Today, on "Impossible engineering,"
the Shanghai tower,
the most technologically advanced skyscraper
on the planet...
...built to withstand earthquakes and typhoons...
...using technology never before seen in a skyscraper...
...to make the impossible possible.
Captions by vitac www.Vitac.Com
captions paid for by Discovery communications
Shanghai is a megacity.
With 24 million inhabitants and rising,
it's one of the most densely populated cities in the world.
With a population of 10,000 people per square mile,
the only place left to build is up.
By the mid 1990s,
development reached an area of farmland
on the east river bank known as Pudong.
And in 2008, work began
on the most impressive building of them all...
The Shanghai tower.
Over 2,000 feet tall,
it's the second tallest building in the world
and the tallest ever built in a seismic zone.
It's the most technologically advanced skyscraper
on the planet,
with 128 floors and 9 indoor gardens,
where 16,000 people will work, sleep and play.
It truly is a city in the sky.
For lead structural engineer Dennis Poon,
the project was an exciting challenge.
The engineering challenges for the Shanghai tower
began at its foundations because, not only
is Shanghai in an active seismic and typhoon zone...
...it's also sinking.
The land under this massive Metropolis
is deflating like a giant air mattress.
It's shallow-water table
is collapsing under the weight of the city's modern buildings.
Solid bedrock is 650 feet down.
Above the bedrock is a soft layer of sand, clay, and soil.
Without a solution,
the 850,000 ton Shanghai tower would surely sink.
The engineers only have one shot.
There's no room for error
when you're building a tower this tall.
A modern world full of skyscrapers
was once inconceivable.
Early man was limited by what nature provided.
Ah!
Aw... For the ancient Egyptians,
taller meant wider and an awful lot of manpower,
unless you believe in some of the more otherworldly theories.
When it comes to building towers,
the ground below has frequently thrown a wrench in the works.
Mamma Mia!
In order to create a skyscraper 11 times
taller than Pisa's famous learning tower,
the designers of the Shanghai tower
will need to draw inspiration
from the work of a 19th-century engineering pioneer.
Chicago is home to some of the world's most iconic skyscrapers.
But just over a century ago,
building anything taller than just a few stories
was thought to be impossible.
You wouldn't know it to look at it,
but Chicago is actually one of the least logical places
that you could ever attempt to build a skyscraper.
We've got soil here that is incredibly squishy.
Underneath the kind of shorter, smaller layer of earth,
we've got a very, very deep layer of soft, squishy clay.
This is a really difficult thing
to build a skyscraper on of course because,
when you load the building, the building's going to sink.
As Chicago began to boom
and property downtown became more valuable,
the demand to grow higher and maximize space
posed a problem for city planners.
Taller buildings meant heavier buildings.
And, as they had discovered,
there was a limit to weight the soil could handle.
This is the auditorium building of Roosevelt university,
designed by Adler & Sullivan in 1889.
It's a national landmark
and so important to Chicago as well.
The auditorium building at Roosevelt university
is 236 feet tall.
When it was completed in 1889,
it was the tallest building in the city.
The radical idea that made this building possible
came from engineer Dankmar Adler.
We're headed down to see Adler's specially designed foundations
to deal with the soil here in Chicago.
Previously, the weight of a building
would bear down on its walls.
It would sink into the clay like a cookie cutter.
Adler's idea was to use wood and steel crossbeams
encased in concrete to create a reinforced concrete raft
for the 110,000 ton building to sit on.
I'm gonna illustrate what's happening here with this piece
of modeling clay used to represent the clay
that's under our feet here in Chicago, this sort
of peanut-butter-jelly-like substance.
The clay is really quite deep,
and the bedrock doesn't start in Chicago
until 75 to 100 feet below the surface.
So I've got my chopstick here to sort of illustrate.
And I take my structure,
and I go through the hardpan.
And they just didn't have the technology in the 1880s
and the 1890s to excavate that far down to bedrock.
So instead, architects and engineers here in Chicago
are coming up with new ways to solve this problem.
The method that we're standing on here
is sort of the equivalent
of this kind of penny that I'm gonna illustrate.
So this pad or this raft is put down,
and then the building, the column on top of that
is put on top of that.
And you can see that I can push it down a little bit
into the clay, but not really that far.
This is distributing the load.
Adler's revolutionary engineering solution
proved that building on substandard soil was possible.
Today, Chicago's tallest building,
the Willis tower, is 1,450 feet tall.
That's more than six times the height
of Adler's auditorium.
But despite its influence on the world of skyscrapers,
Adler's design wasn't perfect.
So, on the north edge of the building,
we've got this large, heavy exterior walls
that are much heavier than what...
What's happening on the interior of the building.
And we can see the challenge with that,
the fact that this is much heavier
and this is much lighter in the building
with this long crack here in the floor.
We can also illustrate that pretty well with these marbles.
Dennis Poon and his engineering team
may owe a debt to Dankmar Adler,
but they can't afford to have the Shanghai tower subside
like the Chicago auditorium.
They'll have to take Adler's innovative idea
and supersize it.
At 2,073 feet tall, the Shanghai tower
is the second tallest building in the world.
Engineers can't afford to have it sink unevenly
like Dankmar Adler's 19th century Chicago auditorium.
So Dennis Poon and his team of engineers
have taken Adler's concrete raft design and supersized it.
In 2008, the two-year operation
to build the Shanghai tower's foundation begins.
First, they sink hundreds of deep supporting piles
into the soil.
Then, they pour the concrete raft or mat foundation.
It takes 60 hours of continuous pouring
to create the concrete raft.
2,000 workers and 450 concrete trucks
are needed to complete the operation.
The mat soaks up over 2 million cubic feet of concrete,
breaking a world record.
Without the revolutionary work of Dankmar Adler,
building a tower this tall on the soft Shanghai soil
would be impossible.
But the foundation of the Shanghai tower
is just the beginning.
The tower's structure must be strong enough to support
128 floors,
each weighing in at around 6,500 tons.
To design a structure with the strength
to support over 800,000 tons,
Dennis and his team look to past engineering solutions
for the answer.
At one time, the height of a building
was determined by the thickness of its walls
because the weight of each story
had to be supported by the floors below.
Tall buildings were the realm of the rich and powerful.
Medieval religious architects figured out a way
to design thin walls with large stained glass windows.
But they needed external supports
called flying buttresses.
These made the buildings
grow sideways and were exclusive to the wealthy church.
Bless you, my child.
But there was a revolution on the horizon.
And this picturesque region surround the river severn
in england was at the center of it all.
Shropshire was at the heart of the industrial revolution.
It was the silicon valley of the 18th and 19th century.
It's engineers were at the cutting edge of technology
because they had mastered the production of iron.
This area gave birth
to some of the greatest engineering pioneers of our time
and enabled the construction of iconic structures
like this... iron bridge,
the first cast-iron bridge of its kind in the world.
But just a few miles upriver is a less iconic
but much more significant building.
It wasn't until about 20 years ago
that the historical importance of this building
was properly understood,
which is why its fallen into disrepair.
This crumbling mill is one of the most important buildings
in architectural history.
This incredible,
but rather sad and dilapidated building in shrewsbury
is arguably the world's first skyscraper.
It's the first time that iron was used
in a multistory frame construction.
And it really paved the way
for tower blocks and skyscrapers that we know today.
Built in 1796, ditherington flax mill
was the brainchild of engineer Charles Bage.
He took advantage of the region's groundbreaking use
of iron to build the first metal-framed building
on the planet.
Previous to the iron frame,
the taller the building,
the thicker the walls had to be to support them.
But with Bage's design,
the walls could be thinner,
which meant that the rooms could be much larger.
It also meant that you could design buildings much taller.
In Bage's design, the weight of the building
lies on its iron frames instead of the walls,
making the sky the limit for the first time.
This main building had five floors,
including this attic, which was previously unheard of.
It had a working area of over 2,800 square meters
or 31,000 square feet.
And these narrow, relatively lightweight metal beams
would be able to support much more weight
than the solid brick walls of previous buildings.
Bage's simple but brilliant design
made the flax mill the forerunner
of almost every large-scale building
in the modern world,
including the Shanghai tower.
What Bage achieved in this building was truly remarkable.
Today's engineers
are using the same principles employed by Charles Bage...
But with some revolutionary engineering of their own.
The 128-story Shanghai tower
will have a steel frame instead of iron.
Because the steel frame bears the weight of the structure,
the external walls no longer need to be load-bearing.
They don't even need to be flat or straight.
They can be made from a variety of lightweight materials,
even glass.
Architects can mold the external walls into any shape they want.
The whole building is covered in glass.
The glass is suspended over many floors,
like a giant curtain, thanks to the strength
of the steel rods that hold them in place.
Because of the Shanghai tower's lattice-like steel frame,
its architects can let the building breathe.
Between the curtain wall and inner core,
where offices and hotel rooms are located,
is a massive open atrium.
But creating a skyscraper
in which 16,000 people work, sleep, and play
comes with a unique challenge...
How to move all those people around the massive structure.
With 24 million inhabitants,
Shanghai is one of the most densely populated cities
on earth.
The only way to expand is by going up.
Over 2,000 feet tall,
the Shanghai tower is a city in the sky.
It will house offices, shops, and hotel rooms,
as well as concert halls and conference rooms.
But building a supertower in which 16,000 daily users
will work, sleep, and play poses a unique challenge...
How to transport all those people
around the massive structure.
It's an engineering feat
that would've been impossible just a few centuries ago.
By the mid 19th century,
the world's skylines were still relatively skyscraper-free
for one reason... no one wanted to take the stairs.
Today, penthouses rule the top floor.
But back then, the higher you lived, the poorer you were.
Mustn't grumble.
Steam-powered and hydraulic lifts were being used in mines
and factories for freight,
but they were too dangerous for people.
The ropes on the pulley system would often break.
But city skylines were about to change because,
in 1852, a man named Elisha Otis
came up with an idea that would revolutionize the way
the world thought about living on the upper floor.
He pioneered a simple mechanism
that changed the elevator forever.
So we're here in Bristol, Connecticut,
at the Otis elevator company test facility.
This is where they test the newest elevators
that they're gonna install in buildings across the world.
But they also have this replica of a device that Elisha Otis
first constructed for the crystal palace exhibition,
the world's fair that ran from 1853 to 1854.
Otis was a showman as much as he was an inventor.
The world's fair was the perfect stage for his invention.
He knew that the eyes of the world would be upon him
if he could prove that elevators can be both safe and practical.
So I think it's important to remember that Otis
didn't invent the elevator.
Certainly, there had been ways of moving goods and people
up and down from floor to floor
using hoists and pulleys for... for centuries.
But what Otis did do was to recognize
that people were afraid of going into an elevator.
So at the 1853-1854 world's fair,
he builds this... this device to provide a break, a safety
in case the rope broke.
Like a true showman,
Otis decided that the best way to prove his idea
was to put it to the test using himself as a Guinea pig.
In front of a live audience,
he stepped onto the platform, rose above the crowd,
and gave the signal for the rope of his elevator to be cut.
So let's see if Mr. Otis' invention still works.
Ready whenever you are, rich.
Otis' system features a wagon spring.
It's held up by a rope,
keeping the spring in a state of constant tension.
When the rope is cut,
the tension in the spring releases,
causing pins fixed to the side of the spring
to lock into a ratchet located in the wood frame.
This brings the elevator to a complete stop,
preventing it from falling and injuring any passengers.
And all these years later,
every single elevator today around the world
has a similar safety device
that is allowing passengers to feel safe in tall buildings.
And I didn't plunge to my death.
Otis' invention transformed the world's skylines.
Cities like New York that couldn't expand sideways
could now reach for the skies.
In 1913, it was the Otis company
that was commissioned to provide the elevators
for one of New York's most iconic skyscrapers...
The woolworth building.
By 1916, more than 100,000 people
had paid their 50 cents to ride the elevator
to the observation deck at the top.
And now, 100 years later, those original Otis elevators
are still being used to carry office workers up and down.
Because of Otis, instead of the poor being consigned
to a building's upper levels,
the value of floor space now increased as you went higher.
Penthouse living was what everyone dreamed of.
As we drive through New York, it's easy to forget, I think,
that within just a short span of time,
just about 160 years,
all of these skyscrapers have been constructed.
And so the rise of the elevator
and the rise of the skyscraper are so,
so closely linked.
Otis' first passenger elevator traveled 8 inches a second.
At that speed, it would take nearly an hour
to reach the top of the Shanghai tower.
The Shanghai tower will have 106 elevators,
including one that travels
a world-record-breaking 1,898 feet.
Along with residents, shoppers, and office workers,
the elevator will transport thousands of tourists
to its top-floor observation deck each day.
The Shanghai tower is the most technologically advanced
skyscraper in the world,
the tallest building in China
and the tallest ever built in a seismic zone.
This massive skyscraper contains 106 elevators,
moving thousands of tourists, residents, shoppers,
and office workers throughout the structure each day.
The Shanghai tower provides stunning views
of the city below,
but it's also a massive obstacle to the wind.
Shanghai is in a typhoon zone.
Defending the second tallest building in the world
from the powerful winds
that sweep through the city is a major challenge
for Dennis Poon and his engineering team.
Building the Shanghai tower without first testing its design
in a wind tunnel would be inconceivable.
But it wasn't always this way.
The first wind tunnel was constructed in 1871,
but they were traditionally built
with airplane testing in mind.
That was until engineer Jack e. Cermak
designed the first wind tunnel meant for buildings.
In the late 1950s, Cermak and his contemporaries
pioneered the use of new wind tunnels.
Professor Rhys Morgan
is visiting wind engineering firm rwdi.
They take advantage of Jack Cermak's innovative design,
which is much larger than a traditional tunnel
and uses irregular shapes
to mimic the unpredictable nature of the wind.
Blocks like these on the floor
create the kind of turbulent atmosphere,
turbulent winds that you see in cities and urban environments
so they're perfect for testing structures
that we want to build in cities.
One of the first skyscrapers to be tested
in Cermak's wind tunnel was New York's World Trade Center.
The discoveries made while testing the twin towers
influenced the design of every skyscraper that followed,
including the Shanghai tower.
A scale model of the World Trade Center
is being placed into a model of the London skyline
to demonstrate the effect wind can have on tall buildings.
Wow, it's really windy.
As wind rushes past the structure,
it forms into Eddies of low pressure on either side.
So the wind is coming in here.
It's hitting the side.
And then, as it comes around the corner,
it produces a low-pressure region here.
And that causes the movement...
The building to move this way.
But then that means that the wind coming around this end
starts to cause a little bit of movement
this side and low pressure.
So we start to get this low pressure,
low pressure, low pressure, low pressure.
And that causes this oscillation back and forth.
This is just amazing.
This is the kind of... this is real engineering happening here.
That's moving a good 5 centimeters either side.
I wouldn't want to be on the top of this building if it was a...
A real building in the city.
For architects, the challenge is to come up with a shape
that reduces those vortices.
Okay, let's try this one.
This time, the building is tapered
like an elongated pyramid.
You can see there's very, very little movement.
Let's turn it up a bit more.
We're running at three times
the wind speed of that very first model that we saw.
And the building's just not
moving anything like as violently.
Because of the tapered shape of the building, the wind
creates vortices of different sizes at different heights.
It's causing some oscillations down here,
but then much slower than the oscillations
occurring at the top end.
Different parts of the building
are trying to shake at different rates,
canceling each other out.
And so it prevents the building
from oscillating quite so violently.
Jack Cermak's wind tunnel
allowed city skylines around the world
to grow taller safely.
Today, no one would think of building a skyscraper
without testing it first in a wind tunnel.
The Shanghai tower is tapered,
but it also has a distinctive twist,
a direct influence from wind tunnel testing.
It's a unique design
that reduces wind loads on the building by 24%.
Architects also designed a notched "v"
running the entire length of the building.
The notched- "v" shape on the Shanghai tower
started out as an aesthetic touch.
But when engineers tested it in a wind tunnel,
they made a surprising discovery.
The Shanghai tower
is the most technologically advanced skyscraper in the world
and the tallest building in China.
The tower's tapered,
notched- "v" design maximizes its aerodynamic performance,
making it one of the most wind-resistant skyscrapers
on the planet.
But the Shanghai tower faces a natural force
even more destructive than high winds...
Earthquakes.
Shanghai is in a level three seismic zone.
Building the Shanghai tower strong enough to survive
an earthquake will be a daunting task.
Earthquakes can be
some of the most devastating natural disasters on the planet,
leveling buildings and triggering tsunamis.
China's neighbor, Japan,
is the most seismically active country on the planet.
But for years, no one could understand
why modern buildings would collapse in an earthquake
while traditional pagodas stayed standing.
The secret to the pagoda's survival is hidden inside.
The typical pagoda consists of five floors.
Its floors have the ability
to move independently of each other.
When an earthquake strikes,
its snake-like pattern keeps the center
of gravity more upright than a rigid building would.
And the wooden joints that support each floor
are made up of several separate components
so each part can slide and move.
The friction the parts create acts like a damper
to soften any movement.
Today's engineers will need to take the five-floor pagoda's
innovative earthquake proof design
and apply it to the 128-floor Shanghai tower...
...with a 21st century twist.
The Shanghai tower's design is similar to an ancient pagoda.
Its structure is divided into nine vertical zones
around a central composite steel and concrete core.
To further strengthen the tower,
huge perimeter columns and outriggers
have been attached to the central core.
The earthquake-proofing measures
extend from the base of the tower to its tip.
So, why is this room so important?
The answer is suspended above Dennis' head.
So, why would engineers take up valuable floors
and sacrifice the revenue they can generate with a steel block
the weight of 600 four-door sedans?
Boston's John Hancock tower was completed in 1976.
Its futuristic, glass-clad design was ahead of its time.
But not long after it opened,
upper-floor occupants complained of motion sickness
as the building swayed with the wind.
Engineer William lemessurier
came up with an ingenious solution.
What I've got here is a very simple model of a skyscraper.
It's a, um, beam structure going up several stories.
Turning a handle at the base of the structure
mimics an earthquake.
With steel structure buildings and glass buildings,
of course we're reducing the weight of those buildings.
So you can actually go much taller.
You can build them much taller.
But then you do have this problem with sway.
Lemessurier's idea was to counteract the sway
at the John Hancock tower.
He installed two steel boxes on the 58th floor.
Each box was filled with several hundred tons of lead
and placed on a steel plate.
You have to imagine this is an 800-ton weight
that I'm lifting up onto my skyscraper now.
And I'm just gonna tie it to the top of my structure.
The tuned mass damper,
or tmd is became known, had a dramatic effect.
It's amazing.
The structure is hardly moving.
I mean it's quite phenomenal.
So what we're seeing here is the mass damper oscillating
out of phase with the vibration of the structure.
In a building like this,
you wouldn't have an 800-ton ball flying around violently
and smashing into the walls.
The principle is simple.
As the building sways one way,
it pulls the damper with it.
As the building starts to sway back,
the damper is still traveling in the opposite direction.
So it stops the building from going too far.
It's amazing how, uh, how much of an impact it has.
It really does just stop the structure from swaying around.
Without tuned mass dampers today, uh, we just
wouldn't have any of the kind of megastructures that we have.
The Shanghai tower's engineers
have taken lemessurier's damping system to a whole new level.
Despite taking up five floors and weighing over 1,000 tons,
the Shanghai tower's tuned mass damper actually
makes the building cheaper and lighter to construct.
It took 15 years of planning, design, and testing
and 7 years of construction to raise this supertower
from its foundations deep in the Shanghai soil
to the tip of its 128th floor over 2,000 feet up.
By drawing on innovations of the past and making
groundbreaking discoveries of their own,
the engineers, designers, and workers of the Shanghai tower
have overcome unstable soil,
high winds, and earthquake risks to make the impossible...
Possible.