Paper bridges demonstrate engineering techniques, the physics of force and gravity, as well as how simple materials can create strong structures. The paper bridge building activity is one that can be adapted to younger students in addition to more complex and competitive lessons. The key to the paper bridge building exercise is to use primarily paper to build a bridge that supports weight, either a specified amount or a test of how much the bridge will support before failure.
Stack three books on a table or desk edge and the other three on an opposite table or desk edge. Set the tables the same distance apart as a sheet of standard white paper, less an inch on either side for the paper to rest on top.
Fold the white paper in whatever way the students choose, they should discuss different methods and try different ideas for this part of the exercise.
Lay the paper across the top of the book supports. Add pennies one at a time, laying them across the span of the folded paper the students have created. Do no place pennies on the book ends of the paper. Let the students continue putting pennies on the bridge until they see how many it supports until it fails. Have them try different designs to see which is the strongest.
Draw out a bridge design using different span techniques and determine which is the one you will use to construct your bridge. Various types of bridges such as the Warren Span conform well to using paper to construct the bridge, others such as cable suspension bridges do not.
Roll tubes of paper to create some of the elements of the bridge. Create as many tubes as you think you may need. You can seal them by running a thin line of glue on the outside end of the paper just before you reach the end of rolling it. Let the tubes dry.
Cut tubes down to create shorter elements. You can flatten tubes by pressing them down to create a strong level element as well. Flattening ends of some tubes and gluing them together is a good way to create strong joints. Begin putting your bridge together. As you go use the clothespins to hold joints or areas you have glued, but these must be removed later.
Insert toothpicks into certain areas of the bridge for support if it is allowed. You can overlap tubes by placing a smaller tube inside a larger one, insert the toothpicks through the joint then clip off the ends at the outside edge of the tube. Toothpicks should not be used for building any portion of the bridge, only as added joint support if that technique is allowed.
Create the span of the bridge by putting together trusses and a platform along the bottom of the bridge. Use standard flat paper, cut to fit, to cover the road surface of the bridge. Glue all the elements in place. Set the bridge across the wood blocks. Use the pennies to continue adding weight to test the strength of the bridge, or bridges if this is a group activity.