Truss Designs

Many bridges use a truss structure to provide strength and stability.  A truss design is when you use triangle forms in buildings/bridges.  Many beam and suspension bridges use truss systems in their designs to aid in making the bridge stronger and more stable.  A truss design is an efficient use of materials and can help lower the cost of building bridges.

The kids were given gum drops and toothpicks and once again given the challenge to build a bridge using a truss design.  The 2 challenges.......How far apart can you make the unsupported bridge span? And, how much weight can it hold?

Most of the kids started with a cube-like structures.

As they continued to work and the bridges got longer, they started adding cross beams to form triangle shapes.

We talked about how the bridge has to support its own weight and the weight of people using the bridge.

Then, we started load testing.  Most of the bridges could hold several testing weights.

The kids learned that if bridge failure was going occur, it would most likely happen in the center of the span, where the bridge connected to the pier supports, or at the connections where the gum drop and toothpicks met.  Learning from failure is an important part of this process.

This group was 2 separate groups when we started, then they decided to work together and share materials.

We started load testing....and you can see, their bridge was pretty sturdy!

You have to love their faces!

It finally held 120 pennies.  The bridge didn't technically break aprt, but it did slip under the weight of the pennies.....this bridge wasn't equally balanced on both sides.....another important lesson to remember as we continue this process.

The final group had a very interesting design....they weren't concerned with have a longer bridge, they wanted to make the strongest bridge.  They tripled each set of toothpicks.

Their bridge held all 16 testing weights....160 pennies in all.  The bridge looked like it could hold another 16 penny weights.  Only 14 weights are pictured here....

So, we broke out the heavy reading textbooks.  How many of those could this toothpick bridge hold, if you said one, you would be incorrect!

Now THAT is a stable, strong bridge!!!!