CABLES

CABLES (WIRE ROPE)

• The term cable is often used interchangeably with wire rope.

• Wire rope is a type of cable which consists of several strands of metal wire laid (twisted) into a helix.

• However, in general, "wire rope" refers to diameter larger than 3/8 inch (9.52 mm).

• Sizes smaller than this are designated cable or cords.

MATERIALS

Initially wrought iron wires were used, but today steel is the main material used for wire ropes.

Stainless steel:- Used where corrosion resistance is prime factor. Galvanized carbon steel :- Used where strength is prime factor.

StructureIndividual wires are first twisted into a strand then six strands are twisted around a core which is used to cushion off stress forces when bending the rope.

(No of strands x No of wires in a strand)

6x19 cable

7x7 cable

7x19 cable

USES OF CABLESStructural uses:-• Suspension bridges• Cable stayed bridges• Long span roof structure• Inflatable membrane roofs• Elegant railings• Cable net glass walls

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.

Load transfer mechanism In suspension bridges, large main cables (normally 2)

hang between the towers (normally 2), and are anchored at each end to the ground. This can be difficult to implement when ground conditions are poor. The main cables, which are free to move on bearings in the towers, bear the load of the bridge deck. Before the deck is installed, the cables are under tension from their own weight. Along the main cables smaller cables or rods connect to the bridge deck, which is lifted in sections. As this is done, the tension in the cables increases, as it does with the live load of traffic crossing the bridge. The tension on the main cables is transferred to the ground at the anchorages and by downwards tug on the towers.

Cable stayed bridge

• A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck.

Types of Cable stayed bridge

Load transfer mechanism In the cable-stayed bridge, the towers are the primary

load-bearing structures which transmit the bridge loads to the ground. A cantilever approach is often used to support the bridge deck near the towers, but lengths further from them are supported by cables running directly to the towers.

This has the disadvantage, compared to the suspension bridge, that the cables pull to the sides as opposed to directly up, requiring the bridge deck to be stronger to resist the resulting horizontal compression loads; but has the advantage of not requiring firm anchorages to resist the horizontal pull of the main cables of the suspension bridge.

By design all static horizontal forces of the cable-stayed bridge are balanced so that the supporting towers do not tend to tilt or slide, needing only to resist horizontal forces from the live loads.

Elegant railings

Long span roof structure

Cable net glass walls

Inflatable membrane roofs

A low cost method and device for diverting water away from a flat roof's low spots, thus preventing it from puddling there during a rainstorm.

Other use :-

i. Cable transportii. Elevatorsiii. Cranesiv. Tightrope walkingv. Cargo derrick

Cable transportCable transport is a broad class of transport modes that have cables as foundation for transporting things, people, or vehicles.

The cable may be driven or passive; items may be moved by pulling, sliding, sailing, or by drives within the object being moved on cableways. The use of pulleys and balancing of loads going up and down are common elements of cable transport.

They are used in mountainous areas.

Elevators

CranesA crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally.

Tightrope Walking

Tightrope walking, also called funambulism, is the art of walking along a thin wire or rope. It has a long tradition in various countries and is commonly associated with the circus.

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