The newly constructed San Francisco-Oakland Bay Bridge features a new quality: the ability to sway. The engineers who’ve designed the bridge did so with the future in mind. The bridge is anchored in blocks called “deadmen”, which are cast into the structure. Cables are then run from deadmen to deadmen, which allow for tightening as the bridge ages and sags.
The span is also designed to sway during an earthquake. Steel piles are driven at an angle, 300ft into the ground, to increase bridge stability during an earthquake. Additionally, 13 concrete piles, 8ft in diameter, are driven 200 feet into the ground to keep the tower stable; equivalent to a 20-story building.
http://www.nytimes.com/2012/02/07/science/to-survive-a-quake-new-bay-bridge-span-will-offer-least-resistance.html?_r=1&partner=rss&emc=rss
Interested in teaching your students more about engineering? Check out SSR's Vol 41 DVD, episode Engineering – Bridges by Design. If your school would like to receive this free resource, visit http://www.ssrvideo.com/nhcmsp.html.
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