1. Let’s Learn About Bridges

2. Beam Bridge Simplest bridge form
A log across a street was the earliest form of a beam bridge
Consists of a horizontal beam supported at each end by a pier
The weight of the beam pushes down on the piers
The farther apart the piers, the weaker the beams
Beams can be placed at points other than the beginning and end
Usually these bridges are not longer than 250 feet.
Horizontal Beam
Pier
Beam Bridge

3. Beam bridge examples

4. Beam Bridges Why are these bridges a good idea….
Usually pretty easy to build
Inexpensive when compared to other bridge types
Can be used in rural or urban areas
Why are these bridges not such a good idea….
Ships cannot go under them
Construction not attractive
Costly if many piers are needed
Concrete used is cheaper but not as strong as steel
Beam Bridges

5. Truss BRidge Made of a series of triangles
One of the oldest types of bridges
A flat bridge is laid and then supports are built on both sides in triangle shapes both above and below the flat bridge
Can be any length
Many are railroad bridges
Truss BRidge

6. tRuss bridge

7. Truss Bridge Why are these bridges a good idea…. Very strong
Can support heavy loads
Made or steel
Economical to build
Easy to build and design
Why are these bridges a bad idea…
Difficult to construct
Take a lot of time and money to repair
Difficult to widen the bridges
Not very attractive
Truss Bridge

8. Arch Bridge Difficult to build Built a long time ago by the Romans
One of the most popular types of bridges
Different styles of arches can be used
Some of these bridges were built using stone and have stood the test of time
Arch Bridge

9. Arch Bridge

10. Arch Bridge Why are these bridges a good idea…
Can be made from a wide range of materials including wood, stone, concrete, and steel
Considered attractive
strong
Why are these bridges not such a good idea….
Expensive to build
Limited to where can be placed because ground needs to be strong enough to support it
Arch Bridge

11. These bridges can span 2,000 to 7,000 feet -- much farther than any other type of bridge!
Cables are hooked on vertical suspenders that support the road.
Found in harbors with lots of boat traffic.
Usually longer than other types of bridge.
Suspension Bridge

12. Suspension Bridge

13. Suspension Bridge Why are these bridges a good idea… Very strong
Can span long distances
Attractive
Allow boats and ship traffic to pass under them
May withstand earthquakes better than other kinds of bridges
Why are these bridges not such a good idea….
Expensive
Long time to build
Require large amounts of material
Suspension Bridge