(I wrote this in February of 2006 for a project I did with fourth and fifth graders during National Engineering Month.)

Introduction
Welcome to Bridge Building brought to you by the fourth and fifth grade class at Chrysalis Experiential Academy. We built bridges because we thought it would be fun to see how many pounds we could hold. Would you belive one bridge held over 100 pounds?

Here’s how we did it.

— Stephanos, grade 4
Rules
The class first agreed on ground rules for the project. They agreed to abide by these restrictions:

• Made only of school glue and craft sticks.
• Bridge must span 12″ minimum.
• Bridge must be at least 2″ tall and no more than 12″.
• Bridge roadway must be big enough for a Hot Wheels car to pass.
• Bridge must hold weight for at least 15 seconds to count.

Design the Test Apparatus
We used less than \$20 to buy simple hardware from Lowe’s. We knew we wanted to hang weight from the center of the bridge’s span, so we were looking for a plate from which we could suspend weight.

Testing Procedure
Another important part of the project was agreeing on the testing procedure.
We developed the following before any building began.

1. Weigh the bridge.
2. Weigh the testing rod.
3. Attach testing rod to the bridge.
4. Hang weight on the testing rod, incrementing by 1.25 pounds.
5. Start timer for 15 seconds.
6. Record weight and comments about bridge’s reaction.
7. Continue adding weight until bridge fails.

Tips
Stephanos

• “…make the stick supports double layered.”
• “Don’t put a ton of glue on. Use medium dots instead.”
• “Put binder clips on before glue dries to help make the bond stronger.”
• “Take your time. Neater bridges are stronger.”
• “Have a lot of popsicle sticks, glue, and clips ready when you start.”

Jake

• “The popsicle stick is stronger when on its side.”
• “When you make the roadway, stack the support sticks sandwich-style.”
• “Make your bridge strong on the ends, not just in the middle.”