Build a bridge
Overarching question;
How do bridges work?
Unit Outcomes
Stage
ES1
Big idea
Outcome
Bridges span gaps
1
There are different kinds of
bridges
Four main types of bridge are
beam (including cantilever),
arch, and suspension. Bridges
act against the force of gravity
The different kinds of bridges
work by managing forces in
different ways
Bridges deal with the forces of
compression and tension in
different ways
2
3
4
Students explain that a bridge is a way around an
obstacle
Students describe and name different kinds of bridges
such as beam, arch and suspension
Students recognise different types of bridge and
explain that they act against gravity
Students identify forces of pushes and pulls acting in
different kinds of bridge
Students compare different types of bridge in terms of
forces of tension and compression acting
At a glance
Phase
Lesson
At a glance
Engage
Lesson 1
A bridge somewhere
Students look at images of different bridges and identify what
they know about what stops them falling down
Optional: video of bridge collapse
Explore
Lesson 2
Bridge the gap
Students use limited materials to construct different kinds of
bridges
Explain
Lesson 3
Take the strain
Students role play bridges, match them to one of 4 types and
identify where forces act.
Elaborate
Lesson 4
Walking the talk
Students link types of bridges to those seen on the River
Ramble
Elaborate
Lesson 5
Strong enough?
Lesson 6
Bridge Blog
Students conduct an investigation into beam strength
Evaluate
Students use images from lesson 4 to prepare a poster or
webpage representing what they know about different types of
bridges
Teacher background information
Bridges are structures that are designed to get over an obstacle – often a gap. To do this a bridge has to
support it’s own weight, the weight of any traffic and any forces from the weather.
There are three main ways they do this:
1. Beam bridge (spans up to 60m)
A single beam is supported by two piers. The force acts across the beam and down on the piers.
A truss bridge has the beam is strengthened by a triangular framework
cantilever bridge has arms supported from one end
2. Arch bridge (spans up to 250m)
is part of a circle which transfers all the forces to the foundations. Needs strong foundations on
good soil.
3. Suspension bridge (spans up to 2000m)
hangs from tall towers. The forces are in the hanging cable and the towers which are anchored
by another cable.
cable stayed bridge has the road hung off either side of the towers
Types of Bridges
A, beam
B: arch
C: suspension
D:cantilever
Engage
Lesson 1 A bridge somewhere
At a glance
To capture students interest in bridges and find out what they know about how they work.
Students
 Look at a range of images of bridges and identify what the know about them
Assessment focus
Diagnostic assessment to find out what students know about types of bridge design
Key lesson outcomes
 Students will represent their understanding as they annotate images of different kinds of bridge
Equipment
 Images of different kinds of bridges on poster or Smartboard and photocopied Bridge Hot Potato
sheets for students to use
 Optional access to : Collapse of the Tacoma Narrows Bridge
http://www.youtube.com/watch?v=3mclp9QmCGs
Preparation
Lesson steps
1. optional: show students video of Tacoma Narrows bridge collapse. Ask what made bridge
collapse.
2. show students image of Sydney Harbour Bridge. Ask what they know about it. Steer discussion
towards
What is its purpose (take traffic between Sydney and Northern suburbs)
What it has to be able to do (support weight of traffic)
How does it do that (accept students’ explanations). You could ask what forces might be acting
on the bridge? What might cause it to collapse?
3. Introduce other images of bridges. Students to work in groups to annotate their copies showing
what they know about how bridges support their loads. This can also be done as a hot potato.
4. collect & display students responses
Lesson 2 Bridge the Gap
At a glance
To give students hand on experience in constructing bridges to solve problems.
Students
 Use limited range of materials to solve the problem of bridging the gap.
 Discuss different solutions to the problem
Assessment focus
Diagnostic assessment to find out what students know about types of bridge design
Key lesson outcomes
Students will:
 Construct one or more kinds of bridges
 Describe how they work
Equipment (for 10 groups)
 Bridge the gap task photocopy sheet or smartboard file
 10 x 3 popsticks
 10 x 1m cotton
 10 x 2 marble sixed pieces of blutac
 Student tables
 Optional heavy duty scissors for cutting popsticks
Preparation
Lesson steps
1. Explain bridge task to students and allow them time to complete.
Literacy focus Remind them about labelled diagrams as a way of communication when the original
model is not available.
2. When the first bridge is completed set the challenge. They may ask for more cotton if 1m is not
enough. The may make a cut or notch in the popstick to help attach the cotton.
Explain
Lesson 3 Take the strain
At a glance
To support students to represent their understanding of how bridges manage forces and stay in place.
Students
 participate in a role play of different types of bridge.
 Annotate a diagram of the role play with pushes and pulls
 Apply the annotations to images of real bridges
Assessment focus
Formative assessment to give feedback on their developing understanding of the forces involved
Key lesson outcomes
Students:
 Explain that bridges have to overcome forces from own weight, weight of traffic and forces from the
weather
 Explain that these forces cause tension and compression in bridges
 Identify where these forces act in different bridges
Equipment

Preparation
Lesson steps
1. Revise the forces that bridges have to withstand (own weight, weight of traffic, weather forces)
2. Explain that we are going to use our bodies to find out more about these forces.
3. Ask students to push down on the table. Where can they feel the force? Tell them we will call it a
push (compression) because it feels like our arms are being pushed or might bend and buckle.
Demonstrate using →← to represent this
4. Ask students to pull up on the seat of the chair they are sitting on. Tell them we will call it a pull
(tension) because it feels like our arms are being stretched and might snap. Demonstrate using
←→ to represent this
5. Show students the sheet showing how to role play different kinds of bridges. Demonstrate for
each kind. Send students in groups of 3’s to role play each kind and record on the sheet where
they felt the pushes and pulls.
6. Give students sheet of different kinds of bridge types and ask if they can identify where the
forces are in the real thing.
7. Discuss with class.
Elaborate
Lesson 4 Walking the talk
At a glance
To provide opportunities for students to apply their understanding of bridge design to real life.
Students
 Identify types and forces acting on real bridges
Assessment focus
Key lesson outcomes
Students are able to identify the type and forces acting on one or more different bridges in real life
Equipment
 Access to camera
Preparation
Lesson steps
1. provide access to a number of different bridges e.g Torrens Linear Park walk (could be done in
real life or with images).
2. Ask students to work in a group to identify the type of bridge and get a photo taken of them role
playing that type with the bridge as a background.
3. give students feedback on how they know what type of bridge it is.
Elaborate
Lesson 5 Strong beams
At a glance
To give students the opportunity to conduct an investigation into the strength of different beams.
Students
 plan and conduct an investigation into the strength of different kinds of beams
Assessment focus
Summative assessment on investigation
Key lesson outcomes
Students
 formulate a testable question about the role of one variable in the strength of beams (e.g. different
laminated beams made by sticking paper layers together, trusses made by folding strips into
triangles)
 plan and carry out a fair test of the variable
 make and record investigations
 interpret patterns in graph
 provide evidence for conclusions
Equipment
 paper/ card strips of uniform size
 glue
 tape
 uniform sized weights, e.g. nails, bolts etc
 paperclips
 copies of variables grid and investigation planner
Preparation
Lesson steps
1. revise the forces in a beam bridge
2. explain that students are going to conduct an investigation into how beams can be
strengthened. They will be using paper strips as beams.
3. demonstrate how to measure the strength of a paper strip beam by systematically loading it with
weight
4. as how the beam could be strengthened (laminating two or more with glue or folding into
triangles are two possibilities
5. remind students about fair test – change one variable, measure one variable and keep
everything else the same
6. remind students about using replicates to check results
7. allow them time to plan and conduct investigation
Evaluate
Lesson 6 Bridge Blog
At a glance
To provide opportunities for students to represent what they know about bridges design.
Students
 prepare a poster of bridges showing what they know about bridges
Assessment focus
Summative assessment of the
Key lesson outcomes
Students will be able to:
 identify the type and forces acting on different types of bridges
Equipment
 poster materials either paper or electronic
Preparation
 make photos from lesson 4 available to students
Lesson steps
1. revise the types of bridges and the forces involved
2. explain that students will be using the images they organised in lesson 4 to construct a poster
showing what they know about types of bridges and how they support their weight.
Literacy focus: A poster is a multi modal representation of information and ideas. It might include
images, text, labels, arrows, graphs etc. It needs to have visual interest.
3. ask students to plan and produce a draft of their poster, Give them feedback before completing the
final version.
Bridge the Gap
Background
Bridges are structures that allow us to get over obstacles such as rivers, gaps, roads, railways
etc.
Challenge:
Build the simplest bridge you can to support a paperclip over an 8cm gap between 2 tables
using only the materials given.
Materials:
 3 popsticks (representing wood or steel beams)
 2 marble sized pieces blutac can’t be split up and must remain attached to the tables
(representing cement foundations)
 1 metre cotton thread (representing steel cable)
Presentation
Draw a diagram and/or take a photo of your bridge. Add annotations to explain how it holds up the
paperclip.
Going further
Make a bridge that can span the largest possible gap. Record as above.*
*
resource sheet for lesson 2 Bridge the Gap
A Bridge Somewhere*
*
Resource sheet for lesson 1 A bridge Somewhere
Bridges *
*
A
D
B
E
C
F
Resource sheet for lesson 3 Take the Strain
Bridge Hot Potato*
* *
What is this used for?
What does it need to be able to do?
How does it do this?
What forces are there?
Resource sheet for lesson 1 A Bridge Somewhere
Bridge Hot Potato*
*
What is this used for?
What does it need to be able to do?
How does it do this?
What forces are there?
Resource sheet for lesson 1 A Bridge Somewhere
Bridge Hot Potato*
* *
What is this used for?
What does it need to be able to do?
How does it do this?
What forces are there?
Resource sheet for lesson 1 A Sridge Somewhere
Bridge Hot Potato*
* *
What is this used for?
What does it need to be able to do?
How does it do this?
What forces are there?
Resource sheet for lesson 1 A Bridge Somewhere
Take the Strain*
Use arrows to show the forces in each bridge
→←for pulls (tension)
→← for pushes (compression)
*
Beam bridge
Beam bridge
Arch bridge
Arch bridge
Suspension bridge
Suspension bridge
Cantilever bridge
Cantilever bridge
Resource sheet for lesson 3 Take the strain
Image acknowledgements
A. garden bridge
image http://www.mooseyscountrygarden.com/garden-bridges/garden-bridges-no-cat.jpg
B. Forth Bridge
image http://www.edinphoto.org.uk/0_my_p_f/0_my_photographs_forth_bridges_-_calm_evening_xu34_large.jpg
C. Bottesford Bridges
image: http://www.bottesfordhistory.org.uk/images/uploaded/scaled/Bottesford_bridges_3_Arch_horizontal_crop.jpg)
D. Hell Gate Bridge (image: http://inqueens.com/bridges/hell_gate_bridge/hell_gate_bridge_triborough_7apr02.jpg)
E. Brooklyn Bridge (image
http://www.google.com/imgres?imgurl=http://www.tropicalisland.de/NYC_New_York_Brooklyn_Bridge_from_World_Trade_Cent
er_b.jpg&imgrefurl=http://www.shotinthedark.info/wp/%3Fp%3D1664&usg=___F7es5IigP5BuD4uCYAbFdcSGcA=&h=864&w=1
286&sz=236&hl=en&start=146&sig2=vM0_8b10qolsNrOo9vhKQ&um=1&itbs=1&tbnid=i_sS0WHI0G0pjM:&tbnh=101&tbnw=150&prev=/images%3Fq%3Dbridges%26start
%3D144%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1G1GGLQ_ENZZ261%26ndsp%3D18%26tbs%3Disch:1&ei=TM8i
TJW6N4ugkQXT7KDnBA)
F. Bunker Hill bridge
(image: http://www.google.com/imgres?imgurl=http://www.top-things-to-do.com/unitedstates/United-State-America/golden-gate-san-francisco.jpg&imgrefurl=http://chimprefuge.com/2009/12/07/favoritebridges/&usg=__2FY0jq75sSCq9ahMvctnOZe3ZE=&h=493&w=625&sz=142&hl=en&start=306&sig2=4C2nBM9s27RRuvXMeFyNKQ&um=1&itbs=1&tbnid=lcyp
SEACGpdnEM:&tbnh=107&tbnw=136&prev=/images%3Fq%3Dbridges%26start%3D288%26um%3D1%26hl%3Den%26sa%3
DN%26rlz%3D1G1GGLQ_ENZZ261%26ndsp%3D18%26tbs%3Disch:1&ei=2dAiTJfzEMGTkAWci6DuBA)
Staff training and development session
Purpose: to familiarise staff with the Build a Bridge inquiry unit
Engage:
Come up with as many questions as you can that your students might ask about
bridges. (or ask your students before hand)
Group the questions in some way that you can explain
Regroup with those that relate to the structure/design/working of bridges. How many
could be answered by first hand collection of data about bridges?
Explore/ Explain:
Try activities from unit. Discuss thinking behind and rationale for them
 Hot potato
 Bridge the Gap
 Take the strain
Elaborate:
What pitfalls, concerns, issues are there?
Evaluate:
Teach unit to class. Annotate your copy to describe how it went.
Websites
http://science.howstuffworks.com/bridge.htm
video – understanding bridges
http://science.howstuffworks.com/framed.htm?parent=bridge.htm&url=http://www.pbs
.org/wgbh/buildingbig/bridge/basics.html
Bridge challenge
http://science.howstuffworks.com/framed.htm?parent=bridge.htm&url=http://www.pbs
.org/wgbh/buildingbig/bridge/basics.html
Brad’s bridge simulation
Tacoma Narrows bridge collapse
http://www.youtube.com/watch?v=3mclp9QmCGs
Amazing bridges
http://www.google.com/imgres?imgurl=http://www.tensionnot.com/pics/albums/Amazi
ng/Amazing_Bridges/Pics_Amazing_Bridges_3.jpg&imgrefurl=http://www.rankfunny.
com/Amazing/Amazing_Bridges&usg=__Ph7W6QD5H5Ik4KMpumn1UxBCnLQ=&h=
300&w=400&sz=27&hl=en&start=19&sig2=Km90DLh3OR7O3QLbKEuv4w&um=1&it
bs=1&tbnid=m6IIcGKs5ZYV6M:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dbridg
es%26start%3D18%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1G1GGLQ_E
NZZ261%26ndsp%3D18%26tbs%3Disch:1&ei=yssiTJGvEYugkQWl6fzmBA
Images
Hell gate bridge
http://inqueens.com/bridges/hell_gate_bridge/hell_gate_bridge_triborough_7apr02.jp
g
Bottesford arch bridge
http://www.bottesfordhistory.org.uk/images/uploaded/scaled/Bottesford_bridges_3_A
rch_horizontal_crop.jpg
Forth Bridges
http://www.edinphoto.org.uk/0_my_p_f/0_my_photographs_forth_bridges__calm_evening_xu34_large.jpg
Brooklyn Bridge
http://www.google.com/imgres?imgurl=http://www.tropicalisland.de/NYC_New_York_
Brooklyn_Bridge_from_World_Trade_Center_b.jpg&imgrefurl=http://www.shotinthed
ark.info/wp/%3Fp%3D1664&usg=___F7es5IigP5BuD4uCYAbFdcSGcA=&h=864&w=
1286&sz=236&hl=en&start=146&sig2=vM0_8b10qolsNrOo9vhKQ&um=1&itbs=1&tbnid=i_sS0WHI0G0pjM:&tbnh=101&tbnw=150
&prev=/images%3Fq%3Dbridges%26start%3D144%26um%3D1%26hl%3Den%26s
a%3DN%26rlz%3D1G1GGLQ_ENZZ261%26ndsp%3D18%26tbs%3Disch:1&ei=TM
8iTJW6N4ugkQXT7KDnBA
garden bridge
http://www.mooseyscountrygarden.com/garden-bridges/garden-bridges-no-cat.jpg
USA bridges
http://www.google.com/imgres?imgurl=http://www.top-things-to-do.com/unitedstates/United-State-America/golden-gate-sanfrancisco.jpg&imgrefurl=http://chimprefuge.com/2009/12/07/favoritebridges/&usg=__2FY0jq75sSCq9ahMvctnOZe3ZE=&h=493&w=625&sz=142&hl=en&start=306&sig2=4C2nBM9s27R
RuvXMeFyNKQ&um=1&itbs=1&tbnid=lcypSEACGpdnEM:&tbnh=107&tbnw=136&pr
ev=/images%3Fq%3Dbridges%26start%3D288%26um%3D1%26hl%3Den%26sa%3
DN%26rlz%3D1G1GGLQ_ENZZ261%26ndsp%3D18%26tbs%3Disch:1&ei=2dAiTJf
zEMGTkAWci6DuBA
poster
http://antodebedout.edublogs.org/files/2008/04/bridges.gif