Tensile Materials

7/27/2019 Tensile Materials

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TENSILE MATERIALS


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HISTORY OF TENSILE MATERIALS

The first such structures were used in 1946 by the

engineer W. Bird (USA) for the housing of a radar

antenna structure.They subsequently became popular in many

countries and were soon put to use as covers for

swimming pools, temporary warehouses, and

exhibition buildings.

Air-inflated structures are supported by

pressurized air within inflated building elementsthat are shaped to carry loads in a traditional

manner.

TYPES OF TENSILE STRUCTURES

CABLE SUPPORTED STRUCTURES CABLE STAYED STRUCTURES


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TENSILE MATERIALS

Tensile materials are mostly

Uncoated fabrics

Simple woven fibers

Canvas, nylon

Coated fabrics

High strength woven fibers.

Pvc-coated polyester, relatively short

service life.

Ptfe-coated glass fiber ,high strength,long service life.

Foils

Pvc and etfe foils.


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ADVANCED TENSILE MATERIALS

ETFE-ethylene tetra fluroethene

This has been used in various structures likeBejing olympics stadium a sthe outer flexible strips.

Tensile structures are various types depending on the use of

Materials and their quality properties. They are:

Stayed

Suspended

Anticlassic

Membranes

Pneumatic

Cable truss


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MEMBRANE STRUCTURES

Membranes

The structural membrane acts

also as the weather shield.

The membrane can only resist forces in tension, so forces perpendicular

to the membrane cause large deformations and large membrane forces.

Tensile roofs are susceptible to vibration Reverse curvature and or prestressing can bring these forces to zero.


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SYNCLASTIC STRUCTURES

SYNCLASTIC SURFACES

the centers of curvature of the

membrane are on the same side of

the membrane. Example-sphere or

balloon.


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STAYED STRUCTURESTo span roads, brigdes, the truss roofs

are span under concrete pylons.

Stayed structures resists both gravity

loads and wind loads.


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SUSPENDED STRUCTURES

GOLDEN GATE BRIDGE , PETER CRAIG


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There are few stability issues in the use of suspended structures. They

are:

Point-load deformation

Wind load deformation.

Stabilizing cable to resist wind uplift.

Dead load to resist wind uplift.

The suspension span directly depends

on the stress of the suspension


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SUSPENDED STRUCTURES


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ANTICLASTIC STRUCTURES

ANTICLASTIC SURFACES

the centers of curvature of the

membrane are on opposite sides of themembrane .example- hyperbolic

paraboloid, torus.


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ANTICLASTIC STRUCTURES

1. opposing strings

Stabilize a point in space.

2. several opposing strings

Stabilize several points.

3. Anticlastic curvature

Stabilizes a membrane.

4. Membrane shear

Causes wrinkles in fabrics.

5.Stress without wrinkles

6. Hp surface

Quadriatic equation.

7.Minimal surface


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SADDLE SHAPES


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PNEUMATIC STRUCTURES

AIR INFLATED

STRUCUTRES

AIR SUPPORTED STRUCUTRES


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A very lightweight enclosed structure, usually fabricated of a membrane

of an impervious material and supported by the difference in air pressure

between the exterior and the interior of the structure rather than by a

structural framework.

Fans must maintain the interior pressure slightly in excess of normal

atmospheric pressure to prevent the structure from slowly deflating and

collapsing.

Used primarily as a temporary enclosure or to house sports facilitiessuch as tennis courts and swimming pools. Also called an air-supported

structure.

The envelopes of pneumatic structures are made of industrial fabrics

coated with polymers, including rubber, or from reinforced films. Threads

of synthetic fibers, or less frequently glass fibers, provide thereinforcement for the films and fabrics.

PNEUMATIC STRUCTURES


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Pneumatic structures are divided into two types:Air-supported structures, in which air under low pressure (excess

pressure, 0.11 kilo newton per sq. m [kN/m2]) is fed directly under the

envelope,

Air-inflated structures, in which air under high pressure (excess

pressure, 30700 kN/m2) fills only the supporting elements of the

structure.

ConstructionIn the erection of air-supported pneumatic structures, the envelope is

tightly fastened to the foundation.

Airlocks are constructed for entering and leaving the building.

Air-inflated structures are subdivided into inflated-frame and inflated-

panel types.

Also in use are hybrid envelopes of air-supported and supporting

structures, as well as reinforcing cables, nets, stays, and membranes.


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PNEUMATIC STRUCTURESADVANTAGES

light weight,

the possibility of covering large

spans without internal supports.

complete prefabrication,

rapid assembly,

portability,

transparency to light and radio

waves, low cost.

DISADVANTAGES

The need for continuousmaintenance of excess pressure in

the envelope.

The relatively short service life,

and the poor fire resistance and

acoustic insulation.

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Tensile Materials