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.