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Saturday, September 25, 1999 Published at 16:54 GMT 17:54 UK

World: Europe

Basilica gets quake protector

Once the scaffolding comes off, the basilica will be stronger than before

Technology used to straighten spectacles and receive mobile phone signals is being used to prevent earthquake damage.

The BBC's Tim Hirsch: "Protecting the treasures"
Engineers working on repairs to the Basilica of St Francis of Assisi hope the new approach will protect the shrine from future earthquakes.

The Basilica, in the Umbria region of central Italy, was severely damaged by an earthquake in 1997. Two monks were killed and priceless frescos by Giotto destroyed.

Repair work includes inserting bundles of metal wires, which can stretch like elastic and return to their original shape, into the Basilica.

The wire bundles will attach walls to roofs allowing each to move independently during a tremor, and then returning to their original position.

If another earthquake strikes, the new wires will be able to flex and absorb the movement far better than traditional steel.

Laboratory successes

[ image: The secret is in the bundles of elastic wires]
The secret is in the bundles of elastic wires
Dozens of the specially-designed bundles of wires have been installed in the Basilica.

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."

The idea came out of a European Union project called ISTECH which was based at the European Laboratory for Structural Assessment in Italy.

[ image: The test wall survived a simulated earthquake]
The test wall survived a simulated earthquake
Tests were done on four-metre-high masonry walls built in the laboratory. Results showed that, even at double the shaking actually experienced in the Assisi earthquake, 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.

Strength in numbers

[ image: The basilica's roof fell in]
The basilica's roof fell in
The key to the new protection system is the 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.

For the Basilica bundles of up to 80 nickel-titanium alloy wires, each 1mm in diameter and up to 70cm long, will be used to make the flexible link between walls and roofs.

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

Costly exercise

David Willey's 1997 report on the first earthquake
The Franciscan monks are delighted at the speed of the work, and visitors and pilgrims are returning to Assisi.

The loss of an entire season of tourism was a huge blow to the local economy.

But it is unlikely that the technology will be used to protect other historic Italian monuments.

People shy away from the expense, says Allessandro Martelli of the Italian Technology Agency.

"It should be done but unfortunately the mentality does not yet exist to prevent damage rather than repair it afterwards," he says.

But for Assisi the application of this technology should mean that the Basilica will survive well into the new millennium.

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