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Leaning tower of

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by

Neil Herbstritt

on 4 April 2017

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Transcript of Leaning tower of

Leaning tower of Pisa
By: NeIl HerstrItt
1.The Leaning Tower of Pisa is surely one
of Italy's most famous structures. Looming 186 feet over the Piazza del Duomo, the Leaning Tower is named for its inimitable tilt.

For visitors to Pisa, the must-have souvenir is an optical illusion photo in which a traveler can be seen "pushing" the Leaning Tower of Pisa, but equally memorable is the climb to the top of the tower. After scaling the 294-step spiral staircase, the reward is a spectacular panoramic view of the city.
The project was plagued with interruptions, as engineers sought solutions to the leaning problem, but the tower was ultimately topped out in the 14th century. Twin spiral staircases lined the tower’s interior, with 294 steps leading from the ground to the bell chamber (one staircase incorporates two additional steps to compensate for the tower’s lean).
I
n 1990 the tower was closed and all the bells
s
ilenced as engineers undertook a major
s
traightening project. Earth was siphoned from
u
nderneath the foundations, decreasing the lean by
1
7 inches (44 cm) to 13.5 feet (4.1 metres); the
work
was completed in May 2001, and the structure
was
reopened to visitors.
The tower continued to straighten without further excavation, until in May 2008 sensors showed that the motion had finally stopped, at a total improvement of 19 inches
6.The British engineer who has overseen the work to stabilise the tower,
Professor John Bu
rland, says it is hard to explain why the tower did not fall.

Computer models suggest that it should have toppled once it reached a tilt of 5.44 degrees - but by 1990 it was leaning by 5.5 degrees, with the seventh level, just below the belltower, overhanging the ground by 4.5 meters
The tower’s foundation had begun to settle unevenly on the ground beneath it, a dense mixture of clay, sand and shells. As a result, the structure had begun to tilt visibly toward the south.
It Was tilting at 0.05 inches a year, the park had to close it down 'till they found a solution.
Despite various attempts to reinforce it, Pisa’s tower continued to subside at a rate of some 0.05 inches per year, placing it in increasing danger of collapse. By 1990, it was leaning 5.5 degrees (or some 15 feet) from the perpendicular–the most extreme angle yet. That year, the monument was closed to visitors and the bells removed as engineers started extensive reparations to stabilize it.
The tower slowly sank into the cavity created. Steel cables were attached to the tower, not to pull it upright, but to hold it up in case anything went wrong.
THE END
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