GWS' say !

The Leaning Tower of Pisa is still leaning – only less so. Its incline is a congenital defect, a kind of childhood disease from which the tower never recovered. It has leaned for as long as any Pisan can remember, as though it deliberately refuses to thrust itself skywards. Work on the Romanesque-style 56-metre campanile, or bell tower, began in 1170 and was defective from the start because of the porous clay soil into which the foundations were laid. Five years later its construction was interrupted for 90 years.
But Tuscans are a stubborn and ingenious people, so they picked up their tools again. In 1272 they started building four floors on a diagonal to offset the incline, but work was interrupted again between 1301 and 1350 and the last bell chamber was only completed in 1372. But there was no doubt about it; the tower was still leaning, and not just a little. In 1350 the vertical incline was 1.4 metres (or 1.47 degrees). By 1817 it was 3.8 metres and as much as 5.4 metres in 1993.
Has a miracle now occurred in the Piazza dei Miracoli or miracle square, where the tower stands?
On 15 August the scientific committee charged with monitoring the tower revealed in its annual report that it had spontaneously recovered 2.5cm of its vertical incline between 2001 and 2013. In the torpor of summer, when Silvio Berlusconi's political future and Enrico Letta's new government vied for press coverage, news of this "spontaneous straightening" was perceived as the latest demonstration of Italian genius. The TV cameras rushed to Pisa.
Giuseppe Bentivoglio, engineer and technical director of the Opera del Duomo, the body supervising the monuments in the Piazza dei Miracoli, was far more prosaic. "It was expected," he said, as a result of the major restoration programme carried out between 1991 and 2001by Michele Jamiolkowski, engineer and professor at the Technical University of Turin.
The Tower of Pisa's greatest incline was observed in early 1990 and there was a risk that it might collapse altogether. It was closed for 10 years while some serious safety work was carried out. The water beneath it was drained, the foundations were reinforced with 15-metre concrete pillars and 60 cubic metres of clay was removed. The tower itself was encircled with steel cables. The Italian state spent €30m ($40m) million on the tower. The results of this massive restoration programme were almost immediate. The tower recovered 50cm and returned to the incline it had two or three centuries earlier. "According to studies by researchers at Stuttgart University, with whom we worked, the tower will continue to straighten another couple of millimetres and then stabilise before starting to lean again, but at a much slower rate than previously," Bentivoglio said.
Some people predict that the 14,500 tonne tower will straighten up completely by the year 2300, but Bentivoglio believes that more work will have to be carried out by future generations. "In theory," he said, "it would be possible to straighten it completely, but nobody really wants that!" The tower was born leaning and leaning it shall remain."
"The people of Pisa are delighted that the tower has been restored, but not that it has been straightened," said Marco Filippeschi, the mayor of this town with a population of 85,000. And why would they want it straight when every year some 3m tickets are sold to visit a leaning tower, and another six million people pour into the Piazza dei Miracoli.
"The city has been living off this for too long," said the mayor, who would like to diversify the town's cultural offering and provide more competition to nearby Florence.
To this end €60,000 has been invested in restoring Pisa's other treasures, including its medieval walls, and making them better known. That renovation programme should be completed in 2014. It will be the 450th anniversary of the birth of Galileo, a native Pisan. By throwing various items off the tower, Galileo proved that the speed of their fall was the same whatever the weight of the object – whether or not the tower was leaning.
This article appeared in Guardian Weekly, which incorporates material from Le Monde

Structure of Pisa Tower
This post continues our series on famous structural failures. More details can be found by taking a look at the seminars located on the “articles” page of www.AeroNavLabs.com The leaning tower of Pisa is probably the most famous example of placing a structure in a very problematic location. Construction was started in 1174 and completed in 1272.
The tower is 200 ft. high. The sketch shows the subsoil conditions below the tower to a depth of about 150 ft. The tower started to lean almost immediately with the highest rate of inclination around the end of the 13th. Century. The rate of leaning has been continuously reduced since that time. Various stabilizing features have been incorporated in recent times such as concrete pumped into the ground and the use of support cables.
What are the conclusions we can draw from the tragedy in New Orleans and the structural problems of the Leaning Tower of Pisa? It cannot be forgotten that another hurricane like Katrina or even stronger could hit New Orleans, and the Leaning Tower could continue to become more and more structurally unstable. It is from these failures that we could learn and become more prepared as a society of engineers.


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> Tags: Architecture, Italy