6/24/2023 0 Comments Leaning tower of pisaThe tower was designed by architect Bonanno Pisano, who began construction in 1173. The Leaning Tower of Pisa was constructed in the 12th century as a bell tower for the nearby cathedral. Despite its unintentional lean, the tower remains one of the most popular tourist attractions in Italy, drawing millions of visitors from all over the world each year. Located in the Italian city of Pisa, the tower is known for its distinctive tilt, which has made it famous throughout history. “I could not have said that when I first started the project, but such optimistic statements are now easy to make.The Leaning Tower of Pisa is one of the most iconic and recognizable landmarks in the world. “I can’t see any reason why it shouldn’t be standing in 200 years,” Burland says. The underground tunnels and wells have also made the ancient building highly resistant to seismic activity, which is especially important in Italy, where earthquakes have destroyed historic structures recently. “The thing was never straight.”Įngineers expect the tower to last at least 200 years before it needs another intervention, based on projected soil condition and stone quality. They made pillars on the third and eighth floors taller on the north side. Engineer Bonnano Pisano, who designed the tower, sought to correct it by simply curving it upward as the builders continued. Shortly after construction began in 1173, the tower had begun to lean noticeably. In fact, the tower could never be straight, even if the incline were completely corrected. Given that, Burland says, “I don’t expect it to ever be completely straight.” He hopes the building will now be stable and not start to lean further again as the soil underneath naturally erodes and shifts. The engineers waited until the latest annual checkup to declare that they think the auto-correct has stopped. The tower continued to settle, but that stopped several years ago. “It is about what I expected," he says, although he had made no projections at the time. That’s when the city closed the edifice to tourists and cleared the land below, assuming it would fall.īurland calls the additional 4 cm gained since the intervention was completed in 2001 an added bonus. It gradually leaned more each year until 1989, when it surpassed the 5.5-degree incline. That year marked the beginning of a period of tremendous movement-and failed interventions. When all was done, the tower had straightened 40 cm, bringing it to the same inclination it had in 1810. They also attached metal rings around the fifth floor of the tower, which had cracked during repair, and hitched heavy weights with steel cables on the opposite side to help settle the building into the newly drained foundation. While digging, Burland says they found the remnants of a concrete foundation that had been built in 1828 they attached the tower to it with massive chains, creating even stronger footing. The reparations raised the base on the north side by four meters and lifted the entire tower along with it. When the project ended in 2001 the slope has been reduced to just under five degrees, leaving the tower about 13 feet from the perpendicular.īurland’s team painstakingly extracted about 20 liters of soil at a time from under the south side of the base and steadily installed a system of tunnels and wells to drain the water that was keeping the soil wet, causing the base to sink. At that time the north side of the tower’s base had sunk, leading to a 5.5-degree slope toward the north of the 187-foot, 14,700-metric-ton structure. “The height and weight coupled with the porous soil meant it should have fallen centuries ago.” Although today he still cannot explain for sure why it still stands, he is certain it would not have lasted much longer if the commission had not intervened. “No matter how many calculations we made, the tower should not have been standing at all,” Burland told Scientific American. The top-heavy bell tower, built in 1173 on spongy ground, seemed to defy the laws of physics. Back in 1989 the soil-mechanics expert had been approached to lead a 13-member commission to save the structure from collapsing. The news came to John Burland, an emeritus professor at Imperial College in London, by way of a 4 A.M. Although that may seem small, it is a welcome gift after centuries of worry that the building would simply topple. The surprise gain straightened the landmark by four centimeters. Last week they announced that the tower had been self-correcting for more than a decade and had finally stopped. Once every year, engineers measure the Leaning Tower of Pisa’s precarious tilt.
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