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Cable Suspension Bridge

Cable Suspension Bridge:

A Cable Suspension Bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders.

The different components of a Cable Suspension Bridge are mentioned below:

Based on the components described in the diagram, let us understand the different materials used the key components such as Main cable, Suspender Cables, Pylon/ Pier/ Tower, Decking and Stiffening Truss or Girder and Anchorage.

Main Cable:

The main function of cables is to support the deck which carries the traffic loadings and to transfer these traffic loadings to the towers and anchorages by direct tension forces.

Materials used for Main Cable:

  1. Bamboo or Simple Ropes
  2. Wrought Iron Chain Cables
  3. Steel Wire Cables
  4. Galvanised Steel Cables
  5. Twisted/ Spiralled and Galvanised Steel Cables (Helical Shaped Cables wrapped onto a straight centre core wire)
  6. Spiral Bridge Strand
  7. Locked Coil Strand
  8. Parallel Wire Cable

Suspender/ Hanger Cables:

The main function of hangers is to connect the bridge deck and stiffening girder to the main cables. Vertical hangers are used with equal intervals along the span. There are two types of Hanger arrangements that can be created in a suspension bridge based on the connecting ends of the Hanger cables namely: Two-part Hangers (ends are tied to the deck using sockets) and Single part Hangers (ends are tied to the deck using pin connections or simple bearing socket)

Materials used for Suspender/ Hanger Cables:

  1. Steel Wire Ropes (Two-Part Hanger type)
  2. Spiral Strand (Single-Part Hanger type)
  3. Parallel Wires (Single-Part Hanger type)

Pylon/ Pier/ Towers:

The main function of the Tower is to support the main cable. The ends of the main cables are connected to the tower which at a sufficient height to provide cable sag. Tower also supports the stiffening girder and side span. The initial loadings on the tower will be the vertical load acting at the top of the tower, applied by the main cables, together with the loads acting on cable and bridge deck due to wind load and load acting on stiffening girder. The flexible fixed base is provided for the tower and cable saddles are fixed on the top of the tower.

Materials used for Pylon/ Pier/ Towers:

  1. RCC
  2. Concrete
  3. Steel
  4. Wooden Piers
  5. Stone Masonry (For Shallow depths/ heights)

Deck with Truss or Girder:

The main function of the deck is to support the load. The deck is suspended on the main cables by using vertical hangers. The most important load that the deck has to carry is traffic loadings. The self-weight of the deck should be low because the deck is carried by the cables. Stiffening girders should be provided in the deck to transfer the loads from the deck to hanger. Stiffening Truss or Girder also help in reducing the impact of Wind Loads (Swaying)

Materials used for Stiffening Truss or Girder:

  1. Steel Girders or Truss
  2. Wooden Girders and Decks (for short spans)
  3. RCC (Beams) or Girder System
  4. Metal Decking with concrete

Anchorage:

The main function of Anchorage is to support the ends of the main cable and to prevents any movements in the main cable by transferring the force from the main cable to the ground.

Materials used for Anchorage:

  1. Concrete Blocks with Socket/ Hinge points bolted to the ground or with foundation.
  2. Steel Ball & Socket Joints with foundation.
  3. Stone Boulders with rope ties and steel bolts.

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