Tensile structures are membrane structures stabilized by internal air pressure or tensioned cables. They include pneumatic structures supported by pressurized air within inflated building elements shaped to carry loads. Common tensile structures are cable-supported structures like bridges, and membrane structures used as roofs that can economically span large distances. Advanced materials like ETFE have been used in tensile structures like the Beijing Olympics stadium.

1. TENSILE STRUCTURES

2. WHAT ARE TENSILE STRUCTURES?
•Membrane structure that is stabilized by the pressure of compressed air.
•Air-supported structures are supported by internal air pressure.
•A network of cables stiffens the fabric, and the assembly is supported by
a rigid ring at the edge.
STRUCTURES THAT IS FORMED BY THE USE OF TENSILE
MATERIALS ARE TENSILE STRUCTURE
•A tensile structure is a construction of
elements carrying only tension and no
compression or bending.
•Most tensile structures are supported by
some form of compression or bending
elements, such as masts, compression
rings or beams.
•Tensile membrane structures are most
often used as roofs as they can
economically and attractively span large
distances.
PRINCIPLE
The air pressure within this
bubble is increased slightly above
normal atmospheric pressure and
maintained by compressors or
fans.

3. 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 elements
that are shaped to carry loads in a traditional
manner.
TYPES OF TENSILE STRUCTURES
CABLE SUPPORTED STRUCTURES CABLE STAYED STRUCTURES

4. 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.

5. ADVANCED TENSILE MATERIALS
ETFE-ethylene tetra fluroethene
This has been used in various structures like
Bejing olympics stadium as the 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

6. 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.

7. SYNCLASTIC STRUCTURES
SYNCLASTIC SURFACES
the centers of curvature of the
membrane are on the same side of
the membrane. Example-sphere or
balloon.

8. STAYED STRUCTURES
To span roads, bridges, the truss roofs
are span under concrete pylons.
Stayed structures resists both gravity
loads and wind loads.

9. SUSPENDED STRUCTURES
GOLDEN GATE BRIDGE , PETER CRAIG

10. 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

11. SUSPENDED STRUCTURES

12. ANTICLASTIC STRUCTURES
ANTICLASTIC SURFACES
the centers of curvature of the
membrane are on opposite sides of the
membrane .example- hyperbolic
paraboloid, torus.

13. 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.Minimal surface

14. SADDLE SHAPES

15. PNEUMATIC STRUCTURES
AIR INFLATED
STRUCUTRES
AIR SUPPORTED STRUCUTRES

16. •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 facilities
such 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 the
reinforcement for the films and fabrics.
PNEUMATIC STRUCTURES

17. Pneumatic structures are divided into two types:
•Air-supported structures, in which air under low pressure (excess
pressure, 0.1–1 kilo newton per sq. m [kN/m2]) is fed directly under the
envelope,
•Air-inflated structures, in which air under high pressure (excess
pressure, 30–700 kN/m2) fills only the supporting elements of the
structure.
Construction
•In 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.

18. PNEUMATIC STRUCTURES
ADVANTAGES
•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 continuous
maintenance of excess pressure in
the envelope.
•The relatively short service life,
and the poor fire resistance and
acoustic insulation.