Hindi
Study 3rd stanza of lesson-16 for a review on Tuesday,
15/3/16.
Science
Save the
following content and draw images of the following bridges as discussed in class in your science note
book.
Utility of Bridges
The bridges are very useful. They help to:
avoid traffic jam
cut down traffic
shorten trade routes
reduce travelling time
Structure of the bridge is an important factor. It determines the
Quality and strength of the bridge.
Types of Bridge
1. Girder Bridge or Beam Bridge: It is the simplest and the
oldest type of bridge. It is made of horizontal beams called girders. These are supported by
pillars at each end. The pillars bear the load of the beam. In a modern beam
bridge, large numbers of pillars are used to support the beam. So the bridge
does not become weak. The flyovers and the pedestrian bridges are examples of beam
bridge.
2.Cantilever bridge:
It is a balanced projecting structure built using cantilevers. Cantilever is a horizontal beam supported at one end. It carries
the load on the other end or along its length.
3. Arch bridge: It is an old type of bridge but very
strong. It is characterized by semicircular structures called arches. It spreads weight outwards
and downwards around the whole length of each arch. Earlier, these bridges were
made of stones and bricks. Now they are made of steel, concrete and bricks.
4. Suspension bridge: It is the longest type of bridge. It
is used to span wide rivers or bays. It is made using strong cables. The cables that support the
bridge are made from strong steel wires twisted together. These cables hang from
high towers on either side of the bridge. The modern suspension bridge can be
more than 2 km long.
For example, Akashi Kaikyo
in Japan is the longest suspension bridge in the world.
5. Cable stayed bridge: It is similar to the suspension
bridge. It is also supported by cables. But in this type of bridge, less cable is used. Also the
towers holding the cables are shorter.
6. Bamboo bridge. It is found commonly in villages. It is
built across a stream. The trees logs are used as pillars. The flat wooden
pieces are tied to the pillars using ropes.
