Flexible bridge bounces back after quake test

[Dover]

After spending nine months carefully building a 33.5-metre (110-foot) bridge, US engineers then tried their best to knock it down again.

That apparently paradoxical behaviour was designed to test a new bridge able to "remember" its shape after a quake modelled on the 1994 Northridge Earthquake in Los Angeles, which killed 72 people and injured 9000.

Earthquakes put bridge supports under enormous stresses because of the way one end is hit by a quake before the other. Simulating that effectively requires nothing short of a large-scale replica of the bridge.

..snip..

The concrete used in the bridge was reinforced with "smart" nickel titanium - Nitinol - a "shape-memory" alloy commonly used in bendable spectacle frames. The alloy retains a memory of the shape it was cast into and, after deformation, springs back to its intended form.

"The nickel-titanium rods replace steel bars in critical segments of bridge columns," says Saiid Saiidi, a member of the research team...cont'd

http://www.newscientist.com/article/dn16311-flexible-bridge-bounces-back-after-quake-test-.html

See Video of test.