributio n on site. Channel (with grommets) and lacing. Used with PVCcoated polyester fabric where the edge has grommets spaced at frequent intervals. Rope is laced thro ugh the grommets and to a tie rod within the channel. Water dreainage via Membrane plates
  14. 14. There are many great advantages and functional benefits of tensile membrane structures and here are few reasons why: Flexible Design Aesthetics - Tensile membrane structures provide virtually unlimited designs of distinctive elegant forms that can be realized because of the unique flexible characteristics of membrane resulting in an iconic and unique structure or feature for any building owner, city or even region. Outstanding Translucency – In daylight, fabric membrane translucency offers soft diffused naturally lit spaces reducing the interior lighting costs while at night, artificial lighting creates an ambient exterior luminescence. Excellent Durability – With several different membranes in the market place such as PTFE fiberglass, ETFE film, PVC, and ePTFE, the durability and longevity of tensile membrane structures have been proven. Lightweight Nature - The lightweight nature of membrane is a cost effective solution that requires less structural steel to support the roof compared to conventional building materials, enabling long spans of column-free space.
  15. 15. Low Maintenance – Tensile membrane systems are somewhat unique in that they require minimal maintenance when compared to an equivalent-sized conventional building. Cost Benefits – Most tensile membrane structures have high sun reflectivity and low absorption of sunlight, thus resulting in less energy used within a building and ultimately reducing electrical energy costs. Types of structures: •Stayed •Suspended • Anticlastic • Pneumatic •Trussed
  16. 16. STAYED: To span railroad trucks underneath, the truss roof is suspended by stay cables. SUSPENDED STRUCTURES:
  17. 17. GOLDEN GATE BRIDGE.
  18. 18. ANTICLASTIC STRUCTURES INCLUDE CURVATURE , SADDLE SHAPES IT INCLUDES:ARCH SHAPEWAVE SHAPEPOINT SHAPE ARCH SHAPE WAVE SHAPE POINT SHAPESADDLE SHAPE
  19. 19. GRID SHOWSTHE BASE OFCABL E INSTRUCTUR ES ADVANTAGES FABRIC TENSILE STRUCTURE ADVANTAGES: •UNIQUE DESIGNS. •LIGHTWEIGHT •FLEXIBLE •ENVIRONMENTALLY SENSITIVE
  20. 20. DISADVANTAGES : •NO RIGIDITY. •LOSS OF TENSION IS DANGEROUS FOR STABILITY. ADVANTAGES FABRIC TENSILE STRUCTURE One of the main advantages of fabric structure is that you can install it rapidly and easily. Tension fabric buildings provide abundant daytime lighting that is bright and natural, the interior of a fabric structure is an inviting environment that people, plants and animals thrive in. Fabric buildings are Acoustics exceptional; no sounds of pelting rain. Fabric buildings have Low cost per square foot, Initial investment is low. Fabric buildings are self cleaning; never needs painting; dust, dirt, pollutants wash off with Water no rotting parts to replace. Fabric structures are durable, corrosion resistance. salt, fertilizer and other corrosive materials have virtually no effect on polyethylene fabric. Flexibility, when a large clearspan building with tall overhead clearances is needed, a fabric structure is an economical solution.

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