Bridges should be beautiful

Bridges need to be functional, safe and durable, but they should also be elegant and beautiful, says structural engineer Ian Firth. In this mesmerizing tour of bridges old and new, Firth explores the potential for innovation and variety in this essential structure -- and how spectacular ones reveal our connectivity, unleash our creativity and hint at our identity.

The world needs bridges.

Have you ever thought about
what it would be like not to have any?

It's hard to imagine
a civilization without bridges

because they're so essential

for growth and development
of human society,

but they're not just about a safe way
across a river or an obstacle.

They shout about connectivity --

community.

They reveal something about creativity,

our ingenuity --

they even hint at our identity.

And when bridges fail,

or are destroyed in conflict,

communities struggle,

development stagnates, people suffer.

Even today,

there are over one billion people
living in poor, rural communities

around the world

that do not have safe, year-round access

to the things that you
and I take for granted:

education, medical care,
access to markets ...

which is why wonderful organizations
like Bridges to Prosperity

build bridges in this kind of place --
this is in Rwanda.

And they make such a difference,

not only to those lives
immediately around the bridge,

but the impact of these bridges is huge,

and it spreads over the whole community,

far, far away.

Of course bridges have been around
for an awfully long time.

The oldest ones are stone
because it's a very durable material.

I don't know about you --

I love to look at
the development of technology

to learn about what people did
with the materials

and tools available to them at the time.

So the Pont Du Gard in the center
is a wonderful example --

Roman aqueduct in the South of France --

fantastic piece of technology
built using massive stones put together,

dry -- there's no mortar in those joints.

They're just dry stone joints --

fantastic

and almost as good as new today.

Or sometimes up in the mountains,

people would build
these suspension bridges,

often across some dizzy canyon,

using a vine.

In this case, this is in Peru.

This is using grass which grows locally

and is woven into ropes
to build these bridges.

And do you know
they rebuild this every year?

Because of course grass
is not a durable material.

So this bridge is unchanged
since Inca times.

And bridges can be
symbols of their location.

Of course, Golden Gate
and Sydney are well familiar.

In Mostar the bridge was synonymous
with the name of the place,

and to such an extent
that in the war in 1993

when the bridge was destroyed,

the town all but lost its identity
until the bridge was reconstructed.

And bridges are enormous
features in our landscape --

not just enormous,
sometimes there's small ones --

and they are really significant features,

and I believe we have a duty
to make our bridges beautiful.

Thankfully, many people do.

Think of the stunning Millau Viaduct
in the South of France.

French engineer Michel Virlogeux
and British architect Lord Foster

collaborated together to produce something

which is a really spectacular
synergy of architecture and engineering.

Or Robert Maillart's Salginatobel Bridge
in the mountains in Switzerland --

absolutely sublime.

Or more recently,

Laurent Ney's beautiful
and rather delicate bridge

for Tintagel Castle in the UK.

These are spectacular
and beautiful designs

and we need to see more of this.

Bridges can be considered
in three convenient categories,

depending on the nature
of the structural system

that they adopt
as their principal support.

So, bending, of course,
is the way a beam will behave --

so, beams and bending.

Or compression is the principal
way of operating for an arch.

Or for the really long spans
you need to go lightweight,

as we'll see in a minute,

and you'll use tension, cables --

suspension bridges.

And the opportunity
for variety is enormous.

Engineers have a fantastic scope
for innovation and ingenuity

and developing different forms
around these types.

But technological change
happens relatively slowly in my world,

believe it or not,

compared to the changes
that happen in mobile phone technology

and computers and digital
technologies and so on.

In our world of construction,

the changes seem positively glacial.

And the reason for this
can be summarized in one word:

risk.

Structural engineers like me manage risk.

We are responsible for structural safety.

That's what we do.

And when we design bridges like these,

I have to balance the probability
that loads will be excessive on one side

or the strength will be
too low on the other side.

Both of which, incidentally,
are full of uncertainty usually,

and so it's a probabilistic problem,

and we have to make sure

that there's an adequate margin
for safety between the two, of course.

There's no such thing, I have to tell you,

as absolute safety.

Contrary to popular belief,

zero risk doesn't exist.

Engineers have to do their calculations
and get their sums right

to make sure that those margins are there,

and society expects them to do so,

which is why it's all the more alarming
when things like this happen.

I'm not going to go into the reasons
for these tragedies,

but they are part of the reason

why technological change
happens quite slowly.

Nobody wants this to happen.

Clients don't want this to happen
on their projects, obviously.

And yet of course they want innovation.

Innovation is vital.

As an engineer, it's part of my DNA.

It's in my blood.

I couldn't be a very good engineer
if I wasn't wanting to innovate,

but we have to do so from a position
of knowledge and strength

and understanding.

It's no good taking a leap in the dark,

and civilization has learned from mistakes
since the beginning of time --

no one more so than engineers.

Some of you may have seen
this film before --

this is the very famous
Tacoma Narrows Bridge collapse

in Tacoma, Washington state,

1940.

The bridge became known
as "Galloping Gertie"

because she -- she?

Is a bridge female? I don't know.

She was wobbling like this
for quite a long time,

and notice this twisting motion.

The bridge was far too flexible.

It was designed by a chap
called Leon Moisseiff,

no stranger to suspension bridge design,

but in this case he pushed the limits
just that little bit too far

and paid the price.

Thankfully, nobody was killed.

But this bridge collapse stopped
suspension bridge development

dead in its tracks.

For 10 years nobody thought
about doing another suspension bridge.

There were none.

And when they did emerge in the 1950s,

they were an understandable overreaction,

this sort of oversafe response
to what had happened.

But when it did occur in the mid-60s,

there was indeed a step change --

an innovation,
a technological step change.

This is the Severn Bridge in the UK.

Notice the aerodynamically
streamlined cross section

in the center there.

It's also a box which makes it
very torsionally stiff --

that twisting motion which we saw
at Tacoma would not happen here.

And it's also really lightweight,

and as we'll see in a moment,

lightweight is really
important for long spans,

and everybody seems
to want us to build longer spans.

The longest at the moment is in Japan.

It's just under 2,000 meters -- one span.

Just under two kilometers.

The Akashi Kaikyō Bridge.

We're currently working on one in Turkey
which is a bit longer,

and we've designed
the Messina Bridge in Italy,

which is just waiting to get started
with construction one day,

who knows when.

(Laughter)

I'm going to come back
to Messina in a moment.

But the other kind of long-span bridge
which uses that tension principle

is the cable-stayed bridge,

and we see a lot of these.

In fact, in China they're building
a whole load of these right now.

The longest of these is the Russky Bridge
in Vladivostok, Russia --

just over 1,100 meters.

But let me take you back to this question
about long-span and lightweight.

This is using Messina Bridge
as an example.

The pie chart in the center represents
the capacity of the main cables --

that's what holds the bridge up --

the capacity of the main cables.

And notice that 78 percent
of that capacity

is used up just holding the bridge up.

There's only 22 percent of its capacity --

that's less than a quarter --

available for the payload,

the stuff that the bridge
is there to support:

the railway, the road and so on.

And in fact,

over 50 percent of that payload --

of that dead load --

is the cable on its own.

Just the cable without any bridge deck.

If we could make that cable lighter,

we could span longer.

Right now if we use the high-strength
steel wire available to us,

we can span, practically speaking,
around about five or six kilometers

if we really push it.

But if we could use
carbon fiber in those cables,

we could go more than 10 kilometers.

That's pretty spectacular.

But of course superspans is not
necessarily the way to go everywhere.

They're very expensive

and they've got all sorts
of other challenges associated with them,

and we tend to build multispan

when we're crossing
a wide estuary or a sea crossing.

But of course if that sea crossing
were somewhere like Gibraltar,

or in this case, the Red Sea,

we would indeed be building
multiple superlong spans

and that would be
something spectacular, wouldn't it?

I don't think I'm going to see
that one finished in my lifetime,

but it will certainly be worth waiting for
for some of you guys.

Well, I want to tell you about something
which I think is really exciting.

This is a multispan suspension bridge
across very deep water in Norway,

and we're working on this at the moment.

The deep water means that foundations
are prohibitively expensive.

So this bridge floats.

This is a floating,
multispan suspension bridge.

We've had floating bridges before,
but nothing like this.

It stands on floating pontoons

which are tethered to the seabed
and held down --

so, pulled down
against those buoyancy forces,

and in order to make it stable,

the tops of the towers
have to be tied together,

otherwise the whole thing
would just wobble around

and nobody will want to go on that.

But I'm really excited about this

because if you think
about the places around the world

where the water is so deep

that nobody has given a second thought
to the possibility of a bridge

or any kind of crossing,

this now opens up that possibility.

So this one's being done
by the Norwegian Roads Administration,

but I'm really excited to know

where else will this technology
enable development --

that growing together,

that building of community.

Now, what about concrete?

Concrete gets a pretty bad name sometimes,

but in the hands of people
like Rudy Ricciotti here,

look what you can do with it.

This is what we call ultra-high
performance fiber-reinforced concrete.

It's a bit of a mouthful.

Us engineers love those kinds of words.

(Laughter)

But what you do with this --

this is really superstrong,
and it's really durable,

and you can get this fantastic
sculptural quality.

Who said concrete bridges are dull?

We could talk about all sorts
of other new technologies and things

which are going on,

robots and 3-D printing
and AI and all of that,

but I want to take you back to something
which I alluded to earlier on.

Our bridges need to be functional, yes.

They need to be safe -- absolutely.

They need to be serviceable and durable.

But I passionately believe
they need to be elegant;

they need to be beautiful.

Our bridges are designed for a long time.

We tend to design for 100 years plus.

They're going to be there
for an awfully long time.

Nobody is going to remember the cost.

Nobody will remember
whether it overran a few months.

But if it's ugly or just dull,

it will always be ugly or dull.

(Laughter)

Bridges --

beauty enriches life.

Doesn't it?

It enhances our well-being.

Ugliness and mediocrity
does exactly the opposite.

And if we go on building
mediocre, ugly environments --

and I believe we're becoming
numb to that stuff --

if we go on doing that,

it's something like
a large-scale vandalism,

which is completely unacceptable.

(Applause)

This is a bridge in Lyon in France,

which was procured
through a design competition.

And I think we need to start talking
to those people who procure our bridges

and our structures,

because it's the procurement
which is often the key.

Design competitions
is one way to get good design,

but it's not the only one.

There's an awful lot
of procurement going on

that is absolutely prejudiced
against good design.

So yes, technology happens
a bit slowly sometimes in my world.

But I'm really excited
about what we can do with it.

Whether it's saving lives in rural Africa

or stretching the boundaries
of long-span technology

or just crossing the road next-door,

I hope we continue to build
elegant and beautiful stuff

that save lives and build communities.

Thank you.

(Applause)