S P A C E F R A M E S
S U S P E N D E D R O O F S
M E M B R A N E S T R U C T U R E S
C A B L E S T R U C T U R E S
AND THEIR CONSTRUCTION
TECHNIQUES OF ERECTION
WHAT IS SPACE FRAME
AND WHY SHOULD WE USE
A three-dimensional structural
framework which is designed to
behave as an integral unit and to
withstand loads applied at any
SPACE FRAMES PROVIDE A
LIGHTWEIGHT SOLUTION TO THE
PROBLEM OF CREATING LARGE
Space Frames are typically used for
Roofing of Large Span Structures
without center columns which are
extremely useful in projects like:
Sports Stadiums, Airports,
Shopping Malls, Coal,
Cement & Sugar Storage Domes,
Skywalks, Pedestrian Bridges, Metro
Large Warehouses, Swimming Pools, Toll
Gates, Border Security Gates, Petrol/ Gas
2. LOAD TRANSMISSION
5. TYPES OF CABLE STRUCTURES
6. DIFFERENCE BETWEEN CABLE STAYED BRIDGE AND
CABLE SUSPENSION BRIDGE
Cable structure, Form of long-span structure that is subject to
tension and uses suspension cables for support. Highly
efficient, cable structures includes the suspension bridge, the
cable-stayed roof, and the bicycle-wheel roof.
A cable structure is a type of structure that utilizes tensioned
cables to support or transmit the major loads of the structure.
In conventional structures concrete columns are usually used
to support the self-weight of the structure as well as the
downward loads but there are cases where this system is
undesirable. Take for instance a soccer stadium. A major
column to take the dead load of the roof of the stadium
cannot be place in the middle of the structure because it
would land in the middle of the field.
An exoskeleton could be used, but it would probably mean the
structure would have to be very large to be able to support
such a large heavy roof
From ancient Roman canopies and rope bridges, to
modern day tents and suspension bridges cable structures,
also known as tensile structures, are applications of
"tension-only" members. It was not known that steel
cables, which first appeared during the industrial
revolution, could effectively be used in structures until the
late nineteenth century, when Vladimir Shukhov of Nizhny
Novgorod, Russia constructed the first tensile steel shell
The world's first diagrid hyperboloid structure by
Shukhov, Nizhny Novgorod, 1896
Based on arrangements of the cables
Based on the shape of pylon
A pile cap is a thick concrete mat that rests on concrete or timber piles that
have been driven into soft or unstable ground to provide a suitable stable
foundation. It usually forms part of the foundation of a building, typically a
multi-story building, structure or support base for heavy equipment. The cast
concrete pile cap distributes the load of the building into the piles.
It is a long slender foundation member made either of timber, structural steel or
concrete to transfer the load of the structure in deep foundation.
ADVANTAGE OF PILING
To take the structure deep into the ground and hence preventing over turning.
To provide a strong bedrock soil (i.e. higher bearing capacity) for the structure
and transfer the total load of the structure.
To distribute the weight of the structure over a large area.
To prevent unequal settlement.
radial : cables connect evenly throughout the deck, but all converge
on the top of the pier
harp : cables are parallel, and evenly spaced along the deck and
fan : a combination of radial and harp types
star-shaped : cables are connected to two opposite points
on the pier
A cable may be composed of one or more structural ropes, structural strands, locked coil strands or
parallel wire strands.
A strand is an assembly of wires formed helically around centre wire in one or more symmetrical
A strand can be used either as an individual load-carrying member, where radius or curvature is not a
major requirement, or as a component in the manufacture of the structural rope.
A rope is composed of a plurality of strands helically laid around a core. In contrast to the strand, a
rope provides increased curvature capability and is used where curvature of the cable becomes an
SELECTION OF CABLE CONFIGURATION
Cables are made of high-strength steel, usually encased in a plastic or steel
covering that is filled with grout , a fine grained form of concrete, for protection
The selection of cable configuration and number of cables is dependent
mainly on length of the span, type of loadings, number of roadway lanes,
height of towers, and the designer’s individual sense of proportion and
Cost also plays important role in deciding the selection.
Using less number of cables increases concentrated load at a single point
thereby requiring additional reinforcement for the deck slab as well as pylon .
Positions of the cables in space
Two plane system
Two Vertical Planes System
Two Inclined Planes System
The Single Plane System
Types of Cable Structures
Suspension bridges: the earliest method of crossing
• Early bridges realized from a walkway suspended
from hanging ropes of vines.
• To walk a lighter bridge of this type at a reasonable
pace requires a particular gliding step, as the more
normal walking step will induce travelling waves
that can cause the traveler to pitch
(uncomfortably) up and down or side-to-side.
• Suspension bridge realized following the simple
design of early bridges: cables (catenaries) / light
deck hangers & suspending the deck on catenaries
• Lack of stability in high winds
• Very flexible under concentrated
loads, as the form of the cable
will adapt to loading form
• Improved behavior under traffic
and wind loads: stiffening trusses
at the level of the deck, that
distributes concentrated loads
over greater lengths
• Alternatively: restrain vertical
movement of the catenaries by
inclined cables attached to the
top of the towers or inclined
struts below the deck
Cable-stayed bridges - A bridge which consists
of a superstructure of steel or reinforced
concrete members that is supported at one or
more points by cables extending from one or
more towers. The cables transfer their tensile
load to the towers .This load is then
transferred to the main column on which the
tower is constructed
• A cable-stayed bridge consists of one or
more piers, with cables supporting the
• Few of the main reasons for the
development of these types of bridges was
their low cost of construction, the speed of
erection and the fact that they had the
potential to cover a relatively longer spans.
• Basic idea: reduce the span of
the beam (deck) several times
compared to the clear span
between the piers
• Steel cable-stayed bridges are
regarded as the most
economical bridge design for
spans ranging between 200 and
• Reducing the span of a beam
greatly improves the maximum
stress and deflection
1. Cable-stayed bridges can be either concrete or steel though a combination of both materials is often
2. For concrete cable stayed bridges free cantilever construction is considered economical. With this method
the deck segments can be either precast or cast-in-situ by travelling shutter arrangement.
3. In a cable stayed bridge, depending on its design, the cables carry the bridge deck from one or both sides
of the supporting tower. The stay cables carry the deck and transfer all bridge loads to the foundations. This
is done by transmitting the cable stay forces, through its extremities, at it anchorage points. Stay cables are
firmly attached to the anchorages which are designed to resist the buckling forces of the loads.
Fig: Stay cable anchorages on a concrete deck
DIFFERENCE BETWEEN CABLE STAYED BRIDGE AND CABLE
A multiple-tower cable-stayed bridge may appear similar
to a suspension bridge, but in fact is very different in
principle and in the method of construction.
In the suspension bridge, a large cable hangs between
two towers, and is fastened at each end to anchorages in
the ground or to a massive structure.
These cables form the primary load-bearing structure for
the bridge deck. Before the deck is installed, the cables are
under tension from only their own weight.
Smaller cables or rods are then suspended from the main
cable, and used to support the load of the bridge deck,
which is lifted in sections and attached to the suspender
The tension on the cables must be transferred to the earth
by the anchorages, which are sometimes difficult to
construct owing to poor soil conditions.
Advantages of cable stayed bridges
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
for a symmetrical bridge (i.e. spans on
either side of the tower are the same), the
horizontal forces balance and
large ground anchorages are not
1. One benefit of cable structures is that the
tension forces in the cables can be used as points
of references in the analysis of structures. For
example, Figure 1 involves a weight (w) which
causes tension in the cable. This weight pushes
the cable down. The cable is now in tension.
2. Stability is another benefit of tensile structures.
The tension in the cables cause the resulting
structure to be stable. This is commonly
demonstrated in tents. As tents, or any structure
of that nature, are held by guy wires, which are
connected to a grounded point located at the
center of the structure, loads are free to act
anywhere on the structure. This is because the
guy wires are initially in tension.
1. One of the major benefits of cable structures is
that they allow you to displace loads from one part
of a structure to another part of the structure. In
the previous example the roof load of a soccer
stadium which was located at the center of the
structure was displaced to the extremities of the
structure. In contrast the loads from a structure
can be displaced from its extremities to a central
2. Another benefit of cables structures is that
compared to reinforced concrete, cables weigh
significantly less and they can generally hold
materials such as Kevlar vinyl and other 'soft
materials'. These soft materials act like a sheet or
blanket being pulled out at each corner, tension in
the material opens it up and gives it structure.
Cables supply the required tension to keep these
‘soft materials’ open and rigid.
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