Will there ever be a mile-high skyscraper? - Stefan Al

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In 1956, architect Frank Lloyd Wright proposed a mile-high skyscraper, a building five times as high as the Eiffel Tower. While this massive tower was never built, today bigger and bigger buildings are going up around the world. How did these impossible ideas turn into architectural opportunities? Stefan Al explains how these megastructures became fixtures of our city skylines.

Lesson by Stefan Al, directed by TED-Ed.

In 1956,

architect Frank Lloyd Wright

proposed a mile-high skyscraper.

It was going to be the world’s
tallest building,

by a lot —

five times as high as the Eiffel Tower.

But many critics laughed at the architect,

arguing that people would have to wait
hours for an elevator,

or worse, that the tower would collapse
under its own weight.

Most engineers agreed,

and despite the publicity
around the proposal,

the titanic tower was never built.

But today,

bigger and bigger buildings are going up
around the world.

Firms are even planning skyscrapers
more than a kilometer tall,

like the Jeddah Tower in Saudi Arabia,

three times the size of the Eiffel Tower.

Very soon,

Wright’s mile-high miracle
may be a reality.

So what exactly was stopping us

from building these megastructures
70 years ago,

and how do we build something
a mile high today?

In any construction project,

each story of the structure needs to be
able to support the stories on top of it.

The higher we build,

the higher the gravitational pressure
from the upper stories on the lower ones.

This principle has long dictated
the shape of our buildings,

leading ancient architects to favor
pyramids with wide foundations

that support lighter upper levels.

But this solution doesn’t quite translate
to a city skyline–

a pyramid that tall would be roughly
one-and-a-half miles wide,

tough to squeeze into a city center.

Fortunately, strong materials like
concrete can avoid this impractical shape.

And modern concrete blends are reinforced
with steel-fibers for strength

and water-reducing polymers
to prevent cracking.

The concrete in the world’s tallest tower,
Dubai’s Burj Khalifa,

can withstand about 8,000 tons of pressure
per square meter–

the weight of over 1,200
African elephants!

Of course, even if a building
supports itself,

it still needs support from the ground.

Without a foundation,

buildings this heavy would sink, fall,
or lean over.

To prevent the roughly half a million
ton tower from sinking,

192 concrete and steel supports called
piles were buried over 50 meters deep.

The friction between the piles
and the ground

keeps this sizable structure standing.

Besides defeating gravity,

which pushes the building down,

a skyscraper also needs to overcome
the blowing wind,

which pushes from the side.

On average days,

wind can exert up to 17 pounds of force
per square meter on a high-rise building–

as heavy as a gust of bowling balls.

Designing structures to be aerodynamic,

like China’s sleek Shanghai Tower,

can reduce that force by up to a quarter.

And wind-bearing frames inside or
outside the building

can absorb the remaining wind force,

such as in Seoul’s Lotte Tower.

But even after all these measures,

you could still find yourself swaying back
and forth

more than a meter on top floors
during a hurricane.

To prevent the wind from
rocking tower tops,

many skyscrapers employ a counterweight
weighing hundreds of tons

called a “tuned mass damper.”

The Taipei 101, for instance,

has suspended a giant metal orb
above the 87th floor.

When wind moves the building,

this orb sways into action,

absorbing the building’s kinetic energy.

As its movements trail the tower’s,

hydraulic cylinders between the ball
and the building

convert that kinetic energy into heat,

and stabilize the swaying structure.

With all these technologies in place,

our mega-structures can stay
standing and stable.

But quickly traveling through buildings
this large is a challenge in itself.

In Wright’s age,

the fastest elevators moved
a mere 22 kilometers per hour.

Thankfully, today’s elevators are much
faster, traveling over 70 km per hour

with future cabins potentially using
frictionless magnetic rails

for even higher speeds.

And traffic management algorithms
group riders by destination

to get passengers and empty cabins
where they need to be.

Skyscrapers have come a long way since
Wright proposed his mile-high tower.

What were once considered impossible ideas

have become architectural opportunities.

Today it may just be a matter of time

until one building goes the extra mile.