Contest rules

Materials

Limit the structural parts of your bridge to only corrugated or shirt cardboard, white glue, cotton string, staples, brass fasteners, and masking tape.

Bridges may also be decorated with paint, markers, crayon, or construction paper if you wish.

Size

Your bridge must span at least 12 inches between its piers and have 6 inches of clearance under the road deck. The road deck should not be wider than 8 inches.

Judging

Vote as a class or ask an impartial judge to choose the Best-Looking and Most-Ingenious bridges.

The simplest test for the Strongest Bridge is to carefully pile on more weights (like books) until the bridge starts to sag. The bridge that holds the heaviest stack wins.

A more accurate way to judge the Strongest Bridge, though, is to divide the number of poinds each bridge holds by the number of pounds the bridge weighs all by itself. The bridge with the highest number (ratio) wins, because the best designs use the least materials to gain the most strength.

Variation

Decide on the rules together, but remember the special challenges that all bridges face:

1. They must span a minimum distance;
2. Use as little material as possible;
3. Hold as much weight possible.

See how many different ways you can devise to test these attributes of bridges, then choose the method that the most students agree is fair. Then build the bridges according to the rules you've established and judge them! You'll learn as much from determining the rules as you will from building the bridges!