Original subtitles

Today on Impossible Engineering, the world's tallest construction, a record

-breaking supertower.

Construction has never been attempted before at a building this tall in

London. And the tallest bridge on earth.

The deck is about 150 meters above the Plateau de France.

It took revolutionary engineering.

Look at the crazy amount of glass that this building uses.

11 ,000 separate pieces.

to make the impossible possible.

London.

Some of the world's most iconic buildings dominated skyline.

And in 2012, a modern marvel was constructed, altering the city's look

Meet the Shard.

At 1 ,016 feet tall, this futuristic skyscraper is the tallest in London.

Wow, look at that.

That's an incredibly audacious piece of architecture and some very impressive

engineering.

The Shard rises up from the heart of downtown London.

This jaw -dropping tower is over three times the height of the Statue of

Liberty. Its facade is made out of a staggering 11 ,000 glass panels.

That's enough glass to cover 130 basketball courts.

Beneath the 196 -foot spire lies the spine of the building.

The colossal concrete core supports 72 levels,

totaling over a million square feet of floor space.

Building these buildings is always exciting.

You're building up.

taller than anybody's gone in Europe.

But this one was particularly difficult.

The population in London is surging.

It's estimated that the city could reach 10 million inhabitants by 2030.

With limited room to grow, designers of any new buildings are looking to the

sky.

Finding enough open space to build a megatower in this bustling city is a

seemingly impossible challenge.

It's smack in the center of London, with London Bridge Station on one side,

Guy's Hospital Tower on the other, the Jubilee line of the two passing very

close underneath.

Building the shard on this site would be impossible without help from a great

innovator from the past.

In the 1950s, the bustling Italian city of Milan wanted to build a subway.

But engineers needed to figure out a way to build without disrupting city life.

We've come here to a site where the metro network is being expanded.

And being here and seeing the scale of this site, you can imagine the

disruption that would be caused if you tried to do this in the center of the

city. Really an enormous challenge.

Poor soil conditions make tunneling beneath the city streets here nearly

impossible. This is actually a really good illustration of one of the key

problems here in Milan.

You can see how much water is flowing in. So these are about the worst

conditions you could hope to be digging tunnels in.

To contend with watery soil, tunnelers historically used a technique called cut

and cover.

Let's imagine that I want to dig a trench down between these buildings.

And you can see what happens when I do that in this sandy soil.

Initially, there's no problem. But if I push just a little bit too far, you can

see that eventually I destabilize the soil and my structures will fall into

trench. And obviously that's completely unacceptable on a site in a congested

urban center.

But engineer Dr.

Christian Bader turned the cut -and -cover concept on its head.

Instead of building one big trench initially, he built two little trenches

the sides of the buildings, and into those trenches he inserted reinforced

concrete walls.

And these then became known as diaphragm walls.

After dropping in diaphragm walls, Vader built a roof over the tunnel, allowing

city traffic to resume above.

Digging, tunneling, and construction could take place without disrupting life

Milan and in cities across the world.

Instead of cut and cover,

Vader's technique covered, then cut.

It's now known as hop down.

Standing down here in one of the new tunnels of the Milan metro, it simply

wouldn't exist without that construction technique.

But to speed up construction, engineers at the Shard take Vader's top -down

method and turn it on its head.

Normally, a building like this would be built by building a basement first and

digging a big hole down to the bottom level of the basement and then starting

the core from that lowest level and building upwards.

Now, we built the core on stilts, effectively, that held up the core while

were building it upwards, and then we were... at the same time digging

underneath it and going downwards.

That had never been done before.

It was an innovation for the Shard.

Just 23 piles support the Shard's concrete core as it rises from a void in

basement level two.

As excavations of the underground floors continue around the presunt columns,

the core rises, as if balanced on a tabletop above.

This allowed the engineers to shave literally months off this project, and

shard was built much more quickly and much more cheaply than it could

have been.

But huge ambition comes at a price.

The $618 million project required more than 1 ,400 workers on site.

The flow bit of construction is building a concrete core that is the real basis

of stability for the structure.

And getting that in place quickly is a real challenge.

The Shard's concrete core consists of over 350 ,000 cubic feet of concrete.

Pouring this much concrete would have been impossible had it not been for a

groundbreaking method developed over 100 years ago.

Minneapolis was known as the flower capital of the world.

Raw grain was brought here from across the northern prairie, processed here,

then shipped across the country and around the world.

But flower production in the 19th century was dangerous business.

Dry millstones could ignite flower dust, causing catastrophic explosions inside

wooden silos.

With modern materials, Engineer Charles Hagelin and grain trader Frank Peavey

designed a safer, stronger silo.

By using concrete in 1908, Hagelin built the Washburn Crosby Elevator 1, part of

the Washburn A Mill.

At its peak, it could safely produce almost 2 million pounds of flour a day.

The most innovative thing about wood design are these 15 cylindrical silos,

measuring about 100 feet tall.

To build the silos, Hagelin developed an ingenious new method called slip

forming.

So what we've got here is a simple demonstration of how slip forming works.

I've got this bucket of slightly wet sand here.

This is going to represent our concrete.

And I've got this other bucket here with the hole cut in the top. This is going

to represent our slip form.

And here's how the process works.

A little of the concrete goes in.

And slowly, about a few inches every hour, the slip form gets raised up and

And then I add a little more.

And raised up a little bit higher.

The slip form rig is continually forced up by hydraulic jack, while concrete is

poured non -stop.

The concrete at the top remains wet and fluid.

By the time the concrete emerges from the bottom of the moving mold, it's dry

enough to support the growing structure.

Hagelin's use of slip form construction revolutionized the way that tall

buildings are constructed.

And today, concrete has become one of the most widely used materials in

construction, allowing us to build higher and faster than ever.

At over 800 feet.

The Shard's concrete core is nearly eight times taller than the Washburn

elevator silos.

Engineers used a supersized version of Hagelin's slip form rig, measuring 85 by

72 feet.

Thanks to a high -capacity concrete pump, the system was so efficient, it

reached the 21st floor in just 10 weeks.

It's amazing to think the first 21 stories of this concrete structure went

before they'd even finished the foundations below.

The concrete core is still sitting on just 23 piles in the center of the

basement. Engineers need to pour the rest of the foundation before they can

continue building up the core.

It took 32 hours.

We poured the whole thing in one go, and it was 5 ,500 cubic meters of concrete.

It was tremendously exciting to see all that concrete arriving on site.

Built from a central concrete core, the tower's unique hybrid superstructure is

pulled up around it.

Forty floors constructed of steel, 29 stories of concrete, topped off by a

monumental 23 -story spire at the pinnacle of the building.

When you're building a tower that's over 300 meters high, one of the real

challenges is getting the people and the materials up to these incredible

heights when you're doing the construction.

And the higher the tower gets, the harder that challenge becomes.

So how do you get enormous amounts of building material to the top of a mega

tower like the Shard?

The Shard in London is the tallest building in Western Europe, but getting

materials to the top during its construction would have been impossible

the innovators of the past.

Heavyweight lifting gained its footing in the 19th century in an unlikely

Venice, Italy.

It was a time of great change in the maritime industry, and old wooden

propelled by ore and wind were being replaced by steel -hulled ships and

big engines.

Traditional manually operated cranes couldn't handle heavy loads like these.

This seriously compromised the Italian Navy's boat -building program.

In 1885, British engineer Sir William Armstrong developed an ingenious

Because of the growing trend of metal hull construction, the Navy decided to

commission just the thing for the Arsenale.

And here is the stunning Armstrong crane.

And the way it works is like this.

This huge boiler would generate enormous amounts of steam, and that steam would

flow up through the pipework down into these chambers below.

The steam drove these enormous systems back and forth, back and forth, and they

in turn helped pressurize the hydraulic circuit.

Hydraulics allowed the Armstrong crane to lift what was at the time an

unimaginable 160 -ton load.

It transformed the fortunes of Arsenale.

It opens up a whole new frontier in crane technology.

Engineers at the Shard took Armstrong's historic crane design to the next level.

Building this superstructure meant building some of the tallest, most

tower cranes in the world.

They started with four cranes at ground level. Those went up to about 160

meters. But above that, we've still got 140 meters of the building to go.

How do we get the structure, the construction equipment up to that

Engineer John Parker and his team came up with a radical idea.

Mounting a tower crane to the Shard's concrete core.

What was unique about the Shard was that the tower crane was supported on that

slip wall.

Usually you have to fix the crane to the concrete.

We avoided all that so they could both go up together.

Installing the Shard Spire required an even more radical approach.

We then had to use the crane that was attacked. to the split form to build

another crane which can't leave it off the main building and allow them to

this final spire on the top of the structure.

Engineers elevate the tower crane to a staggering 1 ,040 feet, enabling them to

install the custom -built steel sections that form the 23 -story spire.

Over 500 tons of steel is installed in nearly 100 separate lists.

But this isn't the only way the designers of the Shard are pushing the

architecture.

Its facade is made out of a staggering 11 ,000 glass panels.

That's enough glass to cover 130 basketball courts.

Look at the crazy amount of glass that this building uses.

It's extraordinary.

It just extends above me in a great big ribbon of glass up to the sky.

But glass is structurally weak.

So how do you create London's tallest building out of it?

It would be impossible without an architectural risk taken 150 years ago.

The Shard in London is the tallest building in Western Europe.

Comprised of over 11 ,000 pieces of glass, its bold facade would have been

impossible without an architectural risk taken 150 years ago.

In the 19th century, as cities like Liverpool grew ever more dense and space

buildings became smaller, architects were faced with a real problem.

They had to build upwards, but in doing so, they had to build thicker and

thicker walls to support the increasing weight of their structures.

Local architect Peter Ellis came up with a revolutionary design for his high

-rise building.

This is the Oriel Chambers building.

It contains one of the world's most important engineering and architectural

blueprints.

That's because the Oriel Chambers building doesn't need exterior

walls. An iron framework carries the load of the structure on the inside.

This allowed Ellis to create a facade on the outside that doesn't have to

support the building.

Ellis' iron frame structure opened up a whole new world of architectural

possibilities.

Ellis created the glass curtain wall.

The building has 56 road -facing bay windows over five floors.

The windows flood the interior with light.

150 years later, the benefits are still clear.

And to compare it with the building across the street, where the stone

construction means the windows are very small, this would have been an amazing

place to work in.

Without Ellis' pioneering use of the curtain wall concept, The glass -clad

supertowers of today which dominate cities across the world might not ever

been invented.

It's a real masterpiece of engineering.

Engineers at the Shard are building on Ellis' glass curtain wall with 13 acres

of glass.

What's incredible is that from outside the Shard, it looks like it's a

made entirely of glass. But actually, this glass takes none of the weight.

That's all borne by the steel and the concrete structure inside.

An incredible piece of engineering.

The Shard's extraordinary superstructure holds eight sloping facades, defined by

the tower's iconic vertical fractures.

It's often called the shard of glass, and the idea was to have a beacon here

that would shine out. And this sloping shape is very good at reflecting the

sunlight and making it shine.

It's a once -in -a -lifetime achievement.

Also scraping the sky and rising 1 ,000 feet over one of Europe's deepest

valleys. It's higher than the Eiffel Tower.

It's the tallest bridge on Earth.

It was a very, very big adventure.

Why did engineers take on such a massive construction?

The small medieval town of Miu lies directly in the path of the busiest

route between Paris and the Mediterranean coast.

Miu is not at all adapted to the motorway traffic.

It could be necessary to have three hours to cross Miu.

To free MeU from this plague of traffic, engineer Michel Villajour is attempting

what was previously thought to be impossible. Build a road high above MeU

the gargantuan Tarn Valley.

The result.

The MeU Viaduct.

The tallest bridge on Earth.

This massive bridge spans a staggering one and a half 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.

Many thought it was impossible to build that bridge.

We had this very important series of problems to solve.

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.

This would be impossible without help from the great innovators of the past.

The MiU Viaduct is the tallest bridge on Earth, but constructing it across one

of Europe's deepest, widest, and windiest canyons would have been

without strong building materials developed by a great innovator of the

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.

Eddystone Rock is 14 miles from the busy port of Plymouth, England.

The rock has sunk countless shifts over the centuries.

In the 17th century, a lighthouse was built to warn passing vessels.

A building that can withstand the elements out here, the pounding of the

day after day and the wind and the rain, requires a real engineering

achievement.

And engineer John Smeaton had a unique idea for the Eddystone Lighthouse.

He believed that the sea must give way to the building, and, unlike earlier

lighthouses made of wood, he built a lighthouse made of stone.

But 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

Ho.

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 going to try to demonstrate the innovation that Smeaton accomplished at

tower. Here we have a traditional cob mortar. This is a mixture of sand and

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 going to do the same with the traditional earth mixture.

Got both tubes now filled with the mortar.

We're going to go away for about a half an hour, and then we're going to come

back, and hopefully we'll see a pretty dramatic difference in terms of how

they've performed.

First, we're going to look at the tube that's filled with the traditional mud

mortar. We're going to 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

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 engineers at the MeU Viaduct are using John Smeaton's hydraulic line

technology on an epic scale.

All the piers represent something like 90 ,000 cubic meters or more than 200

,000 tons of concrete.

And this is the concrete which is of very high strength.

Engineers built each of the seven piers in 13 -foot sections using a state -of

-the -art self -climbing frame. A hydraulic -driven system pushed the

reinforced concrete mold upwards in stages.

One of the big problems, of course, was to lift concrete because this pier, this

one, is 245 meters high.

Cranes lift buckets of concrete, which is then poured into the concrete mold.

After each pour is set, the mold is dismantled.

The frame carrying the mold is then mechanically pushed by the hydraulic

up the pier and re -anchored in the set concrete.

The mold is then reassembled for the next pour.

Each cycle takes about three days.

The piers are completed in just over two years.

Developing solutions to erect the seven piers at the same time, it was a very,

very big adventure.

With the bridge pierce complete, Michel is ready to tackle his next challenge.

Construct MeU's one and a half mile long bridge deck, long enough to span the

vast Tarn Valley.

The staggering height of the bridge makes this a unique challenge.

The great enemy of the design of the bridge is the wind.

The deck.

It's about 150 meters above the Plateau de France, and so this means that we

have rather high winds.

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

-force winds high above the town of Miu?

Designers look to an ingenious innovation made by a British civil

half a century ago.

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.

Lying inland from the Atlantic Ocean, the River Severn begins where the

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.

Civil Engineer Sir Gilbert Roberts was the man tasked with building a bridge

across the River Severn.

He investigated how aerodynamic objects handled strong winds, which led him to a

truly groundbreaking idea for a bridge.

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.

There we have our starting weight, 45 grams.

What I'm going to attempt to show you is with this hairdryer to generate some

wind.

Right, so there we go.

The engineers here didn't want that to happen to the bridge deck.

But when Luke flips the airplane over, the lift effect is reversed, creating a

downward force.

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

and the high pressure above presses down.

And, of course, this is exactly the principle that the engineers used on the

Severn Bridge.

With this breakthrough, Sir Gilbert Roberts and his team created an

steel box girder deck.

The first of its kind in the world.

Engineers at the MiU viaduct have created a bridge deck that's over 3 ,000

longer than the Severn bridge deck and weighs a colossal 40 ,000 tons.

It has a continuous shape, very, very limited inclination, helps the wind

passing. below and reduces automatically the wind forces.

To build MiU's colossal steel deck, engineers had to assemble it in pieces

a gigantic steel jigsaw puzzle.

The pieces were cut in factories all across France before being transported

MiU.

Core, which could be the spine of the bridge, has been assembled in segments

20 meters and brought with trucks to the side.

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 piers are so slender that classical launching techniques would have been

very critical.

It would not have been possible.

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.

Reducing friction on this scale would be impossible without help from an

accidental innovation from the past.

The Minou Viaduct in France is the tallest bridge on Earth.

To construct it, engineers had to build the road deck from each side of the

valley and meet in the middle without causing friction, which would collapse

bridge. This would have been impossible without an accidental innovation from

the past.

In 1938, an American chemist... Roy Plunkett was experimenting with the gas,

tetrafluoroethylene, when it unexpectedly solidified, coating the

test tube with a waxy resin.

Called polytetrafluoroethylene, or PTFE, 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

bricks and sand.

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.

So that's about 120 newtons of force to pull those along.

Next, Andrew uses a metal sheet coated with PTFE.

So let's give it a go.

I've got 2 kilograms, 5, 6, 7, and look, it's starting to move already.

7 kilograms here to overcome the friction.

And you compare that to 12 kilograms, that's 120 newtons. That's about 50

newtons difference to move the same amount of weight.

PPFE 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

outside forces.

Slippery substance.

Engineers at the MiU Viaduct are using PTFE in a unique mechanism that will

launch the massive bridge deck across the Tarn Valley.

Call the translator.

The machine uses the slipperiness of PTFE and hydraulic jacks to lift the

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 two feet.

All the launching systems are moving in the same time, by the same distance.

And so you can understand very clearly that it's not producing any force in the

pier.

15 months after starting, the two sections of deck meet above the Tarn

This system was really the key of the success.

But supporting 40 ,000 tons is no small feat.

Additionally, 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.

I wanted to design a cable state bridge because cables are very strong.

They allow to make very, very modern structures.

Constructing a multi -span cable -stayed bridge on such a huge scale would be

impossible without groundbreaking work from over 60 years ago.

The MiU Viaduct is the tallest bridge on Earth, but supporting its 40 ,000 -ton

steel deck. by a single row of 154 table stays would be impossible without the

innovation done by a German engineer over 60 years ago.

Franz Dissinger helped rebuild Europe after World War II.

With some 15 ,000 bridges in need of repair, Dissinger's construction

were both cost -effective and efficient.

What Dissinger built was this, the Stromson bridge.

A cable state design that has since been recognized as a landmark in engineering

history.

This cable state support system in Stromson, Sweden 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 on to.

I'm going to use this rope here to represent the stay cables attached to

bridge deck.

And I'm going to 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.

Engineers at MIU have taken Dissinger's method to the next level, creating a

structural masterpiece.

The origin of this bridge is a cable set bridge, but with multiple spans. This

is really very special.

Dissinger's Stromson bridge has only one central span.

The massive Miu Viaduct, 6.

After a little more than three years of construction, the integrity of the

bridge can now be tested.

28 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.

Today, I'm, of course, extremely proud because there are many steps in erecting

a bridge like this.

Finally, when the bridge was completed, it was an enormous success.

For engineer Michel Villajour, it represents the achievement of a

You know, when you have past years working and fighting for a bridge, you

and that suddenly it's finished.

There is really a moment where you don't know what to do.

By learning from the great pioneers of the past, adapting, upscaling, and

innovations of their own.

Engineers of the Shard and the MiU Viaduct have made the world's tallest

structure.

They've made the impossible possible.

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