Original subtitles

In today's impossible engineering.

If you're a civil engineer and a project like this doesn't excite you, you're

probably in the wrong game.

The planet's longest triple tower cable stayed bridge.

There's no doubt the Queen's Ferry Crossing is a phenomenal bridge and it's

recognised across the world.

It's remarkable engineering, Super Bowls and the best of British engineering.

Structural engineering on a colossal scale.

You're talking 40 meters to the bedrock.

You only get one chance to get that foundation installed.

And the pioneering historic innovations.

So beautiful.

It's a really elegant structure.

So they've made it here to the other side. Really an extraordinary thing to

That made the impossible possible.

Scotland, a land of imposing peaks and deep waters.

This unique landscape presents huge challenges to the team keeping the

connected.

For project manager Lawrence Shackman, keeping this crucial link up and running

is top priority, and the nation depends on his success.

The fourth estuary divides Scotland into two halves.

So from a transport point of view, it's a huge natural obstacle.

1890, the world famous fourth railway bridge was built.

And in 1964, the fourth road bridge was built to allow cars and heavy goods to

cross.

But half a century later, traffic has more than doubled.

And the road bridge is no longer up to the job.

A large degree of corrosion was found.

Thousands of the individual strands were actually found to be broken.

If the bridge continued to decay, it might need to close to all vehicles by

2021, bringing the central belt of Scotland to a standstill.

A new bridge was urgently needed to keep the nation moving.

So engineers have designed a structure like no other on Earth.

This is the Queensferry Crossing.

A gigantic triple -towered cable -stayed bridge, the largest in the world.

This undoubtedly has stretched the limits of what we believe is possible.

It's incredibly light, it's incredibly slender, and yet it is massive.

The cruise very cross in itself is an engineering icon which takes its place

beside the other two great bridges.

It's a world beater.

This is the longest two -span cable structure in the world.

This really is engineering pushed to the limit.

Standing 180 feet over the water below, this $1 .8 billion project stretches a

whopping 1 .6 miles from shore to shore.

It's supported by three gigantic towers, reaching 680 feet high, the equivalent

of 48 double -decker buses stacked one on top of the other.

The north and south towers sit on record -breaking underwater concrete

foundations.

The largest reaching 160 feet deep, dwarfing the Statue of Liberty.

And 122 deck pieces make up the 85 ,000 -ton roadway, secured by

almost 23 ,000 miles of cable.

Hanging over the channel, this giant marks the dawn of a new age of

superstructure.

So here we are inside the Queen's Free Crossing, our 2 .7 -kilometer -long

solution to keep Scotland moving.

It's an amazing place to come to and see such amazing technology and civil

engineering skill come to reality.

But this beast of a bridge isn't just super long.

See you at the top.

Its three towers are the tallest of any bridge in the country, soaring

680 feet over the landscape.

The Queensferry Crossing offers an exceptional bird's -eye view to workers

enough to make the climb.

It's very rare for anyone to come up here to be able to see out across to

across to Edinburgh, over to the right there.

It's absolutely stunning.

To construct a record -breaking piece of engineering, the team faced a list of

seemingly impossible challenges.

How do you erect enormous towers in a deep and formidable sea channel?

To build your structural foundations, you have to get down to deep depths of

meters deep.

And reinforce a slender bridge deck to stay strong and rigid across such a vast

span.

There's heavy traffic that needs to be supported, and this creates huge

imbalances that really challenges the performance of the deck itself.

And where vehicles on the old bridge had no protection from high winds, how will

the new crossing take on Mother Nature?

The wind speeds can get up to 120 miles an hour. That puts road users at risk.

To achieve this, engineers must draw inspiration from the pioneers of the

The first challenge fell to engineer Douglas Halliday and his team.

who needed to create a solid foothold at the bottom of the sea.

Want to build your foundations is a major undertaking.

This is a major channel. It's a major estuary.

It's great. It's all sorts of problems.

You're talking 40 meters plus below water level to the bedrock.

You only get one chance, really, to get that foundation installed.

Where deepwater foundations are fundamental to the superstructure.

the team had to take the plunge.

The South Tower and the North Tower foundations were constructed within

because of the depth, twin -walled steel tubes, open -ended, top and bottom, and

gradually we just tilted and shoot that caisson down to bedrock level,

constantly monitoring the position of the caisson using GPS techniques.

That was an immense achievement.

With the caissons placed with extreme precision, pumps completely emptied them

of seawater.

And in an unparalleled 15 -day operation, running 24 hours a day, the

executed the planet's longest -ever continuous concrete pour below water

It's quite hard to appreciate the full magnitude of the scale of what's below

the water here.

Just to give you an idea, you've got roughly 50 meters of tower on display

Below water, you've probably got another 40 meters before you hit the bedrock.

So that's the sort of scale we're talking about below the water here.

It is an amazing engineering achievement.

But for the Central Tower Foundation, engineers saw an opportunity that they

couldn't pass up.

This location was chosen because of the existence of a dollarite, very, very

hard volcanic rock, rocky outcrop in the middle of the front of the floor. So it

was ideal to set the central tower foundation on because of the immense

that that rock is going to take.

To prepare the super tough rock,

the team blasted away roughly 175 ,000 cubic feet of material with powerful

explosives.

and shaped it to hold 140 ,000 cubic feet of concrete.

So there's a robust reinforced concrete base below that tower, on which we've

placed some decorative rock effectively to try and create the illusion that the

tower is coming straight out of the rock.

With the rock -solid foundation in place, teams set to work erecting the

country's three tallest ever bridge towers.

Over 800 ,000 cubic feet of concrete was poured in incremental stages,

pumped all the way from barges on the water up to the tower's 680 -foot -high

apex.

And after almost two years of perseverance through moody Scottish

towers were finished and finally ready to support a roadway.

But to reach them from the shore, engineer Jill Baker and the team faced

obstacle.

There were many challenges to constructing both the north and the

viaducts. And this very steep sloping ground made it very unsuitable for heavy

craneage. You need a good, secure, stable, level space for any use of

Without traditional cranes, the team will need to draw inspiration from the

pioneers of the path to link the record -breaking towers.

So they've made it here to the other side.

This is the Queensferry Crossing.

A record -breaking structure the likes of which the world has never seen

38 ,000 tons of steel has gone into the bridge deck alone.

The approximate weight of 200 747 passenger jets.

Every day it carries 80 ,000 cars and heavy goods vehicles, keeping Scotland

the move 24 -7.

But the banks on either side of the 4th estuary are not compatible with

traditional crane construction.

To find a way to erect their bridge towers in this challenging location, the

team is looking to the engineers of the past.

At a South Yorkshire limestone quarry in the UK,

engineer Luke Bisbee is on the hunt for an innovation that

changed the course of history.

During World War II, Hitler ordered his troops to start destroying bridges. And

this was a very clever idea to slow down the Allied forces.

No bridge means the Allied forces have a massive detour in order to get where

they're going.

To fight back, the Allies needed to rebuild bridges and fast.

Knowing that bridges were vital to the war effort, British engineer Sir Donald

Bailey started sketching up an idea on the back of an envelope.

In 1940, he developed a concept that changed the war.

This is a Bailey Bridge.

Wow, so this is the modern version of the Bailey Bridge.

A portable, quick -to -build bridge that can be adapted to suit just about any

location. And this one here is spanning 42 meters from side to side over a drop

of about 20 meters.

Pretty spectacular.

Over 80 years after conception,

Bailey's flat -packed bridge design is being erected to connect two important

areas of this quarry without the assistance of heavy lifting crane.

So you can see here, this is one panel section of the bridge from here over to

there. By adding more panels along the bridge, you can adapt this for your

particular location.

No single piece weighed more than 570 pounds.

And this meant that any piece could be lifted by six soldiers, which crucially

meant that no cranes or heavy lifting was required, which is absolutely

in a combat situation.

Super light bridge sections could be easily transported to the battlefield

assembled by hand.

And its modular design meant that the Bailey Bridge could be progressively

launched, growing as it inches forward.

Okay, boys, pull the spikes.

But how were Bailey Bridges built across rivers and ravines without a crane?

Nice and slowly, if you please.

By counterweighting one end of the structure, it could be pushed out and

the valley.

The key thing about the Bailey Bridge is that you can launch it from one side.

It's absolutely extraordinary.

104 tons of bridge just sliding past me on some rollers. Unbelievable.

But without supports to hold up the span.

there's an additional challenge to overcome.

A key problem that you have is that the front of the bridge is going to want to

angle down under the weight of the structure.

And so it's really important when you're launching a bridge in this way to keep

the nose of the bridge up, because otherwise, as you're pushing it across,

might just bump into the other side.

But Bailey had thought of everything and angled the front section of his bridge

up to ensure it cleared the bank on the other side.

Here it comes.

I think this is actually a pretty critical moment right here.

So they've made it here to the other side.

They've actually done it.

Really an extraordinary thing to see.

By the end of the war, around 700 ,000 Bailey Bridge panels had been made.

Both British and American generals have praised the Bailey Bridge as one of the

key factors leading to an Allied victory.

With his ingenious yet simple design for a bridge that could be built and

launched by hand and without a crane, Donald Bailey had helped bring an end to

World War II.

This is an amazing thing. To see this technology still doing its job so many

years later is really wonderful and a real testament to the innovation that

involved.

In Scotland, engineers have taken the same concept and supersized it.

The only way to the Queensferry Crossing's towers from the shore is with

gigantic, progressively launched Approach Viaduct.

The chosen solution for the South Approach Viaduct was a progressive

It was launched span by span.

We achieved this launch, which goes out virtually half a kilometer to where the

cable stay bridge is.

This eliminated the need for any large cranes.

Where heavy lifting cranes can't be erected on the steep slopes, six

piers were evenly arranged out towards the towers.

The team then inched the bridge deck forward from the abutment piece by

Each time they reached a pier, a new section was welded to the back, and the

process would repeat until the viaduct reached almost half a mile out over the

supporting piers.

And just like the Bailey Bridge, the overhanging deck had to fight gravity.

As the launch progressed, the tip would want to deflect under its own weight.

This could have been catastrophe if the tip actually put load, lateral load,

into these piers.

But we had this king post system in place, a 35 -meter vertical temporary

and there was a strand system coming over the king post.

and connected to the tip. As these strands were tensioned, it would lift

and land it on the pier.

It was a pretty remarkable solution.

But where the North Shore slopes are even steeper, a more extreme approach

needed.

We would have had to excavate a lot more ground to assemble the girders at the

right profile for the launch.

So the solution here, rather than being a progressive launch...

The whole structure, 220 meters, was assembled as one unit, and then it was

launched in one massive launch.

In a single daring maneuver, engineers pushed the enormous deck span directly

forward and then pivoted over the supporting pier to tilt upwards and

the rest of the bridge structure.

It was a big relief when we finally achieved our desired solution.

I don't know of another launch so large, 6 ,000 tons, being pushed out 220

meters, and then having to do this pivot.

It was remarkable engineering, super balls, and it's the best of British

engineering.

But with the approach viaducts in place, It takes more impossible engineering to

join this megastructure together.

The sort of equipment that you need to build those units are very special

of equipment.

For a solution, engineers must turn to the great innovators of the past.

You really get a sense of how long this bridge is.

We can barely see the other end of it.

In Scotland is a superstructure that defies the impossible.

In a bid to keep the country connected.

The triple -towered Queensferry Crossing boasts two enormous 2 ,100 -foot spans.

Over 2 ,500 concrete pours executed across the project.

pumped a staggering 165 ,000 tons of concrete into the megastructure.

But before vehicles can cross the channel, they're going to need a road to

on.

Engineer Richard Hornby oversaw the operations behind crucial deck segment

construction.

This is a port here.

This was the sort of the marine nerve center for the project.

For the deck itself, the deal was made in China.

The units were delivered on four ships on this quayside here.

122 steel deck sections, each weighing up to 400 tons, were offloaded by an 1

,100 -ton megacrane.

and taken one by one to the concrete casting shed to be capped by another 300

tons of reinforced concrete.

But to get these super heavy deck pieces from the dockyard up onto the

megastructure would be a battle with the elements.

The conditions on the east coast of Scotland are not benign.

There's long periods of strong wind. There is a strong tidal flow.

The sort of equipment that you need are very special pieces of equipment.

Big plate and crane that are stable in essentially open water.

But where the water depth varies, a one -size -fits -all solution just won't cut

it.

The floating cranes need significant depth of water, and towards the ends of

bridge, there really isn't enough water depth, and so you might well have had to

have two different lifting systems, one using the floating crane and one to deal

with the areas where the floating crane couldn't get to.

In a varied seascape where multiple systems would be needed, floating cranes

not an option.

The team must find another way to install heavy deck segments.

by turning to history's innovators.

In the rugged landscape of Lethbridge, Alberta... Watch your steps.

Mechanical engineer Agnes D 'Entremont is exploring the deep ravines that kept

southern Canada divided.

Connections by rail within southwestern Canada were really important at the end

of the 19th century to get southern Alberta coal into British Columbia.

But they had to deal with terrain like this, deep ravines.

A real solution was needed for the railways to cross these dangerous river

valleys.

Tasked with making this dream a reality was Assistant Chief of Engineering at

Canadian Pacific Railway, John Edward Schwitzer.

In 1909, he unveiled a revolutionary structure that changed the world of

engineering.

The Lethbridge Viaduct.

Wow, it's incredible!

Almost a mile long and 315 feet high, it's the longest and highest steel

railroad trestle in the world.

So this is it. This is Switzerland's solution to keeping southwest Canada

connected. The Lethbridge Viaduct, which you can see above me, spans this entire

valley but keeps the rails almost level.

At this point, the bridge is nearly 100 meters above us.

Imagine having to lift massive steel beams that high in the air to construct

this bridge. Having a crane down here would be impractical. Not only because

terrain is rugged and there's a river, there are varying land heights.

Just like in Scotland, the varied landscape meant that a single crane

would be useless.

So instead of putting the crane down here, Schwitzer put it up there.

Schwitzer's cunning solution was to use a deck -mounted erection traveler crane,

an enormous mobile gantry that traveled along the track on top of the bridge.

Agnes is inspecting a scaled -down model of Schwitzer's design.

It doesn't really look much like a crane. It looks more like a house on

The giant shed at the back housed not only the engines to move the crane along

the tracks, but also six hoisting engines that operated the jib arm.

This is such a cool piece of engineering. You don't really see

this anymore.

Standing almost 65 feet tall.

the 350 -ton Erection Traveler crane rode on the external walls of the

allowing wagons to travel on the rails underneath the engine room to deliver

materials to the boom at the front.

And with 10 miles of cabling swinging components into place, the Erection

Traveler built its own platform to migrate onto as the bridge deck grew.

By shifting forward one piece at a time, Workers reached the West Bank in 10

months.

A century later, the Lethbridge Viaduct still carries enormous trains weighing

thousands of tons.

Without the erection traveler crane, this viaduct and the robust connection

between Alberta and British Columbia wouldn't exist.

What a remarkable piece of engineering.

To build the longest triple tower cable stay bridge of all time, the team behind

the Queensferry Crossing will need to take Schwitzer's revolutionary concept

supersize it.

Over a hundred years after John Edward Schwitzer pioneered the erection

crane to do heavy lifts in difficult locations, the concept has been crucial

big construction.

For the Queensferry Crossing, the longest structure of its kind ever

Scotland's engineers have created a system that Schwitzer could have only

dreamed of.

With not one, but six erection traveler cranes, or in this case, gantries.

Lifting 770 ton deck units from floating barges and progressing forward as the

structure grew.

Breaking another world record.

Until the giant balancing act was sealed together to become a secured

superstructure.

Their engineering secrets are now only found deep within.

This is the joints between two segments.

This is the front edge of the already erected deck, and the front foot of the

gantry needed to be stressed down to all of this stiffening here, ready to lift

up the 700 tonnes in front of it.

The segment would have been drawn together, and then if we look up here,

see that there's a metre -wide strip of concrete that gets cast between the two

segments and joins the two segments together.

With the cutting -edge iteration of the erection traveler crane, engineers have

created a masterpiece.

The lifting of these 700 -ton segments with lifting gantries was a hugely

innovative piece of construction engineering, a development, actually, of

lifting gantry technology that has been around for centuries.

But keeping Queensferry Crossing's enormous mile -and -a -half -long

in the air once the gantries are gone requires a colossal cable stay system.

But this extremely slender bridge hangs delicately over the sea.

And a conventional cable arrangement could not provide sufficient support.

As you see, it's a very elegant, slender structure.

But if there was a traffic jam and all the traffic backed up, there would be

this weight on one side and none on the other, and the deck on the other side

would lift up, and the deck on the loading side would go down.

This long, slim deck profile needs additional support to stay standing.

If you don't provide that stiffness, the structure cannot resist the load on one

side and would fall down under these asymmetric loadings.

To find a way to stiffen the bridge deck, inspiration can be found with the

innovators of the past.

Straddling the border between France and Spain.

are over 200 miles of deep precipices and deep ravines.

Marvellous journey.

So beautiful.

On the French side of the Pyrenees mountain range, civil engineer Claude

is hunting down a relic from the golden age of train travel.

20th century, the most efficient way to connect this region was by rail.

To cross the Tet River, the gorge was very deep and Stonebridge would have

taken a lot of time, a lot of money.

The suspension bridge is also a marvelous structure, but it's not

for railway.

The train is a very heavy loader. And when the train enters the bridge, it

creates a huge deflection of the structure.

Like the Queensferry crossing bridge, it was going to need special

reinforcement.

In 1900, French military engineer Albert Gisclar patented a clever system

that enabled him to build a bridge in a brand new way.

I can see it now.

It's just after this curve.

This is the Ponzi Sklar.

And there we are.

A cable -supported railroad crossing.

It's not a standard suspension bridge.

Look at the cross cable.

There, in the middle of the structure.

It's so impressive.

It's a really elegant structure.

Very clever.

Hanging 260 feet over the valley below.

It's the oldest cross -cable railroad suspension bridge in existence.

And the innovative engineering that keeps it standing over 100 years later.

You can see the fantastic and clever cable arrangement.

It's something very, very special.

could be the key to holding the Queensferry crossing bridge steady for

to come.

Civil engineer Claude Lecaire is investigating the brilliant design

Pont Gisclar, the oldest cross -cable railroad suspension bridge in the world.

Oh, wow.

What a great view from here.

It's impossible to see it when you are in the train, but from this point of

view, you can see the fantastic and clever cable arrangement. It's something

very, very special.

There is no single suspension cable. There is two suspension that cross in

middle of the bridge, and that makes all the suspension system very stiff.

Weighing only 873 tons.

This seemingly fragile structure stands strong after 110 years, thanks to

Gisclar's ingenious reinforcement concept.

A traditional suspension bridge has a pair of cables strung across the

supporting towers and vertical wires that hold the deck up.

But when a heavy load like a train enters or leaves one side of the bridge,

imbalanced heavy weight could cause disastrous deflections in the deck,

the structure in the wrong direction.

Gisclar solved this by continuing the cables from each tower across to the

at the opposite side, crossing them in the middle.

Now the heavy load is shared across the intersecting cables to both solid ground

abutments.

And with the complex web of cables creating triangular truss -like

even more stiffness is introduced into the deck.

Here comes the train.

As the train enters the bridge, the heavy gravity load on that side is

by both sides and both pylons.

This cloud idea was really brilliant.

It's a very innovative idea.

Although many had attempted traditional suspension bridges for railroads, none

had the strength and stiffness to stand the test of time, quite like the Pont

Gisclar.

This bridge is a really great design.

It's an inspiration for engineers today.

In Scotland, engineers have built a cross cable system on a colossal scale.

Enhancing structural strength and depth for a super long, super slim deck

profile.

The height of where those cables intersect at their very highest is the

depth of structure.

If you haven't load on one fan,

these stays here will be delivering this load here.

And these stays coming down from the north tower will actually act to

load from the fast fan all the way back to terra firma.

Where the conventional cable stay method would have failed.

The team opted to extend their cable stays further, crossing at mid -span,

allowing the force of uneven weight loading to be transferred all the way

the intersecting cables to the opposite abutment.

Introduction of additional stiffness through an overlapping stay system.

This is the first time it's been done on a cable stay bridge of this scale.

At over 1 ,300 feet, these cables are some of the longest in the world.

When they inevitably need repairs, the team has a remarkable

system in place.

Here's a good view of a cable anchorage.

You can actually just see the strands disappearing through a hole in the deck,

and each of those strands is individually anchored so that you can

and remove it.

Inside each cable are between 50 and 100 strands of woven wire.

which from under the deck can each be pulled out and re -threaded without

disrupting the other strands in the cable.

The replacement of individual cables with minimum disruption to traffic was a

fundamental requirement.

But maintenance work isn't the only thing that can bring traffic to a

halt. Mother Nature can, too.

For the Queensferry Crossing Bridge to withstand Scotland's dramatic natural

forces, the team needs to engineer one last solution.

The Queensferry Bridge Crossing is a remarkable engineering achievement.

The team has designed the longest three -tower cable stay bridge structure in

the world.

But to ensure the structure remains safe and stable, they must account for

Scotland's extreme weather.

As you can see from the site, it's a very open environment.

We're very close to the sea and very exposed to the wind.

The wind speeds can get up to 120 miles an hour.

On the bridge, these high rectangular vehicles, they just act like a trail and

they have the same impact as the wind has on a yacht.

On the old road bridge, gale force winds had such power that the structure could

violently ripple and swell.

And the ferocious gust could even tip over high -sided trucks.

For the safety of drivers and residents living on the banks below, bridge

closures were essential.

But the engineers of the Queens Ferry Crossing have a solution for that.

So the solution they came up with was a six Louvre wind bar, which basically

deflects the wind over the top of the road and protects the vehicles from the

wind. The bottom two Louvres are this way round, which allows the wind to come

in and start to fade over the top. As you go up, higher up, then the wind has

helped to take over the traffic.

It's fantastic because it's allowing the traffic to move uninterrupted at all

times of the year.

Since the bridge opened, over that period, if we were still on the 4th Road

Bridge, the bridge would have been shut 86 times to traffic.

It's a genius solution to allow the traffic to keep moving.

It's a phenomenal piece of engineering.

For the team behind this daring project.

The sense of achievement is immeasurable.

It's an incredible feeling knowing that you're part of one of the key pieces of

infrastructure in the UK.

Really, there are none like the Queen Street Crossing in terms of its scale

significance.

By building on the work of the pioneers of the past, overcoming huge challenges,

and pushing the boundaries of innovation.

I think if you're a civil engineer and a project like this doesn't excite you,

you're probably in the wrong game.

It's a groundbreaking project. It's just an immense engineering achievement.

Engineers are succeeding in making the impossible possible.

There was a lot of challenging days out there.

We worked 24 hours a day.

The outcome is a phenomenal bridge and it's recognised across the world.

There's no doubt the Queen's Ferry Crossing provides a lifeline for

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