Paper Bridges

A civil engineering project from Science Buddies

June 11, 2015

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What shape makes the best bridge? Become a paper bridge engineer and learn about how shape plays a role in designing sturdy structures. Can you come up with an even stronger shape?

Key conceptsGravityCivil engineering

Introduction

Background

Both the bending stiffness and the shape are very important for civil engineers to consider when designing bridges. Lots of cars drive over a bridge all at once, and cars are very heavy. If the bridge's bending stiffness is not high enough, it could sag under the weight of all the cars or even collapse! So, whether a bridge is made out of stone, wood, steel or another sturdy material, civil engineers still have to carefully consider its shape.

Materials

• Four thick books (such as school textbooks, cookbooks, etcetera) that are roughly the same thickness
• At least six pieces of construction paper
• Scotch tape
• Ruler or measuring tape

Preparation

• Create two stacks of two textbooks each. Place them just under two feet apart from each other on a table, floor or other flat surface.
• Line up two pieces of paper end to end, so the short edges are overlapping just slightly (by about a quarter of an inch). Use long strips of Scotch tape to bind the pieces of paper together on both sides. These two pieces of paper will make one "bridge."
• Repeat this process for four more pairs of paper, so you can make five bridges total.

Procedure

• Take one of your taped-together bridges and lay an end on top of each pile of textbooks, with about half an inch of overlap. You might need to slide your textbooks closer together or farther apart a bit.
• Now take your next taped-together bridge. Tightly roll it into a long tube and use a few pieces of tape to hold the tube shut. Place the tube on top of your textbooks as you did before.
• Take your next taped-together bridge and fold it into a "W" shape lengthwise (meaning, when you look at the short end, you should see a W shape). Do this by folding in half lengthwise first, then folding each half again in the opposite direction (for a total of three fold lines, dividing the paper into four equal sections). Place the W shape on your textbooks like you did before.
• Extra: Create two new bridges and come up with your own designs. Now test them out.
• Extra: Put your bridges higher up, for example between two tables and chairs. Use some string and a plastic cup to hang weights from them. (You can use coins as weights.)

Observations and results

More to exploreBridge Science Project Ideas, from Science BuddiesFeel the Forces of a Suspension Bridge, from Bridge Facts, from Science KidsScience Activities for All Ages!, from Science Buddies

Science Buddies

Special thanks to Margot Vigeant at Bucknell University for this idea

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