Lesson title: Bridge Building Challenge
Pausch Bridge, Carnegie Mellon
Brief Summary: Student teams can design and build a bridge in response to a variety of challenges, using a variety of materials. Through this challenge the students explore the ways that different shapes and materials impact the overall success of their design.
Objectives: Students will work together as a team to design and build a bridge that meets a challenge such as:
- Span Challenge: Build a freestanding (not connected to anything for stability and without piers/support structures along the span) bridge that is at least -- cm. long. [Distance can be determined based on the materials being used and the age/grade of the students.]
- [Secondary] Load Challenge: at a minimum, the bridge must be able to hold – pennies.
This can also be varied to include a competition to determine which bridge design can hold the greatest load.
- Optional Design Challenge: prior to testing, the students can discuss and vote on the visual appeal of the bridge
Be creative – choose supplies that are available to you. Some popular materials for bridge building challenges are:
- Spaghetti noodles and marshmallows
- Newspaper and tape
- Cardboard and tape
- Toothpicks and gumdrops
- Popsicle sticks and glue
Other supplies that can be available include: scissors, meter stick
To simulate the constraints faced by engineers, who do not work with an unlimited supply of materials, the students should be given a budgeted amount of each item.
Students should be reminded not to eat any of the bridge building components, if edible materials are used.
- Deck: A bridge’s roadway or surface that allows traffic to cross
- Load: The forces that a bridge must resist, including the weight of the bridge and anything on it
- Span: The part of the bridge deck between supports
Vocabulary adapted from Noyce, Pendred E, Engineering Bridges Connecting the World, Boston: Tumblehome, Inc., 2019.
The class should be introduced to the importance of bridges to people around the world and the changes in bridge design over time. Key messages may include:
- Historically, people used resources that were available in their environment to find the materials such as wood, stones, vines or rope that they used to build bridges
- From Engineering Bridges, by Pendred Noyce: A bridge is a structure that spans a gap, usually over a river, a harbor, a canyon or a highway. The challenge is to build something strong enough to allow people, animals, vehicles or sometimes just water to cross safely.
Prior to the building challenges, student teams should be given time to explore and experiment with the materials that they will be using. They can also examine photographs of bridges to see how geometric shapes are incorporated into the design before testing the ways that they can make and connect shapes with their materials. After exploration students should work as a team to draw the design that they will build in response to the challenge. Each bridge must have a deck on which the load can be placed during the challenge. Changes can be made; however, the goal is for the groups to have a plan in mind prior to building.
The supplies and time given for the building challenge should be limited, just as these would be limited when an engineer is building a bridge.
Note: Since some bridges are likely to fall apart if a load competition is held, it is recommended that photographs are taken of each of the bridges, from a variety of angles. Following the competition the students can analyze the bridges to determine the design features that contributed to the strength of the most successful bridges.
For the Span Challenge, each group of students should describe their bridge design elements to the class and demonstrate that it is able to stand freely for a specific period of time. You can use blocks or books to create the space that must be crossed or you can use two desks that are a specific distance apart.
For the Load Challenge, the weights (pennies, washers, other uniform items that are determined in advance) should be added to the bridge deck until the bridge collapses or the maximum number is reached. Use a cup to keep the items from falling off of the side of the bridge. Pennies can be added in increments of 5, to a maximum of 100 [or some other preset number], depending on the materials that were used for the bridge. It is possible to conduct a second challenge to test those that held the initial maximum to determine their breaking point; however, in the interest of having all groups take a turn during the initial demonstration session, a pre-set limit for the first test makes sense.
Wrap-up and Reflection:
Students can work individually or in teams to reflect on and evaluate the bridge building and testing challenge, responding to questions such as:
- Did your team build the bridge that was on the original design sheet? If no, what did you need to change?
- Which elements of your final design worked well?
- List materials or tools that you wish you would have had to make the bridge building process more successful.
- If you could change anything that your team did when responding to the challenge it would be:
- What was the best part of the bridge challenge?
Next Generation Science Standards Alignment:
- K-2-ETS1-2 Engineering Design
- MS-ETS1-2 Engineering Design