A Brief Overview of
Bridges
Preparation for Lab
Grade 7 Science
Ms. Willis
Learning Goals /Success Criteria
• I can describe different bridge types.
• I can identify geometric shapes used in bridge design.
• I will understand my expectations for the science lab in
building our a model bridge.
Bridges
Bridges provide important links between places. They
enable us to get to resources, conduct commerce, travel
and visit other people.
The design of bridges is important to the transportation
networks we depend on.
Types of Bridges
• There are many kinds of bridges, but generally they can
be classified into 4 main groups:
•
•
•
•
Beam bridge (includes truss bridges)
Arch bridge
Suspension bridge
Cable-stayed bridge
Arch Bridges
• The Arch bridge is the shape of a curved arch with
abutments at each end.
• Arch bridges work by transferring the weight of the
bridge and its loads partially into a horizontal thrust
restrained by the abutments at either side.
• This type of bridge was often used by the Romans who
built structures out of stone.
Arch Bridges
This is a Roman Aqueduct in France. It was difficult to span wide
distances without using several arches with supports. The piers
to support these arches can restrict water flow which can be
hazardous. These bridges can date as far back as the 1300s!
Arch Bridges
A modern arch bridge.....
This bridge is located in
Southern California.
Arch Bridges
Note: A voussoir (pronounced /vuˈswɑr/) is a
wedge-shaped element, typically a stone, used
in building an arch or vault.
Suspension Bridge
• A suspension bridge is a type of bridge in which
the deck (the load-bearing portion) is hung
below suspension cables on vertical suspenders.
The first modern examples of this type
of bridge were built in the early 19th century.
• These bridges can support tremendous weight
and span a wide distance.
Suspension Bridges
Mackinaw
Bridge in
Michigan
Total Length: 8 038m
Length of main span: 1 158m
Height: 168m
Longest suspension bridge in
Western Hemisphere.
Suspension Bridges
Cable-Stayed Bridges
• A cable-stayed bridge has one or more towers (or
pylons), from which cables support the bridge deck.
• There are two major classes of cable-stayed bridges:
harp and fan.
Harp bridge in Dublin, Ireland
Fan bridge in Washington, USA
Cable-Stayed Bridges
• Cable-stayed bridges differ from their suspension
predecessors in that they don't require
anchorages, nor do they need two towers.
• Instead, the cables run from the roadway up to a
single tower that alone bears the weight. The
tower of a cable-stayed bridge is responsible for
absorbing and dealing with compressional forces.
Cable-Stayed Bridges
Beam Bridges
• The beam ends rest on two or more piers or columns.
• A simple beam bridge is made of horizontal rigid beams.
Beam Bridges
The size and the material of the beams
determine the amount of force the bridge
can withstand.
Beam Bridges
• Truss bridges distribute the weight differently and are
often used for heavy car and railroad traffic.
• Truss bridges are a type of beam bridge.
Beam Bridges
• There are several different styles of Truss
Bridges:
Beam Bridges
Truss bridges distribute the weight making the
beam bridge much stronger with less material.
Let’s Take a Look....
• A closer look at how bridges are built:
• https://www.youtube.com/watch?v=hwzXXXUAKVU
• For interest: 25 Scariest Bridges!
• https://www.youtube.com/watch?v=_OIHRh6dto8
Review!
• Quiz to check your knowledge about bridges:
• http://science.howstuffworks.com/engineering/structural
/bridge-quiz.htm
• Decide the best place to put each type of bridge:
• http://www.pbs.org/wgbh/nova/tech/build-bridgep1.html
Your Assignment!
• Now it’s your turn!
• In groups of 2 or 3, you will build your own bridge.
• Follow the steps on your assignment sheet!
Review of Unit
• A review of our unit, Structures:
• https://www.youtube.com/watch?v=u2iPj4Cjajk (Bill
Nye)