Bridges have to be strong enough to hold a load of weight. That load could be one person walking across a small footbridge, or hundreds of cars driving across a huge bay bridge. Engineers and architects must choose the support pieces—such as beam, arch, truss, and suspension cables—that will make each bridge strong enough.

You can build a simple beam bridge, arch bridge and truss bridge, all made from paper. Test which holds the heaviest load of pennies, then compare your test data online with other paper bridge builders.

  • 8 ½ “ X 11” card stock or construction paper (7-10 pieces)
  • 5-ounce paper or plastic cup
  • Pile of pennies
  • 2 same-size, empty boxes from cereal, shoes or crackers, for example (If you have 4 or 6 same-size boxes, you can test all 3 bridge designs at once.)
  • Scissors
  • Tape or glue
  • Tabletop or flat surface

BUILD YOUR BRIDGE

FOR ALL BRIDGE MODELS:


Stand 2 boxes up vertically, so the inside edges of the boxes are 6 inches apart inches (cm) apart.


Build the bridge. (See specific bridge instructions below)

BEAM (horizontal piece supporting the roadway)

Place one piece of paper—the beam—across the tops of the two boxes, making a bridge between them.

ARCH (upward-shaped curve supporting the roadway)

Tape or glue 3 pieces of paper together to make a long piece. Curve the long piece like an upside down U to make an arch. Place the arch between the two boxes. The top of the arch curve should be as high as the tops of the boxes. Now place a paper beam over the arch.

TRUSS (side panel supporting the roadway)

Fold a piece of paper in a lengthwise accordion fold. Glue flat pieces of paper over and under the folded sheet.

TEST YOUR BRIDGE


Place the cup on top of the middle of the bridge roadway.


Test each bridge by putting pennies in the cup, one at a time, until the roadway collapses under the load.

RECORD YOUR DATA


Write down how many pennies each bridge could hold.


Enter your penny data below to see how your bridges compare to others.

How many pennies did the beam bridge hold before it collapsed?

How many pennies did the arch bridge hold before it collapsed?

How many pennies did the truss bridge hold before it collapsed?

REVIEW YOUR PROJECT

Using the same materials as before, are there ways you could change the design to make a stronger bridge? Test your new design with pennies again, and see what happens.