Will Overstressed Bridges Survive Earthquakes?

Rebecca Goodwin, Class 11
The Meridian School, Provo Utah

Rebecca won the 1996 science fair with her project on the survivability of overstressed bridges in an earthquake.

For my science fair project, I decided to test different bridge structures to see how they reacted to ground shaking associated with earthquakes. I began by building four model bridges, each having a different support system. Using hydraulics, I stressed two of the bridges until I heard strain in the structure. Careful inspection of the structure revealed no visible damage. I then placed all four bridges on a shaker table which simulated an earthquake. The unstrained bridges both survived the shaking with no apparent damage. Both of the strained bridges experienced structural failure. Even though these structures had no visible damage prior to shaking, their failure indicated that they had indeed been seriously damaged.

Conclusion: My experiment indicates that overstressing of structures can have disasterous consequences even if no apparent strain is induced. Invisible internal damage can lead to catastrophic failure in an earthquake.

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