Bridging the Gap
Grade Level: 5
Total Time Required: (Identify the number of
class sessions and minutes)
5- 45 minute class sessions
Prepared by: Lauri Mitchell & Matt Dillingham
Lesson Objectives: (List any 3 to 5 that directly apply to the lesson)
Students will be able to:
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Identify two types of bridge structures (beam and truss)
Define what a structure is and the importance of particular characteristics through diagrams and oral
recall.
Explain different types of forces and provide real examples of their occurrence.
Define mass and weight and describe what makes them different from one another.
Design and build a bridge prototype using the principles of the type of bridge being modeled.
Indiana Standards: (Identify 2-3 content/subject-specific standards and 3-5 design process-specific
standards)
Content specific
5.1.1
5.1.2
Describe and measure the volume and weight of a sample of a given material.
Describe the difference between weight and mass. Understand that weight is dependent on gravity and
mass is the amount of matter in a given substance or material.
The Design Process
Process Standards (Nature of Science)
 Use measurement skills and apply appropriate units when collecting data.
 Keep accurate records in a notebook during investigations and communicate findings to others using
graphs, charts, maps and models through oral and written reports
Process Standards (Design Process)
 Select the most appropriate materials to develop a solution that will meet the need.
 Create the solution through a prototype.
 Test and evaluate how well the solution meets the goal.
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Concepts and Vocabulary
Science Concepts / Vocabulary: (List and define relevant science/engineering/mathematical terms will
use or need to know)
Term
Force
Load
Stability
Compression
Tension
Torsion
Abutment
Truss
Biomimicry
Structure
Defined by a scientist or engineer
Influence causing an object to change in speed, direction, or
shape
A mass or weight supported by something
Resistant to change of position or condition
A force that squeezes a material together
A force that stretches a material apart
An action that twists a material
Part of a structure bearing the weight, the end of a bridge
In architecture and engineering, a supporting structure or
framework, usually made of one or more triangles
Studies nature's best ideas and then imitates these designs
and processes to solve human problems
Something constructed, such as a building. The way in
which parts are arranged or put together to form a whole.
Defined by a 5th grade student
Push or pull
Something that weighs down an object
Solid, not use to move around
Squeezing together
Pulling apart, like a tight rubber band
Twisting around, like a plastic ruler
Bridge end
Diagonal support pieces to help hold
something up.
the way designs are similar to real
things in science and nature
Things that stand up on their own, like
tables and houses.
Equipment, Materials and Tools
List the quantities of all materials and equipment needed:
Tools
Meter stick
Scissors
Quantity
1
1 pair per group
Materials
Drinking straws
Masking tape
Textbooks
Rubber ball
Pennies
Paper cups
Notecards
2
Quantity
20 per group
1 meter per group
6 per group
1
40-50
2
10 per group
Special Materials Notes and Comments
Materials Note: May need to look into using standard supportive braces since students will need their
textbooks for class. Shoe boxes could be a viable option if collected prior to the activity implementation.
Forces terminology sheet provided as last page of lesson. All vocabulary is interrelated: as students begin
to understand mass and weight as the idea of a load, the idea of forces will become easier to explain. The
specific forces that will be used to demonstrate the idea of load are tension, compression, and torsion.
Students will learn how these forces must be accounted for in structure design, which will introduce
abutment and truss as vocabulary, using the idea of biomimicry to show examples of nature overcoming
those same forces.
No specific special measures need to be taken into account with this lesson. If the design brief is intended
to be altered for different use, different bridge structures (suspension, arch, etc.) may be more ideal. The
type of bridges created by students should be suitable for the task provided to retain as much connection
to real scenarios as possible.
Different material could be used (toothpicks, popsicle sticks, glue, etc.) However, using only masking
tape and straws, this task is limited to the structure itself and eliminates the need for drying time as well.
Beam bridges
A beam or "girder" bridge is the simplest kind of bridge. In the past they may have taken the form of a log
across a stream but today they are more familiar to us large box steel girder bridges. There are lots of
different types of beam bridges.
A beam bridge needs to be stiff. It needs to resist twisting and bending under load.
In its most basic form, a beam bridge consists of a horizontal beam that is supported at each end by piers.
The weight of the beam pushes straight down on the piers.
Under load, the beam's top surface is pushed down or compressed while the bottom edge is stretched or
placed under tension. If we imagine that there is an imaginary line running down the centre of the beam
this line remains at its original length while the material above is compressed and the material below is
stretched. This line is referred to as the neutral axis.
The farther apart its supports, the weaker a beam bridge gets. As a result, beam bridges rarely span more
than 250 feet. This doesn't mean beam bridges aren't used to cross great distances it only means that there
may be a series of beam bridges joined together, creating what's known as a "continuous span."
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Information from http://www.design-technology.org/beambridges.htm
Covered Bridges in Tennessee-What is a Truss Bridge?
A truss is a series of individual members, acting in tension or compression and performing together as a
unit. On truss bridges, a tension member is subject to forces that pull outward at its ends. Even on a
"wooden" truss bridge, these members are often individual metal pieces such as bars or rods.
Compressive forces push or compress together and are heavier. The individual members form a triangular
pattern.
One bridge historian describes a truss bridge in this manner: "A truss is simply an interconnected
framework of beams that holds something up. The beams are usually arranged in a repeated triangular
pattern, since a triangle cannot be distorted by stress. In a truss bridge, two long - usually straight
members known as chords - form the top and bottom; they are connected by a web of vertical posts and
diagonals. The bridge is supported at the ends by abutments and sometimes in the middle by piers. A
properly designed and built truss will distribute stresses throughout its structure, allowing the bridge to
safely support its own weight, the weight of vehicles crossing it, and wind loads. The truss does not
support the roadway from above, like a suspension bridge, or from below, like an arch bridge; rather, it
makes the roadway stiffer and stronger, helping it hold together against the various loads it encounters."
(Eric DeLony, The Golden Age, Invention and Technology, 1994).
The pattern formed by the members combined with the stress distribution (tension and compression)
creates a specific truss type, such as a Warren or Pratt. Most truss types bear the name of the person(s)
who developed the pattern, such as the Pratt truss that is named for Caleb and Thomas Pratt who patented
it in 1844. For instance, the configuration or pattern of a Pratt and Howe truss appears identical (a series
of rectangles with X's), but a Howe's diagonals are in compression and the verticals in tension. In a Pratt,
the reverse is true.
In theory, a truss bridge contained no redundant members. Builders considered each member or element
essential to the functioning of the truss, although some were more important than others were. While most
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trusses could sustain considerable damage and lose the support of some members without collapsing,
severe traffic damage to a member could result in the collpase of the bridge.
Tennessee's four remaining historic covered bridges utilize one of these three truss types:
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Kingpost (the Parks Covered Bridge)
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Queenpost (the Harrisburg Covered Bridge and the Bible Covered Bridge)
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Howe (Elizabethton Covered Bridge)
Kingpost
Builders first developed the Kingpost as the most basic and earliest truss
type. The outline consisted of two diagonals in compression and a bottom
chord in tension that together formed a triangular shape. A vertical tension
rod (called a Kingpost and thus the origin of the truss name) divided the
triangle in half. After the mid-19th century, builders used metal (not wood)
for tension rods. Builderstypically used the Kingpost truss for shorter
spans, up to about 35 feet.
Queenpost
The Queenpost, another early and basic truss type, is a variation of the
Kingpost truss. AQueenpost truss contains two vertical members (rather
than the one in a Kingpost). These vertical members require the use of a
top chord to connect them. This arrangement forms a three panel span in
which the center rectangular area may or may not have crossed
diagonals. Again, the outer members act in compression and the vertical
rods (wood or metal) act in tension. This truss type can support spans up
to about 70 feet.
Howe Truss
William Howe patented the Howe truss in 1840. End diagonals connect the top and bottom chords, and all
wood members act in compression. Each panel has a diagonal timber compression member and a vertical
metal tension member, a material that conducts tensileforces
better than wood. The metal tension member eliminated a heavy
wooden member and reduced the dead load weight, and builders
could more easily join the screw and nut connections between iron
and wood than between wood members. Builders could use
multiple panels to increase the length of the bridge, typically
ranging between 100 and 150 feet.
Information from http://www.tdot.state.tn.us/bridges/trussbridges.htm
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Lesson Plan #1
Guiding Question – What is a structure?
Time: 45 minutes
Procedures / Steps: (Include and/or number the steps or procedures to follow. Note key
questions for students to consider / discuss)
1. Begin by showing students Powerpoint slides of arches and structures in nature (Arches
National Park, arch bridges, cantilever rock structures).
Ask:
 What do you see in these pictures?
 How are these designs being supported?
 Have you seen other examples like this in your community or on vacations?
2. Present the word biomimicry to students. Break the word into two parts, bio- and mimicry and encourage students to develop their own working definition before
providing a scientific one.
Ask:
 What do you think of when you hear the word part bio?
 What do you think of when you hear the word mimic?
 What do you think the word might mean if it has these two parts together?
3. Discuss how engineering and design often imitates successful structures in nature.
Provide definition and instruct students to write it down.
Ask:
 Where have you seen man-made designs that are similar to these pictures?
 What elements did they keep the same?
 What elements have they changed?
4. Explain that these are all types of structures (both natural and the man-made examples)
Ask:
What do you think makes something a structure?
What structures do you know or use on a regular basis? Inside? Outside?
What designs have you created in this class that focus on structures?
Why is it important to think about how different forces act on these structures?
5. Have students look around the room and spot a variety of different structures. Encourage
them to volunteer their observations and discuss the characteristics of each.
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6. Show student several pictures of structures with trusses (roofs, bridges, etc.)
Ask:
 What is the name of these structures?
 Have you seen these structures before? Where?
 What purpose do they serve?
 What geometric shape do these trusses usually have?
 How do they change the angles of the structure’s design?
7. Knowing that these elements of a structure are meant to add durability and strength,
discuss why that is necessary. Review key vocabulary with Powerpoint descriptions and
partner demonstrations.
Ask:
 Why is it important for these structures to be strong?
 What are the forces that may be acting on them?
8. Using pictures of bridges, tables, and other familiar structures, have students place Post-it
notes on the locations where they think compression, tension, and torsion may take place.
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Lesson Plan #2
Design Challenge – How do you build a bridge structure?
Time: 45 minutes
Preparation:
1. Students will read the design prompt on the following page.
Ask:
 What is the problem?
 Who is the client or user?
 What are the constraints?
 What do we already know about structures and geometric design?
 What do we know about structures from our previous engineering tasks?
 What are the different types of bridges we have discussed?
 What ideas about loads, compression, tension, and torsion do we know?
 How can we incorporate all of those ideas into our final design for this challenge?
2. Instruct students to record all important information in their design notebooks as always
(date, title of challenge, problem, client, constraints)
3. Explain to students that because the park is unsure of which type of bridge they want to
use, they want to see designs with a variety of types. Assign a different bridge structure
(beam, suspension, or arch) to each group.
Note: If possible, take a photo of the actual location of the proposed bridge so
students will have an idea of what they are working to achieve. Remind them that
this bridge will provide a safe means for them to travel to and from school each
day.
4. Provide time for students to work individually designing a bridge structure. Allow time
for teams to communicate after, share their plans with one another, and work to create
one final, detailed team design with a written description and rationale of why they
selected particular key elements. They should note in their designs the specific areas
where they think the forces will be acting most strongly.
Note: Students will be instructed to build their bridge structure using textbooks as
the abutments. They will use the additional materials to create the span of the
bridge. They should be drawing their designs with these features and the
characteristics of their assigned bridge type in mind.
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5. After the team design has been approved, students can gather the provided materials and
begin to build their structures. Students should be reminded that their bridge will be
tested for both stability and durability.
Lesson Plan #3
Design Challenge – Testing the Prototypes
What makes a structure successful?
Time: 1 hour
Procedures / Steps: (Include and/or number the steps or procedures to follow. Note key
questions for students to consider / discuss)
1. Students will present their bridge design to the class.
Ask:
 Which type of bridge structure did you model?
 Where are the key elements in your model that show us this is a ______ bridge?
2. Students will note all predicted areas where they forces would be acting most strongly
and explain how they used that knowledge in their design.
Ask:
 Where did you predict compression to take place most? Tension? Torsion?
 How did you use those predictions when creating your design?
3. Students will point out key geometric patterns they chose to incorporate in their design.
Ask:
 Which geometric shapes do you have in your design?
 What types of angles did you use in your bridge?
4. The ball stability test will be performed, placing a small rubber ball in the center of the
bridge to see if it rolls away or stays stationary.
5. They durability test will be performed using cups and pennies. After discussing mass
(discovering how much mass one penny has), pennies will be placed one by one until the
bridge can no longer support the weight of the load.
Ask:
 Where can you see compression, tension, and torsion acting on the bridge?
 Explain how mass and weight affect your design. Relate the description to load.
Follow up
Ask:
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
Suppose all the bridges in a large city (New York City, for example) were closed.
What effect would that have on that city? What are some specific ways that people
would adapt to not using bridges?
Assessment
Formative: Students work together as a group and all participate. Students answer questions
asked of them during the discussion. Students share notebook entries from the design challenge.
Students talk about what bridge type they created and why they felt it was effective or
ineffective. Students also talk about which bridge type they would choose if they were to design
another bridge using whichever bridge type they wanted.
Summative: Students will present their final designs and artifacts and test the durability of their
structures. Their design notebooks and artifacts will be assessed with attached rubrics. Also,
students will create a two-fold foldable to explain the two different bridge types following the
first half of teaching on the first day. The outside should have the name and a picture, and the
inside should have defining characteristics and examples of that type.
Rubric: Design Notebook (foldable included)
POOR (1)
Sketch
Clarity
Meets client’s needs &
design constraints
Written description
Understanding of
scientific concepts
FAIR (3)
EXCELLENT (5)
Team and/or individual
design missing, no use of
labels or measurements
Insufficient detail, messy
work and difficult to read
Both designs included,
minimal details and
labeling
Some details missing or
unclear, neatly presented
Follows assigned bridge
type in design, limited
creativity, fails to follow
two or more design
constraints, not ideal for
client’s needs
Missing key elements of
design notebook
elements, materials listed
without specific details,
Meets clients needs,
follows most design
constraints and assigned
bridge structure, limited
creativity
Individual & team design,
clear & sufficient labels/
details, drawn to scale
Clearly understood, plan
capable of being
reproduced by reader,
neatly presented
Exhibits creativity in
design, follows assigned
bridge type, meets all
constraints
Fails to include science
vocabulary in the
notebook or uses all
terms in correctly, does
not complete foldable
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Problem, client,
constraint identified,
title and date included,
specific & quantified
materials
Vocabulary recorded in
notebook and included
in conclusion but some
used incorrectly, proper
completion of foldable,
some mistakes in
terminology, explains
Exemplary explanation,
all necessary information
included, detailed
materials
Correctly recorded
science vocabulary and
definitions, quality
descriptions of two bridge
types in foldable, proper
use of vocabulary in
conclusions section,
that mass is the load,
properly labels different
forces in design
exhibits strong
understanding of where
forces act on structure
and how trusses and
abutments are used to
overcome the forces
Rubric: Artifact Design
Not met (0 points)
Constraints
Met (1 point)
Used 20 straws or less
Used 1 meter of tape or less
Bridge reached 25 cm apart
Modeled after the assigned
bridge type
Held at least 25 pennies
Lesson Extensions and Resources
Activity Extensions:
1. Depending on available time, students can consider the pros and cons of their designs and
draw redesign sketches in their notebooks.
2. In discussion of suspension bridges, students can create a human bridge using two strong
ropes as pictured here
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Lesson idea from http://teachers.egfi-k12.org/activity-build-a-human-suspension-bridge/
Interdisciplinary Activities
1. Math enrichment activity:
 Add expenses to the materials provided, requiring students to purchase building
supplies.
2. Literacy and writing activity:
 Have students write a persuasive letter to their local government expressing their
reasoning for the need of such a walking bridge near their school.
3. Social studies activities
 Students can learn about famous bridges in the United States or the world,
including bridges of a variety of types (e.g. covered bridges at link below).
 They will discuss how and why these bridges were created and how they have
affected the area in which they were built.
Web Resources:
Information about biomimicry:
http://biomimicryinstitute.org/about-us/what-is-biomimicry.html
International Bridge Contest at Purdue University:
https://engineering.purdue.edu/CE/AboutUs/News/Structures_Features/2010International
BridgeContest
Covered Bridges in Parke County Indiana
http://www.coveredbridges.com/
Activities on Tension and Compression (made for secondary level students but adaptable)
http://www.teachersdomain.org/resource/phy03.sci.phys.mfw.lp_tension/
Architecture: It’s Elementary! (Structure and design lessons made for 2nd grade but adaptable)
http://www.k5architecture.org/pdf/g2%20-%20Grade%202.pdf
Triangles in Truss Bridges Design Activity
http://www.education.com/science-fair/article/effect-triangle-size-strength-truss/
Photo References:
Natural Arches and Bridge Structures from
 http://2.bp.blogspot.com/_mcmWQYdjPAA/TQsdEe4LGUI/AAAAAAAAAjM/M_P7h_
M73cM/s1600/rock%2Bcantilever%2Bstone.jpg
 http://biosensing.files.wordpress.com/2009/05/cantilever_bridge1.jpg?w=499&h=373
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http://www.holywellramblers.org.uk/Cantilever%20Rock.jpg
http://mi9.com/wallpaper/0arch-arches-national-park-utah_75274/
http://www.gsi.ie/NR/rdonlyres/6923786C-CD2F-4697-B6C6-FE337A22BF4C/
0/P211442_green_bridge_wales.jpg
http://yuny-id3124.wikispaces.com/file/view/030_Beam_bridge.jpg/198822576/030_
Beam_bridge.jpg
http://rooftrussdesign.net/files/2011/04/wood_roof_trusses.jpg
http://www.vermonttimberworks.com/home/commercial/trusses/images/hotel-lobbytruss.jpg
http://www.builderbill-diy-help.com/image-files/belfast-truss.jpg
http://www.stevecapps.com/family/Assets/Images/cave_cades_putt_putt/Steve%20Cross
es%20Little%20River%20on%20Log%20at%20Cades%20Cove%20August%2024%202
002%20P8250052.jpg
http://www.yokogawa-bridge.co.jp/english/05_steelbridges/img/Arakawa.jpg
http://www.brewerplans.com/Image%20bucket/Thru-Truss-Bridge-drawing.gif
Tension & Compression Partner Activity Pictures from
http://teachers.egfi-k12.org/activity-build-a-human-suspension-bridge/
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Design Activity
Student Resource
Due to budget cuts, the City of Lafayette is cutting the number of crossing guards
used in the area. They have decided to put pedestrian bridges over high traffic
areas for Sunnyside and Lafayette Christian students walking to and from school,
such as 26th Street and South Street as well as 26th Street and Union Street. They
have decided to ask for your input on the design of a pedestrian walking bridge and
are deciding which type of bridge, either a beam bridge or truss bridge, would be
best to implement. They have asked for you to design prototypes to determine
which bridge type will be the strongest and use the least amount of materials.
This bridge needs to be safe for walking—it should be stable and durable for
several kids to walk across at the same time. It needs to span across the two lanes
of 26th Street and be tall enough for cars and trucks to pass underneath.
Guidelines
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Use only supplied materials (20 straws, 1 meter of tape, & 10 note cards)
Bridge spans 25 cm in length.
Bridge is built on abutments, with a bottom at least 15 cm off the ground.
Bridge can be fastened to the books being used as abutments, but no
materials can be secured to the floor or table.
 Bridge must be completed within the provided time limit
 Bridge must be able to support the mass of at least 25 pennies.
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 Bridge must fit the style of bridge assigned to
the team.
Load- A mass or weight supported by something
Compression- A force that squeezes a material together
Tension- A force that stretches a material apart
Torsion- An action that twists a material
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