The Egyptian pyramids were the skyscrapers of their time - and have stood for 5,000 years. Will modern skyscrapers be able to repeat such a feat? The first cracks appeared in April. By June 29, 1995, a large network of cracks had spread across the ceiling of the fifth floor of one of Seoul's busiest department stores. A few hours later, loud bangs came from the roof. The cracks grew.
An emergency council meeting was called, but the chairman flatly refused to evacuate, citing lost profits. Then he left the building.
At five in the evening, the ceiling of the fifth floor began to crumble. Shopping continued as usual until the alarm was sounded almost an hour later. But it was too late. First, the roof collapsed, and then the main supporting pillars of the building were brought up, as a result of which the entire southern wing of the building collapsed into the basement. 1,500 people were trapped - including the chairman's stepdaughter - and 502 never got out of it.
The Samsung department store collapse is an example of how fragile modern structures can be. Even with the latest materials, equipment and an advanced understanding of physics, this building didn't last five years, let alone 5000.
Meanwhile, the Egyptian pyramids gathered crowds of onlookers for many millennia. Earthquakes, erosion, vandalism - the pyramids have survived even the collapse of civilization and the transformation of the Sahara from a lush pasture to today's vast desert.
The Great Pyramid of Giza - built in 2540 BC - is unmatched in materials, design, and engineering, both before and after buildings. Ancient Greek tourists walked thousands of kilometers to look at its blocks, polished to the point where they were described to glow; the names of travelers can be found carved into the walls of the pyramid to this day.
Cleopatra lived closer to the tallest building in the world today - the Burj Khalifa - than to this monumental tomb. When the last mammoths died out, she was already 1000 years old.
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The pyramid of Giza was the skyscraper of its time, surpassing any building in the world, until finally, about 700 years ago, Lincoln Cathedral was built. “The ancient Egyptians created - I hate to say it - a launching pad for the dead to travel to the sun and stars,” says Donald Redford, who has studied the pyramids for forty years.
Fast forward to 2016, where we have already covered the sky with skyscrapers, clock towers and 20-story robots, and we plan to build a building one and a half kilometers high. Although it is not yet known whether it can be built at all. We are entering the era of skyscrapers as more and more people travel from villages to crowded cities.
These buildings must withstand tremendous forces in order to remain upright, including constant lightning strikes and winds sweeping at 150 km / h - not to mention the constant effect of gravity. In some areas, powerful earthquakes can be added to this list. What is the secret of the pyramids? Can modern skyscrapers survive them?
In fact, the impressive age of the pyramids is no coincidence. The ancient Egyptians believed that life after death would be eternal, and made great efforts to keep their tombs well too. The design of the pyramids changed for thousands of years as their builders experimented with materials and architecture to suit their ambitions.
“They always said it was a building 'for eternity', 'forever and ever' - these phrases were constantly in their vocabulary,” says Redford, currently at Penn State University. They were so confident in their abilities that “millions and millions of years” were included in the names of many pyramids.
Despite all their attempts and exaggerations, the Egyptians did not know exactly what they were doing, and this was more their advantage than a disadvantage. To fill the gaps in understanding the laws of physics, the first pyramids were built taking into account all possible fortifications. They knew about the pillars, but did not know that they could support the roof. Therefore, additional walls were added just in case.
Another explanation is its huge size. Take the Great Pyramid, which is more of a man-made mountain than a building made of nearly six million tons of solid rock. Five thousand years is nonsense, considering that the limestone that makes up the pyramid blocks has been in the ground for 50 million years or so.
Modern skyscrapers, by comparison, are efficiently lightweight and smart. It took just 110,000 tons of concrete and 39,000 tons of steel to build the Burj, which is six times the height of the Great Pyramid. “They designed buildings that will last forever - not a priority today. We're designing practical buildings to live in,”says Roma Agrawal, a civil engineer working on the Shard building in London.
Like the first pyramids, the earliest generation of skyscrapers may be the most reliable. When a B-52 plane crashed into the Empire State Building in 1945, the building was reopened a couple of days later. “In the early 20th century, everything was hand-calculated, so engineers added extra steel just in case,” says Agrawal. Although the Empire State Building is half the size of the Burj, it weighs two-thirds more.
In addition to all the usual risks, a building in the clouds carries its own weight. To survive until 7000 AD - that is, live as long as the pyramids lived - skyscrapers have to fight rain, wind and thunderstorms for thousands of years.
“The wind is a particular problem for tall buildings,” says Bill Baker, Burj's design engineer. When the wind rushes past a streamlined object, such as a tree or a lamppost, it swirls into one organized gust that goes around the object first to the left, then back to the right, then again to the left, and the object sways due to the change in wind directions. In strong winds, Burj can swing up to one and a half meters in each direction.
The trouble is, the higher, the faster the wind. To keep the skyscrapers from falling - and the people above to get rid of seasickness - engineers are designing irregularly shaped buildings that obstruct the wind and destroy its organization. From an architectural point of view, the building may appear a little too fancy, but the distinctive serrated profiles of Burj and Shard are more for safety than beauty.
Even a hurricane won't shake them. “If it's a normal building, it has to be able to withstand a hurricane that happens once every 700 years,” says Baker. Important buildings like the Burj Khalifa will be able to cope with events that occur once every several millennia.
And there is also lightning. The United Arab Emirates, where Burj is located, experiences about 10 thunderstorms a year. A single lightning strike of billions of volts can be as strong as a nuclear reactor. “I was in Dubai during a thunderstorm and Burj is like a lightning rod for the entire city - lightning strikes it every minute,” says Baker.
Fortunately, there is a solution. During construction, the steel shell of the building is tied together - every steel bar, every window frame - right down to the base. And it works as a giant Faraday cage, a protective enclosure similar to the wire mesh on microwave ovens that keeps contents safe by limiting them from electricity. “I have spoken to work crews after a particularly powerful thunderstorm and they have not seen any damage,” says Baker.
Even during earthquakes, skyscrapers hold up extremely well. The faster he cowards, the better. It's all about such a thing as resonance. If the ground shakes at a frequency that matches the speed of the building's swing, it will swing faster and faster until it collapses, possibly. “Narrow buildings will take longer to rock back and forth - 11 seconds for Burj - so they will move, but not collapse,” Baker says.
But it is not entirely reliable: just as we break paper clips, bending and unbending them repeatedly, if the steel is disturbed too often, it will burst.
Much more dangerous is water.
In the 1930s, 96 of the world's 100 tallest buildings were made of steel. Today, most urban buildings are constructed of steel-reinforced concrete (reinforced concrete), which combines the tensile strength (ability to resist stretching) of metal and the compressive strength (ability to resist crushing) of stone.
When stored dry, reinforced concrete is an amazing material that can last forever. But in areas with a high level of sediment, weak acids in the water slowly react with the limestone in the cement and carry it out - the steel rusts and holes appear in the building.
“That the pyramids are in a dry environment is incredibly important,” says Michelle Barsum, a materials scientist at Drexel University in Philadelphia. Even in the sun-dried Sahara, the first pyramids fell under the ravages of water.
For many years it was believed that the Egyptians eventually figured it out and learned how to cut blocks with a tighter fit, but how exactly remained a mystery. Then, in the early 2000s, someone finally got the idea to study the rocks under a high-resolution microscope. It was Michel Barsum, and he noticed that these rocks were not natural limestone, but rather were molded from an early form of cement.
As an expert on ceramics - Barsum had never studied pyramids - he couldn't resist the tempting prospect of finding out for sure. Deep inside the ancient blocks, he found eloquent clues: microscopic algae, diatoms, whose hard shell was partially eroded by alkaline cement. “About 90% of the pyramid is made of carved stone, the rest is cast,” says Barsum.
The Egyptians made their stones from four main components: limestone, lime, water and mud. They react with each other to form a chemical adhesive. Most importantly, as the adhesive ages, it returns to its original state of the components, converting the cement back into stone. “It smells and looks like natural limestone,” says Barsum.
But if the main concrete shell of the skyscraper is relatively strong, the fate of the windows in it is less transparent. Glass weighs like granite and has the stiffness of aluminum; it will take 10 tons of pressure to crush a cubic centimeter. Even the sea will take 50 years of grinding to turn glass into colored smooth pebbles on the beach. And yet the glass is not perfect. It can crack spontaneously. Nobody knows why.
Even with a double layer of glass, if not maintained, most windows will not last long. "Glass is not particularly affected by the environment, but due to the vibrations of the wind, thunderstorms and other influences, it eventually breaks," says Konstantinos Tsavdaridis, a materials scientist at the University of Leeds.
Finally, will the glass eventually drain into the bottom of the frame? This idea is based on the fact that medieval windows were usually thicker at the bottom and that glass is, in fact, an extremely viscous liquid: and over hundreds of years glass can drain into the bottom of the frame.
In 1998, this popular idea was vigorously refuted by a group of physicists, who calculated that it would take time “much longer than the age of the universe” for any noticeable change in glass to occur at room temperature. The uneven thickness of ancient glass was completely random - making even glass a couple of hundred years ago was not so easy.
So can modern skyscrapers make time fear them?
Bill Baker thinks it is. “Building materials are quite good these days. Except for those moments when they fail, and if supported."
Agrawal agrees. "If you take care of them, why not."
According to Konstantinos, concrete structures will last longer, since the rust that forms in reinforced concrete kills him. But Redford doubts our buildings will last long enough. After all, these are functional structures that simply do their job. It will be easier to throw them. Most of the skyscrapers will be demolished before they fall. After all, the Great Pyramid was not the only amazing building 4,500 years ago.
The so-called Labyrinth is said to have been even more unusual. “When the Greek historian Herodotus saw him, he gasped. He couldn't describe the size and weight of the largest blocks that went into the building,”says Redford. You won't find such a building today. The maze was plundered, and its bricks were used to construct other buildings. If you walk along the streets of old Cairo and study the foundations of old buildings, sometimes you can find hieroglyphic inscriptions from that very building.
If we do not demolish skyscrapers, for example, in New York, and they do not fall, then at the current rate of construction by 7000 there will be 10,000 buildings over 160 meters high. Perhaps we will have something to be proud of. Why are we worse than the ancient Egyptians?
ILYA KHEL