Bridge Expansion Joints

To compensate for the temperature fluctuations, among other things, bridges cannot be connected to the roads. Instead engineers use expansion joints to allow the bridge to move.

Possible Guiding, Compelling and/or Anchoring Questions

• Is the bridge connected to the road?
• Why were they put in?
• How does temperature influence the bridge?
• What would happen if they were not put in?

Classroom Suggestions

• This phenomena would be used to introduce particle motion.
• As things heat up they expand, as they cool they contract. Bridges are no exception to this. As bridges heat up they get longer, and smaller as they cool. Engineers need to account for this if they want their bridge to hold up to Iowa’s temperature fluctuation. 
• To introduce this in a lesson, begin by showing the picture of the expansion joint to see if students recognize it. Then have students research what it is. After students find out the name, and understand what it is for, move on to the questions below to expand their thinking. After the students have a good understanding of expansion joints, move onto why objects expand and contract with temperature. 
• Extension: The last website provided goes more in depth on types of expansion bridges if students need a challenge. What type of expansion joint should be on this bridge?

Related Resources

How and why bridges are made to move: This is an introduction about why bridges are made to move. There is a video on the site as well, but you can get all of the information from the reading as well.
Why do solids expand when heated?: This site is above the 6th grade level, but it can give you (the teacher) a better understanding on why solids expand. If you go down to the bottom it shows the ball and ring demonstration that could also help teach the phenomenon. 
RJ Watson Inc.: Expansion Joints: This is a more in depth website on all the different types of expansion joints. It goes into detail on how each one works, and the specific application where it would be used.