Bridge Construction Lesson for Kids

Instructor: Tammie Mihet

Tammie has taught elementary school for 14 yrs. and holds an MA in Instructional Technology

Did you know that building Lego structures is a lot like constructing bridges? In this lesson, you'll discover the questions that engineers ask themselves when designing the world's bridges, and maybe even get some tips for improving your Lego structures, too.

A Lego Engineer

Do you play with Legos? Have you ever thought about the process that you go through when you build with Legos? For example, imagine you want to build a bridge out of Legos. You will need to think about how you will use the bridge, how long you want it to be, and even what type of bricks you will need to make it durable and strong. Well, guess what? You're thinking just like an engineer!

A special kind of engineer called a civil engineer designs and constructs bridges. When civil engineers set out to construct bridges they ask themselves several questions: where will it be built, how will it be used, and how long does it need to be?

Bridge Under Construction

Where Will It Be Built?

Engineers must consider where a bridge will be built, as weather can have a big effect on bridges. Is hot or cold? Does it snow? Is it windy? These weather factors will impact the types of materials that are used to construct the bridge. For example, in places where there are great changes in temperature, engineers must use expansion joints to allow the concrete to expand and contract with the changes in temperature. Also, in places where it snows, engineers must consider the extra weight of snow build-up when designing a bridge.

Engineers must also consider resonance. Even though you can't see it, bridges naturally vibrate, or move. Resonance happens when an outside force, like wind, an earthquake, or even people walking, increases the natural vibration of the bridge and causes violent swaying, which can lead to collapse!

Let's break this down. Think of a snowball that starts out small, but as it rolls downhill, it collects more and more snow until it becomes huge. Now imagine a bridge, which naturally vibrates, but just a little. However, an outside force pushes on the bridge in just the right way, so that it continually increases the vibration of the bridge, causing it to rock back and forth more and more. In June of 2000, the pedestrians crossing the Millennium Bridge in London caused this scary swaying, and the bridge was closed for nearly two years to fix the problem. Wow, is resonance powerful!

London Millennium Pedestrian Bridge

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