Download Lesson Plan

Build the Brent Spence Bridge
Author(s)
Amy Dimmerling
Bethany Vice-Bowling
Emma Massie
Subject(s)
Geometry
Grade Level
10
Duration
3 – 80 min periods
Rationale (How this relates to engineering)
Steel fabricators take the engineer’s drawings and produce the steel pieces so that the contractor
can erect them. Generally engineers do not put angles measures on the blueprints. They only put
the necessary information to calculate the correct angles and lengths. This task requires basic
geometry and trigonometry skills. The students will be playing this role in this lesson.
Activity Summary
This lesson requires the students to do the job of a steel fabricator for a truss bridge. The bridge
used in this lesson is the Brent Spence Bridge in Cincinnati, Ohio. This bridge was divided into 8
different sections. Each group of students will be responsible for one section of the bridge. They
will use their geometry skills to find all of the angles and lengths of each member of this truss in
their section. The students will then scale down these members and create a scale drawing. From
these drawing the students will build a scale model of their section of the bridge and then combine
it with the other sections to create one large bridge.
Objectives
1. Students will utilize the basic geometric conjectures and theorems to determine missing
angles and member lengths
2. Students will use ratios to scale down their bridge section
3. Students will develop scaled drawings using their measurements
4. Students will construct at model of their bridge section
Standards
Mathematics
Geometry and Spatial Sense Standard
Grade 10
Construct congruent figures and similar figures using tools, such as compass, straightedge, and
protractor or dynamic geometry software.
Grade 9
Apply proportions to solve problems involving missing lengths and angle measures in similar
figures.
Grade 8
Determine and use scale factors for similar figures to solve problems using proportional reasoning.
Grade 7
Use proportions in several forms to solve problems involving similar figures (part-to-part, part-towhole, corresponding sides between figures).
Background Knowledge
1. Students must know basic geometry conjectures and theorems including but not limited to
triangle similarities.
2. Students must know how to use scale factors
3. Students must be able to construct figures using a ruler and protractor.
Materials Required
Handouts
Calculator
Ruler
Protractor
Building Materials – Option 1
 350 Wide Craft Sticks (like tongue depressors)
 Drill
 7/16” Drill Bit
 200 – No. 4 Machine Screws & Nuts
 Scissors
 Tape
 50 – “L” brackets
 100 – Washers for No. 4 or No. 6 Machine screws
Building Materials – Option 2
 350 Wide Bract Sticks (like tongue depressors)
 Scissors (one pair per group)
 Binder Cliips (Figure 1)
 Wood Glue
 100 – No. 4 Machine Screws & Nuts
 50 – “L” brackets
 100 – Washers for No. 4 or No. 6 Machine screws
Figure 1
Activities
Background
There are three major steps in constructing a bridge. First, the engineer designs the structure for
the loads. They calculate the size of the pieces (members) of the bridge. Second, the fabricator
takes the engineer’s design and produces each member. Once the members are produced the
contractor can build the structure. When designing the bridge the engineer is careful to only put
the information that is needed on the blueprints (drawings). They also do not want repeat
information on the drawings. This is to safeguard against changes. Although this keeps the
drawings consistent it is difficult for the fabricator to produce. The fabricator typically creates their
own drawings of the pieces of the bridge. They calculate all of the angles and member lengths to
place on their drawings.
Introduction – Day One
The warm-up is designed to remind the students about the principles they will need to use on this
project before getting started.
The first few slides of the presentation are to show different examples of triangles in bridge
construction. Triangles are the strongest, most efficient structural shape. They next slides
introduce the bridge in the project, the Brent Spence Bridge, to the students. Explain that the
bridge is symmetric about the middle. The rest of the presentation is breaking down the project to
the students.
The packets are distributed to the students and the procedure is repeated. The rest of the class is
spent working in groups to figure out all of the angles and lengths.
Day Two
The warm-up for day two is the scaling triangles handout. This problem is used to illustrate that
when scaling down a figure the lengths are multiplied by the scaled factor but the angles remain
the same. The scale factor at the bottom of the page is to be used during Part Two of the project
packet. The students then work together scaling down their figure.
Once all of the students scale down their sections of the bridge they can start to draw these
sections using the scaled down measurements. They will need to tape together sheets of paper to
draw their section.
Day Three
Day three is construction of the bridge. Each group will get the necessary supplies for their section.
Once all of the sections are built, the students can start to join the sections together to create each
side of the bridge. There are 16 sections for one bridge. If the classes are small then one class
can create one side of the bridge. If the classes are large then one bridge can be constructed per
class. To put the sides of the truss bridge together
Assessment of Student Learning
Portfolio project packet and the final bridge
Assessment of the Activity
Attached survey
Reflections
I used building materials, option 1, in this lesson. I measured and marked the holes for each of the
pieces. I grouped them in no more than 16 pieces and taped them together. I used two different
methods for drilling the pieces: (1) a cordless hand drill with a 7/16” pit and (2) a drill press with the
same bit. The most time consuming part was getting the correct materials. Once the pieces were
marked it only took a couple hours to drill and cut the pieces. These craft sticks can be easily cut
with a pair of scissors. Although the preparation was lengthy the lesson went very smoothly.
One set of pieces (Section 2 and 6 on the second bridge) did not go together quite right. I allowed
the students to try to figure out what went wrong and mark new holes on the pieces. I then drilled
the new holes to help get these pieces to go together better. One group made it work but the other
group couldn’t seem to figure out the problem. We were running out of time in this bell so we didn’t
get to put both sides of the bridge together but the students were still really proud of what they did.
There isn’t anything that I would change as far as the lesson is concerned. The teacher that I
worked with added the warm-up to review some key concepts before the lesson. It really helped
the students have an idea of what skills they would need.
This lesson can be adjusted for more advanced students. If the students are familiar with right
angle trigonometry functions then some of the lengths or angle measurements can be deleted to
make more advanced.