*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.
A bridge collapse, like that of the I-35W Mississippi River Bridge shown below, can be a major disaster. Bridges that cannot hold enough weight to do their intended job can be a serious public safety issue. And if they collapse, they can also cause economic damage due to costly rebuilding and people and companies scrambling to figure out how to circumvent the months of traffic impacts.
On August 1, 2007 the I-35W Mississippi River Bridge collapsed killing 13 people and injuring 140 others. The collapse
was captured in a series of photos from a nearby security camera. It was later determined by the NSTA
that a design flaw was the primary reason for the bridge's collapse (U.S. Army Corps of Engineers, 2007).
You can investigate how different bridge designs are ideal for different situations. Do some bridge designs hold more weight than others? Do they require more materials? What is the strongest bridge that can be built for the least amount of materials? Try your hand at building and testing a couple of bridges. You may be interested in creating your own bridge designs or modeling some existing designs. Or you can read more about the I-35W Mississippi River Bridge collapse, or other famous bridge collapses, and model that disaster.
This is an engineering project, so the materials you use will depend on your engineering goals. Here are
suggested materials, all of which are available in a kit from AquaPhoenix Education:
Graph paper, for drawing bridge schematics
Popsicle® sticks (about 60–100 per bridge, depending on the design)
Wire cutters, for cutting Popsicle sticks
Elmer's® Carpenter's Wood Glue or Elmer's® Glue-All
Cotton swabs, for applying wood glue (about 100)
Binder clips, in both medium and small sizes, for clamping joints on Popsicle stick bridges (12 of each size per bridge; you will need more if you build more than one bridge at a time)
Plastic straws, straight (about 20–30 per bridge, depending on the design)
Clear tape, ½ inch width
Gram balance for weighing bridges, such as the Fast Weigh MS-500-BLK Digital Pocket Scale, 500 by 0.1 G , available at
Loading block with hook or eyebolt, for testing bridge strength
Container for holding bridge load, such as a large bucket
Rope, ¼ inch to ½ inch diameter (about 3 feet)
Weights for testing bridge strength (can use metal weights, sand, or water in a container)
Bathroom scale, for weighing how much weight it takes to break the bridge. The basic version of the AquaPhoenix Education kit does not include a bathroom scale. A deluxe version that has the bathroom scale is also available.
If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: I am trying to print the schematics from the website, but they are not printing at full size, or only half the schematic is printing. What can I do?
A: The schematics are made for 11 inch by 17 inch paper. If you are printing them on smaller paper, then the schematics will not print correctly. Depending on your printer, only part of the schematic may print, or the entire thing might be shrunk to fit on your printer's paper. Try printing the schematics on a printer that prints on 11 inch by 17 inch paper. You can find these at most copy centers. Or, check your printer's owner's manual to see if your printer can tile a larger page onto multiple, smaller pages.
Q: How long should I let the glue dry before unclamping the clamps on a Popsicle stick bridge?
A: Let the glue dry completely before removing the clamps. 8 hours of drying time is a good rule-of-thumb, but the glue may take shorter or longer to try, depending on the temperature and humidity of your workplace. When comparing bridge designs, make sure to let each bridge dry for the same amount of time.
Q: I am having a hard time finding two things that are the same height to lay my bridge across. Is it important than the supports the bridge rests on are the same height?
A: Yes, it is important that both sides supporting the bridge are the same height, otherwise the force of the load will not be symmetrically distributed across the bridge. If you are having problems finding two objects that are the same height, you can put some cardboard, books, or paper on top of the shorter object to make it as tall as the taller object.
Q: My bucket or loading container is all the way full, but the bridge has not broken. What should I do?
A: You built a strong bridge! You have a couple options. First, you could detach the bucket or loading container from the bridge and replace it with a larger bucket. Or, you could fill the bucket with a denser material. Sand, for example, is denser than water, so a bucket full of sand will weigh more than a bucket full of water, if the two buckets are the same size.
Q: How do I make this into a science project?
A: This science project (or engineering project, to be more precise) is very open-ended. Once you have built the two bridges whose designs come with the project, use the Engineering Design Project Guide [http://www.sciencebuddies.org/science-fair-projects/engineering-design-process-guide.shtml] to help you refine your goals. Think about what criteria you want your bridges to meet (how much weight to hold, a particular strength-to-weight ratio, how long the bridge can be, etc.) and then design a bridge to meet those criteria. Build and test that bridge, and use what you learn from that first bridge to improve the next one you build. Continue improving your bridge design until you meet your design criteria.
Ask an Expert
If you have other questions about the procedure or need assistance troubleshooting your project or the Experimental Procedure, please post your question in the forum for this kit at Ask an Expert: http://www.sciencebuddies.org/science-fair-projects/phpBB3/viewforum.php?f=73. Our team of volunteer Experts is available to assist. We attempt to reply to questions within 24 hours. Please note that you will need a free Ask an Expert account in order to post questions.
If you like this project, you might enjoy exploring these related careers:
If you turned on a faucet, used a bathroom, or visited a public space (like a road, a building, or a bridge) today, then you've used or visited a project that civil engineers helped to design and build. Civil engineers work to improve travel and commerce, provide people with safe drinking water and sanitation, and protect communities from earthquakes and floods. This important and ancient work is combined with a desire to make structures that are as beautiful and environmentally sound, as they are functional and cost-effective.
Have you ever visited family members for the holidays? You might have started your trip by taking the subway or a train to the airport. Then you jumped on a plane and flew to your destination. Finally, a family member picked you up in his or her car and drove you home. You traveled hundreds of miles in just one day. How did this happen? Who planned the subway route to the airport? Who decided the position of the airport runway? Who designed the highways and roadways? The answer to all of these questions is the transportation engineer. The goal of the transportation engineer is to move people and goods safely and efficiently.
Civil Engineering Technician
Do you dream of building big? Civil engineering technicians help build some of the largest structures in the world—from buildings, bridges, and dams to highways, airfields, and wastewater treatment facilities. Many of these construction projects are "public works," meaning they strengthen and benefit a community, state, or the nation.
The essayist and poet Ralph Waldo Emerson called Greek architecture the "flowering of geometry." Architects blend art and science, designing structures for people, such as houses, apartments, schools, stores, malls, offices, places of worship, museums, sports stadiums, music theaters, and convention centers. Their designs must take into account not only the structure's appearance, but its safety, function, environmental impact, and cost. Architects often participate in all phases of design, from the initial consultation with the clients where the structure is envisioned, to its completion. Architects can enrich people lives by creating structures that are as beautiful to look at as they are functional to live, work, or shop in.
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