Bridge Technology Unit – Part I

As I am the only 6th grade science teacher at my school, ideas and suggestions are sometimes hard to come by.  I often turn to the internet my PLN to see what others are doing and borrow/get inspired from there.  Construction technology is a unit that I have found pieces for, but no example or explanation of how other teachers teach it.  It’s far from perfect – I’m forever tweeking the unit – but I want to share what I do in hopes it might help someone along the way.

At my school, there is no “technology” teacher dedicated to cover the technology portion of the Massachusetts Science/Technology/Engineering frameworks;  it’s done by the general science teacher (of which I’m one).  One of the standards I’m tasked with covering is standard 5 – Construction Technologies.   It reads:

5.1 Describe and explain parts of a structure, e.g.,
foundation, flooring, decking, wall, roofing systems.
5.2 Identify and describe three major types of bridges (e.g.,
arch, beam, and suspension) and their appropriate
uses (e.g., site, span, resources, and load).

5.3 Explain how the forces of tension, compression, torsion,
bending, and shear affect the performance of bridges.
5.4 Describe and explain the effects of loads and structural
shapes on bridges.

Before I begin my bridge unit, I teach a unit on forces and friction.  Here, we discuss balanced and unbalanced forces and their impact on objects; various types of friction; and Newton’s Laws of Motion – complete with demonstrations and opportunities for students to push, pull, and fling me around the room.  This establishes a collection of background knowledge that is useful when discussing tension, compression, and loads.

Building Big is a PBS miniseries hosted by David Macaulay, author of the book by the same title.  One of the episodes is on bridges, and this video serves as the entry to the unit.  It covers a variety of bridge designs, their history, and their uses.  Next, the class participates in a bridge webquest designed to have students research and gain understanding on four bridge types.  Several years back, I came across a webquest by Mike Whitman, a technology teacher in the Newton, MA school district, and I’ve been using it since (with minor tweeking).  I find the strength of this webquest lies in getting students to read between the lines and make logical conclusions based on the information they are presented; there is very little spoon-feeding of answers here, perfect for a sixth grade student.  From here, the class engages in an exploration and discussion about the forces, loads, and shapes using the interactive labs provided by PBS at their Building Big website.

The next phase in my unit has students designing their own truss bridges before they go and build.  Each bridge has a specific amount of material available for use – no more (this is to simulate working within a budget).  Also, each bridge must span a distance of 50cm and must support its dead load (its own weight).  To begin,  students first create rough sketches illustrating their side, top, and bottom (deck) designs.  Next, the class will use bridge simulation software to test out their designs and see where potential weaknesses may reside.  Traditionally, I like to use West Point Bridge Designer, but it only works on Windows & Apple machines, neither of which we have anymore.  This year, we used Bridge Constructor for the iPad.  Finally, just before the class builds their bridges, each group creates full-sized “blueprint” drawings of their side, top, and bottom pieces of their bridge, which will be used as templates during their build.

In the next post, I’ll talk about the building and testing process.

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