The mystery of the leaning tower of Pisa (Italy) - Why is it leaning forever but not falling for more than 800 years?

The famous 58m-high leaning tower of Pisa still stands tall and does not fall. Why is this leaning structure still standing for hundreds of years?

Leaning Tower of Pisa is one of the world famous works and is the pride of Italians, still surviving 4 strong earthquakes, to 2 world wars. Although leaning and standing precariously, the famous 58m-high leaning tower of Pisa still stands tall and does not fall. Why is this leaning structure still standing for hundreds of years?

Recognized by UNESCO as a world heritage site, the Leaning Tower of Pisa is a bell tower located on the Square named Miracle in the North, in the city of Pisa, Italy. This is a work in a cluster of religious architectural works including: Cathedral (built from 1063 to 13th century), Baptism hall (built from 1063 to 14th century). , Bell Tower (main leaning tower of Pisa and Cemetery Area (built in 1174).

The Leaning Tower of Pisa, Italy is a great work of art in Medieval Europe and until now it has not been determined who designed it.

As of 2021, the tower of Pisa is 848 years old. This work was built in 1173 and completed in 1372, with a vertical original design with 8 floors of towers. When it was first built, the tower still had a vertical structure. However, when work progressed to the 2nd floor in 1178, it was stopped. The building is 55.86m high from the ground to the low side roof, and 56.70m high if calculated from the ground to the high side roof.

After 5 years, 3 of the 8 floors of the tower of Pisa were completed. But after completing the 3rd floor, the tower began to tilt because of the 0.2 degrees northward subsidence. At that time, engineers tried to adjust the tilt. After the structure increased in height, the tower finally tilted one degree to the south. According to the Guinness Book of Records, the inclination of the building is 3.97 degrees. It is the unique inclination and important historical landmarks of Pisa that every year attract many visitors to visit.

The tower is still being built as well as its tilt. People tried to counter the inclination by making the upper floors rise to one side, but the increased weight caused the foundation, which was built on the sand, to sink even more. Construction was interrupted and people took about 200 years to complete, because while construction was halted for 199 years due to the outbreak of war.

During World War II, Germany used the Leaning Tower of Pisa as an observatory and shelter. However, the tower still stood firm against the fierce bombs of the war.

Tower of Pisa consists of 8 floors connected by round pillars of diamond or quartz stone. On the 1st floor, there are many sculptural decorations and the 8th floor is designed as the top of the bell. The tower body is gradually reduced, the foot is 19.6m in diameter and the top is 12.7m. From the bottom up, this tower has a total of 294 steps. The tower wall is 4.09 m thick at the base of the tower, then thins as it goes up. When reaching the top of the tower, the thickness of the tower wall is only 2.48m. The total weight of the tower is about 14,500 tons.

Thanks to this rather impressive design "hole", the Leaning Tower of Pisa has become one of Italy's most iconic sights. Leaning 3.9 degrees from the vertical, the Romanesque bell tower is located nearly 4 meters across and has one side higher than the other.

Why does the tower tilt forever without falling?

Its tilt and "precarious" position have long fascinated engineers and scientists around the world, who are constantly trying to understand why the tower has stood tall over the years. especially after 4 strong earthquakes occurred in the area over the past centuries, until 2 world wars. Benito Mussolini ordered Italian engineers to repair the tower in 1934, but the plan failed.

Historically, Italy has experienced many devastating earthquakes. Because the center of this country is located right at the boundary where the Asian and European tectonic plates meet Africa, large earthquakes often occur.

To correct the tilt and reduce the risk of collapse, the engineers tried a few more tricks, including adding lead counterweights to the base and placing scaffolding in the weakest part of the tower. But by the 1990s, the tilt had reached 5.5 degrees.

During the period from 1990 to 2001, the city government and architects made renovations and repairs by removing 70 tons of soil at the site of the incline and replacing it with lead-cement cement to increase the endurance of the building. tower, the northern foundation was dug and the slope was halved. In 2008, the scientific community announced that the tilt of the tower of Pisa had stopped at 3.9 degrees, which is expected to last for at least another 200 years.

If only considering the structure of the tower, it is common sense that it should soon collapse or be more or less heavily affected by earthquakes. But surprisingly, the building remained unharmed after a series of incidents.

So far, engineers have solved the mystery of how this structure has stood for hundreds of years.

Ironically, the leaning tower is also the reason it has survived for so long. "It's the soil that creates the unstable tilt and causes the tower to collapse, which helps the structure to survive the series of earthquakes," said George Mylonakis of the University of Bristol.

As it turned out, the ground that caused the tower to tilt, was also the cause of the construction being protected when the ground shook. The tower is built of marble, which also plays an important role in changing the structure's vibrations.

In other words, the height and stiffness of the tower combined with the softness of the foundation soil create a protective structure during earthquakes. The researchers say that this work holds the world record for the DSSI effect, so the leaning tower of Pisa will remain safe for many years to come.

If only considering the structure of the tower, it is common sense that it should soon collapse or be more or less heavily affected by earthquakes. But surprisingly, the building remains unharmed after a series of events since 1280?

Over the years, the Italian government has carried out a lot of relief efforts to help the tower stand, from using liquid nitrogen, to removing soil from the base of the tower.

Currently, the tower of Pisa is still the most attractive destination for tourists in Italy. Experts predict that the structure can still survive earthquakes if the magnitude does not exceed 6.0 on the richter scale. When visiting the leaning tower of Pisa, visitors must divide into groups of 30 people and last 30 minutes without stopping. Visitors will climb continuously nearly 300 inclined stairs.

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