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John Witherspoon Middle School
Engineering Club
Lesson Plan:
Bridging the Great Divide
Objective:
To encourage independent analytical thinking and engineering design through hands-on
learning.
To address the engineering principles in bridge design.
Materials:
A set number of K’Nex pieces (Per Team of 3-4 Students)
Two level surfaces
Small, stackable weights
Procedure:
Form groups of 3 or 4 students each, preferably with varying levels of engineering skills and
background.
Give brief introduction to the engineering principles in bridge design.
(10 minutes)
Work on the bridges.
(30 minutes)
Assess the weight capacity of the bridges and award prizes.
(15 minutes)
Worksheet for Students:
The worksheet will include a page for a sketch of the final bridge design and space for
explanations of the key design components.
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Guidance:
A truss-like form provides stability for the bridges, with the diagonal bracing aiding in
stiffening the structure and transferring loads.
An improvement upon this truss-form is to build a cantilever bridge, similar to the Quebec
Bridge (see below).
http://www.civeng.carleton.ca/Exhibits/Quebec_Bridge/images/p2.gif
A cantilever is a beam supported on only one end; to build a bridge like the Quebec Bridge,
two cantilevers would be constructed, and then a deck inserted in the middle (this can be
dropped down in between the structures).
An easy way to think of cantilevers is to picture the form as a diving board. Much like this,
the bridge is constructed outwards, with—until construction completion—one “arm” hanging
in the air.
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Another Approach:
Another approach to the bridge construction could be a simple arch bridge.
http://www.westcoastroads.com/california/images151/ca-154_cold_spring_bridge_10.jpg
In an arch bridge, the loads (e.g., live load (the weight applied to the structure, like cars or
trains passing over)) are transferred from the deck to the arch, which then can transfer
those loads to the supporting abutments (concrete connection to the mountain, as shown in
the picture above). Essentially, the loads flow from the deck to the arch and then to the
abutments.
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K’Nex Examples:
Arch Bridge
http://www.brightminds.co.uk/products/images/large/B7836.jpg
Arch Bridge
http://images.amazon.com/images/P/B00005KANP.01.LZZZZZZZ.jpg
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Truss
http://blockplay.blogspot.com/2007/06/bridges-towers.html
Awarding of Prizes:
All groups will be awarded small prizes. The group whose bridge can support the maximum load
will be awarded an additional prize.