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Friday, September 10, 1999 Published at 12:06 GMT 13:06 UK


Sci/Tech

Weird wires to protect basilica

The rubble has been sifted for fragments of the frescoes

Metal wires which can stretch and then snap back like elastic will soon be added to the Basilica of St Francis of Assisi to protect it from future earthquakes.


David Willey's 1997 report on the first earthquake
The historic Italian shrine was severely damaged by earthquakes in 1997, killing two monks and destroying priceless frescos by Giotto.

It will be the first time the technology has been used. Dr Gabriella Castellano, an engineer with FIP Industriale, led the research and told BBC News Online: "We think this approach will be important in the future because it solves problems which cannot be solved using traditional materials."


[ image: The test wall survived a simulated earthquake]
The test wall survived a simulated earthquake
By the end of September, dozens of specially-designed bundles of wires will have been installed in the Basilica. If another earthquake strikes, the new wires will be able to flex and absorb the movement far better than traditional steel.

The idea came out of a European Union project called ISTECH which cost £890,000 and was based at the European Laboratory for Structural Assessment in Italy.

Tests were done on four-metre-high masonry walls built in the laboratory. These showed that, even at double the shaking actually experienced in Assisi, the new flexible wires protected the wall.

"We estimate that structures protected with the new devices can survive an earthquake at least 50% stronger than one which would destroy structures reinforced with the traditional steel bars," said Dr Castellano.


[ image: The Basilica's roof fell in]
The Basilica's roof fell in
The key to the new protection system is the strange properties of "shape memory alloys". These metals can be bent and stretched but recover their shape automatically afterwards. Their most commonly seen use is in spectacle frames.

Nickel-titanium alloy will be used in the Basilica. Wires one millimetre wide and up to 70 cm long will be used in bundles of up to 80.

It will take 47 bundles to secure two masonry tympanums in the roof. One of these partly collapsed in 1997 and the falling debris caused great damage.



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