tensile structures

					 A PowerPoint presentation on Structures
            By group no - 2

Tensile Structures
        Tensile Structures
    A tensile structure is a building that is made from
  materials under tension — this could be a cable-net
supporting a fabric or sheet material, or it could be made
entirely from fabric. Most often used just for the roof of a
   building, it is a relatively new form of construction

    Tension roofs or canopies are those in which every
    part of the structure is loaded only in tension, with no
    requirement to resist to compression or bending



 A separate a member of structural cables & sides
vertically supports a non–structural weathershield.
A separate grid of structural cables supports a non–
             structural weather shield.
The tension force is created by an interior positive
pressure and the membrane acts as the weather shield.
   Types of structure with
significant tension members

• Linear structures

• Three dimensional structures

• Surface-stressed structure
        Linear structures

• Suspension bridge

• Draped cables

• Cable-stayed beams or trusses

• Cable trusses

• Straight tensioned cables
Three-dimensional structures

 • Bicycle wheel (can be used as a roof in a
                  horizontal orientation)

 • 3D cable trusses

 • Tensigrity structures

 • Tensairity structures
      Membrane materials
Common materials for doubly-curved fabric structures
are PTFE coated fibreglass and PVC coated polyster.
These are woven materials with different strengths in
different directions. The warp fibres (those fibres which
are originally straight—equivalent to the starting fibres on
a loom) can carry greater load than the weft or fill fibres,
which are woven between the wrap fibres.
Other structures make use of ETFE film, either as single
layer or in cushion form (which can be inflated, to
provide good insulation properties or for aesthetic
effect—as on the Allianz Arena in Munich
A tent is a shelter consisting of sheets of
fabric or other material draped over or
attached to a frame of poles or attached to a
supporting rope. While smaller tents may be
free-standing or attached to the ground, large
tents are usually anchored using ropes tied to
stakes or tents pegs.
                         TENT Types

Pole-supported tent:
     A tent that features a set of individual
  poles arranged beneath the fabric roof to
support and define the shape of the structure.
     The fabric roof is tensioned over the
  poles and attached to ropes and/or cables
    at designated spots around the fabric’s
   edge. The ropes/cables are anchored to
 the ground using stakes, augers or weights
     around the perimeter of the tent. Also
        referred to as a “push-pole tent.”
                         TENT Types

Pipe frame-supported tent:
      A tent with an assembled framework
   made of aluminum or steel pipes, tubes or
   other extrusions, which supports the fabric
  roof and defines the shape of the structure.
     The rigid framework allows the tent to
  be free-standing without additional support,
      but requires the same rope or cable
  anchoring system as a pole-supported tent
 to hold it in place, as specified by applicable
               fire or building codes.
           TENT Types

Box-beam, frame-supported tent
   A tent that features an assembled framework
       of box beams, I-beams or truss arches
     that support the fabric roof and define the
    shape of the structure. Also referred to as a
                   “free-span tent.”
                         TENT Types
         Tensile tent
    A fabric structure that shares some
        with the pole-supported tent,
  but relies more on the tensioning of the
  fabric roof for its structural integrity and
shape. The use of tensioned fabric to resist
   applied loads and to shape the fabric
    means less of a traditional support
     structure is needed to maintain it.
• Camping – This is perhaps the most common use of
tents. Lightweight, compaction for travel, and easy installation
make a tent an ideal solution for camping. Small size also makes a
tent desirable because it can be placed virtually anywhere.

• Carnivals – Tents used for carnivals are also very popular. It can
provide shelter for a large number of people. Carnivals are short-
term occasions; hence tents are an appropriate choice because
they are temporary structures.

•Ceremonies – Tents used for ceremonies (parties, weddings, etc.)
is similar to that of a carnival. It provides temporary shelter for a
short term that has a large number of people.
Other common uses of tents include:
-     Medical Shelter
-     Storage
-     Maintenance Buildings
-     Military Enclosure
-     Circus
-   Cannot withstand abnormal weather conditions

-   Not available to be used for multi-storey construction

-   Impractical for long-term use

-   Not comfortable relative to permanent structures

-   Limited privacy
     Construction Issues
The construction of tent may take minutes or days
depending on size. Construction usually begins by
rolling out the membrane. Then the poles are
inserted into the membrane either with sleeves or
with the top end being placed into the reinforced
holes. Then the poles are anchored into the ground
using stakes or ropes attached to the poles. For
smaller tents it is a relatively simple process, but
larger tents usually need several people to erect.

Great Indian Palace,Noida (India)
     Typical Materials
-   Poles: aluminium, composites (plastics)

-   Outer membrane: waterproof (also can be
     fireproof) canvas, nylon, Gore-Tex, polyester

-   Floor membrane (if it has one): plastic (similar to
     a plastic tarp), canvas

-   Stakes: metal, wood, or plastic

-   Zippers: metal (nickel in particular), plastic

-   Support ropes (if needed): nylon, cloth, twine

Tent structure for various purposes
    A cable stayed structure is a structure that is
    characterized by a tensioning of the fabric or
pliable material system generally with wire or cable
     to provide the critical structural support the

   Cable structures utilize technical fabric roof
membranes, a combination of catenary cables and
   clamping systems, and a minimal amount of
    framing to create proportionally lightweight
 structures capable of spanning great distances.
Tensile membranes are available in exterior grade
     vinyl and woven fabrics and Teflon coated
  Purpose of Cable Structure
Cable structures are fabricated as permanent or
temporary canopy structures for commercial or public
assembly, temporary event structures, modular
industrial construction and landscape artwork. This
unique fabric canopy strives for a light and airy look by
minimizing the amount of framing and utilizing the
strength of the fabric to help support the stability and
equilibrium of the structure.

Fabric tensioned structures are typically used as a
lightweight roof, protective cover, shelter, skylight,
advertisement and/or identification for stadiums,
arenas, shopping malls, amphitheaters, bandshell, stage
cover, tents, and shade structures for airport and
transportation depots.
            Suspension bridge
• A suspension bridge is a type of bridge in which the
  deck (the load-bearing portion) is hung below
  suspension cables on vertical suspenders.
• This type of bridge has cables suspended between
  towers, plus vertical suspender cables that carry the
  weight of the deck below, upon which traffic crosses.
  This arrangement allows the deck to be level or to
  arc upward for additional clearance.
  Advantages over other type of
• A suspension bridge can be made out of simple
  materials such as wood and common wire rope.
• Longer main spans are achievable than with any
  other type of bridge
• Less material may be required than other bridge
  types, even at spans they can achieve, leading to a
  reduced construction cost
• Except for installation of the initial temporary cables,
  little or no access from below is required during
  construction, for example allowing a waterway to
  remain open while the bridge is built above
• May be better able to withstand earthquake
  movements than can heavier and more rigid bridges
Disadvantages compared with
other bridge types:

Considerable stiffness or aerodynamic profiling may
be required to prevent the bridge deck vibrating
under high winds
The relatively low deck stiffness compared to other
(non-suspension) types of bridges makes it more
difficult to carry heavy rail traffic where high
concentrated live loads occur
Some access below may be required during
construction, to lift the initial cables or to lift deck
Suspended-deck suspension bridge with a distinctly arched deck
An early bridge of this type, the Clifton Suspension Bridge
   Types of cable structure
   based on roof cladding
Cable roofs can be divided into categories based on whether the roof
                      cladding is supported by:

 •Simple suspended cables

 •Pretensioned cable beams

 •Pretensioned cable nets

 •Pretensioned cable grids
     Simply suspended cable
The cladding of roof which are
rectangular or trapezoidal in plan can
be supported by a series of simply
suspended cable hanging in vertical
         In roofs which are circular or
elliptical in plan,the cables are
suspended radially and attached at the
perimeter of the roof to a compression
ring and at the centre to a tension ring
.For roof which in plan are ellipsoids or
of similar shapes,a combination of the
above two geometrical patterns.
 Pretensioned cable beams
Lighter & stiffer systems
than those above can be
achieve if a second set of
cables with reverse
curvature is connected to
the suspension cables.
             The resulting
system of cable beams
will be quite stuff if
tension under any
combination of applied
       Pretensioned cable nets
The 3rd type of cable roof structure is that in which
suspension & pretension cables all lie in one surface
and form a large net.

      As with cable beams for a net to be stiff the cable
must be in tensioned & it follows that the geometry of a
net must be such that all the surface is anticlastic or
saddle shape.
   few example are given below:
Pretensioned cable nets
     Pretensioned cable grid
Cable grids may be considered as double layer nets or
as multidirectional systems of intersecting cable

          However, from the point of view of structural
efficiency and practical consideration only those which
can be constructed as too or possibly 3 directional
convex, concave and convex –concave system are
practical possibilities
Stiffness of cable structures
The stiffness of cable structures is mainly a function of :

• The curvature of cables

• The cross sectional areas of cables

• The level of pretension

• The stiffness of the boundary and
   supporting structure.

The frame and cables are typically constructed
with steel. The cables will either be stainless
steel or coated with a clear PVC finish to
protect against corrosion. The steel frame will
be finished with a smooth layer of powder
coat over a base of primer. If the structure is
located near a harsh marine environment, then
an epoxy wet paint finish is provided.
  Cables Joints

Football ground in Madrid, Spain
Perspective view of cable
    dome structure
Notable cable supported roof

      Olympic Stadium, Munich
Notable cable supported roof

 Carlos Moseley Music Pavilion, New York ( U.S.A.)
Notable cable supported roof

    Millennium Dome(now The O2), London
Notable cable supported roof

  Denver International Airport Terminal, Denver
       Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one
or more column (normally referred to as towers or
pylons), with cables supporting the bridge deck.
       There are two major classes of cable-stayed
bridges: In a harp design, the cables are made nearly
parallel by attaching cables to various points on the
tower(s) so that the height of attachment of each cable
on the tower is similar to the distance from the tower
along the roadway to its lower attachment.
       In a fan design, the cables all connect to or pass
over the top of the tower.
Compared to other bridge types, the cable-stayed is
optimal for spans longer than typically seen in
cantilever bridges and shorter than those typically
requiring a suspension bridge.
  Key advantages of the cable-stayed
         form are as follows:
Much greater stiffness than the suspension bridge, so that
  deformations of the deck under live loads are reduced
 can be constructed by cantilevering out from the tower -
the cables act both as temporary and permanent supports
                    to the bridge deck.

A further advantage of the cable-stayed bridge is that any
 number of towers may be used. This bridge form can be
as easily built with a single tower, as with a pair of towers.
 However, a suspension bridge is usually built only with a
                        pair of towers.
Sectional view of deck &
Cable & clamp joints
Well known existing cable

 Frampton-Kenneth Pub Bridge,Zurich,Germany
Well known existing cable

Bandra -Worli sea Link,Mumbai,india
Pneumatic structures
 Pneumatic structures
• These are air inflated and air supported
  structures. the pressure differences
  between the enclosed space and the
  exterior are responsible for giving the
  building its shape and stabilizing the hull.
Pneumatic structures
 How pneumatic structures work?
 • A network of cables stiffens the fabric and
   the assembly is supported by a rigid ring at
   the edge. the air pressure within this
   bubble is increased slightly above normal
   atmospheric pressure and maintained by
   compressors or fans. air locks are required
   at entrances to prevent loss of internal air
   Pneumatic structures
• The membrane’s minimal weight and small
  size when deflated allow for easy
  manipulation and
 transport, hence offer a lot of perspectives
  towards repeated use at different locations.
  Pneumatic structures
• One of the main disadvantages of pure
  pneumatic constructions however is that a
  constant high air pressure is required to
  keep the elements in shape. This leads to
  higher energy costs, a parameter which
  cannot be relentlessly denied in a century
  of energy awareness.
   Pneumatic structures
• Form
Pneumatic structures follow strict physical
 rules, which influence their form-finding
 and their design process. The form of a
 pneumatic structure can always be derived
 from a specific formula: p = nk / rk+ ns / rs.
  Pneumatic structures
• Based on the results of this formula, a
  classification of three different types of
  constructions can be drafted.
Pneumatic structures
A first group of
are the air-supported halls,
which are fixed
circumferentially to a
foundation . The external
loads like forces of nature
and weight of the skin itself,
are supported by the air
residing inside the hall.
  Pneumatic structures
• Secondly, cushion structures
  are pneumatic structures in
  two layers. implement them as
  a cover on a primary structure
  and allowing them to guide
  horizontal forces into the main
  structure. Compression load is
  carried by an increase in
  pressure on the other side of
  the cushion.
   Pneumatic structures
• In modern constructions, we
  tend to notice the use of air
  beams mostly. Air beams are
  cushions in the form of a tube
  or sphere. These can be used
  for either compression struts or
  beams, as compression of
  bending leads to a reduction of
  the implemented volume.
  Therefore, inner pressure is
  increased, as well as pressure
  and bending resistance.
Pneumatic structures
• Materials
• Made from laminated membranes such as
  fiberglass, nylon, or polyester, coated with
  polyvinyl chloride (PVC), silicon rubber or
  Teflon for weather protection, the
  electronically welded components are
  tailored to define the building shape.
• The durability and heat and light-filtering
  properties of the membrane are
  determined by the careful choice of
  surface finishes and inner lining. Because
  of its lightness, the air-supported structure
  is among the most efficient structural
  forms combining high-tensile strength
 materials with the shell form.
• In structures where cables are necessary
  to maintain the form, mostly steel cabling
  is used.
 Although Kevlar and glass fiber cables are
  stiffer and stronger, they are not widely
  used because of a high cost and
  degradation issues when exposed to
  ultraviolet light.
Pneumatic structures
• Method of construction
 The fabric is not made and shipped in one
 piece. It is made in sheets, usually about
 3,6m wide and with varying length. The
 easiest and most common method of
 joining the fabric
together is the standard lap joint.
• The two pieces of fabric are overlapped by
  approximately 8cm and Teflon FEP
  (fluorinated ethylene-propylene) film is
  inserted between them. The joint is then
  heat welded together. When completed,
  the joint is stronger than the fabric, and
  completely water- and airtight.
View of pneumatic structure

  Yorkshire Pavilion - VA (Norway)
          Yorkshire pavilion

• The project is an attraction in itself with a
  striking exterior in the form of inflatable
  tubes arranged in the atomic structure of
  diamonds. The 20 x 26 x 10 meter
  diamond grid volume is mined out to
 form a cavernous interior space reminiscent
  of the coalmines of Yorkshire.
• A focus on flexibility gives the pavilion
configurations that allow it to be used for
  everything from small gatherings to large
  conferences or public presentations. The
  voluminous internal space will surprise
  and delight when installed in close
  quartered public squares. The pavilion can
  also be turned ‘inside out’ to open up a
  large covered area to open outdoor
  spaces to create the ultimate
mobile venue for concerts or big-screen
Air forest(mass studies)
             Air forest
• Air Forest is a 56.3 by 25 meter
structure, composed of 9 hexagonal
  canopy units, at 4 meter height. These
  units are interconnected as one large
  piece of fabric, which are then inflated
  from the 14 blowers that are located at
  the base
  inside its 35 columns.
• These columns are 5m apart, and are
  weighed down by dirt and lighting
  elements, which are also inside the
  columns, which light up at night and
  provide a public space after dark as well
     Each 6 of these pneumatic columns
  form a unit as they are connected in a
  hexagonal manner creating a circular
  opening from their inside perimeter
• Out of the 9 total hexagonal units formed,
  3 of them are left open-air while the
  remaining 6 have vortex shaped meshes
  that hang from them, providing shades for
  the public from any harsh sunlight. The
  nylon fabric is coated with a gradient of
  silver dots, whose reflective surface
  mimics the colors of its surrounding
  environment, as well as providing a playful
  dotted shadow on the people under the
View of pneumatic structure

  Yorkshire Pavilion - VA (Norway)

Biochemical Forest Research Study centre

Inflatable Teahouse-Kengo kuma, Frankfurt, Germany

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Puneet  Arora Puneet Arora - www.archibooks.tk