Read the following text about bridges:
Spanning the gap
The world’s first bridge was probably built by an inquisitivemember of some prehistoric tribe who put a tree-trunk across a
stream to find out what was on the other side.
Today there are four main types of bridges - rigid beam bridges
which are based on the idea of simply putting a beam or plank
across a stream; cantilever bridges, where two beams are used,
one extending from each bank; suspension bridges consisting of
steel cables strung between high towers, with a roadway below
and the arch bridge, in which one or several arches are the main
support.
The earliest bridges were built from whatever material was at
hand - stone, tree trunks or vines. They were useful for crossing
narrow stretches of water.
The Romans made a great advance in bridge building, by using
the arch. They built hundreds of stone arch bridges throughout the
empire.
The use of metal in bridge building was another great breakthrough.
The ‘Iron bridge’, built in 1779 over the River Severn in
Engand, is the oldest cast-iron bridge still standing.
The Humber Bridge in England is the world’s longest
suspension bridge with a main span of 1,410 metres. The bridge
is made of giant steel cables strung over 163 metre high concrete
towers. The concrete towers are hollow. Inside are lifts that carry
engineers to the top, to carry out cable inspection.
The Sydney Harbour Bridge in Australia is 48 metres in width –
the widest in the world. It has eight lanes of traffic and two overhead
railway lines. Built in 1932, the bridge is a familiar part of the Sydney
skyline and is fondly called the ‘old coat hanger’.
The longest steel arch bridge in the world is the New River Gorge
Bridge in WestVirginia in the USA. It has a span of 518 metres. The
bridge completed in 1977, took just three years to build. Sections of
steel arch, weighing up to 86 tonnes, were lifted into place with special
cranes.
Task 1: Prepare a flow-chart, to show the history of bridges:
Pre historic times to Bridges today
Task 2: Name three of the world famous bridges and say why
they are famous.
Task 3: Work in pairs. Four main types of bridges have been
mentioned in the passage. Name them. Then say how
they are different from each other. If you don’t know,
refer to an encyclopaedia / your teacher / an architect.
Draw/collect pictures of different types of bridges.
1 comment:
mon really qualify as a valid reason to forego full third party
pok. Of course, what really sets the 3DS apart, though,
are the amazing stereoscopic 3-D graphics, which are totally customizable
using a 3-D depth-slider at the side of the 10%-larger top screen.
When the Nintendo 3DS is released in March,
it is going to be packed with features, some old and some new
but the main selling point is going to be the 3D gaming experience without
the need for 3D glasses but you will still be able to play your old
DS and DS Lite games in 2D using it.
my weblog 3ds emulator
Post a Comment