Avoiding Disaster: The Right Bridge Design *
|Time Required||Average (6-10 days)|
|Cost||Average ($50 - $100)|
A bridge collapse, like that of the I-35W Mississippi River Bridge, 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.
Figure 1. 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.
For this civil engineering project, try making your bridges out of popsicle sticks or straws. The Science Buddies' The Effect of Bridge Design on Weight Bearing Capacity project idea has detailed information and tips on how to build popsicle stick and straw bridges.
Sandra Slutz, PhD, Science Buddies
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Last edit date: 2017-11-10
Materials and Equipment
This is an engineering project, so the materials you use will depend on your engineering goals. Here are suggested materials:
- 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 Amazon.com
- Masking tape
- 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 following equipment is optional:
- Camera for before and after photos, and/or
- Video camera for live movie of bridge testing,
- Tripod or helper for video recording.
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