Engineers Have Figured Out How the Leaning Tower of Pisa Withstands Earthquakes

iStock
iStock

Builders had barely finished the second floor of the Tower of Pisa when the structure started to tilt. Despite foundational issues, the project was completed, and eight centuries and at least four major earthquakes later, the precarious landmark remains standing. Now, a team of engineers from the University of Bristol and other institutions claims to have finally solved the mystery behind its endurance.

Pisa is located between the Arno and Serchio rivers, and the city's iconic tower was built on soft ground consisting largely of clay, shells, and fine sand. The unstable foundation meant the tower had been sinking little by little until 2008, when construction workers removed 70 metric tons of soil to stabilize the site. Today it leans at a 4-degree angle—about 13 feet past perfectly vertical.

Now researchers say that the dirt responsible for the tower's lean also played a vital role in its survival. Their study, which will be presented at this year's European Conference on Earthquake Engineering in Greece, shows that the combination of the tall, stiff tower with the soft soil produced an effect known as dynamic soil-structure interaction, or DSSI. During an earthquake, the tower doesn't move and shake with the earth the same way it would with a firmer, more stable foundation. According to the engineers, the Leaning Tower of Pisa is the world's best example of the effects of DSSI.

"Ironically, the very same soil that caused the leaning instability and brought the tower to the verge of collapse can be credited for helping it survive these seismic events," study co-author George Mylonakis said in a statement.

The tower's earthquake-proof foundation was an accident, but engineers are interested in intentionally incorporating the principles of DSSI into their structures—as long as they can keep them upright at the same time.

7 Historic European Castles Virtually Rebuilt Before Your Very Eyes

A reconstruction of Spiš Castle in eastern Slovakia.
A reconstruction of Spiš Castle in eastern Slovakia.
Budget Direct

While some centuries-old castles are still standing tall, others haven’t withstood the ravages of time, war, or natural disaster quite as well. To give you an idea of what once was, Australia-based insurance company Budget Direct has digitally reconstructed seven of them for its blog, Simply Savvy.

Watch below as ruins across Europe transform back into the formidable forts and turreted castles they used to be, courtesy of a little modern-day magic we call GIF technology.

1. Samobor Castle // Samobor, Croatia

samobor castle
Samobor Castle in Samobor, Croatia
Budget Direct

The only remaining piece of the 13th-century castle built by Bohemia’s King Ottokar II is the base of the guard tower—the rest of the ruins are from an expansion that happened about 300 years later. It’s just a 10-minute walk from the Croatian city of Samobor, which bought the property in 1902.

2. Château Gaillard // Les Andelys, France

Château Gaillard in Les Andelys, France
Château Gaillard in Les Andelys, France
Budget Direct

King Richard I of England built Château Gaillard in just two years during the late 12th century as a fortress to protect the Duchy of Normandy, which belonged to England at the time, from French invasion. It didn’t last very long—France’s King Philip II captured it six years later.

3. Dunnottar Castle // Stonehaven, Scotland

Dunnottar Castle in Stonehaven, Scotland
Dunnottar Castle in Stonehaven, Scotland
Budget Direct

Dunnottar Castle overlooks the North Sea and is perhaps best known as the fortress that William Wallace (portrayed by Mel Gibson in 1995’s Braveheart) and Scottish forces won back from English occupation in 1297. Later, it became the place where the Scottish monarchy stored their crown jewels, which were smuggled to safety when Oliver Cromwell invaded during the 17th century.

4. Menlo Castle // Galway City, Ireland

Menlo Castle in Galway City, Ireland
Menlo Castle in Galway City, Ireland
Budget Direct

This ivy-covered Irish castle was built during the 16th century and all but destroyed in a fire in 1910. For those few centuries, it was home to the Blake family, English nobles who owned property all over the region.

5. Olsztyn Castle // Olsztyn, Poland

Olsztyn Castle in Olsztyn, Poland
Olsztyn Castle in Olsztyn, Poland
Budget Direct

The earliest known mention of Olsztyn Castle was in 1306, so we know it was constructed some time before then and expanded later that century by King Casimir III of Poland. It was severely damaged during wars with Sweden in the 17th and 18th centuries, but its highest tower—once a prison—still stands.

6. Spiš Castle // Spišské Podhradie, Slovakia

Spiš Castle in Spišské Podhradie, Slovakia
Spiš Castle in Spišské Podhradie, Slovakia
Budget Direct

Slovakia’s massive Spiš Castle was built in the 12th century to mark the boundary of the Hungarian kingdom and fell to ruin after a fire in 1780. However, 20th-century restoration efforts helped fortify the remaining rooms, and it was even used as a filming location for parts of 1996’s DragonHeart.

7. Poenari Castle // Valachia, Romania

Poenari Castle in Valachia, Romania
Poenari Castle in Valachia, Romania
Budget Direct

This 13th-century Romanian castle boasts one previous resident of some celebrity: Vlad the Impaler, or Vlad Dracula, who may have been an early influence for Bram Stoker’s vampire, Dracula. It also boasts a staggering 1480 stone steps, which you can still climb today.

[h/t Simply Savvy]

Drunken Thieves Tried Stealing Stones From Notre-Dame

Notre-Dame.
Notre-Dame.
Athanasio Gioumpasis, Getty Images

With Paris, France, joining a long list of locales shutting down due to coronavirus, two thieves decided the time was right to attempt a clumsy heist—stealing stones from the Notre-Dame cathedral.

The crime occurred last Tuesday, March 17, and appeared from the start to be ill-conceived. The two intruders entered the cathedral and were immediately spotted by guards, who phoned police. When authorities found them, the trespassers were apparently drunk and attempting to hide under a tarpaulin with a collection of stones they had taken from the premises. Both men were arrested.

It’s believed the offenders intended to sell the material for a profit. Stones from the property sometimes come up for sale on the black market, though most are fake.

The crime comes as Paris is not only dealing with the coronavirus pandemic but a massive effort to restore Notre-Dame after the cathedral was ravaged by a fire in 2019. That work has come to a halt in the wake of the health crisis, though would-be looters should take note that guards still patrol the property.

[h/t The Art Newspaper]

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