Original subtitles

in today's impossible engineering.

This must be one of the most complex engineering projects ever undertaken.

The world's largest free -spanning dome.

The Singapore National Stadium is really a marvel of engineering.

You put 65 ,000 people in a place like this, it's pretty fabulous, really.

Stadium engineering on an extraordinary scale.

9 ,000 tons of steel was used to carry this roof above me right now.

And the pioneering historic innovations. Here we are, up on the roof.

It's huge.

It's actually disorientating to see the dome rotating.

It's truly impressive.

That made the impossible possible.

Singapore is the second most densely populated country on the planet.

with about 5 .7 million people spread over 281 square miles.

This presents unique challenges for engineers designing something as massive

an athletic stadium.

We need a facility to enable us to host world -class international sporting and

entertainment content.

At the same time, it has to be multi -purpose given our land constraints and

need to optimize every available acre of land.

But in Singapore's tropical environment...

space to build isn't the only problem.

So we are one degree north of the equator, which means that we are warm

humid, and we have rainfall almost one -third of the year.

So the stadium has to provide protection against the weather.

To take on this colossal challenge, engineers have created a structure like

other on Earth.

This is the Singapore National Stadium, a gigantic

multi -purpose sports arena.

Eight enormous arches create a 270 -foot -high freestanding shell with enough

space inside to contain the Sydney Opera House.

50 ,000 spectator seats can be increased to 55 ,000. by an advanced

reconfiguration system.

And at the push of a button, two gigantic roof leaves, each 107 ,000

feet in size, will close to protect from Singapore's turbulent weather

conditions.

The largest free spanning dome the world has ever seen marks the dawn of a new

age of superstructure.

I think the engineers have achieved something which is truly incredible.

Everything from the smallest boat to the entire free -spanning dome is a work of

wonder.

It's a huge achievement in terms of engineering and design solutions, and

all about integration of architecture and engineering working together.

It's up to Stadium CEO Lionel Yeo to oversee this one -of -a -kind arena.

Well, think about the scale of the project.

You have a dome which is this size, 310 meters wide, 82 .5 meters high.

I think it is an engineering marvel.

It's a very complex project.

The domed roof in particular makes this stadium a unique challenge.

And engineer Mok Sui Chiang was part of the team responsible for its

construction.

The dome is really a very iconic structure here in Singapore.

If you look across the city skyline, you can definitely see it.

So 9 ,000 tons of steel was used to carry this roof above me right now.

But how have they erected this structure to stand strong with no columns or

support?

The dome wants to flatten out.

That's the nature of a dome.

You really need to prevent that from happening.

And how do you transform an enormous stadium to accommodate huge concerts and

sporting events?

The national stadium will need to cater for various events.

And it's not an easy task to move such a structure.

And how can such a record -breaking structure be sheltered against Mother

Nature?

It rains a lot and it rains hard.

But the stadium's design calls for this open roof.

that needed to provide a serious amount of shading and protect the spectators

from the rain.

Engineers knew from the very beginning that this project would raise numerous

complications.

The seating arrangement that was designed by the architect leaves a very

space for engineers to design a roof that covers it.

With columns, you'll be obstructing the view of the spectator.

So it's quite critical to have the columns removed.

So to preserve spectator views, the team has come up with a remarkable form that

requires no columns at all.

To support the dome of this scale, the solution is to have a three -dimensional

rib truss system.

What we have here is six runway trusses that run from left to right.

And then you have, at 90 degrees, two transverse trusses running across to

it up.

In addition to that, we have diagonal trusses that connect the corners

to form a very three -dimensional state structure that is able to withstand the

huge load that it's experiencing.

An arch is one of the strongest shapes under gravitational load.

So combining the two transverse arches with the six runway arches creates a

three -dimensional arch or dome.

Once you arrange the trusses in a three -dimensional way, you really get a very,

very stable structure.

It's really the most efficient way to channel all the forces down.

During construction, giant cranes erected the steel truss.

while 90 temporary pylons supported the structure from beneath.

After nine months, the final piece was raised into position.

The temporary pylons were removed, and the truss configuration could finally

support itself.

But with the framework in place, engineers faced another problem.

The Singapore Stadium, in fact, is built on reclaimed land, which essentially is

Singapore marine clay.

And Singapore marine clay is like butter.

It is almost impossible to be supported on.

With soft ground and a massive dome structure prone to flattening out, the

must turn to the pioneers of the past.

In Orange County, Indiana,

architect Todd Rotman is exploring a site that may hold the key to keeping

Singapore National Stadium standing.

This is what started it all, the Mineral Springs.

The secret to this area's popularity can be found in its artisanal waters.

People thought the water here had medicinal qualities, so people would

they would bathe in it.

And this ended up becoming a playground for the rich and famous.

The draw to this area was enough to make the owners want to build a hotel resort

that could rival even the finest spas in Europe.

Tasked with making this dream a reality were architect Harrison Albright and

bridge engineer Oliver Westcott.

In 1902, they revealed a building that changed the world of structural

engineering. Oh, wow.

That is gorgeous.

This is the West Baden Springs Hotel.

It's just so huge. It's amazing.

And its crowning jewel, a gigantic free -spanning dome sitting high above the

atrium.

At the time, it was the largest dome in the world, over 130 feet tall in the

center point, over 200 feet in diameter.

So what can Singapore Stadium's engineers learn from this spectacular

And what keeps it standing over 100 years after its design? What makes this

amazing is the technology and the engineering that went into making it

because it hadn't been done before.

Creating one of the world's largest multipurpose facilities requires

to radically rethink every aspect of stadium design.

This is the Singapore National Stadium.

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

8 .8 million cubic feet of concrete has been poured into this megastructure,

creating a 2 .9 million square foot floor area, large

enough for an enormous seating bowl, capable of accommodating 55 ,000

spectators.

But to encase this vast arena, engineers needed to draw inspiration from the

design of a record -breaking 1902 structure.

The West Baden Springs Hotel.

What an amazing view.

Designers Albright and Westcott constructed the largest dome in the

title it held for over a decade.

But how does it stay supported above the atrium without a single column?

So if you look up at the roof, you can see 24 steel trusses that terminate a

drum in the middle.

and extend down and out to the columns along the perimeter.

The problem is there's a lot of weight being pushed out on them.

So to take that load, pushing out, they put two steel tension rings around

the perimeter. So if you look out across the dome, above and below those windows

are those tension rings, and those are structural components that hold this

building up.

To demonstrate how the inspired tension ring beam solution works, Todd has

scaled it down.

We've got a simulated dome structure with the trusses.

We've got a weight.

Let's put the weight on it and see how the trusses hold up.

So as you can see, the ends of the trusses kicked out. There was nothing to

them in place, and we've got a failure.

Now, if we add a tension ring around the perimeter of it,

And we use the exact same trusses.

Let's see how the tension ring helps.

No failure.

It's able to support the weight.

And we can even put additional weight and it still holds it.

The tension ring is taking all of that lateral force, it's containing it, and

making all of the load go straight down. So imagine the innovation of making one

out of steel and supporting a 200 -foot diameter dome. It's a simple concept,

but used in a big way.

Albright is rumored to have been so confident in the dome's design that he

on top of it as the construction supports were removed.

To get a closer look, Todd is braving the climb to an area very few people

get to see.

All right, here we are, up on the roof.

Yeah,

but this isn't our final destination.

At the very apex of the dome, its trusses are tied together in a central

structure, suspended high over the hotel lobby.

All right, so this, to me, is a little bit more scary than being on the roof.

These boards date back to 1901.

You know, this is kind of where the structure starts, right? This is where

all comes together, and from here the forces go out down the trusses to those

tension rings.

With the world's largest free -spanning dome as its showpiece, the hotel

attracted visitors from around the world.

More than a century later, the domed roof has stood the test of time, thanks

its ingenious tension ring support.

To build this magnificent structure with such a large dome, it's just a

testament to the incredible engineering.

It's truly awe -inspiring.

Here we are today, over 100 years later, the same structure is in place, still

standing tall, just as beautiful as it ever was.

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

The only way to hold a record -breaking dome together is with the planet's

largest tension ring beam.

So the ring beam is positioned below the transverse, and it is actually

somewhere behind these walls.

The ring beam is 6 meters in width and 1 .5 meters in depth.

Taking six months to complete, the gigantic concrete ring has a

over half a mile encircling the stadium.

350 ,000 cubic feet of concrete is reinforced by 14 steel tendons, which

threaded through the ring beam and tightened.

squeezing it in towards the center like an elastic band.

As the weight of the dome tries to spread out, the ring beam pinches back

from 360 degrees, holding the structure in place.

Buried in the foundations is the largest ring beam in the world.

But above ground are the final components that tie the system together.

So the forces from the arches actually come down the truss and then hit the

truss block.

And there are about 20 of these truss blocks around the length of the ring

The truss block will transfer the forces down to the ring beam.

And there's a lot of things happening at the truss block.

Forces in all directions will interact and work the truss block quite hard.

175 metal studs tie the foot of each arch to the thrust blocks reinforcing

rods.

Transferring the force of the dome's weight into the ring beam and holding it

firmly in place.

120 years since West Baden held the record for the world's largest dome.

Singapore has taken that mantle with a structure Albright and Westcott could

have only dreamed of.

So the ring beam is actually a very crucial and clever idea to withstand the

forces coming down from the dome.

But with the domed roof held firmly in the ground... It takes more impossible

engineering to turn this shell into a world -class venue.

And Singapore's tropical climate means additional challenges.

It's hot and humid all year round.

It's 33 degrees, 34 degrees every day.

You put 55 ,000 people in a place like this, you basically raise the

by about 3 degrees.

Spectators are sticky, it's uncomfortable.

When you sit through a two -hour show, it's a chore rather than enjoying the

event. But the roof is 80 meters high, 20 stories.

It's a large volume.

You can't cool all of that space.

Instead of attempting to chill the enormous room, engineers came up with a

creative solution.

We can cool the venue much more energy efficiently from below.

So we deliver cool air at around 23 degrees, just under the seat.

So we create a comfort zone, a bubble.

But to deliver localized cool air to each seat, it first needs to be chilled

a subterranean climate control system.

This is the heart of the system.

We're producing chilled water in here at 8 degrees.

We push that chilled water out to the stadium.

It goes through an air handling unit associated with each zone of the bowl

cooling system.

The chilled water arrives there at 8 degrees. We pass air across a cooling

provides the cooling to the seat.

But huge events filling the whole stadium require a cooling system that

handle the high capacity.

Deep in the subcellars are four tanks.

Each one contains 300 ,000 glycol balls, a material chosen for its thermal

storage properties.

These balls are frozen so that as water flows through, it is chilled before

being delivered to the seating galleries.

and then re -chilled as it is recycled through the system, meaning it's more

than able to cool a full house.

It's pretty fabulous, really, when you think we can sit here and we can air

-condition 55 ,000 seats.

We put the spectators in a space which is really quite enjoyable. You can sit

here for 10 hours in a day and you not raise a sweat.

But this tropical country is also short on space.

Randall Lim's team of engineers face another challenge to minimize the

of a multipurpose arena.

We have events ranging from track and field to concerts to football.

For football events, you want to be seated as close as possible to the

And then for track and field events, you want to be seated as close as possible

to where the runners are.

For a typical stadium where you have the pitch surrounded by the track, you

could be as far as 15 meters away.

It is crucial to find a solution to design a stadium that caters for various

events.

To provide the optimal spectator experience, regardless of the event, the

must look to another iconic stadium for inspiration.

It may not seem obvious at first because of the size of the stadium, but this

place can actually move.

To build a versatile arena like no other, the team behind the Singapore

Stadium will need to take the innovations of the past and supersize

So in total, we have eight sections, and that gives us over 24 ,000 teams to

shift.

Engineers have created the Singapore National Stadium, one of the largest

and entertainment venues on earth.

The colossal roof encases over 100 million cubic feet of completely open

That's enough room for the arena to be filled with water from 1 ,200 Olympic

swimming pools.

But to succeed as a multi -event venue, this stadium needs to have structural

versatility. To achieve this monumental goal, Engineers will look to the

pioneers of the past.

It's so beautiful here. I love living in Hawaii.

Engineer Kenan Koga is searching for the answer.

Having this awesome weather here and great environment, it makes a lot of

for Hawaii to try to host a lot of different sporting events, but there's

lot of space here to actually do that.

On an island where space to build is limited.

Sports fans need one venue to serve all purposes.

A football field is a rectangular shape, and a baseball field is a diamond

shape. So if you're watching a football game in a baseball stadium, the fans way

out here in left field can't see the action happening on the football field

here.

Charged with finding a solution,

architect Charles Luckman hit a home run.

In the 1970s, he came up with a design that would change the world of stadium

engineering.

Well, here we are, guys.

This is the Aloha Stadium.

This place is massive.

An enormous superstructure, affectionately known as the Metal Mecca.

You can just imagine this whole place packed with fans, everybody.

cheering, stomping all over the stadium, feeling it shake.

And it may not seem obvious at first because of the size of the stadium, but

this place can actually move.

The curved sections at the far ends of the field would remain permanently

in place, but the flanking seats divided into four sections could pivot to

create an open -sided baseball diamond or a closed rectangular football field.

So if you can imagine, this is where the stadium would part like the Red Sea and

move in a given direction. If someone didn't tell you that these sections

move, you would never know.

But to shift 28 ,000 seats weighing over 6 ,000 tons was a huge task.

Watch your head.

So Luffman installed innovative devices underneath the stadium to make the heavy

stands float on air.

So underneath each one of these beams, you had an air skate, which is

essentially like a little balloon.

The compressed air is filled through this line up here and funnels down and

distributed to each one of the air skates.

That balloon fills up and there's a box around that balloon that allows the

compressed air to funnel directly down and push this piece up.

To move this colossal structure, 416 of these air skate discs are distributed

across the stadium.

Feeding them with a constant flow of air pressure creates a thin, frictionless

film between the skate and the ground, requiring the force of only one pound to

move 1 ,000 pounds of weight.

And to see this concept in action,

Keenan has taken up another sport.

So here we're trying to illustrate the actual stadium.

When the air hockey table is off, there's a greater amount of frictional

between the table and the stadium.

So to remove the human factor of the amount of force that I could actually

insert onto the stadium, we'll use a piece of paper here, and we're trying to

move this piece into the stadium, move it around, change the configuration, but

we can't really do that just because of the amount of frictional force that's

keeping this piece in place.

I can't move this at all.

But as you can see, when you turn the machine on, it's mimicking the air

in the stadium, creating a very small gap between the piece and the surface.

which is decreasing the amount of surface tension and friction.

So therefore, you only need a small amount of force to actually move the

stadium. And now we can actually guide this piece into place similar to our

stadium.

Between 1975 and 2007, the stadium would be transformed twice a year,

each reconfiguration taking up to two weeks to complete.

Weighing 14 million pounds, the Aloha Stadium's movable stands were once the

heaviest load to ever be carried on an air film.

After 46 years of youth, the stadium's days are drawing to a close.

It's really quite an honor for me to be one of the last few people that are

standing here before demolition crews start to begin work on the stadium.

But thanks to Luckman's initiative, its engineering legacy lives on.

What they did here is they took a simple concept and blew it up on an enormous

scale. The concepts applied here have provided inspiration to so many modern

stadiums around the world.

For the next generation all -purpose venue, engineers have adapted the Aloha

Stadium's pioneering technique for the 21st century.

But this auditorium doesn't just move.

It can grow its capacity from 50 ,000 to 55 ,000 spectators' beats.

The lower tier, as you see behind me, will shift outwards towards the pitch

area, creating a void between the lower tier structure and the building.

And then the concourse platform will be listed up to fill the void in between.

To transform such a massive structure... Be careful of the track.

...takes some incredible engineering solutions.

We are now underneath lower tier structure.

Each tier weighs around 900 to 1 ,000 tons.

There are 3 ,000 seats in each of the lower tier sections.

So in total, you have eight sections, and that gives us over 24 ,000 seats to

shift.

Like the Aloha Stadium, the Singapore engineers have employed a similar

technique to move their seats.

So these are the front set of loading points.

Before the shifting, We will slide in this, what we call the air skid.

Compressed air comes into this distribution module where we will

compressed air to every single air skid to lift the structure slightly and also

to reduce its frictional weight.

Reducing the ground friction of these immense seating tiers allows just a

handful of engineers to push the 1 ,500 -ton structures closer to the action.

leaving a void between the stadium wall and the seating tier.

To make the most of this additional space, engineers will need to take

air skate technology and combine it with even more innovative engineering.

This is definitely a remarkable machine, even this capability.

At Singapore National Stadium.

Engineers have been inspired by Aloha Stadium's innovative use of air skate

technology. They've devised a system allowing just a few people to move

seating sections closer to the action.

Watch your head.

This new configuration leaves room for an additional 5 ,000 concourse platform

seats. Where we are in now is a trench that runs across the stadium.

It's underneath the concourse platform.

And the trash is built for sole purpose for the concourse platform handling

machine.

This machine will leave the concourse platform upwards to fill the void

the two structures.

This innovative machine performs like a scissor lift, but instead of hydraulics,

it's driven by rigid chain technology.

In the lowered position, the flexible chain is coiled up for storage.

But when driven upwards by the rack and pinion motor, the chain links lock

together to form a rigid column.

And thanks to even more air skate technology, this 70 -ton machine can be

by just one person along a track running the length of the trench.

Meaning only one of these devices is needed to transform the whole middle

Concorde.

And once in position with the concourse platform secured, the machine itself

will lower and will move to the next location to perform another shift.

This is definitely a remarkable machine, given its capability to raise up to 95

tonnes of weight and have a lifting height of almost 10 metres.

Without this machine, lifting of the concourse platform is not possible.

With this system in place, engineers have created one of the world's most

versatile stadiums.

Able to accommodate 50 ,000 spectators for athletics.

And grow to feed up to 55 ,000 for football and rugby.

All while keeping the fans close to the action.

To have a retractable seat system that can shift over 24 ,000 seats and 14 ,200

tons of weight.

It's definitely mind -blowing.

But to battle Singapore's inclement weather, they have one last challenge to

conquer.

Engineer Randall Lim and his team need a structure that can adapt at a moment's

notice.

Having an open air stadium allows natural light and fresh air into the

However, there are also downsides to having an open -air stadium.

The stadium internals and spectators will not be shoot from the harsh weather

Singapore.

A clear day in Singapore can see temperatures of over 85 degrees when the

stadium's occupants would benefit from open -air seating.

But without warning, everything can change.

The thing about Singapore weather is that a typical storm will change in

minutes.

We do experience heavy downpour and we get as low as 100 meter visibility.

Immense storms can bring flash floods.

And Singapore's annual rainfall exceeds six feet.

In an unpredictable climate,

versatility is key.

From an engineering perspective, the solution is definitely non -negotiable.

It has to be a marvel of structural engineering.

To achieve a structure that can provide open -air views and protect from

inclement weather, engineers must turn to the innovators of the past.

At one of Britain's oldest scientific institutions,

Historian Louise DeVoy is in search of a groundbreaking structural innovation.

This is the Royal Observatory at Greenwich, the historic home of British

astronomy, navigation and timekeeping.

It's world famous as the basis for the international time zone system.

In the 1880s, the observatory procured a new telescope.

But this instrument's enormous size caused a problem.

The astronomers wanted to reuse the existing dome that rose up directly from

building. But the new telescope was too long, and so a new design had to be

found.

To overcome this challenge, a new, extraordinarily adaptable dome would

be constructed.

So how could the observatory protect its valuable telescope from the element,

while also providing an ideal view of the night sky?

We can really see the genius of Christie's design, how it extends across

whole extent of the dome.

The groundbreaking engineering that made it possible might hold the key to

keeping Singapore National Stadium dry in a downpour.

There we go.

Wow.

When the Royal Observatory acquired a new oversized telescope in the 1880s,

discovered the building's original dome wasn't large enough to accommodate the

device.

For astronomer royal William Christie, the solution was crystal clear.

He came up with a revolutionary proposal to house the new instrument.

This is the Great Equatorial Dome.

Wow, certainly worth a climb up those steps.

Standing out on the Greenwich skyline, this unusual onion -shaped bulb houses

the observatory's most prized instrument.

Our whole view is dominated by the giant Victorian telescope.

Absolutely fabulous.

But today we're more interested in the building around it, this wonderful

structure. Christie had to develop a design that could expand to 36 feet

and he came up with this very distinctive onion -shaped profile.

Expanding outwards from the base, the dome is five feet wider than the tower.

But with the telescope protected from the weather, it still needs a way to see

out to the night sky.

Oh, it's quite stiff, a bit reluctant at first.

Christy's remarkable solution.

There we go.

Wow.

An enormous adjustable shutter spanning the entire dome.

You can just see all the daylight starting to flood into the dome. That's

brilliant.

So as we open up the shutters to their fullest extent, we can really see the

genius of Christie's design, how it extends across the whole extent of the

from horizon to horizon.

To create this vast seven -foot -wide partition across the roof requires some

ingenious engineering.

It can be operated by just one person turning this wheel.

So this then turns up a series of interconnected rods up and across over

crown section.

You have two tail pieces supported by a series of wheels on tracks that move

together and move apart.

So Christy wanted to keep this very simple with a minimal number of moving

that could go wrong.

And this incredible structure has another useful feature.

A clever rack and pinion mechanism rotates the dome to align with the night

It's actually quite disorientating to see the dome above your head rotating

while you're still stationary yourself.

It's truly impressive.

Christie's innovation was ahead of the curve and it stood the test of time.

Still in use today, over 120 years later.

This telescope really paved the way for Greenwich astronomers to observe double

stars and the planets.

particularly Jupiter and Mars.

And this was all possible thanks to Christie's innovative design for this

and the retractable section.

To put the finishing touches on the record -breaking Singapore National

engineers will need to take Christie's idea and supersize it.

The roof is definitely an engineering model.

Inspired by William Christie's 19th century design,

Singapore National Stadium's engineers have built an adaptable domed roof

on a colossal scale to beat the

tropical rainstorms before they hit.

The engineering solution is to have a fully operational retractable roof that

can open and close so that we can host events of various nature.

At the push of a button, these symmetrical leaves will open or close in

minutes.

The National Stadium's 215 ,000 square foot opening is an engineering

marvel that Christie could have only imagined.

To shift these colossal panels on a curved dome, takes some remarkable

engineering.

The retractable roof is curved to fit the world's largest spanning dome.

And because it's curved,

getting them to move is a big hurdle.

Weight must be optimized and reduced while the retractable leaves need to be

flexible.

To minimize weight and maximize flexibility, engineers designed a

and covered it with pliable material that can be inflated.

The mobile roof consists mainly of ETFE membrane, and this is lightweight and

also allows flexibility in the roof movement.

Flexibility is important as we are moving a structure of that massive size.

Keeping components to a minimum, the huge roof panels are shifted by just 16

motorized winches,

hoisting the leaves along five fixed rails on sets of wheels known as bogies.

There are 20 boogies carry each lift, and total 40 boogies on the entire roof.

Each boogie has a four -wheel contact point to the fixed rail.

This minimizes the contact points.

When you see the thing from afar, the entire mower roof looks incredible.

The roof is definitely an engineering marvel.

For the team behind this daring project, it's an immense engineering

achievement.

This project is so groundbreaking because of the sheer size.

It's the world's largest free -spanning dome and that makes it quite incredible

on its own.

This must be one of the most complex engineering projects ever undertaken.

By building on the work of the pioneers of the past.

Overcoming huge challenges and pushing the boundaries of innovation.

It is really out of this world and with the amount of complex challenges that we

have faced, the Singapore National Stadium is really a marvel of

Engineers are succeeding in making the impossible possible.

I often take a step back and look at the stadium in Wonderment.

It's really quite an amazing architectural achievement.

I'm very proud to be part of this project.

It's just incredible.

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