Cable and tensile structures

1. CABLE &TENSILE STRUCTURES
Rohan Joshi -Assignment 3

2. Cable structures
Cables are made of a series of small strands
twisted or bound together to form a much
larger cable. Steel cables are either spiral
strand, where circular rods are twisted
together and "glued" using a polymer, or
locked coil strand, where individual
interlocking steel strands form the cable.
Cable is a flexible structural component that
offers no resistance when compressed or
bent in a curved shape. Technically we can
say cable has zero bending rigidity. A cable is
the main component of cable supported
bridge or suspended roof structures.
Classification of cable structures
Suspension type cable structures :
The basic structural components of a
suspension bridge system include stiffening
girders/trusses, the main suspension cables,
main towers, and the anchorages for the
cables at each end of the bridge. ... The main
load carrying member is the main cables,
which are tension members made of high-
strength steel.
Cable-stayed type structures :
A cable-stayed bridge is a structural system
with a continuous girder supported by
inclined stay cables from the towers. Form
the mechanical point of view, the cable-
stayed bridge is a continuous girder bridge
supported by elastic supports.

3. Tensile structures
A tensile structure is a construction of elements carrying only tension and no compression or
bending. The term tensile should not be confused with tensegrity, which is a structural form with
both tension and compression elements. Tensile structures are the most common type of thin-
shell structures.
Tensioned Fabric Structure :
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.
Tensile Structures :
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.

4. Advantages of tensileStructures
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.
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.

5. A two-dimensional tension fabric membrane can take planar tensile forces, but it cannot take
significant forces perpendicular to this plane. Therefore, in addition to being pre-stressed,
tension fabric must take a certain three-dimensional shape, in order to remain stable. These
shapes were discovered by Otto and Berger during their investigation of natural forms, such
as soap bubbles.There are two types of general shapes:
Types of Tensile structures
Anticlastic Shapes :
Anticlastic Shapes are created by having the
radii of the principal curvatures on opposite
sides of the tension fabric surface. As a result,
when loaded at a particular point, tension will
increase on one curve of the membrane and
leave the opposite curve. Thereby, preserving
equilibrium and keeping the structure stable. In
order to keep anticlastic shapes, some kind of
structural frame or support is necessary in the
form of cables or steel beams. Some examples
of anticlastic shapes are saddle, cone and wave
forms.
Synclastic Shapes :
Synclastic Shapes are characterized by having
the radii of the principal curvatures on the same
side of the fabric. In order to counteract external
forces, pressure from the within is necessary.
This is why synclastic shapes are associated with
air-inflated structures. The difference of
pressure created by air pumped into the
building is able to counteract the external
forces, in the form of wind or snow.

6. Whether it’s a permanent durable structure that needs to last longer than 30 years, an
insulated membrane system for thermal performance or a deployable flexible application,
there are a variety of tensile membranes to choose from to meet specific performances for
your next building project.
By using translucent tensile fabric membranes like PTFE, PVC, Insulated Tensile Membrane or
transparent ETFE films, daylight is maximized in building interiors, thus reducing the costs for
electric lighting.
The following are types of tensile membranes which are widely used in India –
• PVC (Poly-vinyl Chloride)
• FRP (Fiberglass Reinforced Plastic)
• PTFE (Polytetrafluoroethylene)
• FILM
Types of Tensile Membranes

7. PVC (Poly-vinylChloride)
PVC coated polyester can be a great material choice for both permanent and temporary tensile
fabric structures. PVC coated polyester is known for its excellent strength, flexibility, translucency
and affordability compared to FRP and PTFE. The PVC coating, which is applied to polyester
includes UV stabilizers, fire retardant additives, and anti-fungicides. PVC coated polyester fabrics
have a structural lifespan greater than 20 years.
PTFE (Polytetrafluoroethylene)
PTFE coated glass cloth was developed by DuPont in the 1960s and has been used to create
tensile fabric structures since the early 1970s. Originally, the material had a lifespan of 25 years;
however, this has already been exceeded, with present day expectations lying somewhere
between 30 and 50 years. Today, it is considered to be the highest quality material for creating
tensile fabric membranes and the best choice if you desire a long lifespan and low maintenance.

8. FRP (Fiberglass Reinforced Plastic)
FRP (Fiber Reinforced Polymers) material is a type of composite material that is increasingly
used in the construction industry in recent years. Due to their light weight, high tensile strength,
and corrosion resistance and easy to implementation makes these material preferred solutions
for strengthening method of reinforced concrete structural elements. In this study it is aimed to
discuss advantages of FRP usage as a composite material. It is noted that the mechanical
properties of these materials shows a useful behavior for strengthened theoretically to satisfy
safe cross-section with FRP materials.
NAME FEATURES BUILT TYPE SPAN MARKET RATE
PVC Easily assembled
Eco friendly
Prefab 20-30m 300/sq.ft
PTFE Superior quality
Water proof
easy installation
Panel Build
Modular
25-45m 1750/sq.ft
FRP Light weight
High tensile strength
Corrosion resistance
Prefab 40-60m 75/sq.ft
Film Waterproof
Easily available
Post-
stressed
25-45m 350/sq.ft
The following table constitutes the properties of different tensile membranes in the Indian market

9. References
• https://www.rstensile.in/tensile-structure-manufacturer-in-india.html
• https://www.rstensile.in/tensile-fabric.html#tensile-fabric
• https://architizer.com/blog/product-guides/product-guide/tensile-fabrics/
• https://www.slideshare.net/MimiAlguidano/cable-and-tensile-structures-for-architecture-
and-engineering