Bridge Building Competition

Objective: 

This summer, at Johns Hopkins’ Explore Engineering Innovation Program, I designed a spaghetti bridge for a weight-bearing competition and did decently well. When given a second opportunity to build a bridge for a competition at my high school, I was determined to win!

Competition parameters:

• Bridge must be at least 35 cm long

• Bridge cannot dip more than 10 cm below the starting block

• Allowed materials: wood glue, popsicle sticks, cardboard

• Bridge must  allow two lanes of Hotwheel car traffic to cross (at least 4 inches wide)

• Maximum of 180 popsicle sticks

• Minimum bridge weight to hold for full marks was 20 pounds

Brainstorming process:

Based on my previous experience at  Johns Hopkins' engineering program and the limited allotted build time, I chose a simple truss bridge design. Additionally, I decided to use an interlocking layering design, because I knew that the joints would be the weakest point. Given that the weight would be hooked onto the middle of the bridge, I also decided to build a platform within the bridge for the hook to lay on using vertically rotated popsicle sticks. 

Assembly:

I built the side layers of the bridge one layer at a time, with a total of 9 layers on each truss of the bridge. Then, I connected the two sides using diagonal popsicle sticks to increase the strength. Finally, I added a cardboard roadway for the Hotwheels cars to pass over. I ended up using 178 popsicle sticks, just under the maximum amount.

Results:

Success! The bridge far surpassed the minimum requirement of 20 pounds, holding an incredible 285 pounds before the buckets holding the weights broke. There was no damage sustained by the bridge and had there been a way to add more weight, the bridge could have conceivably held much more. 285 pounds held -- I had broken the all-time record at my school by around 85 pounds!