All language subtitles for Impossible Engineering s02e02 Worlds Tallest Bridge.eng

Today
on "Impossible engineering,"

the Millau viaduct,
the tallest bridge on earth...

Rising 1,000 feet over one
of Europe's deepest valleys...

Built on pioneering innovations
from the past...

All right, now,
this is what I'm talkin' about.

Today, the stromsund bridge is

a real landmark breakthrough
in the world of engineering.

...To make
the impossible possible.

Captions by vitac
www.Vitac.Com

captions paid for by
Discovery communications

Nestled in the Southern corner
of the massif central in France

is the tranquil
medieval town of Millau.

But every summer,
that tranquility is shattered.

Millau lies directly in the path
of the busiest travel route

between Paris
and the mediterranean coast.

To free Millau
from this plague of traffic,

engineer Michel Virlogeux
is attempting

what was previously
thought to be impossible...

build a road high above Millau

across the gargantuan
Tarn valley.

The result...

the Millau viaduct,

the tallest bridge on earth.

This massive bridge spans
a staggering 1 1/2 miles,

towering over 500 feet
above the Tarn valley.

Just seven concrete piers
support

the 40,000-ton steel deck,

which is held in place
by a single row

of 154 super-strength
cable stays.

Michel had to design a bridge
that could span

one of Europe's deepest,
widest, and windiest canyons,

using an uneven valley floor
as a foundation.

To build
the tallest bridge on earth,

Michel and his team need
strong building materials,

something
that would be impossible

without help from the great
innovators of the past.

Man's earliest
building materials were sourced

from nature.

Neanderthals built shelters
from the bones

and tusks of wooly mammoths.

Mongolian nomads used sheep wool

to line the walls
of their yurts.

And from the time
of ancient civilizations,

many houses have been built
with straw and clay bricks...

Reinforced
with a touch of animal dung,

which works perfectly...

as long as you're standing
in the right place.

To create
a truly enduring structure,

engineers at Millau would look
to the achievements made

by a British civil engineer
250 years ago.

Professor Luke Bisby is heading
out into the English channel

to visit what's left of
a truly revolutionary structure.

I'm heading
out to the Eddystone,

one of the most
treacherous rocks

in the English channel.

It's a place that arguably marks
one of the most important

moments in
civil-engineering history.

Today sits
a 50-meter-tall lighthouse

designed
by James douglass in 1882.

Amazingly,
this is the fourth lighthouse

that's stood in this spot.

Eddystone rock is 14 miles
from the busy port of Plymouth.

The rock has sunk
countless ships

over the centuries.

In the 17th century,

a lighthouse was built
to warn passing vessels.

A building that could withstand

the elements out here,
the pounding of the waves

day after day
and the wind and the rain,

requires a real engineering
achievement.

In 1696, Henry Winstanley built

the world's
first offshore lighthouse.

It was an 82-foot wooden tower.

But just 7 years later,
it was obliterated by a storm.

Its replacement survived
47 years.

But that too was destroyed
by the elements,

this time by fire.

If a lighthouse was gonna last
any substantial amount of time

out here, a new engineering
solution was needed.

Engineer John Smeaton
had a unique idea

for the Eddystone lighthouse.

He believed that the sea
must give way to the building

and decided to build
a lighthouse made of stone.

It was how Smeaton joined
the stones together

that was truly revolutionary,

earning him the title

"the father
of civil engineering."

Smeaton's original lighthouse
stood on this spot

for over 120 years.

And, in fact, we can still see
the bottom half of it

as that stump of a lighthouse
over there.

Smeaton's structure
was so strong,

it was only cracks
in the rocks that it sat on

that forced engineers
to dismantle the lighthouse

and rebuild it on Plymouth hoe.

The secret
to Smeaton's success is

an innovative bonding material
that can survive

the constant pounding
of the sea.

Smeaton experimented
with mixtures of lime,

Clay, and iron slag
to create hydraulic lime.

I'm gonna try to demonstrate
the innovation

that Smeaton accomplished
at the tower.

Here we have
a traditional cob mortar.

This is a mixture
of sand and clay and straw

and lime and a bit of earth.

And these types of mortars
were used traditionally

for many hundreds
and thousands of years.

And the other material
that I have here

is Smeaton's mixture.

Luke places
Smeaton's hydraulic lime

inside a cardboard tube,

then places the tube in water.

And then I'm also gonna do
the same

with the traditional
earth mixture.

Got both tubes now filled
with the mortar.

We're gonna go away
for about a half an hour.

And then we're gonna come back,
and hopefully, we'll see

a pretty dramatic difference

in terms
of how they've performed.

First, we're gonna look
at the tube that's filled

with the traditional mud mortar.

We're gonna see
exactly how much it's set.

And you can see...
absolutely nothing.

This is the one
we're much more interested in.

This is the one with the mortar

that's based
on the hydraulic-lime technology

that Smeaton came up with.

I can immediately feel that
this one is much more solid.

I squeeze it.
Nothing happens.

If I have a look inside,

I can actually see
this now is very, very solid.

That combination
of setting very quickly

and setting underwater
completely revolutionized

civil engineering.

What Smeaton had created

was the precursor
to Portland cement.

Portland cement's
the key ingredient

in all modern concrete.

The strength
of Smeaton's hydraulic lime

allowed engineers to stack
nearly 1,500 blocks of granite,

creating a rock-solid structure
that could stand up

against the forces of nature...

so solid, in fact,
the victorians couldn't

dismantle the base when
the lighthouse was relocated

to Plymouth hoe
over 100 years ago.

So here we have the original
250-year-old granite blocks

re-assembled here
on Plymouth hoe

with mortar
much like the original mortar.

Incredible that it still
looks so good.

And if I look really carefully,

way out there on the horizon,

I can just see the base
of Smeaton's original tower

standing next to the new tower.

This was really the game-changer

in concrete engineering
worldwide.

The engineers
at the Millau viaduct

are using John Smeaton's
hydraulic-lime technology...

On an epic scale

...To build seven
of the tallest bridge piers

on the planet.

The Millau viaduct, soaring high

above the French countryside...

it's the world's tallest bridge.

To support
this engineering marvel,

its designers had to construct

seven of the tallest
bridge piers on earth.

Chief engineer
Michel Virlogeux had

just 4 years
to finish the bridge

or face fines
of up to $30,000 per day.

So, to save time, each pier was
built simultaneously

at seven individual work sites.

Due to the uneven valley floor,

each pier is constructed
at a different height,

the tallest
a record-breaking 804 feet.

Their octagonal shape tapers
gradually,

splitting around 300 feet
below deck height

for added flexibility.

Engineers built each pier
in 13-foot sections

using a self-climbing frame.

A hydraulic-driven system
pushed the giant concrete mold

up in stages.

Cranes lift buckets of concrete,

which is then poured
into the concrete mold.

After each pour has set,
the mold is dismantled.

The frame carrying the mold

is then mechanically pushed
by the hydraulic Jacks

up the piers

and re-anchored
in the set concrete.

The mold is then re-assembled
for the next pour.

Each cycle takes about 3 days.

The piers are completed
ahead of schedule,

in just over 2 years.

With the bridge piers complete,
Michel is ready to tackle

his next challenge...

construct Millau's
1 1/2-mile-long bridge deck,

long enough to span
the vast Tarn valley...

...creating even more
impossible engineering.

The Millau viaduct
in southwest France

is an engineering wonder
of the modern world.

At 1,125 feet, this
superstructure stands taller

than any other bridge on earth.

The staggering height
of the bridge presents

a unique challenge for
chief engineer Michel Virlogeux.

How do you make the world's
tallest bridge stable enough

to handle
the hurricane-force winds

high above the town of Millau?

Protecting the Millau viaduct's
bridge deck from high winds

would be impossible
without an ingenious innovation

made by a civil engineer
a half-century ago.

Professor Luke Bisby
is exploring

one of britain's
most iconic bridges.

All right, now this is
what I'm talking about.

A vertigo-inducing
135 meters below me lies

the severn bridge.

The severn bridge
provides a vital link

between England and south Wales.

The main section
of the bridge is

over 1,598 meters long,
which, at the time,

made it the longest bridge
in the world.

I can actually see
through this hole

about 1,000 meters
down the bridge.

It's absolutely incredible.

The length
of the bridge is impressive,

but its ability
to resist the high winds

that frequent
the river severn is

what makes
this structure revolutionary.

Lying inland
from the Atlantic ocean,

the river severn begins
where the Bristol channel ends.

The high ground of exmoor
on the south shore

and the mountains
of Wales on the north

create a funnel for
the prevailing westerly winds

and Atlantic storms,
increasing their power.

Building a bridge
that could withstand

severe winds
was really essential.

And even
on a relatively calm day,

standing here,
underneath the bridge,

you really get a sense
of the wind

that they were up against.

Civil engineer
sir Gilbert Roberts was tasked

with building a bridge
across the river severn.

His biggest innovation was
a windproof bridge deck.

If you look
at the shape of the deck,

you can start to get a sense
of what the solution was.

And the most amazing thing is
that the shape

of this bridge deck and
the solution they came up with

was actually a happy mistake.

Sir Gilbert Roberts broke

his original
truss-lattsign

while testing it
in a wind tunnel.

As he waited
for a replacement model,

he researched the aerodynamics
of other objects,

leading him
to a truly groundbreaking idea.

So, what I have here is
a model airplane.

And you can imagine
that the wing of this airplane

is representing the bridge deck.

So a wing has a curved surface
on the top.

And it has a flat surface
on the bottom.

And this means that air passing
over the wing

has to travel further
across the top

than on the bottom.

As air passes
over the curved surface,

it speeds up and loses pressure.

The pressure
of the air below remains high

and pushes up
towards the low-pressure area,

creating lift.

What I'm gonna attempt
to show you is,

with this hair dryer,
to generate some wind,

the force of the little model
airplane will decrease.

And that decrease
will signify the...

the lift force that
we've generated on the model.

There, we have
our starting weight... 45 grams.

Right, so, there we go.

The engineers
here didn't want that to happen

to the bridge deck.

When Luke flips
the airplane over,

the lift affect is reversed,
creating a downward force.

What we should see is
that this force should increase

rather than decrease.

You can actually see
the downward force

that's coming from the wind.

And that holds everything
nice and taut and safe

in very strong winds.

Now that the
curved surface is underneath,

air loses pressure
as it speeds up.

And the high pressure above
presses down.

And, of course,
this is exactly the principle

that the engineers used
on the severn bridge.

Sir Gilbert Roberts
and his team created

an aerodynamic,
steel-box girder deck,

the first of its kind
in the world.

Hollow and only 10 feet deep,

the shape of the deck
creates a wind flow

that holds it firmly in place.

Over the years, 13 vehicles

have blown over while
crossing the severn bridge.

But the bridge itself has
always held on strong.

Although this beautiful bridge
has passed on

the burden of heavy traffic
to its youngest brother

just downstream,

it still managed to carry
more than 300 million vehicles

since it was first constructed
in 1966.

And thanks
to sir Gilbert Roberts

and his team, it's set to do so
for many more years to come.

Engineers
at the Millau viaduct have

created a bridge deck
that's over 3,000 feet longer

than the severn bridge deck

and weighs
a colossal 40,000 tons,

making it
one of the longest on earth.

The deck's shallow,
trapezoid shape creates

an inverse aerofoil

resulting in negative lift
in strong winds.

To build Millau's
colossal steel deck,

engineers had to assemble it
in pieces

like a gigantic, steel
Jigsaw puzzle.

The pieces were cut in factories
all across France

before being transported
to Millau.

Staging areas are set up

on each side of the valley
to receive the deck parts.

Two thousand convoys loaded
with cut steel make

the journey to Millau.

Welders use a staggering
165 tons of material

to assemble
the massive bridge deck.

Engineers are ready to tackle
their biggest challenge yet...

moving the deck sections
from the staging area

to their final resting place

hundreds of feet
above the Tarn valley.

The Millau viaduct in France is

a work
of engineering virtuosity.

It's over 8,000 feet long

and taller
than the Eiffel Tower.

For engineer Michel Virlogeux,

building
this gargantuan structure is

the challenge of a lifetime.

Michel's biggest challenge...
figure out a way

to move the bridge's
1 1/2-mile steel deck

from the staging area

out into the open air
high above the Tarn valley.

The extreme height of the piers
rule out using a crane.

The only option for engineers is
to try to slide the two massive

sections of deck together
from each side of the valley.

The leading edge of the deck
weighs 7,700 tons.

The pier's great
height-to-width ratio means

they're susceptible
to lateral forces.

Pushing the deck
across the pier's surface

will create friction,
increasing the lateral force

with potentially
disastrous consequences.

Michel needs to reduce friction
during the launch process,

a task that would be impossible

without help from an accidental
innovation from the past.

Friction has been
a sticking point for builders

for thousands of years.

Heave, ho.
Heave, ho.

Ancient Egyptians struggling
to slide their blocks

across sand...

Realized water created
a smoother, slicker surface...

Whoo-hoo!

...although too much
was not advisable.

D'ohh!

It's believed
the builders of the stonehenge

rolled their giant rocks
across a series of logs.

- Aah!
- Ooh!

It was the perfect solution,
as long as the ground was flat.

Look out!

For the engineers
of Millau viaduct,

a scientific mishap made
in a U.S. laboratory

in the 1930s is their solution.

Most people will recognize
these day-to-day objects.

But what most people don't know

is that all of these harness
the same properties

of a revolutionary product
called PTFE

or, to give it its full name,
polytetrafluoroethylene.

This groundbreaking product
was mistakenly created in 1938

by an American chemist,
Roy Plunkett.

Roy was experimenting
with a gas, tetrafluoroethylene,

when it unexpectedly solidified,
coating the inside

of a test tube
with a waxy resin.

Plunkett had created what would
eventually become teflon.

It has lots
of different properties.

It's very corrosion-resistant.

It's chemically inert.

It doesn't react
with other materials.

And it has a very high
melting temperature.

But above all of these,
it's very, very slippery.

And being slippery means
that teflon is a great tool

for overcoming
the forces of friction,

something that's hard to do
with a standard metal.

So, here I have a sled connected
to a metal tray underneath

and about 45 kilos
of bricks and sand.

And as I pull the sled along,

the tray is gonna have
a huge amount of friction

against the metal sheet here.

And that friction is retarding
the motion.

As I start to pull
against this now,

you can see
I've got 5 kilograms.

And I've still got no movement.

So that's the friction
preventing my sled from moving.

I'm up to 7 kilograms,

10 kilograms, 11, 12.

And there it goes.

Ugh.

So that's about 120 Newtons

of force to pull those along.

To see how PTFE performs,

a metal tray is prepared,

then sprayed
with the slippery coating...

And cured
at 430 degrees fahrenheit.

Wow.
Look at that.

That looks incredibly smooth.

So let's give it a go.

I've got 2 kilograms, 5.

6, 7, and, look...
it's starting to move already.

Seven kilograms here
to overcome the friction.

When you compare that
to 12 kilograms...

that's 120 Newtons.

So that's
about 50 Newtons difference

to move the same amount
of weight.

PTFE is made
of carbon and fluorine atoms.

Fluorine has
a high electronegativity,

meaning it repels other atoms.

The fluorine wraps
around the carbon,

preventing the carbon
from reacting

to any outside forces.

The result is a frictionless,
slippery substance.

The sled can carry
up to 40% more weight

when pulled
across the PTFE-coated sheet,

"the equivalent
of a 5'9" engineer.

- How much are we seeing?
- 12.

There you go...
12 kilograms, 120 Newtons.

How about that?

Engineers at the
Millau viaduct are using PTFE

in a unique mechanism
that will launch

the massive bridge deck
across the Tarn valley.

Called a translator,
the machine uses

the slipperiness of PTFE
and hydraulic Jacks

to lift the deck
off each pier entirely

before moving it deeper
into the valley.

Each translator uses

two wedge-shaped blocks
coated in PTFE.

A hydraulic ram pulls
the upper wedge,

which slides it
up the lower wedge.

This lifts the deck
away from the pier,

pushing it forward
at the same time.

The lower wedge
then slides backwards,

lowering the deck back
onto the pier.

Each cycle moves the deck
approximately 2 feet.

But as they prepare
for their first launch attempt,

engineers hit a snag.

Seven temporary piers
are built across the valley.

But as the 1 1/2-mile deck
is pushed out into the void,

the course is not
straightforward.

As the two colossal sections
approach each other

from opposite sides
of the valley.

Engineers rely on GPS technology
to ensure pinpoint accuracy.

Fifteen months
after the first attempt,

the two sections of deck finally
meet above the Tarn valley.

And, incredibly,
they're only off

by a few millimeters.

But to ensure the tallest bridge
on earth survives

for generations to come,
engineers are looking

to a groundbreaking innovation
from the past...

Today, the bridge is considered
a real landmark breakthrough

in the world of engineering.

...To create
more impossible engineering.

The Millau viaduct is
an engineering wonder.

Connecting the high plateaus
of France's Tarn valley,

this audacious bridge is
one of the tallest in the world

and one of the greatest
engineering achievements

of all time.

For engineer Michel Virlogeux
and architect Norman Foster,

the bridge's
environmental impact

on the French countryside is
a top priority.

Unstable limestone in the region
ruled out a suspension bridge,

which relies
on firm anchor points

at each end to take
the weight of the deck.

So for Michel,
there was only one alternative.

Constructing
a multi-span, cable-stay bridge

on such a huge scale
would be impossible

without the groundbreaking work
done by a German engineer

60 years ago.

Structural engineer
jonatan ledin is paddling

the great stroms vattudal
in Sweden, searching

for the source of a historic
engineering breakthrough.

For centuries, this stretch
of river here in stromsund

has been an obstacle that
travelers needed to overcome.

In the early 1950s,
it was decided

a suspension bridge should be
built across the river.

But German engineer
Franz dischinger had

a different idea.

Franz was a key player
in rebuilding Europe

post-world war II,

where 15,000 Bridges were
in need of repair.

Dischinger's construction
techniques were

cost-effective and efficient.

What dischinger built was this,
the stromsund bridge...

A cable-stay design that has
since been recognized

as a landmark
in engineering history.

A cable-stayed support system
is simple but very effective.

Imagine my arms are
cantilevering

out from my body like this.

And I'm trying to hold
the buckets of water

in place like this.

I need to do
a lot of work with my arms.

This is not exactly easy
to hold onto.

I'm gonna use this rope here

to represent the stay cables
attached to the bridge deck.

And I'm gonna pull that
over my head,

which is representing the piers.

So now the majority
of the weight

is no longer carried by my arms

but through the cables
onto my head

and down to the ground.

And that is exactly
what is going on behind us.

The weight from the bridge
and the loads from traffic

are being transferred
through the cables

and down onto the piers.

Early cable-stayed Bridges

were structurally weak.

Rudimentary cables
and limited understanding

of the forces at play
in the system meant,

by the early 19th century,
the idea was nearly abandoned.

And a problem that the engineers
were struggling with in the past

was designing the cables

so the loads would be
distributed evenly among them.

The consequences
of one or more cables

being overtensioned
can potentially be disastrous.

Dischinger looked
to mathematics for the solution.

He created formulas to calculate

the forces required
of each cable.

Each of those cables was then
precisely tensioned on site,

an engineering first.

After carrying vehicles
for over 60 years,

dischinger's supporting
cable stays are being replaced

for the first time.

Today's engineers are using

the exact same installation
process dischinger used.

So, these are
the brand-new cables

that are gonna be
installed overnight.

And just as would have happened
all those years ago,

they're first gonna be mounted
in place

and then precisely tensioned.

Dischinger's innovative approach
makes this possible

to do in just a few hours.

Post-world war ii
engineer Franz dischinger's

pioneering
construction techniques

have influenced some of the most
iconic Bridges around the world,

including the massive
Millau viaduct,

with its 1 1/2-mile-long
cable-stayed bridge deck.

Dischinger's revolutionary
stromsund bridge is

being restored
to its former glory using

the exact same techniques

dischinger used
a half century ago.

So the work has been going on
here on site all night.

The way in which
all of this is being done

is really not that different

from what would have taken place
here all those years ago.

So, today, the stromsund bridge
is considered

the first true modern
cable-stay bridge

and the real landmark
breakthrough

in the world of engineering.

Engineers at Millau have taken

dischinger's methods
to the next level,

creating
a structural masterpiece.

Dischinger's stromsund bridge
has only one central span.

The massive Millau viaduct...
six.

As the 770-ton pylons are
erected,

engineers had to calculate
the perfect distribution

of rigidity and flexibility
throughout the structure.

The key to their success lay
with the cable stays themselves.

The strongest cables are made
of 91 steel strands

and have a breaking strength
of over 2,000 tons.

They're so strong,

engineers install
just a single axis,

and only when tensioned did
the entire bridge become rigid.

After a little more
than 3 years of construction,

the integrity of the bridge
can now be tested.

Twenty-eight trucks weighing
a total of 900 tons

are driven en masse
to the center.

The deck flexes,
but only a few inches.

The bridge remains firm.

Finished 2 months ahead
of schedule,

the Millau viaduct

marks a significant milestone
in bridge engineering.

It's used by nearly
5 million vehicles a year.

For engineer Michel Virlogeux,

it represents the achievement
of a lifetime.

By learning from
the great pioneers of the past,

adapting, upscaling, and making
innovations of their own,

engineers succeeded
in making the impossible...

Possible.

Many thought
that it would be impossible

to build that bridge,
and now it is there.

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