Lesson Plan – Straw Bridge Design Challenge
Grade Level
Topics Covered
Gr 4 and up
Straw Bridge Design Challenge
Objectives
General:
 Students will work in teams to design and build a bridge
using plastic straws and tape. (masking or scotch) The
models will be tested by adding weight to them until they
collapse.
Grade-Specific Prescribed Learning Outcomes (BC Curriculum):
 SCIENCE: Processes of Science
 Grade 4: Make predictions, supported by reason and
relevant to the content
(Designing a bridge and predicting how it would do)
 Grade 5: Identify variables that can be changed in an
experiment
(Changing the shapes used to build the bridge, number of
straws used, length of straws)
 Grade 6: Apply solutions to a technical problem
(How would you improve on your bridge design? What
geometric shapes could you use?)
 Grade 7: Create models that help to explain scientific
concepts and hypotheses
(Designing blueprint, making predictions, testing those
predictions, reflecting on how we learn from
mistakes/failures)
 MATH: Measurement and 3-D Objects and 2-D
Shapes
 Grade 4: Describe and construct rectangular and triangular
shapes (C4)
 Grade 5: Describe and provide examples of edges and
faces of 3-D objects, and sides of 2-D shapes that are
parallel, intersecting, perpendicular, vertical, horizontal (C5)
 Grade 6: Construct and compare triangles (C4)
 Grade 7: Perform geometric constructions (C3)
Materials
SWBAT (students will be able to):
1. Describe and design different types of bridges
2. Identify effective geometric shapes used in bridge design
3. Identify factors that civil engineers consider when
designing bridges
 50 plastic straws per team
 Tape for each team
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Scissors for each team
Handout for each team
Measuring tape/Ruler
2 tables/desks that can be separated 30 cm apart
A small paper/plastic cup or container and small objects that can be
used as weight. Marbles are a good idea. Each marble can represent
1 car.
Preparation
Beforehand
Teacher Contact:
- Use of tables/desks and scissors
- The activity will align with the processes of science section of the
Science IRP
- It would be helpful if the teacher separates the class into groups of 3
befordhand
Activity Preparation:
- Gather the above materials and separate them into kits for each team.
Background : Lesson plan was prepared by former civil engineer/now teacher candidate

From the Internet: After the Industrial Revolution, bridges became more and more sophisticated as iron
and steel became more commonly available. By using iron and steel, engineers could design bridges
capable of supporting larger loads and spanning greater distances, making it possible to link cities and
communities through shorter, more direct routes and crossing obstacles such as waterways or other
natural features that had previously blocked passage. Sometimes we take it for granted that 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 upon.
Below information can be discussed at any time during the activity. It’s optional and just extra
information. Critical information is embedded into lesson plan.

Connect the fact that while the materials used today will be different. The basic principles such as the
geometric shapes used will be the same for our straw bridges as for the bridges we drive over everyday.

Model making is extremely important for engineers. Would engineers build life-sized models of all their
designs? (Of course not! Money and time!) Nowadays, most of the modeling is done using computers. The
programs used to model bridges and buildings are actually very similar to the programs used to create 3-D
animated films. However, sometimes it is still useful to build physical models…and that’s what we will do
today!

How much would bridges cost to design and build? A small pedestrian bridge crossing a creek could cost a
few thousand dollars. The typical bridges we drive over that cross bodies of water would cost hundreds of
millions of dollars. The most expensive ones cost billions of dollars. Port Mann Bridge = $2.46 billion
Pictures and Example Bridge Designs at the end of this lesson plan
Introduction
Objectives
Identify
factors that
civil
engineers
consider
when
designing
bridges
Time
10 min
Instructions
- Introduce the concept of bridges. Why do we need
them? What are they for? What are some concerns an
engineer may have when designing a bridge? (e.g.
environment, cost, labor, weather, etc.) You could write
down their ideas on the board
-Ask them about bridges in Vancouver so that you are
connecting with the world they know. What bridge
connects ____ and ____? Which bridge will I go over to
get to ______? Which bridge is parallel to ______?
(Linking to their community and math PLO’s)
Draw a picture like the following on the board to help
explain instructions.
-“Today, we will be acting as a team of engineers
making bridge models. We have been asked by the City
of ___________ municipal government to create a
bridge to cross a river. An amusement park is being built
on the other side of the river and visitors need a way to
reach it!”
Design objectives:
 You will be given 50 straws and tape and these
are the only materials you can use to create your
model.
Materials
N/A





It will have to span the river. The distance our
model will have to span is 30 cm so make sure
the bridge is longer than 30 cm!
The river is the spawning area of many species
of fish. Therefore, we should not disturb this
river. No part of the bridge may touch the
‘water’! This means you can’t have pillars
supporting the bridge in the middle.
You cannot tape your bridge to the desks/tables
to help support it.
To test your design, we will be adding weight to
the bridge until it collapses. That means there
has to be an area in the middle of your bridge
where you can securely hold a small
cup/container. “How many cars can your bridge
hold until it collapses?”
Your design should ‘look’ like a real bridge.
That means you should not just tape a bunch of
straws together into a bundle.
-Reinforce in students that taking risks and making
mistakes are perfectly fine. Engineers do it all the time
when building models and testing. We are not trying to
find a winner in this activity.
Part #1 – Science in Bridge Building
Objectives
-Identify
effective
geometric
shapes used
in bridge
design
Time
15-20
min
Instructions
Note to Volunteer:
 Tensile Strength is the maximum stress that a
material can withstand while being
stretched/pulled before failing/breaking
 Compressive Strength is the opposite.
Demonstrate Straw Power: (Optional Extension: This
would be appropriate for higher level classes e.g. grade 7
and up)
1. Have two students come up and try to pull apart a
straw. Discuss “Tensile Strength” if class is at
that level. Otherwise, simply mention it is
difficult to pull a straw apart.
2. Now, cut a short piece of the straw off.
Demonstrate it is very difficult to push it
inwards. Discuss “Compressive Strength” if class
is at that level. Otherwise, simply mention it is
Materials
-Straw
-Optional:
premade
2-D/3-D
shapes
harder to crumple the straw if it is shorter. This
concept applies to all materials! Look at the
pillars and columns around your school. The
shorter they are, the harder they would be to
crumple.
3. Ask students to keep these concepts in mind
when designing their bridge. Where would you
want higher tensile strength? Where would you
want higher compressive strength?
Answer: Imagine loading a car on to a bridge.
You would want higher tensile strength at the
bottom of the bridge. You would want higher
compressive strength at the top of the bridge.
Go over Mathematics (Appropriate for all ages)
Ask students what are some 2-D and 3-D shapes they
know. These could be shapes they see in real life or
shapes they have learned in math (connect to their math
geometry unit and math PLO’s) Which shapes would be
better for constructing the bridge? Why?


Lower-level children: Simply use the reason that
some shapes (triangles, arches, X’s, diagonal
beams) would be stronger. They are sturdy.
Higher-level children: These shapes can bear
large loads without deformation. Distribution of
forces: The forces are distributed equally and
transmitted to the base.
Part #2: Design – Blueprint (Pictures at end of lesson plan)
Objectives
Time
10-15
-Describe
min
and design
different
types of
bridges
-Identify
effective
geometric
shapes used
in bridge
design
Instructions
-Give handout to students
Materials
Handouts
-Talk briefly about forming their engineering company
and assigning roles to each person. They will need a
president/spokesperson, civil engineer, and project
manager. If they are in groups of 4, they can have more
than 1 engineer or project manager. Have students think
of a name for their company
-Have students sketch a design of their bridge. As a
team, decide on one design they would like to build.
Volunteer should walk around and help guide their
thinking. Do not correct their designs unless it would be
impossible to construct it.
Part #3: Building Models (Pictures at end of lesson plan)
Objectives
Same as
previous
Time
45-60
min
Instructions
-Handout materials (straws and tape)
-Remind them that all students should help with the
construction
-The main job will be to keep the students on task. Let
students know how much time they have remaining.
(Write on board and tell them)
Materials
- Straws
- Tape
Part #4: Testing Models (Pictures at end of lesson plan)
Objectives
Same as
previous
Time
15-20
min
Instructions
- Set up tables 30 cm apart
- Gather students
- IMPORTANT: Reinforce to students that taking risks and
making mistakes are perfectly fine. Engineers do it all the
time when building models and testing. We do this to find
the best possible solution. We can learn from other people’s
models and designs. The results of our tests are definitely
important but all designs, regardless of whether they held
up a lot of cars, will teach us something important. It is not
about which group built the strongest bridge; it is about
learning about building bridges and model making. This is
important because some students will inevitably only see it
as a competition and will become upset if they ‘lose.’ Other
students may brag or make inappropriate comments if they
‘win.’
- The above will be the default strategy. However, some
teachers may want to make it into a competition with a
winning design. Most cars = winner. In some classes, this
could work. Please confirm with the teacher.
Materials
-Container
-Objects
to add to
container
(marbles)
-Have 1 group come up at a time; introduce their
companies and why they picked their design,
predictions, etc.
- Test models! If using marbles, put 5 marbles at a time.
Have students count along. You may want to have a
student hold their hands under the bridge to catch the
container with marbles when it falls. Otherwise, you will
have to pick up the marbles after every test.
- For some designs without secure spots for the
container, you may have to balance the cup using your
hands. That’s fine. The test is determining when the
bridge will collapse, not when the cup tips over. (Tell
this to the students so they don’t think it’s cheating.)
Note to volunteer: With bridges designed by grade 4’s to
7’s, most bridges held between 20 and 120 marbles.
You may want to set a ‘limit’ where you only test up to
100 marbles. Outstanding designs could take ~200
marbles.
Part #5: Closure
Objectives
Review
Pictures:
Designing
Time
2-5
min
Instructions
- After results, ask them some questions. What was
difficult about this challenge? What shapes did you
find useful in designing a bridge? Why were some
shapes better than others? What improvements could
you make after having observed all the tests?
- Praise students on excellent and varied designs.
- Have students clean up all materials/floors (Confirm
with teacher on how they want this to be done)
Materials
Building
Testing
Example Bridge Models
Example Designs Used in Real Bridges