BREAKING NEWS

Science Behind the Fiction: Skyscraper

Science Behind the Fiction: Skyscraper
10 Jul
2:43

Legendary Pictures, the company behind Godzilla, King Kong, and Pacific Rim, in partnership with Universal Studios, brings you another movie about something giant. Only this time it’s a building.

If we’ve learned anything from the aforementioned movies, it’s that making something bigger isn’t always better, at least not for the characters faced with dealing with the challenges.

Skyscraper introduces us to Will Sawyer (Dwayne Johnson), an ex-FBI agent turned security chief. Will is tasked with assessing the potential risks for The Pearl, the new reigning champ in the unending contest for world’s tallest building.

In real life, the tallest building in the world is the Burj Khalifa, a 2,717 foot tower located in Dubai. Designed by American architect, Adrian Smith, It bested the previous world’s tallest building, Taipei 101, by more than a thousand feet. Though, even this won’t be enough to hold the title for long.

Smith has plans for a new structure in Saudi Arabia to be completed in 2020, Jeddah Tower, planned to be the world’s first kilometer tall building.

Skyscraper puts us inside The Pearl, a 3,500 foot tower. If real, it would top Jeddah by roughly 200 feet. The Pearl is meant to be not only the world’s largest building but also a self-contained city complete with living quarters, gardens, shops, and everything a person might need to live comfortably without ever touching the ground.

The idea is ambitious, and may soon become a reality. By some estimates, 80 percent of the world’s population will live in cities within a few decades, and with population densities of that magnitude, horizontal real estate comes at a premium. A reasonable solution would be to become upwardly mobile.

Video of Skyscraper – Official Trailer [HD]

As Johnson’s Will Sawyer says in the trailer for Skyscraper, building a structure like that comes with its own set of challenges, and no one really knows what will happen if things go wrong.

But that shouldn’t stop us from trying. So what are some of the challenges of constructing a building of that size and how can we address them?

Weight

The most obvious concern when building massive structures is the weight.

We’ve written before about the square-cube law and how it impacts large objects. In short, as an object gets larger, its surface area is cubed while its internal area is cubed. This means that a cross section of the object must deal with more and more force the larger it gets. This law impacts buildings just as much as it impacts gorillas. The Rock should be familiar by now, this isn’t his first square-cube rodeo.

Engineers must concern themselves not only with ensuring a skyscraper is sturdy enough to support itself, but that the ground can support it without shifting or sinking.

As a structure gets taller, the pressure placed on the lower levels increases. This is the guiding principle behind the design of large ancient structures like pyramids. The lowest levels must grow larger the taller a building is.

Video of Burj Dubai Foundations YouTube

Modern engineering and the advent of iron and steel beams allowed us to break the boundaries placed on us by stone bricks in order to create truly impressive narrow structures.

As materials science continues to increase, the upper limit of skyscrapers will only keep growing.

Already we’re setting our sights on some truly massive projects, the Jeddah tower mentioned above was originally planned to be a mile high before it was scaled down.

A tall, slender building acts like a pin pressing down into the earth. The foundation not only has to anchor a building in place but has to disperse the weight such that it doesn’t plunge into the ground. Depending on the location of a skyscraper, this can require some serious engineering.

The Shard in London is built over soft clay. In order to anchor the building in place over soft soil required a foundation 53 meters deep.

The Burj had its own set of concerns. On top of poor load-bearing soil, it had to deal with concentrated salt water saturating the ground. To get around this, the construction team bored holes 50 meters down and filled them with a polymer. The polymer was more viscous than the salt water and prevented the holes from being filled back in. The holes were then filled with concrete which displaced the less dense polymer before hardening.

200 of these spires were anchored into the ground to support the massive weight of the structure and keep it from sinking.

Wind

Having dealt with earth and water, a building now has to face the wind. Tall structures have to deal with wind speeds not often felt at the surface. It’s not unlikely, on any given day, for a skyscraper to sway anywhere from a few inches to a couple of feet. This amount of shift, while frightening on paper, isn’t really much of a concern. Buildings are built to withstand these pressures and most of the time it isn’t even noticeable to the people inside.

The bigger concern is when wind speeds reach such high speeds that they no longer hug the building as they pass, creating pockets of empty space that allow wind to travel back toward the building in the opposite direction.

Video of Burj Khalifa – How To Build Higher

The danger here is that a building may start to wobble back and forth rather than just tilt in one direction. When that happens it’s possible that a building can fall into a cycle where energy is stored during each wobble, gaining speed and toppling further each time.

Engineers and architects have a number of strategies to prevent this from happening.

The first step is to test the building before it’s ever constructed. This is accomplished by building a scale model and placing it into a wind tunnel, which allows builders to discover potential problems before the first proverbial brick is laid.

One strategy for diminishing the negative effects of wind on a building is to install mass dampers inside. These are essentially huge free-floating counter weights inside the guts of the building.

Because they are free-floating, they don’t immediately move with the building when pressed upon by high winds, earthquakes, or other external forces. This allows them to absorb and counteract some of the momentum and keep the building stable.

Video of Taipei 101 tuned mass damper moving during earthquakes

Another strategy, one that was used in the Burj, is to use the design of the building itself to prevent wind eddies from forming in the first place.

The Burj Khalifa employs alternating levels that spiral around the building as it rises. This means that wind coming from any direction never has a wholly flat surface to press against. Instead, the wind is broken up before it has a chance to circle back.

Other buildings get around the problem of wind in a more straightforward way — by putting holes in them.

Engineering problems are one thing and we’ve gotten pretty good at throwing math and science at them until they submit. But there’s another type of problem that isn’t quite so easy, the human element.

Living in the sky

Our fictional building, The Pearl, is said to be Tokyo’s largest building at 3500 feet. Tokyo’s own elevation is negligible at just 161 feet, placing the top of The Pearl at 3661 above sea level.

At just 3661 feet, elevation isn’t much of a concern to the people inside The Pearl, especially because the atmosphere and oxygen levels would be maintained by internal systems.

But the trailer makes it clear that the integrity of the building isn’t maintained for long, putting The Rock and his family at odds with the elements.

At this elevation, the oxygen content of the air is roughly just above 18 percent instead of the 21 percent we’re all used to.

This wouldn’t have much measurable impact on your average office worker, but when engaging in physical activity such as chasing down terrorists to save your family, 18 percent is not sufficient to adequately oxygenate your cells. Couple that with smoke inhalation and The Rock risks oxygen deprivation that could impair not just his cells, but his mental faculties as well.

We all know that The Rock is superhuman. If he wasn’t, his leap from the skycrane back into the building wouldn’t be possible. So maybe he’s able to handle the combined lack of oxygen from the elevation and smoke inhalation. In any event, the real trouble of living in this sort of environment isn’t the physics, it’s the people. Especially if those people are hell bent on bringing the building down.

Skyscrapers are incredible feats of engineering, literal symbols of humanity’s ability to reach higher. Skyscraper promises to be an incredible feat of effects and physics defying action-hero fun when it hits theaters July 13.


Video of Skyscraper: Science Behind The Fiction

Source: http://www.syfy.com/syfywire/science-behind-the-fiction-skyscraper-0

Recommended

« »