The Arch Bridge

Arch bridges are one of the oldest types of bridges and have been around for thousands of years. Arch bridges have great natural strength.
They were originally built of stone or brick, and can be seen crossing rivers or roads all over the world. Modern arch bridges are built of reinforced concrete or steel.
The use of modern materials allows arch bridges to be longer with lower spans.
Instead of pushing straight down, the load of an arch bridge is carried outward along the curve of the arch to the supports at each end. The weight is transferred to the supports at either end, and then transmitted to the surrounding earth. 
These supports, called the “abutments”, carry the load and keep the ends of the bridge from spreading out.

The Stone Arch Bridge

The Arch Bridge is a very common bridge.
They were built with stone before iron and steel bridges were introduced.
The Romans built and used arch bridges throughout Europe and many of them are still standing today. The early engineers who built bridges with stone were working only with COMPRESSION forces.
Many ancient Arch Bridges stand today because the amount of stone used to make them, has made them last and last, and they are immensely strong.
THE KEYSTONE
The keystone is the most important stone in an arch bridge, without this stone the arch would collapse. The keystone holds the arch together.
In the exercise below you are going to draw a stone arch and label the keystone. Explain why the Keystone is very important.

Drawing Exercise : Use a compass, protractor, ruler and pencil to draw a Stone Arch Bridge

Follow the instructions to construct your own arch bridge drawing.
Use the drawing tools accurately. Draw faint lines as you will need to erase some lines to produce your completed drawing.
You could stretch and challenge yourself:-
  1. Use geometry techniques to construct and bisect angles of 60o  and 30o  to form 15o Degree angles.
  2. Produce your drawing on card, and then cut out each of the segments of the arch. Get your classmates to construct the arch from the segments.

The Ironbridge Gorge in Shropshire.

The Ironbridge Gorge is a deep gorge formed by the River Severn in Shropshire, England. The area was originally called the Severn Gorge.
The area is very well known across the world, because the industrial revolution started round here in the mid-1700s.
Ironbridge Gorge has mines, factories, workers' housing, and the transport infrastructure that was created in the gorge during the Industrial Revolution. Coke production in the area helped start the Industrial Revolution. The Iron Bridge was the world's first bridge built from iron.
Coke was a very important discovery. Formed from coal, Coke helps to heat iron ore to really high temperatures.
The gorge takes its name from its famous "Iron Bridge", the first iron bridge of its kind in the world. It is a monument to the industry that began there. The bridge was built in 1779 to link the industrial towns on either side of the river severn in the industrial centre of Coalbrookdale.
The Iron Bridge was the first arch bridge in the world to be made out of cast iron. Cast Iron was far too expensive to produce in the 1700s until iron could be produced in a huge blast furnace.
Cast iron works well with compression forces. It is far too brittle to be put into tension, it would fail.

Practical Challenge: Make a model of an Arch bridge using card and wood.

Follow the instructions to make a model of an arch bridge.
Add a second, or even a third arch. What effect or influence does this have to the overall rigidity of the arch bridge?
You could challenge yourself to add some of the decorative features found on the Iron Bridge at Coalbrookdale.

Research Exercise: Famous Arch Bridges around the world

Carry out research into famous Arch Bridges around the world.
Some famous ones are shown in the images opposite, can you identify them?
Find out the location of the bridge.
Find out when the bridge was built.
What does the bridge carry? Pedestrians, Trains, Cars, waterway?
What material is the bridge made from?
What other interesting facts can you find out?
How will you present your information?

 

Handy hint : ponte vecchio italy, Sydney Harbour Bridge, Hell Gate Bridge, Xinguang Bridge, Pont du Diable (Céret), Westminster Bridge, Fingle Bridge.