Bridge Expansion Joints

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.

The top half of this image shows a road surface with a metallic expansion joint running horizontally across the pavement. The bottom half of the image shows of two side-by-side close-up photos of the expansion joint. The left photo shows the joint and ruler at 13°F, with visible gaps between the metal plates. The right photo displays the joint at 68°F, where the metal plates appear to have expanded, reducing the gaps.

Council Bluffs

Iowa Core Standard

6-PS1-4

Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

Driving Question

Is the bridge connected to the road?

Probing Questions

Why were they put in?
How does temperature influence the bridge?
What would happen if they were not put in?
Why do objects expand and contract with temperature?

Classroom Suggestions

Students could:

Examine the picture of the expansion joint to see if students recognize it. Complete a notice and wonder activity using the photos.
Research expansion joints.
Research other types of expansion joints.

Resources

Popular Mechanics | 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.
Wired | 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.

Contributors

Submitted by Nathan Van Zante.