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BRIDGES By Jessica


Contents Introduction .......................................................................................................................................... 3 What is a bridge .................................................................................................................................... 4 Different types of bridges ..................................................................................................................... 5 The beam bridge .............................................................................................................................. 5 The arch bridge ................................................................................................................................ 5 The suspension/cable bridge ............................................................................................................ 6 The cantilever bridge ....................................................................................................................... 6 Sydney bridges ..................................................................................................................................... 7 Other information ............................................................................................................................... 10

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Introduction Bridges are very important to us in our lives. It helps us cross from one place to another. It is one of the greatest inventions in the world history. This book is about bridges. It talks about what is a bridge, different types of bridges,(the suspension/cable, the beam, the cantilever and the arch.), famous Sydney bridges, and some other information about bridges.

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What is a bridge A bridge is a structure. It helps you to cross from one place to another. Bridges are built to carry heavy loads. Some bridges are made for cars, others are made for animals and people. They must be strong and safe. In old days, most bridges were made of wood. Most modern bridges are made of steel and concrete. In ancient times, a log or two vines or woven fibrous ropes were thrown across a stream, to serve as a bridge. Later, arched structures of stone or brick were used. Bridge built from 4000 to 2000 B.C., have been found in the Mediterranean region. The Romans built long, arched spans, many of which are still standing.

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Different types of bridges There are lots of different types of bridges. Common types of bridges include beam bridges, arch bridges, suspension bridges, cantilever bridges, truss bridges, and cable-stayed bridges.

The beam bridge The beam bridge is not that steady. We have to use other types of stronger structures to build stronger bridges. For example, The Harbour Bridge. That needs a cantiliver or arch to build it steady. But beam bridges can be used for little bridges. For example, a bridge across the water. It wouldn't need to be that steady. A beam bridge may collapse in an earthquake.

A beam bridge

The arch bridge The arch bridge is a bridge that bends in the middle like a half circle. A boat when it tries can go above or below the bridge. The arch bridge is stronger than the beam bridge. An arch bridge can go on places that the beam bridge can't manage. That's why the arch is stronger than the beam bridge. For example, The Sydney Harbour Bridge is an arch bridge. It needs to be very strong to carry the massive loads of traffic.

An arch bridge 5


The suspension/cable bridge The suspension bridge is made up with lots of hangings from it. There are two places a suspension bridge can go: in a forest or above the water. The suspension bridge can survive earthquakes. Mostly the suspension bridge is not made out of triangles. The suspension bridge sways in an earthquake but doesn't fall. That’s why it is good if it sways a little. For example, the Golden Gate Bridge is a suspension/cable bridge.

Suspension/cable bridges

The cantilever bridge The cantilever bridge is mostly made of triangles. This helps it to stand still. The red and blue arrows in the diagram below shows the forces in a cantilever bridge.

The cantilever bridge is usually built to supreme strong bridges. In the cantilever type of bridge, two beams support another beam, which is where the deck or traffic way is. The beam must be anchored, and this must be done well.

A cantilever bridge 6


Sydney bridges There are some famous bridges in Sydney. For example, The Sydney Harbour bridge. It is a steel though arch bridge. The Pyrmont bridge. It’s a pedestrian bridge. It opens with electricity. The Anzac bridge. It’s a suspension/cable bridge. The Old grebe island bridge. It’s a beam bridge or called a swing. The Iron Cove bridge. It’s called a truss. The Gladesville bridge. It’s an arch. • The Harbour bridge has to be strong because lots of cars go over it each day. The Harbour bridge is the longest single span bridge in the world. The Harbour bridge is famous to us Australians. The steel Harbour bridge is made from looks curvy but actually straight. This bridge was complete in 1932. Here's a picture of the Harbour bridge.

• The Pyrmont bridge opens by electricity. It is recognised as a national landmark. It was one of the first bridges to be recognised electricity. The central sections are going to get rebuilt. This bridge is made of sandstone. Here is a picture of the Pyrmont bridge.

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• The Anzac bridge is a suspension/cable bridge. They built the Anzac bridge because there was increased traffic. About 9500 cars travel on the Anzac bridges a day. There's an Australian flag and a New Zealand flag on the Anzac bridge. The Anzac bridge is needed to be made of a suspension/cable bridge because 9500 cars travel on it each day. That’s a lot! The Anzac bridge has no triangles so it’s flexible. That’s good. Here's a picture of the Anzac bridge.

• The Old Glebe Island bridge is a beam or called a swing. It has to be opened every day to let cars pass. They built the Anzac bridge because the Old Glebe Island bridge couldn't hold that much cars. This bridge is very old. They finished building this bridge in 1902. Here's a picture of the Old Glebe island bridge.

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• The iron cove bridge is a truss. It was opened in 1955. It is made of concrete. It was the last trust bridge built in NSW and had an extra track lane added. Each of the trust bits is supported. It is made of seven bits. Here's a picture of the iron cove bridge.

• The Gladesville bridge is an arch bridge. It is a high level single arch concrete bridge. It is made from concrete. It was completed in 1964. It used to go in the Parramater bridge. It still has moss on it. It can support heavy traffic. Here's a picture of the Gladesville bridge.

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Other information The first bridges were probably logs laid across streams. Today very long bridges over rivers, roads, railways are vital parts of our transport system. You never know In the future bridges might change. You never know. There are types of bridges called animal bridges or even a spaghetti bridge! That would be cool to try.

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Bridges - by Jessica  

Jessica's Bridge Book

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