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Pisa tower gets 300-year guarantee

celebrations
celebrations marked the completion of the work  


PISA, Italy -- Engineers toasting the completion of work to straighten the Leaning Tower on Saturday issued a 300-year guarantee on the monument.

"It will take 300 years for the lean to get back to where it was in 1990," John Burland, an engineering professor at London's Imperial College, predicted on Saturday.

When the tower was closed in 1990, "it was very, very close to falling over," Burland told the Associated Press. "It was so close that we actually couldn't get it to stand up in our computer model."

The Tuscan town on Saturday began a weekend of celebration coinciding with the feast day of their patron saint, Ranieri, to mark the end of the bulk of the work.

For most of the past decade, the 54.5-metre (180-foot) high marble monument was wrapped in a kind of steel corset and anchored by a pair of slender steel "suspenders" running across the surrounding piazza, which is called Miracle Square. The suspenders and corset are now gone.

Completion of work will give Pisans back the ringing of the tower's bronze bells, which were ordered stilled in 1990 for fears vibrations would threaten stability.

There had been hopes that the celebrations would also include the resumption of tourist visits up the tower, but authorities said Saturday that would likely happen in November.

They said they were still studying how many tourists could go up the tower at any one time and how high they will be allowed to climb.

It is likely that only 30 at a time will be allowed on the tower at one time.

Once, busloads of tourists and entire classes of Italian schoolchildren made the climb. Burland said authorities in this lawsuit-conscious age now worry about the possibility of tourists falling off -- not their collective weight.

The tower, which was started in the late 12th century as a point of pride for the then-mighty seafaring republic of Pisa, began leaning almost immediately as the foundations of the 14,500 ton monument shifted in the sandy soil beneath it.

Using hundreds of tons of lead counterweights at the base and delicately siphoning off soil from under the foundations, engineers have shaved 44 centimetres (17 inches) off the lean, "steering," as Burland put it, the tower back to where it was in 1838.

Tower of Pisa
The tower was started in the late 12th century  

The tower now leans 4.1 metres (13.5 feet) off the perpendicular. The difference is not visible to the naked eye.

Burland said he was sure that with time, the tower will lean again, but much more slowly.

"Even Big Ben leans, by 2 millimetres (0.05 inches) a year," said Burland, cheerfully citing the London tower. "There's no such thing as perfect stability."

A few of the experts recalled some sleepless nights.

Engineer Davide Trevisani said "there was panic" in 1995 when the tower leaned as much in one day -- a millimeter (0.025 inches) -- as it had been doing in one year. Engineers then abandoned initial efforts to consolidate the soil under the tower, opting instead to extract earth.

Still fresh in the Pisa team's memory was the 1989 collapse of a 900-year-old bell tower in Pavia, Italy, which killed four people.





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