Let’s Learn About Bridges

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

Beam bridge examples

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

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

tRuss bridge

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

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

Arch Bridge

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

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

Suspension Bridge

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