The Leaning Tower of Pisa: Torre Pendente di Pisa
The Leaning Tower of Pisa in Central Italy is one of the most recognisable examples of Romanesque architecture in the world. The freestanding torre pendente di Pisa forms part of a cathedral complex in the Piazza di Miracoli, the Square of Miracles, formerly known as the Piazza del Duomo or Cathedral Square.
It stands in the northwestern part of the walled medieval city. The cathedral construction began in 1063, and the baptistery building work began in 1152. The bell tower or campanile was started in 1173, and it was meant to be an upright tower and not a leaning one. It is 55.86m on one side and 55.67m on the other. The weight of the white marble tower has been estimated as 14500-14700 tonnes.
During the three building phases that encompassed almost two hundred years with interruptions, master builders and architects, including Bonnano and Guglielmo Pisano, Guido Speziale and Giovanni di Simone, were associated with the tower.
The Pause in Building Work That Saved the Tower of Pisa From Collapse
The Pisano brothers were widely considered the most likely men to have started the building work, but recent studies have suggested that another architect named Diotisalvi was the master of the early construction.
Work on the tower foundations began on 9th August 1173. The planned tower was seven floors high, with a bell tower at the summit. The walls would be 2.44 metres thick in white marble with columns, ornate sculptures and arches.
By 1178, when the third floor was under construction, a flaw was apparent. The tower leaned 5cm to the southeast because it was not secure on foundations that lay on soft soil. The torre di Pisa was the torre pendente di Pisa. The building work was halted as a solution was considered.
The long pause in construction saved it because the foundations had time to settle into the soil. If the building work had continued without a hiatus, the stability of the campanile would have been threatened as more floors and weight were added, and collapse was a probable outcome.
Construction of the Leaning Tower of Pisa Finally Completed in 1372
Master builder Giovanni di Simone was employed to complete the tower in the 1270s. He intended to build the remaining four floors with walls on one side reaching higher than on the other so that the overall construction with the bell tower would stand upright.
Unfortunately, his plan failed to calculate the effect of the weight of the additional materials used to correct the lean. As work progressed, the tower sank further into the ground, and it became a little curved.
A stream of architects, engineers and builders battled with the leaning campanile, but none of them restored it to an upright position. In 1319 the seventh floor was completed. The bell chamber was added in 1372.
Two spiral staircases were installed inside the tower. One set of stairs was created with 294 steps from the ground to the bell chamber, and the other stairs needed 296 steps to compensate for the leaning issue.
The 5.1 Metre Lean of the Tower of Pisa
Over the next four centuries, seven bells were installed, one for each of the musical notes on a scale. The weight of these bells added to the subsidence, and by the 20th century, the larger bells were not utilised anymore due to the risk they posed to the tower.
In 1835 architect Alessandro Gherardesca removed some of the soil and added a marble base to the tower. It wasn't very successful. The tower that had been increasingly leaning for over 700 years was left with a 5.1 metre lean by 1918.
This increased by 1.2mm every year. In 1964 the Italian government asked for assistance correcting the issue while conceding that the campanile's lean was its draw for tourists. Concrete was injected into the foundations, but the problem was not resolved.
850 Years on and UNESCO World Heritage Site
The cathedral complex has been a UNESCO world heritage site since 1987.
In 1990 the Leaning Tower of Pisa was closed to the public to allow strengthening work. More soil was removed from the foundations, and counterweights were added. The lean was corrected by 44cm, and the tower reopened to the public in spring 2001.
Between 2001 and 2008, the tower shifted of its own accord so that the lean was decreased by another 48cm before the movement stopped completely.
The organisation Opera della Primaziale Pisano monitors the tower's integrity. Engineers believe that the 850-year-old Tower of Pisa will be safe for the next two centuries.
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