STRUCTURAL
BRIDGES
Warm Up Questions
1. What is a bridge?
2. How are bridges used in today’s society?
Warm Up Questions
1. Identify the seven types of bridges.
2. Critique the two truss types and explain
which truss is stronger.
Long Truss
Multiple King
Post Truss
Warm Up Questions
1. Define Bridge.
2. Describe a type of bridge.
3. Explain the type of truss that you have
selected for your bridge.
What is a Bridge?
• A bridge extends a roadway across a land
obstacle or over water (excluding oceans).
• The design of the bridge depends on the
obstacle being crossed and the load the
bridge will carry.
Types of Bridges
•
•
•
•
Suspension
Arch
Beam
Truss
• Cantilever
• Cable-Stayed
• Movable/Draw
Definitions (Copy)
• Live Load – Weight that moves or
changes; A variable weight on a structure,
such as moving traffic on a bridge.
• Dead Load – Weight that does not move;
The invariable weight of a structure, such
as a bridge. It may also include any
permanent loads attached to the structure.
Load Exercise: Using the
definitions, identify which loads on a
bridge are “live” and which are “dead”.
•
•
•
•
•
Trucks parked
Concrete road
Wind
People walking
Grocery in the trunk
•
•
•
•
•
Bridge signs
Snow
Paint lines on the road
Street lamps
Rain water
Bridge Construction Vocabulary Terms
Using internet sources, define the following terms AND
use them in a sentence that relates to bridges:
• Abutment
• Anchorages
• Arch Bridge
• Compression
• Cable-stayed bridge
• Tension
• Cantilever bridge
• Buckling
• Girder
• Snapping
• Pier
• Dissipate
• Span
• Transfer
• Suspension
• Torsion
• Truss
• Deck-stiffening trusses
Compression is the action or state of being
squished down or made smaller or more
pressed together.
Tension is the force created by pulling
something tight or a strain.
Torsion is the process or condition of
twisting or turning one end while the other
end is held firm or twisted in the opposite
direction.
Shear is a force acting in a direction parallel
to a surface with and opposite force acting in
the other direction.
Brief Constructed Response #1
• You are a bridge inspector that has been
hired to inspect truss bridges.
• Write 4 to 6 sentences that explains how
“Live” and “Dead” loads would be handled
in your truss design.
• Use examples to illustrate how these loads
would be supported.
Straw Bridge Activity
• In groups of two’s, student will construct a
prototype of a truss using straws and tape.
• Log on to the class website:
http://technologysystems.yolasite.com
and go to the assignments page;
• Open the file: Truss Types (under BridgeBuilding) and select a truss to build using
twenty straws.
Extended Constructed Response # 1
You are a hired Engineer designed to
build a truss bridge for the new town.
Your employers are not convinced
that your bridge design would be
successful.
Create a BCR that explains how your
truss bridge will withstand the forces
placed on bridges: Compression,
Tension, Shear, and Torsion.
Student Activity #1
Students must identify at least
three different truss bridges in
Connecticut and bring in a picture
of each type of truss bridge.
Student Activity #2
VIRTUAL BRIDGE FORCES EXPERIMENT
• Access the following website:
http://www.pbs.org/wgbh/buildingbig/lab/forces.html
• Students must complete the virtual experiments and
write a 3 to 4 paragraph summary.
– Bridge Location details
– Bridge Span to be covered
– Type of bridge necessary at that location
– Explain how the selected bridge works at that
location and why others won’t work.
Student Activity #3
• VIRTUAL BRIDGE-BUILDING EXPERIMENT:
Students must complete the virtual experiments
as well as see real life examples and write a 4 to
6 paragraph summary.
• Access the following website to do the virtual
bridge-building experiments:
http://www.pbs.org/wgbh/buildingbig/bridge/chall
enge/index.html
Student Activity #4
1. Draw a sketch of your bridge;
2. Identify which popsicle/toothpick sticks
are in compression and tension;
3. In 1-2 paragraphs, explain how your
bridge supports loads.