Soon, a bridge that can bounce back after a quake

December 20th, 2008 - 4:17 pm ICT by ANI  

London, Dec 20 (ANI): Engineers at the University of Nevada in the US have tested a new design for a flexible bridge that can bounce back after an earthquake.

According to a report in New Scientist, the engineers used three large shake tables to test a 33.5-metre-long, 181-tonne (200-ton) bridge sporting an exotic new design.

The bridge, a quarter-scale replica of its projected real-life size, was subjected to 10 seconds of shaking like that created by an earthquake of magnitude 8.0.

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, said Saiid Saiidi, a member of the research team.

Concrete with dumb steel inside is designed to yield to a quakes shocks, flexing to reduce the force it experiences, according to Colin Taylor, an earthquake engineering specialist at the University of Bristol in the UK.

Using shape-memory alloys should mean that, after the quake, a bridge support attempts to return to its former shape instead, and can remain usable.

During the 10-second quake simulation, 400 movement sensors mounted at various critical points along the bridge measured the structures response.

Our results show that not only (did) the Nitinol/concrete combination reduce the residual tilt (after the earthquake) to near zero, the damage was negligible and repairable, said Saiidi.

The test suggests that Nitinol-reinforced concrete could be used to build bridges that dont just avoid collapse during a strong earthquake, but also remain usable afterwards.

The ultimate goal is to improve the emergency response by keeping bridges open, and minimize interruption to the highway network operation to avoid major economic losses, Saiidi said. (ANI)

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