All language subtitles for Impossible Engineering s01e01 Mega Bridge.eng

Today
on "Impossible engineering,"

the Rion-Antirion bridge...

A colossal structure built in
the heart of an earthquake zone.

Spanning 2 miles
across open water,

it took revolutionary
engineering...

...and a look back at some
hard lessons from the past...

The energy release was massive,

and now the specimen has
just catastrophically failed.

...To make
the impossible... Possible.

Captions by vitac

captions paid for by
Discovery communications

August 2004,
the Rion-Antirion bridge

opens to traffic
for the first time.

It's an engineering masterpiece
of the modern age.

This massive structure

spans almost 2 miles across
the Gulf of Corinth in Greece.

It boasts the longest
fully suspended deck

and deepest foundation piers
of any bridge on earth.

For chief engineer
Panayotis Papanikolas,

it was the project
of a lifetime...

...but for centuries,

building a bridge across the
Gulf of Corinth was just a dream

due to a long list
of environmental challenges.

But wind isn't the only threat
to the bridge.

The two land masses on either
side of the Gulf of Corinth

are constantly drifting apart.

This, along with frequent
earthquakes, high winds,

and deep water meant that

building a bridge across the
Gulf would be a daunting task...

...but the need for a safe
crossing was desperate.

The perilous waters
of the Gulf of Corinth

often made ferry crossings
impossible

and cut the peninsula off
from important services.

So in the 1990s,
the government embarked

on one of the most ambitious
engineering projects

in modern history.

The first challenge
was to design a bridge

that could span

the almost 2-mile gap
across the Gulf of Corinth.

The distance was too great
for a single-span bridge,

so engineers has to build
support towers in water

that's over 200 feet deep.

To overcome
the water-depth issue,

Panayotis
and his fellow engineers

would need to look

to history's great engineering
innovations for the solution.

Building in water
has always been a challenge.

Early builders relied on
conveniently placed rocks

for the foundation
of their structures.

Fine for lighthouses,
useless for bridge building.

Creating artificial islands

was time-consuming and
impractical in deep water.

In the 19th century, pressurized
structures called case-ins

were developed to create
underwater building sites.

But they were difficult
to build...

And dangerous.

Fortunately,
in the 20th century,

a new technique was
on the horizon.

In the 1940s,
engineer guy Maunsell

came up with a solution

that finally conquered the
challenge of building at sea.

Professor Luke Bisby is heading
far out into the English channel

to see the remains

of Guy Maunsell's bold creation
firsthand.

Maunsell's influence
on contemporary engineering

I don't think
really can be overstated.

This was really the first time

that this had ever been
attempted,

and so it was really quite
a daring feat of engineering.

Maunsell's innovation

was triggered
by the second world war.

It became clear the river thames
was a prime target

for German bombers
during the war.

The Germans wanted
to destroy London's docks

and lay mines
to disrupt allied shipping.

So Maunsell came up
with a radical new design

for off-shore sea defense...

...naval forts consisting of two
80-foot high concrete towers

each containing four floors
of accommodations

topped with a gun deck.

But the ingenious part
of Maunsell's design

wasn't the layout of the fort...

It was how it would
be constructed

and deployed at sea.

Knock John here was towed out
3 to 6 miles

from where
it was constructed on land,

and then it was sunk in place
exactly where you see it.

Maunsell designed
the bases of his forts

as huge hollow concrete barges.

Despite their enormous weight,

they had enough buoyancy
to float.

Maunsell built the forts

on top of these
large concrete barges

and then calculated how large
the barges needed to be

in order to hold
the weight of the fort

so they could be taken out
and then sunk in place.

The massive
4-1/2 ton concrete forts

were constructed in a dry dock,

then towed out to sea with
a 100-man crew already on board.

When they had it in
the place where they wanted it,

they essentially just pulled out
a stopcock at one end

and let the water flow in.

As the water was flowing in,

the barge started to list
in the water.

Eventually, the nose dipped
under the water.

All 100 men were hanging on

as the fort was sinking
at 35 degrees.

Despite the rough submersion,

Maunsell's groundbreaking design
worked perfectly.

The bottom of the barge
basically filled up with water,

and eventually the entire barge
sunk to the bottom

and flattened out.

Maunsell's forts
helped British forces shoot down

22 enemy aircraft
and 30 flying bombs.

They protected London
from attack

and made engineering history.

The influence of this
type of construction you can see

in all different facets
of engineering today.

You can see it in the
off-shore-oil-and-gas industry

with oil platforms.

You can see it being used as
foundations for wind turbines.

And, of course,
you can see it being used

as a way of placing foundations

for large bridge structures
around the world.

But the most impressive use

of Maunsell's revolutionary
floating concrete design

is at the Rion-Antirion bridge.

The Rion-Antirion bridge

spans an incredible 2 miles

across the deep waters
of the Gulf of Corinth.

To support
this massive structure,

engineers used principles

first exploited by Guy Maunsell
in the 1940s

and super-sized them.

In 1998, construction begins
on 4 enormous pier foundations.

Each one is larger
than a football field

and weighs almost 80,000 tons.

The hollow pier footings
are built in a dry dock

just as guy Maunsell did

but on a scale
he couldn't have imagined.

Before the footings can be taken
out into the Gulf of Corinth,

engineers need a solution
to a serious problem...

A problem Maunsell
never had to deal with.

The Gulf of Corinth
lies in the heart

of one of the most active
seismic zones in the world.

In an earthquake, the soft
seafloor would liquify

causing the piers to sink
and the bridge to collapse.

Unless an answer was found,
the project was over.

The engineers came up
with a radical solution.

They would drive hundreds of
long tubes deep into the soil

where the four piers will sit.

This ingenious idea
stabilized the soft seafloor.

Bridge footings are usually

anchored directly
into the ground.

But for the Rion-Antirion,

they were placed on top
of a 10-foot layer of gravel.

This allowed the footings
to shift with the earth

during an earthquake.

With a solution
to the earthquake problem,

the engineers are now ready
to begin

one of the most audacious parts
of the build...

...maneuvering
the half-constructed piers

into the Gulf.

Engineers continued to build up
the massive structures

while they were still floating.

Each layer of heavy concrete
that was added

sunk the pier further down,

pushing it closer
to its final resting place

200 feet below on the seafloor.

The end result was four enormous
hollow foundation piers.

They're the first
of their kind...

A series of massive
concrete underwater caverns.

The pier footings
for the Rion-Antirion

can survive an earthquake,

but what about its nearly
2-mile long suspended deck?

The builders of this massive
structure will need to produce

even more
impossible engineering.

The Rion-Antirion
bridge in Greece

is a modern engineering marvel.

Over 11 million cubic feet
of concrete,

more than 100,000 tons of steel,
and 39 miles of cabling

make up the longest fully
suspended cable-stayed bridge

on the planet.

Panayotis Papanikolas
and his fellow engineers

had to overcome
a long list of obstacles

before their dream

of a bridge spanning
the Gulf of Corinth

could be realized.

The Gulf of Corinth

is one of the busiest
trade routes in Europe.

Its shipping lanes
cannot be disrupted.

To design a bridge
capable of spanning this gap

without interfering
with shipping,

engineers would need to turn

to the great innovators
of the past for inspiration.

It was the romans who first
engineered solid Bridges

using stone and a simple but
revolutionary shape... the arch.

However, the wider the gap,

the more arches were needed and
the heavier the bridge became.

For hundreds of years, inca
communities in the high andes

crossed gorges using
suspended wooden walkways.

It's said that 16th-century
Spanish conquistadors

arriving in Peru
looked in amazement and fear

at the swaying Bridges
that could break at any moment.

It wasn't until 1826
that a brilliant engineer

utilized new building materials
and a new approach

to change the bridge game
forever.

The Menai suspension bridge

is the ultimate achievement
of Thomas telford...

One of britain's finest
civil engineers.

Telford was
an accomplished engineer.

Of course, at this stage,

he had designed canals
and roads and Bridges.

He had never built anything
on this scale before,

and so, this bridge was to be
really his greatest challenge.

The Menai strait
separates mainland Wales

from the island of Anglesey.

Centuries ago, bridging it
would have been impossible.

A traditional Roman arch design
would not only be enormous,

it would block the passage of
tall ships along the waterway.

Imagine this
as being the strait here,

and these are the valley walls
on either side of the strait.

Basically,
you cut your bits into shape,

and you then have to gradually
build your arch,

adding the bits of the arch
as you go.

And if you imagine that as now
being the completed arch...

And we have our load
coming along here...

You can see that the compression
forces that come from that car

flow down through the various
sections of the arch

and into the abutments
on either side of the valley.

Now, the problem
that telford faced

was that
as you're building an arch,

you would have to have
some supports down here

underneath the middle
of the arch

so that as you're building it,

the blocks don't fall
into the strait.

And that would require
some scaffolding.

And this was just not acceptable
to the admiralty at the time

because this is a very busy
shipping channel

and they required
100 feet of clearance

above the high-water mark.

And that led telford
to have to consider something

that could give him
a very long clear-span

with no supports in the water
even during construction.

Telford's solution

was the world's first major
long-span suspension bridge.

For a suspension bridge, we need
two very strong abutments,

and then you need two towers.

And then what you do is,
once you've built your towers,

you take a cable
like these guys,

and you string these
up and over the towers.

And then you drop hanger cables
down from the main cables

and then put your bridge deck
in place.

And then once your bridge
is completed,

if you have a load that comes
along... say our car here...

It comes along,

and now when the load gets out
near the middle of the span,

the load from the car
then gets transferred up

through the hanger cables

into the main cable
up over the tower.

The tension in that cable

gets anchored
in these strong abutments,

and the compression force here

goes down into the foundations
in the bedrock.

That's essentially how
a suspension bridge works

like this beautiful bridge
we have here.

Telford's suspended deck

was a stroke
of engineering genius.

The key advantages
of a suspension bridge

are that you can span
long distances

with no supports
below the bridge decks.

So you can get very long,
clear, unsupported spans

because all of the support

is coming
from the suspending cables

and the main cables
up above you.

So below the bridge deck,

there's absolutely
no obstructions,

which in a strait is obviously
a very important thing.

A suspended bridge
was the obvious solution

for Papanikolas
and his fellow engineers

in the Gulf of Corinth,

but they would have to do it
on a much larger scale.

The Rion-Antirion
would need to be

an incredible seven times longer

than the Menai
suspension bridge.

Unlike the main anchored cables
of telford's suspension bridge,

this cable-stayed design
would use individual cables

radiating from 4 huge pylons
spaced 1,600 feet apart.

Each cable set would support
a 40-foot section

of the bridge's deck.

In 2003, deck building begins.

Each section is floated out
into the Gulf of Corinth

and attached to either side
of a pylon until the decks meet.

This massive operation took
more than a year to complete.

Just as they had to do
for the bridge's pier footings,

designers had to ensure the deck
could survive an earthquake

in one of the most active
seismic zones in the world.

Expansion joints
allow the deck to stretch

as the two land masses on either
side slowly drift apart.

But protecting it
against a massive earthquake

will require
a groundbreaking new approach.

Instead of resting
on the foundation piers,

the deck hangs just above

creating a single
1-1/2 mile long,

fully suspended floating deck.

When an earthquake strikes,

flexibility will be key
to the bridge deck's survival.

The piers can move
on their foundations.

And if the deck was attached
when this happened,

it would buckle and break.

But it's also important
that the deck doesn't sway

during the frequent high winds

experienced
in the Gulf of Corinth.

Engineers had to ensure rigidity
in normal conditions

but flexibility in the event
of an earthquake.

Their solution... the world's
biggest shock absorber.

If the bridge
begins moving erratically,

a fuse breaks, sending the
massive dampers into action.

This quake-busting design
proved its worth

four years after the bridge
opened

when a 6.4-scale earthquake
hit the Rion-Antirion in 2008.

The innovative damping system
kicked into action

saving the bridge from disaster.

But earthquakes
aren't the only natural forces

that engineers
will need to overcome.

To ensure
the Rion-Antirion's survival,

they will need
to take a look back

of some of history's great
engineering catastrophes.

Designers
of the almost 2-mile long

Rion-Antirion bridge faced
huge environmental challenges.

In one of the most seismically
active regions in Europe,

cutting-edge technology
was developed

to protect the bridge
from earthquakes.

But the bridge faces

another equally destructive
environmental threat

that its engineers
must overcome.

To protect this massive
structure from wind,

engineers will need to take
a lesson from the history books.

When the Tacoma narrow
suspension bridge opened

near Seattle in July 1940,

it was thought to be at
the forefront of bridge design.

But it wasn't long
before the bridge

got the nickname
"galloping gertie."

There was clearly
a very big problem.

Just four months after opening,

the bridge's twisting motion
became so violent,

it suffered
a catastrophic failure...

...crashing almost 200 feet
into the water below.

An investigation found

that the relatively light
40-mile-per-hour wind

was hitting the solid edges
of the deck,

creating an unstable oscillation
that fed off itself,

amplifying to the point
of disaster.

The wind conditions are far more
severe in the Gulf of Corinth.

The mountainous landscape
creates a funnel,

where winds of 70 miles per hour
are common.

The aerodynamics of the bridge
deck are a crucial element.

The fairings safeguard the deck

from gusts
of over 150 miles per hour,

but the massive cables
holding up the deck

also need to be strong enough
to survive extreme wind gusts.

The designers
of the Rion-Antirion

looked to an engineering marvel
created years ago

for the solution...

One that conquered a challenge
once thought to be impossible.

In the second half
of the 19th century,

the growth of New York City

was being stunted by the limits
of the east river.

At that time,
the only way for people

to cross from Brooklyn
to Manhattan was by ferry.

You see here Manhattan to my
left and Brooklyn to my right.

At the time, you could imagine
just a river teeming with boats.

But in 1867,
boat traffic ground to a halt.

A cold spell actually
froze the east river over

and essentially halted commerce

because you could walk across
the east river

at the time on the ice,
but you couldn't actually trade.

So it was at that point when
voices really kind of mounted

demanding a permanent kind of
structural connection

between the two cities
with a bridge

to have this lasting connection

so that you could have reliable
transportation and trade.

The man given the job

was German-born engineer
John Augustus Roebling,

and what he designed still
inspires engineers today...

The Brooklyn bridge.

Just the concept
of actually spanning

over such a long distance
at such a height

was earth-shattering.

No bridge had been built
even close to this span.

The Brooklyn bridge
spans over a mile.

It was made possible
by Roebling's use

of a revolutionary
new material... Steel.

Just thinking
of actually building

a bridge not of masonry

as we'd find in kind of
traditional European style,

but saying, "we have this new
material... steel..."

We will build the entire deck
and the cables of steel."

This is an absolute
engineering marvel.

Steel is stronger, lighter,

and more flexible than iron.

Roebling used this new material

for the bridge's four
massive suspension cables.

He bundled hundreds of parallel
steel wires together,

creating super-strong
and super-safe cables.

Engineer Adrian Brugger

demonstrates just how much safer
Roebling's design is

at Columbia university's
engineering testing lab.

This cable is made up
of actually independent

and small 5-millimeter
circular wires.

In this case,
there's 9,000 wires.

Those wires are then grouped
into what we call strands.

You actually take those and you
compact those into the cable.

This is kind of a huge leap from
the technology we had before.

Because before what we had

was more or less
serialized systems,

such as chains
or these large I-bars.

Where if one
of these I-bars failed,

then generally that meant that
the entire bridge failed.

If one of these wires happens
to be bad or has a crack in it,

then the entire cable still
has 8,999 other intact wires.

Adrian compares the system
used on the Brooklyn bridge

to those that came before it
using a giant universal tester.

And more or less,
a universal testing machine

just means that it's a machine
that is built to crush things

and rip them apart.

First to be tested...
A solid steel bar.

This would be very similar

to what you would have
on an old bridge...

Pre-Brooklyn bridge for example.

The steel bar has been
weakened at a specific point

and will be stretched
under massive tension

to simulate a bridge failure.

So, we expect this bar to fail
at around a good 200 tons.

Right now, you can see
that the necking

is starting at about a quarter
up from the reduced section,

so exactly where we wanted it.

And it'll become more
and more pronounced

kind of as we see it now.

The energy release was massive,

and now the specimen has
just catastrophically failed.

It's broken.

Such an explosive
failure could result

in the collapse
of a whole bridge

as tragically happened
with Silver bridge in Ohio,

causing the loss
of dozens of lives.

Next, Adrian tests
Roebling's steel cable design.

As it's stretched,
he subjects it to extreme heat

to weaken it simulating a fail.

So, we are seeing this cascading
failure right now.

You can see each wire

is actually breaking one
after another.

It's not just this one
catastrophic failure

but rather this cascade.

When the cable starts to fail,

the remaining wires
take up the load.

Even if all the wires fail,

the energy released is gradual
rather than one huge explosion.

So, what you saw there was,
you know, exactly why

the suspension bridge wires
are such a great solution.

But you can see
that you didn't have

this one catastrophic explosion
and just failure of the member

but rather each one
of these wires actually broke.

Steel technology
enabled John Roebling

to design what was at the time
the world's longest

and strongest bridge
and an engineering masterpiece.

This bridge would eclipse

every other structure
in the entire americas.

It would be the tallest
structure anywhere.

So just a person actually
standing on the tower

would be on essentially

the first skyscraper
in the United States.

The designers
of the Rion-Antirion bridge

will need to super-size
the revolutionary ideas

of John Roebling
and the Brooklyn bridge...

This type of oscillation

would be very worrying
to the designers.

The structure could collapse due
to oscillations such as this.

...And create even
more impossible engineering.

180 feet
above the Gulf of Corinth,

cutting-edge suspension
technology

inspired by Brooklyn-bridge
designer John Roebling

keeps the ultra-modern
Rion-Antirion bridge

from crashing into the water.

But unlike New York City,
near-hurricane force winds

are common
in the Gulf of Corinth,

putting a great deal of stress
on the cables.

At a wind-tunnel facility,
professor Luke Bisby

demonstrates just how
destructive wind can be.

All right, so,
we're gonna start it up,

and we'll see what happens.

If this was a cable
in a real bridge,

this type of oscillation

would be very worrying
to the designers

because what this would mean

is that the metal
that forms the cable

would be being stressed
repeatedly back and forth.

And eventually in a metal cable,
that can lead to fatigue,

which can cause cracking

and, hence, potentially failure
of the structure.

So the structure could collapse

due to oscillations
such as this.

When wind strikes
a cylindrical structure

like a cable, it separates,

then rejoins on the other side,

causing the structure
to oscillate...

A phenomenon
known as vortex shedding.

Vortex shedding has been
responsible for the collapse

of several chimneys and towers
over the years.

In 1957, British scientist
Christopher Kit Scruton

discovered that adding a simple
fin to a cylindrical structure

would break up the wind vortices

reducing the vibrations
that could lead to a collapse.

He called the fin
a helical strake.

Just seeing a little bit of
vibration here... not too much.

This is really incredible
that this simple spiral

can completely prevent
the motion

of this simulated bridge cable.

With the helical strake,

we get this disruption
of the flow pattern,

we introduce some turbulence,

and both the formation
of the vortices

and the vibration of the cable
both stop.

The helical strake
seems to be working.

Since >>>Kit Scruton
invented the helical strake

back in the '50s and '60s,

it's been applied to tens
of thousands of structures

and chimneys and Bridges
around the world

and has really saved them from
potential catastrophic collapse

due to wind effects.

Helical strakes are integrated

into all of the nearly 40 miles
of cabling

on the Rion-Antirion bridge.

This, combined with
spoiler-like deck fairings,

makes this bridge
one of the safest on earth.

But a bridge
can't just be functional...

It has to be beautiful.

So once again, engineers

will look to the innovations
of the past for inspiration.

The Rion-Antirion
bridge in Greece

is a wonder
of the engineering world.

Its designers
not only had to ensure

it could survive earthquakes
and high winds,

but they were also forced
to construct it

in extremely deep water
on unstable soil.

Underwater, the bridge may be
an enormous mass of concrete,

but above water,
it has to be elegant

and add to the Greek landscape
around it... not scar it.

Finding the right balance
between strength and beauty

was quite a challenge
for the engineering team...

A challenge that
may have been insurmountable

had it not been for the great
innovators of the past.

In 1928, renowned Swiss
civil engineer Robert maillart

won a competition
to design a bridge

that would link two remote towns

300 feet above the salgina
valley in Switzerland.

The result...
The salginatobel bridge.

Designated an international
engineering landmark,

maillart's bridge
proved to the world

that concrete could be both
practical and beautiful.

Engineer urs meyer
has been a lifelong fan

of the iconic structure,

but he's about to see it from
an entirely new perspective.

Building a bridge in this remote
part of eastern Switzerland

required great ingenuity.

Concrete is strong
in compression,

but reinforcing it
with steel bars

also gives it strength
in tension,

allowing it to be manipulated
into almost any shape.

Maillart designed an elegant
three-pinned hollow box arch

supported by reinforced
concrete columns.

This made the concrete
strong enough

to transmit the bridge loads
to the foundations

but flexible enough
to absorb any ground movement

that could cause dangerous
cracks to form.

Maillart's sleek design also
used less reinforced concrete,

making it cheaper to build.

But there were some skeptics.

When the salginatobel bridge
opened in August 1930,

it was hailed an engineering
and artistic triumph,

proving to the world
that concrete Bridges

could be both functional
and beautiful.

1,000 miles away in Greece,
maillart's influence can be seen

all over
the Rion-Antirion bridge.

The four reinforced
concrete pylons

embody cost-saving minimalism,
flexible strength,

and elegant design.

780,000 tons of reinforced
concrete ensure this bridge

could survive an earthquake
of 7 on the Richter scale.

The Rion-Antirion bridge
has redrawn the map of Greece,

and its designers
have rewritten the rules

of bridge engineering forever.

By modernizing innovations
of the past

and making groundbreaking
discoveries of their own,

the engineers and designers
of this incredible structure

have succeeded in making
the impossible possible.

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