Nova (1974–…): Season 48, Episode 11 - High-Risk High-Rise - full transcript
The science behind the risks of sky-high buildings, from structural limits to threats presented by wind, fire and earthquakes.
♪ ♪
♪ ♪
NARRATOR:
Today, more people are
living or working
in tall buildings
than ever before.
Population surges
in some regions,
economic prosperity in others,
are seeding the world
with tall buildings.
The real driver
for tall buildings
are the twin effects of
population growth
and urbanization.
NARRATOR:
But if the sky is the next
frontier for human life,
this raises a crucial question...
Are tall buildings
as safe as they could be?
And if not...
MAN:
Oh, my God.
NARRATOR:
How can we make them safer?
ENGINEER:
Right there.
NARRATOR:
There have been horrific
blazes in tall buildings
here and across the globe.
(explosion)
CHARLES JENNINGS:
When there's a fire,
one thing
that unites rich and poor,
they all die the same way.
(person screaming)
NARRATOR: Outside the U.S.,
earthquakes have
felled tall buildings
and killed indiscriminately.
Could cities like
San Francisco be next?
It's not if, it's when.
Shut off the gas,
shut off the electricity!
NARRATOR:
And some tall
buildings may go down.
That is what our
modeling tells us.
NARRATOR:
Can the latest generation
of tall buildings
meet these and other challenges
even as we build more of them?
CAROL WILLIS:
Skyscrapers today,
especially the tallest ones,
are very safe buildings.
NARRATOR:
But mistakes can still happen.
REPORTER:
Downtown high rise
sunk 16 inches.
NARRATOR:
And beyond making them safer,
is anyone making
them more appealing?
RAFAEL PELLI:
We want a different model
for organizing office buildings
with constant movement,
flow, and interaction.
It's just an amazing building.
♪ ♪
NARRATOR:
Few structures in the modern era
have had a greater impact
on the way we live or work.
And now, the question is,
can we make them even better?
"High Risk, High Rise"...
Right now on "NOVA."
♪ ♪
♪ ♪
Major funding for NOVA
is provided by the following.
NARRATOR:
Skyscrapers are among
humankind's most awesome
and extravagant achievements.
Engineering marvels
so tall and strong,
their very existence seems
to defy the laws of physics.
♪ ♪
The most daring skyscrapers
are essentially showpieces,
designed to attract
elite businesses
or wealthy homeowners.
Architecturally,
these tallest of the tall
exhibit the extreme
of what is possible.
But it is tall buildings
of all sizes that are today
filling many
of the world's cities,
and for good reason.
WOODS:
United Nations statistics show
that there are almost
200,000 people
urbanizing
on this planet every day.
And the only true way
to address it
is going up in height.
If you build taller,
you could pack more people
onto the same address.
NARRATOR:
Without tall buildings,
it would've been virtually
impossible to accommodate
urban population surges
in Asia and the Middle East.
PELLI:
You see in countries
like China and India
cities which have gone
from two million to 20 million
in one generation.
And so that certainly
generates a need for
buildings to house that density.
NARRATOR:
In the U.S.,
the pressure to build tall
is centered in cities
benefitting from the uptick
in the global economy.
But as most major cities
become crammed cheek to jowl
with tall buildings,
as we spend more of our lives
looking down on the world below,
will we begin to lose
our sense of place?
Of neighborhood?
Of community?
Or can tall buildings
begin to embrace
a more humanistic vision...
One that stresses
livability, interactivity,
and eco-responsibility?
Some designers are certainly
trying new ideas.
But as we build skyward
at a staggering rate,
there's a more basic question.
What have we learned
over the decades about
making tall buildings
as safe as they can be?
Can we ultimately trust
them with our lives?
Many American cities
are identified
by their iconic skylines.
And seeing new skyscrapers join
older ones seemed inevitable...
Right up to 9/11.
WILLIS:
After 9/11, most people said
this is the end
of the skyscraper,
that people will be too afraid
to live in them,
they'll be too afraid
to work in them.
Certainly many people
in the profession believe
that it'd be the death
of the tall building.
NARRATOR:
Even Bill Baker,
one of the world's foremost
tall building engineers,
had his doubts.
BAKER:
I thought that my
specialty was over,
that that was going to be
the end of tall buildings.
And then, quite remarkably,
soon thereafter
I was designing the world's
tallest building.
NARRATOR:
That building
is the Burj Khalifa in Dubai,
largest city in the
United Arab Emirates.
As the world's economy
began to rebound
after the financial
crisis of 2008,
the drive to build tall
in wealthy, urban centers
became a global trend.
WOOD:
Let's be clear on this,
there's been
an explosion of the number
of tall buildings around
the whole world being built.
NARRATOR:
Antony Wood heads the Council
on Tall Buildings
and Urban Habitat.
They showed tallest 20 in 2020,
which we did about
six years ago.
NARRATOR:
The organization charts
the rise in tall
building construction
and classifies the world's
tallest skyscrapers
in three categories.
There's "plain tall,"
up to about 1,000 feet,
or the size of New York's
Chrysler building;
"super tall,"
buildings over 1,000 feet;
and "mega tall,"
buildings over 2,000 feet,
or the size of the Makkah
Saudi Arabia clock tower.
As of 2020, there are only
two other mega talls...
The Shanghai Tower
at 2,073 feet,
and Dubai's Burj Khalifa,
at a staggering 2,700 feet.
That's more than twice as tall
as the Empire State Building.
WOODS:
I often get asked,
what are the biggest barriers
to how tall we can go?
And there's only one barrier,
and it's not technological,
it's financial.
It's who is gonna pay for it?
NARRATOR:
Some of the very tallest
buildings are designed
to bring tourists and prestige
to the cities they tower over.
But most building owners
aren't seeking height records,
they're seeking profits.
WILLIS:
To build the tallest building
in the world is not necessarily
to build the world's
most profitable building.
♪ ♪
NARRATOR:
That tall buildings
can be good investments,
is evidenced by
the number of cranes
sprouting up
in many major cities.
Their proliferation
also seems to indicate
that few people question
tall building safety,
or think twice about
living or working in one.
And for the most part,
tall buildings do have
stellar safety records,
but engineers and designers
are not infallible.
And some threats
can be unpredictable
and difficult to overcome.
(sirens blaring distantly)
Like fires.
Although most fires
occur in homes
and low-rise apartment
buildings,
frightening skyscraper
fires do happen,
as recent blazes
in China and Dubai
so clearly demonstrate.
In the U.S...
NEWSCASTER:
Fire started on the 12th floor
of the Interstate Bank Tower.
NARRATOR:
huge, multi-story
skyscraper blazes
are fairly rare.
But fires in mid-size buildings,
especially older
apartment-type blocks,
lacking basic fire
safety requirements,
are an ongoing concern.
An egregious recent example
of this problem occurred
overseas at the 24-story
Grenfell Tower in London.
(flames roaring)
The fire started in a kitchen,
where flames shot out a window,
igniting the building's
highly flammable
exterior wall
covering, or cladding.
Because of this danger,
flammable cladding
is prohibited in the U.S.,
but not, at the time,
in the U.K.
(sirens blaring)
Although cladding was
the main culprit,
the building also
lacked fire alarms
and a system to communicate
with the residents.
There were no sprinklers,
and just one exit stairway
that would eventually
fill with smoke.
As a result,
more than 70 people died,
making Grenfell
everyone's nightmare
of a tall building blaze.
♪ ♪
And unfortunately,
Grenfell-like safety flaws
exist in many U.S. cities,
particularly with
older apartment buildings,
like these in New York.
JOHN ESPOSITO:
We have a significant number
of housing projects
and buildings that are,
you know, 20 stories.
The code doesn't
require alarm systems,
the code doesn't require
sprinkler systems.
NARRATOR:
As with Grenfell,
the main deficiency in these
buildings is communications.
There's no public
address system, necessarily,
in the older existing buildings.
The only information they
can gather is looking up
for signs of smoke or flame.
And the occupants are left,
really, to their own devices
in terms of figuring out
what to do.
NARRATOR:
At Grenfell, this proved fatal
because many residents
followed the one instruction
they were given...
Stay put unless
instructed to leave.
In Grenfell, the guidance
that had been given
to residents of those buildings,
across the city,
was that you should stay
in place in a high-rise
residential fire, unless
you're immediately threatened.
NARRATOR:
But with no
communication system,
by the time leaving
became obvious,
for many it was too late.
This shelter-in-place guidance
is widely recommended
in the US as well.
ESPOSITO:
It seems counterintuitive
to stay in the building,
but you really are safer
if there's no fire
in your apartment,
'cause to leave and go
through the hallway
where there's gonna be smoke,
you're really exposing
yourself to danger.
JENNINGS:
The problem is,
people don't have
the expertise to evaluate
if there's smoke in their
hallway, is it heavy smoke?
Is it incidental to a fire?
They don't know,
so they are left
and immediately put into
a position of great anxiety.
And so, sooner or later,
some of them are gonna say,
"The heck with this, I'm gonna
try to get out of here."
NARRATOR:
And once in an exit stairway,
there could be even
greater danger.
JENNINGS:
What may appear to be a clear
stairwell on your floor,
may be contaminated with
smoke at a lower level.
People die in stairwells
trying to evacuate fires.
NARRATOR:
And many stairwells are narrow,
creating a dangerous bottleneck
for firefighters trying
to reach and control the blaze.
ESPOSITO:
We do have some
narrow stairways,
so either the people coming
down are gonna get held up,
or the firefighters going up
are gonna be slowed down.
NARRATOR:
Adding to this challenge
is how to get elderly or
disabled people down to safety.
ESPOSITO:
That becomes a problem,
if we have to take them down,
that's very intensive to move
somebody down the stairs.
And that's why our
best advice is
we want them to shelter in
place in their apartments.
NARRATOR:
Elevators could help,
but they can spread
fire or smoke,
and people can
get trapped inside,
so occupants are generally
restricted from using them.
A new generation
of fire-safe elevators
is starting to come online.
And these would certainly
help the aged or disabled.
They are housed in special
closed-door areas
pressurized to keep smoke out,
and there are drains
to keep water out.
They hold great promise.
(elevator chimes)
But there are so few
operating in the U.S.,
they have yet to be
fully fire tested.
ESPOSITO:
So, we don't know
the effectiveness
of those elevators
until they're actually used
in an emergency situation.
NARRATOR:
But there is a proven technology
that can avoid the need
for elevators by keeping
most fires from spreading.
That sprinklers have
the capacity to save lives
and buildings has been
proven time and again,
even at high-profile addresses.
A recent fire in Trump Tower,
New York,
built before sprinklers
became mandatory there,
resulted in the death
of a resident
and several
injured firefighters.
Sprinklers could've
prevented these casualties.
So why don't more
buildings have them?
JENNINGS:
The reason we don't have
sprinklers
in all tall buildings
is because the real estate
industry doesn't want
to spend the money
to put them in.
♪ ♪
NARRATOR:
The good news is
sprinklers are now mandatory
in most recently built
tall buildings.
And these have helped keep fires
and fire-related fatalities
on the decline.
But fires aren't
the only threats
to tall buildings
and their occupants.
Despite a mostly excellent
safety record...
MAN:
Everyone get back, get back.
NARRATOR:
engineering or construction
mistakes do happen.
MAN:
Oh, my God.
NARRATOR:
And when they do,
the results can be terrifying.
(people shouting)
This is San Francisco's
Millennium Tower,
a 58-story luxury condominium
that became a much
sought-after address
when it first opened
about a decade ago.
But in 2016, the news broke
that it was sinking and tilting.
REPORTER:
This 58-story downtown high rise
unexpectedly sunk 16 inches...
This golf ball
rolling down the uneven floor,
toward the direction
the building is leaning.
NARRATOR:
The revelation came
as a shock to condo owners.
HOWARD DICKSTEIN:
The building was still settling
vertically and horizontally,
and it was unclear
when that would stop.
Some people, I think, just left.
There was a concern
that the building
was about to topple over.
NARRATOR:
And in a city with
a history of earthquakes,
this was especially worrisome.
Today, the so-called "Leaning
Tower of San Francisco"
has sunk about 18 inches
on its northwest corner.
When the news broke,
Ron Hamburger,
a veteran structural engineer,
was hired by the building's
developers to find out
why the Millennium was sinking
and if it could be stopped.
RONALD HAMBURGER:
The Millennium Tower
basically is sinking
because it's a taller building
and a heavier building
than most of the other
buildings that have been
constructed in San Francisco.
It imposed greater weight
on these sand layer
that exist about
80 feet below the sidewalk.
♪ ♪
NARRATOR:
Like many cities
bordering water,
San Francisco rests
atop ancient layers
of soft sand and clay.
Whereas in New York,
a hard bedrock-type layer
called schist lies close
to the surface in many places,
so anchoring tall buildings here
is ideal.
But in San Francisco,
bedrock lies deep
below the surface.
And reaching it
with supporting piles
is difficult and expensive,
so tall buildings are often
placed on concrete mats with
piles that don't go to bedrock.
But the piles do transmit
the building's weight
through the weak
upper soil layers
to deeper, firmer layers
and the system normally
works quite well.
But for some reason,
the Millennium's extreme weight
pushed down with enough force
to compress the soil
under some of the piles,
causing the building
to settle unevenly.
The tower's owners claim a
neighboring construction project
called the Trans Bay Terminal
contributed to the uneven
settling by dewatering
the soil under the Millennium.
HAMBURGER:
Dewatering is done in order
to have a dry excavation
so that you can actually
build what you want to build.
♪ ♪
NARRATOR:
Whether the fault was
dewatering or poor engineering,
the sinking has slowed
to about a quarter inch a year
and could stop entirely.
Regardless, Ron Hamburger
is now heading up
a multi-million dollar
foundation fix that will
shore up the building
by extending the concrete
foundation mat
on the sinking corner
and adding additional
supporting piles
that go all the way to bedrock.
It is hoped that the fix
will allay public fears
about the building's stability.
♪ ♪
The Millennium saga
stands out in part
because serious mistakes in
high-profile buildings are rare.
Their engineers have
consistently produced structures
that stand straight,
can support their own weight,
and are capable of
resisting a constant threat
to any tall building...
(wind whooshing)
...the force of the wind.
Although no tall buildings of
note have ever been blown over,
another famous mistake almost
brought that frightening
prospect to New York.
When it was completed in 1977,
the now modest 59-story
Citicorp Center
was the ninth tallest
building in the world.
With its aluminum
and glass exterior,
Citicorp was among
a new generation
of lighter skyscrapers
that avoided
the expense of heavier,
masonry-clad facades,
like the Empire State Building.
But lighter buildings
can sway in the wind.
And when they do,
people inside often complain
about feeling motion sickness.
To counter the sway at Citicorp,
the building's engineer,
William LeMessurier,
had New York's first
tuned mass damper
installed near the top
of the building.
It is basically a 400-ton
block of concrete
that slides on a bed of oil.
When wind pushes against
the outside of the building,
the giant block will slide
in the direction of the sway.
Large piston-like devices
restrain the block,
absorbing the energy
and slowing its movement.
This makes the block lag
behind the moving building,
which, in effect,
counters the sway
and keeps the building steady.
Without dampers,
tall buildings like these
beanstalk-thin luxury condos
could be fairly
uncomfortable to live in.
WILLIS:
The building can't have
the reputation of having
the, kind of, proverbial
waves in the toilet,
where you can feel
the building moving,
because people then
feel uncomfortable.
They won't buy an apartment
where they feel vulnerable.
♪ ♪
NARRATOR:
Back at Citicorp,
the resourceful LeMessurier
solved another problem.
He raised the building
above the street
and placed its four major
support columns under its sides,
rather than at the corners,
as is typical.
He did this to
accommodate a church.
Not this modern one,
but an older one that
had become dilapidated.
So the church struck a deal.
They would get a new
building in exchange
for letting Citicorp
rise above it.
But some engineers were
skeptical of its radical design.
LEMESSURIER:
I got a telephone call from
a student who was assigned
to write a paper on this
building by his professor.
Professor had said there
was something funny
about this building 'cause
the columns were not
in the corners
like they ought to be.
NARRATOR:
Under the facade,
LeMessurier placed a series
of V-shaped steel braces
that channel wind
and gravity forces
diagonally to the columns.
He was confident his
radical design would work,
because computer models
and wind tunnel tests
showed that it would.
Engineers wind test
building models
to see, among other things,
if their shape produces
a dangerous phenomenon
called a vortex.
The model is bolted to a base
that contains censors underneath
and when the fans come on...
(fans click)
the censors measure
the model's response
to the air flowing around it.
BAKER:
One of the issues
with tall buildings
is called vortex shedding.
As wind goes past an object,
it'll go first to one side,
and then the other.
And when it does this,
it'll create little swirls
in the air.
NARRATOR:
Vortex shedding creates
whirlpools that lower
the air pressure
behind a building.
Now, when the wind
hits the building,
it can push it and make
it sway rhythmically,
like a child on a swing.
BAKER:
At first they kick
their feet just randomly
and the swing goes nowhere.
You have to teach them that
they have to kick their feet
at the natural
harmonics of the swing.
So in tall buildings
it's the same thing.
NARRATOR:
Buildings that gain
momentum like a swing
put dangerous pressure
on structural connections.
But changing
the building's shape
can disrupt wind forces
and stop the build-up
of vortices.
Sometimes a very small change
can be the difference
between a building being
successful or not successful.
♪ ♪
NARRATOR:
Citicorp passed its wind tests,
but about a year after
it was occupied,
LeMessurier got
a disturbing message.
One of his students
in one of his classes,
as his thesis,
comes up with a fault
in the building
under certain
circumstances of wind.
He tells Bill,
"You know, my numbers say
that the building
could fall over."
And LeMessurier says
to the student,
"Nice story, sonny,
but, uh, you know,
go check your numbers again."
♪ ♪
NARRATOR:
But LeMessurier began to wonder
if the student might be correct.
LEMESSURIER:
I pursued this and, uh,
found out...
some very awesome
and frightening facts.
NARRATOR:
He discovered that winds
striking the building
diagonally, rather than face-on,
could increase the stress
on some of the V-braces
by 40% or more.
Then he realized that
during construction,
his office had permitted
contractors to bolt
the braces together,
instead of welding them,
as he had originally specified.
He calculated that winds
in excess of 70 miles per hour,
striking the corners
of the building,
could sever
the bolted connections.
LEMESSURIER:
I came to the conclusion...
(thunder rumbling)
that a storm
which had a probability
of occurring once in 16 years,
would cause the building
to fail and collapse.
I can't live with that.
NARRATOR:
LeMessurier recommended
welding six-foot-long
steel plates on either side
of the bolted connections
to strengthen them.
This would certainly
solve the problem,
but would take weeks to finish.
So as workmen began
the arduous task...
Folks, get on
the sidewalk, please.
NARRATOR:
the city drew up emergency
evacuation plans.
HELLER:
Not only would they
evacuate the building,
but they would evacuate
the ten-square block area
around the building just in case
the building falls over...
Can you imagine?
♪ ♪
NARRATOR:
And as fate would have it,
in late August 1978,
Hurricane Ella
began heading for New York.
As its winds intensified
to over 100 miles per hour...
(thunder rumbles)
...the disaster LeMessurier
feared loomed closer.
And there was no way repairs
could be completed in time.
But instead of tracking
toward the city,
Ella veered out to sea.
HELLER:
It all, ultimately, worked out,
but it was a very
dangerous situation.
NARRATOR:
Despite the travails
of Citicorp,
tall buildings have proven
time and again that they can
successfully withstand the most
extreme weather conditions.
And they are also
engineered to withstand
another major force of nature.
(people screaming)
But when it comes
to earthquakes,
the prospects that some tall
buildings may not survive
is a very real
probability indeed.
MAN:
Here comes an earthquake!
♪ ♪
NARRATOR:
It's been over 30 years
since the 1989 Loma Prieta
earthquake in San Francisco.
(sirens blaring)
OFFICER:
Shut off the gas,
shut off electricity!
NARRATOR:
The quake caused major
damage to houses
and infrastructure near the Bay.
But the rest of the city,
including tall
buildings downtown,
escaped relatively unscathed.
That's because
the quake originated
60 miles from the city,
and more importantly,
was not another "big one."
In 1906,
a giant earthquake
on the San Andreas fault,
and devastating
fires that ensued,
basically destroyed the city.
The U.S. Geological
Survey now says
there's a 70% chance
another powerful quake
will strike the region sometime
within the next 30 years.
DAVID SCHWARTZ:
The earthquake could occur now,
it could occur in 20 years,
but it's not gonna
wait a hundred years.
NARRATOR:
There are seven major
faults in the Bay area,
with the most worrisome
being San Andreas
and the Hayward.
♪ ♪
SCHWARTZ:
We're in a parking lot
south of downtown
Hayward, California.
You can see doughnuts,
tire tracks
that kids have made.
NARRATOR:
David Schwartz, a recently
retired USGS seismologist,
has studied the Hayward
fault for years.
And as you're crossing
the parking lot,
you look down and you see
the asphalt
is sort of disturbed.
There's a little
step across it here.
There's a whole series
of cracks here.
This is the Hayward fault.
And the fault is creeping.
It's actually moving
slowly all the time.
And it produces
this type of feature.
When you come to here,
these older buildings,
this separation
expresses creep along the fault.
This building
is moving towards me,
this building is moving away.
When the fault finally decides
to move in its big earthquake,
I really wouldn't want
to be standing against
one of these buildings.
In the end,
the fault always wins.
NARRATOR:
The fault travels northwest
from the town of Hayward
through Oakland
and the Berkeley Hills,
where millions of people
live on or right next to it.
And the force of a big quake
could readily
travel across the Bay,
smack into downtown
San Francisco,
bringing with it the potential
for a major disaster.
And when this
earthquake strikes,
it's pretty clear
what types of buildings
would likely
suffer the most damage.
HAMBURGER:
The worst-performing
buildings are what we call
unreinforced masonry buildings.
These are typically either
common red brick buildings,
or sometimes stone buildings.
The masonry is quite strong,
but it's also very brittle
and under the effects
of severe ground shaking,
the masonry will
crack and crumble
and it's very common, actually,
for the walls to fall away,
creating not only a hazard
for people in the building,
but also people
outside the building.
NARRATOR:
Because masonry buildings
could be vulnerable to collapse,
it was deemed safer
to construct tall buildings
with steel frames.
LUCY JONES:
Steel seemed like
the perfect choice,
because if you push on steel
way beyond its strength,
the steel bends
instead of breaking,
and therefore you wouldn't
collapse the building.
NARRATOR:
And by the 1960s,
the preferred method
for joining the pieces
in a steel frame was
to weld them together.
What engineers call
welded steel moment frames
were deemed one
of the safest designs
for tall buildings
in California.
Oh, God, no!
NARRATOR:
That thinking would
get a severe jolt
after the 1994
Northridge earthquake.
REPORTER:
As you can see,
extensive damage here.
NARRATOR:
The 6.7 temblor struck
densely populated
suburban Los Angeles,
causing scores of deaths
and property losses
in the billions.
It also revealed a serious flaw
in supposedly safer
moment frame buildings.
HAMBURGER:
When the Northridge
earthquake occurred,
a number of these
buildings experienced
unanticipated fractures,
cracking of the steel
connections between
the beams and the columns.
NARRATOR:
Outside, most of the
buildings looked stable.
But inside, inspectors
found weld failures
and cracks in the steel.
Now the question was,
what could happen to these
steel-frame buildings
in an even stronger earthquake?
Swaminathan Krishnan
is a structural engineer
specializing in computer
simulations.
♪ ♪
After Northridge,
he modeled a specific
moment frame building
damaged in that quake
and subjected it to the force
of a stronger
San Andreas earthquake.
KRISHNAN:
In particular, we wanted to see
whether this building
would remain standing
or would it collapse.
NARRATOR:
As the big quake
begins to spread,
his program assesses its effect
on the building's frame.
This building does
fine for awhile,
you can see, you know,
that it's going back and forth
and it's coming back
and staying vertical,
but at some point,
there are several connections
that break inside
of the building
and the building
comes crashing down.
NARRATOR:
Although improved materials
and welding techniques
have made newer steel buildings
far less susceptible
to failures,
older moment frames,
including the famous
Transamerica Pyramid,
and other buildings
throughout California,
remain unfixed
and could even have become
weakened by previous quakes.
HAMBURGER:
So if a building goes
through an earthquake,
even if it is
apparently undamaged,
it's used up some
of its original
earthquake-resistant capability.
♪ ♪
KRISHNAN:
The problem is
right now there are
hundreds of tall
buildings of that kind.
They've not been opened up,
and they have not
been retrofitted.
NARRATOR:
And if a big earthquake comes...
KRISHNAN:
We are going to see
building collapses.
That is what our
modeling tells us.
NARRATOR:
A few moment framed buildings
have been retrofitted,
but a big deterrent is cost.
To remove interior walls
and ceilings
to inspect connections,
much less tear things apart
and fix those connections,
can be extremely expensive,
and may just be unnecessary.
(objects clattering)
In 1985, a powerful earthquake
struck Mexico City,
where taller buildings saw
relatively little damage,
but many mid-size,
ten-to 20-story buildings,
were tremendously damaged
or totally destroyed.
That's because
their particular height
resonated with the shockwaves
from this earthquake.
♪ ♪
HAMBURGER:
Resonance is a phenomenon
that occurs when
the natural frequency
of a structure
closely matches the natural
frequency of an exciting force.
NARRATOR:
Earthquakes send out vibrations
of various wavelengths
or frequencies.
When they reach
a cluster of buildings,
those that suffer damage
are often the ones
whose height best matches
those particular frequencies.
KRISHNAN:
When the ground
shaking has
in it high frequencies,
meaning the shaking is jarring...
it's going to go do this,
boom, boom, boom, boom.
That kind of shaking
will selectively effect
short buildings.
NARRATOR:
Whereas longer wavelengths
can cause tall buildings
to sway rhythmically.
And in extreme cases,
can collapse them.
Other factors,
such as soil conditions
or inadequate
construction materials,
can also make tall
buildings vulnerable.
But there's no factor
more important
to an earthquake's
destructive potential
than location.
JONES:
So, absolutely,
your distance from the fault
is one of the most
important things
about what shaking you receive.
NARRATOR:
In 1995, one of the most
devastating earthquakes
in the modern era
struck Kobe, Japan,
along a fault that
lay close to the city.
6,000 people died,
tens of thousands
were left homeless,
hundreds of thousands
of buildings of all sizes
were damaged or destroyed.
JONES:
There were collapsed buildings
and there were collapse
of steel-frame buildings from
the same problem with welds
that we saw in the
Northridge earthquake.
NARRATOR:
Kobe's proximity to a fault,
as well as its
large concentration
of people and buildings,
raises an obvious question.
Could this be the fate
that awaits cities
like San Francisco?
(trolley bell chimes)
IBRAHIM ALMUFTI:
I think about risk for a living.
NARRATOR:
Ibrahim Almufti...
Ibbi to his friends...
is a structural engineer who's
worried about his city's fate.
You know, I walk to work
through downtown every day,
looking up at the buildings
and I know too much, in a sense.
It is definitely possible that
a few buildings may come down
in a big earthquake.
NARRATOR:
Ibbi's goal is to engineer
a building that will be among
the safest ever built,
even reaching beyond
standard building codes.
ALMUFTI:
The building code
objective for many years has
always been life safety,
to protect it against
full collapse.
NARRATOR:
Recent earthquakes
in Christchurch, New Zealand,
demonstrate the flaw
in life safety codes.
Many heavily impacted
buildings did not collapse,
and therefore saved lives,
but most were
so severely damaged,
they could not be reoccupied
and had to be torn down,
which has depopulated the city
and derailed it economically.
ALMUFTI:
And actually, Christchurch,
you could argue,
is still recovering
from that earthquake
ten years ago.
And so, I always
ask the question,
are we as engineers bringing
our knowledge to bear
on designing these buildings
to be more resilient
and allowing these
cities to recover
more quickly
after big earthquakes?
NARRATOR:
San Francisco city
administrator Naomi Kelly
is hoping to make
tall building resiliency
one of the city's
top priorities.
KELLY:
Downtown San Francisco
is our economic engine
for the city.
We have now 62 tall buildings.
♪ ♪
Many more people
are living downtown.
And so we're now looking
at not just the building codes
where the building's
good enough for you
to get out the building,
but how do we make our buildings
more resilient
and how fast can
we reoccupy those buildings.
Most folks want to not only
just survive the earthquake,
but they want to get
back into their home,
or office building
as soon as possible.
(telephone ringing)
NARRATOR:
And that's exactly what Ibbi
and the engineering team
for 181 Fremont set out to do.
They're triangulating, right?
All of those forces...
NARRATOR:
Located near the Millennium
and Salesforce Towers,
181 Fremont is 56 stories tall,
slim, and angular.
The visionary structure owes
its design to Jeffrey Heller.
As a young architect,
Heller had gone
to Armenia in 1988,
where he saw first-hand
the devastation inflicted
by a huge earthquake.
HELLER:
What really got me was the level
of desolation and devastation.
What we saw was,
in the town of Spitak,
which was the epicenter
of the earthquake.
A city of 25,000, gone.
Nothing left.
♪ ♪
NARRATOR:
Over the years,
Heller designed several
earthquake-resistant buildings,
but 181 was, for him,
the commission of a lifetime.
The building had to be great,
or at least the best I could do.
♪ ♪
181 is 800 feet tall,
two thirds of it is office,
about 45 floors,
and then the top one third
is residential.
NARRATOR:
The views from inside
the upper floor apartments
are nothing less
than spectacular.
As are the appointments
in its luxurious penthouses.
Architecturally, the building's
most defining feature
is its striking exoskeleton,
with long braces that help
support the entire building,
thereby opening up
interior spaces.
HELLER:
It leaves the interior
of the building completely free,
up to the core,
of any vertical support at all.
NARRATOR:
The exoskeleton is key
to the building's ability
to manage earthquake
and wind forces.
ALMUFTI:
So if you look at the building
from the outside,
you'll see these diagonals that
are connected to the columns,
and at the corner connection,
we've introduced dampers
on the ends of the braces
that basically act
as giant shock absorbers.
NARRATOR:
As the building flexes,
the middle brace
stretches or shortens.
When it does, secondary braces
activate the dampers
that compress
and stretch like springs,
absorbing energy
and channeling the force
of these movements
to the main columns.
At the base of the columns,
we see they can lift up
incrementally,
so in an earthquake,
the building acts
as Ibbi notes, like
a skier with ski poles.
ALMUFTI:
And so you've got these columns
that are acting like ski poles,
in a sense,
and some lift up
and you've got more pressure
on this one
to stabilize yourself,
and as you go this way,
same thing.
NARRATOR:
The overall design is so unique,
it earned 181 a first.
ALMUFTI:
We actually received the world's
first
REDI gold rating,
which means that we've
designed it in a certain way
such that building occupants can
get back and use the building
almost immediately
after a very big shake.
♪ ♪
NARRATOR:
This is something some
seismic experts
have been advocating for.
JONES:
We are trying to change
the building code
to say,
"Life safety is not enough."
We need functional recovery,
meaning I can recover
the function of the building
in a reasonable amount of time.
NARRATOR:
But resiliency features
like those on 181
can be expensive,
so until they are
mandated in building codes,
getting developers
to incorporate them
may be a challenge.
HAMBURGER:
It would be wonderful
if American building owners
and developers wanted
to provide society
buildings that
were more resilient,
but for the present,
it seems it will take
government to force that...
or an earthquake.
If we had a major earthquake
and it caused
catastrophic damage,
damage similar to what
New Orleans saw in Katrina,
that might be enough
to change society's attitudes
and foster an era when
we do indeed develop
more resilient construction.
♪ ♪
NARRATOR:
If we have the will
to apply lessons learned,
tall buildings will
continue to become better
at withstanding earthquakes,
wind, or fire.
And this is certainly critical,
since going up is just
about the only solution
to urban population density.
But beside becoming safer,
what else could
tall buildings become?
What other considerations
might go into
their planning and design?
For decades,
visionary thinkers have proposed
making tall buildings more like
eco-friendly vertical villages.
Although some of these designs
are, well, a little bizarre,
they generally
promote light-filled,
open, communal spaces
that can make buildings
more people-friendly.
And today, some designers
are reaching for that vision
with a less fantastic,
but still vibrantly creative
tall building environment.
This bustling atrium is office
central for Bloomberg LP,
the global business, financial,
and communications giant.
The first thing you notice
in this building
is all the stairs...
and people constantly
on the move.
The elevators stop
on every floor,
only for disabled people.
For everyone else...
MICHAEL BARRY:
The elevators,
in fact, only stop on
nine out of the 25 floors
that we occupy.
♪ ♪
NARRATOR:
The stair-stepping helps
promote employee fitness
and is just one of
the out-of-the-box concepts
in this building's
overall design.
The offices are in the lower
half of a tall residential tower
and in a smaller building
connected to the tower
by a dramatically curved,
multi-use space.
Its lead architect
is Rafael Pelli.
PELLI:
There's a theatrical quality
that I hadn't anticipated
as much as, as it truly is.
NARRATOR:
In addition to this active,
light-filled atrium,
the rest of the offices
are also atypical.
PELLI:
The company wanted
a different model
for organizing office
buildings than the traditional,
historical one where you stack
a bunch of very isolated
units on many, many floors,
making a very
siloed environment.
♪ ♪
Instead of that,
they wanted fewer floors,
very big floors, all connected
around a central space.
NARRATOR:
That central space is called,
"the pantry,"
for obvious reasons.
It looks more like a public
space than a corporate office.
The openness and informality
clearly encourages
employees to meet
and exchange ideas.
KAREN TOULON:
You'll be grabbing a cup
of coffee
and you'll see ten people that
you need to catch up with.
And it's a great way
of getting work done.
♪ ♪
BETH MAZZEO:
"Oh I haven't seen you in
so long, we need to catch up.
"I got something
I need to tell ya.
"And, by the way do you
have five minutes now,
'cause we'll grab a coffee
stand around one of the pods."
PELLI:
We wanted the sixth floor
central space to be
the beating heart of what
Bloomberg wanted to be.
NARRATOR:
There are no
closed-door offices here.
Meeting rooms have glass walls.
PELLI:
So it was all done
to be transparent,
everybody could
see what's going on.
NARRATOR:
As part of what the company
calls its Fitwel program,
beside all the stairs,
there are several outdoor decks
where people can get fresh air.
And keeping with its green
buildings initiative...
near JFK Airport in Queens,
the company has
financed a solar array
that generates over
a million and a half kilowatts
of sustainable energy a year.
♪ ♪
That's about five percent
of its power use.
Many of the concepts,
like encouraging bike riding,
as well as the free snacks,
and open interior spaces,
are not new.
They're borrowed from Silicon
Valley companies like Google.
But these companies
are in low-rise buildings,
in roomy, open spaces,
whereas incorporating
these design considerations
in a tall building environment
breaks the mold on how these
buildings can be reimagined.
SIMMONS:
The energy,
the environment,
it's just an amazing building.
♪ ♪
NARRATOR:
As more and more skyscrapers...
office and residential...
come to dominate our cities,
ultimately what will
this mean for our future?
WILLIS:
I think the skyscraper makes
sense in the future of the city
because it does
use land efficiently
and that's a more sustainable
way to live on the land.
It's a smarter way
to build a future city
that consumes less energy,
that accommodates
the lifestyle amenities
for many more people than
if we have to spread out.
WOOD:
Tall buildings are
a huge part of the answer
to the challenges
that face us today...
social, economic,
climate change,
urbanization,
population growth...
But they are only
several baby steps
along the path
they need to tread
to truly deliver
on that potential.
The buildings need
to do the very best
that they can do if we want to
carry on living on this planet.
♪ ♪
ALOK PATEL:
Discover the science
behind the news
with the "NOVA Now" podcast.
or wherever you find your
favorite podcasts.
ANNOUNCER:
To order this program on DVD,
visit ShopPBS
or call 1-800-PLAY-PBS.
Episodes of "NOVA" are available
with Passport.
"NOVA" is also available on
Amazon Prime Video.
♪ ♪
♪ ♪
♪ ♪
NARRATOR:
Today, more people are
living or working
in tall buildings
than ever before.
Population surges
in some regions,
economic prosperity in others,
are seeding the world
with tall buildings.
The real driver
for tall buildings
are the twin effects of
population growth
and urbanization.
NARRATOR:
But if the sky is the next
frontier for human life,
this raises a crucial question...
Are tall buildings
as safe as they could be?
And if not...
MAN:
Oh, my God.
NARRATOR:
How can we make them safer?
ENGINEER:
Right there.
NARRATOR:
There have been horrific
blazes in tall buildings
here and across the globe.
(explosion)
CHARLES JENNINGS:
When there's a fire,
one thing
that unites rich and poor,
they all die the same way.
(person screaming)
NARRATOR: Outside the U.S.,
earthquakes have
felled tall buildings
and killed indiscriminately.
Could cities like
San Francisco be next?
It's not if, it's when.
Shut off the gas,
shut off the electricity!
NARRATOR:
And some tall
buildings may go down.
That is what our
modeling tells us.
NARRATOR:
Can the latest generation
of tall buildings
meet these and other challenges
even as we build more of them?
CAROL WILLIS:
Skyscrapers today,
especially the tallest ones,
are very safe buildings.
NARRATOR:
But mistakes can still happen.
REPORTER:
Downtown high rise
sunk 16 inches.
NARRATOR:
And beyond making them safer,
is anyone making
them more appealing?
RAFAEL PELLI:
We want a different model
for organizing office buildings
with constant movement,
flow, and interaction.
It's just an amazing building.
♪ ♪
NARRATOR:
Few structures in the modern era
have had a greater impact
on the way we live or work.
And now, the question is,
can we make them even better?
"High Risk, High Rise"...
Right now on "NOVA."
♪ ♪
♪ ♪
Major funding for NOVA
is provided by the following.
NARRATOR:
Skyscrapers are among
humankind's most awesome
and extravagant achievements.
Engineering marvels
so tall and strong,
their very existence seems
to defy the laws of physics.
♪ ♪
The most daring skyscrapers
are essentially showpieces,
designed to attract
elite businesses
or wealthy homeowners.
Architecturally,
these tallest of the tall
exhibit the extreme
of what is possible.
But it is tall buildings
of all sizes that are today
filling many
of the world's cities,
and for good reason.
WOODS:
United Nations statistics show
that there are almost
200,000 people
urbanizing
on this planet every day.
And the only true way
to address it
is going up in height.
If you build taller,
you could pack more people
onto the same address.
NARRATOR:
Without tall buildings,
it would've been virtually
impossible to accommodate
urban population surges
in Asia and the Middle East.
PELLI:
You see in countries
like China and India
cities which have gone
from two million to 20 million
in one generation.
And so that certainly
generates a need for
buildings to house that density.
NARRATOR:
In the U.S.,
the pressure to build tall
is centered in cities
benefitting from the uptick
in the global economy.
But as most major cities
become crammed cheek to jowl
with tall buildings,
as we spend more of our lives
looking down on the world below,
will we begin to lose
our sense of place?
Of neighborhood?
Of community?
Or can tall buildings
begin to embrace
a more humanistic vision...
One that stresses
livability, interactivity,
and eco-responsibility?
Some designers are certainly
trying new ideas.
But as we build skyward
at a staggering rate,
there's a more basic question.
What have we learned
over the decades about
making tall buildings
as safe as they can be?
Can we ultimately trust
them with our lives?
Many American cities
are identified
by their iconic skylines.
And seeing new skyscrapers join
older ones seemed inevitable...
Right up to 9/11.
WILLIS:
After 9/11, most people said
this is the end
of the skyscraper,
that people will be too afraid
to live in them,
they'll be too afraid
to work in them.
Certainly many people
in the profession believe
that it'd be the death
of the tall building.
NARRATOR:
Even Bill Baker,
one of the world's foremost
tall building engineers,
had his doubts.
BAKER:
I thought that my
specialty was over,
that that was going to be
the end of tall buildings.
And then, quite remarkably,
soon thereafter
I was designing the world's
tallest building.
NARRATOR:
That building
is the Burj Khalifa in Dubai,
largest city in the
United Arab Emirates.
As the world's economy
began to rebound
after the financial
crisis of 2008,
the drive to build tall
in wealthy, urban centers
became a global trend.
WOOD:
Let's be clear on this,
there's been
an explosion of the number
of tall buildings around
the whole world being built.
NARRATOR:
Antony Wood heads the Council
on Tall Buildings
and Urban Habitat.
They showed tallest 20 in 2020,
which we did about
six years ago.
NARRATOR:
The organization charts
the rise in tall
building construction
and classifies the world's
tallest skyscrapers
in three categories.
There's "plain tall,"
up to about 1,000 feet,
or the size of New York's
Chrysler building;
"super tall,"
buildings over 1,000 feet;
and "mega tall,"
buildings over 2,000 feet,
or the size of the Makkah
Saudi Arabia clock tower.
As of 2020, there are only
two other mega talls...
The Shanghai Tower
at 2,073 feet,
and Dubai's Burj Khalifa,
at a staggering 2,700 feet.
That's more than twice as tall
as the Empire State Building.
WOODS:
I often get asked,
what are the biggest barriers
to how tall we can go?
And there's only one barrier,
and it's not technological,
it's financial.
It's who is gonna pay for it?
NARRATOR:
Some of the very tallest
buildings are designed
to bring tourists and prestige
to the cities they tower over.
But most building owners
aren't seeking height records,
they're seeking profits.
WILLIS:
To build the tallest building
in the world is not necessarily
to build the world's
most profitable building.
♪ ♪
NARRATOR:
That tall buildings
can be good investments,
is evidenced by
the number of cranes
sprouting up
in many major cities.
Their proliferation
also seems to indicate
that few people question
tall building safety,
or think twice about
living or working in one.
And for the most part,
tall buildings do have
stellar safety records,
but engineers and designers
are not infallible.
And some threats
can be unpredictable
and difficult to overcome.
(sirens blaring distantly)
Like fires.
Although most fires
occur in homes
and low-rise apartment
buildings,
frightening skyscraper
fires do happen,
as recent blazes
in China and Dubai
so clearly demonstrate.
In the U.S...
NEWSCASTER:
Fire started on the 12th floor
of the Interstate Bank Tower.
NARRATOR:
huge, multi-story
skyscraper blazes
are fairly rare.
But fires in mid-size buildings,
especially older
apartment-type blocks,
lacking basic fire
safety requirements,
are an ongoing concern.
An egregious recent example
of this problem occurred
overseas at the 24-story
Grenfell Tower in London.
(flames roaring)
The fire started in a kitchen,
where flames shot out a window,
igniting the building's
highly flammable
exterior wall
covering, or cladding.
Because of this danger,
flammable cladding
is prohibited in the U.S.,
but not, at the time,
in the U.K.
(sirens blaring)
Although cladding was
the main culprit,
the building also
lacked fire alarms
and a system to communicate
with the residents.
There were no sprinklers,
and just one exit stairway
that would eventually
fill with smoke.
As a result,
more than 70 people died,
making Grenfell
everyone's nightmare
of a tall building blaze.
♪ ♪
And unfortunately,
Grenfell-like safety flaws
exist in many U.S. cities,
particularly with
older apartment buildings,
like these in New York.
JOHN ESPOSITO:
We have a significant number
of housing projects
and buildings that are,
you know, 20 stories.
The code doesn't
require alarm systems,
the code doesn't require
sprinkler systems.
NARRATOR:
As with Grenfell,
the main deficiency in these
buildings is communications.
There's no public
address system, necessarily,
in the older existing buildings.
The only information they
can gather is looking up
for signs of smoke or flame.
And the occupants are left,
really, to their own devices
in terms of figuring out
what to do.
NARRATOR:
At Grenfell, this proved fatal
because many residents
followed the one instruction
they were given...
Stay put unless
instructed to leave.
In Grenfell, the guidance
that had been given
to residents of those buildings,
across the city,
was that you should stay
in place in a high-rise
residential fire, unless
you're immediately threatened.
NARRATOR:
But with no
communication system,
by the time leaving
became obvious,
for many it was too late.
This shelter-in-place guidance
is widely recommended
in the US as well.
ESPOSITO:
It seems counterintuitive
to stay in the building,
but you really are safer
if there's no fire
in your apartment,
'cause to leave and go
through the hallway
where there's gonna be smoke,
you're really exposing
yourself to danger.
JENNINGS:
The problem is,
people don't have
the expertise to evaluate
if there's smoke in their
hallway, is it heavy smoke?
Is it incidental to a fire?
They don't know,
so they are left
and immediately put into
a position of great anxiety.
And so, sooner or later,
some of them are gonna say,
"The heck with this, I'm gonna
try to get out of here."
NARRATOR:
And once in an exit stairway,
there could be even
greater danger.
JENNINGS:
What may appear to be a clear
stairwell on your floor,
may be contaminated with
smoke at a lower level.
People die in stairwells
trying to evacuate fires.
NARRATOR:
And many stairwells are narrow,
creating a dangerous bottleneck
for firefighters trying
to reach and control the blaze.
ESPOSITO:
We do have some
narrow stairways,
so either the people coming
down are gonna get held up,
or the firefighters going up
are gonna be slowed down.
NARRATOR:
Adding to this challenge
is how to get elderly or
disabled people down to safety.
ESPOSITO:
That becomes a problem,
if we have to take them down,
that's very intensive to move
somebody down the stairs.
And that's why our
best advice is
we want them to shelter in
place in their apartments.
NARRATOR:
Elevators could help,
but they can spread
fire or smoke,
and people can
get trapped inside,
so occupants are generally
restricted from using them.
A new generation
of fire-safe elevators
is starting to come online.
And these would certainly
help the aged or disabled.
They are housed in special
closed-door areas
pressurized to keep smoke out,
and there are drains
to keep water out.
They hold great promise.
(elevator chimes)
But there are so few
operating in the U.S.,
they have yet to be
fully fire tested.
ESPOSITO:
So, we don't know
the effectiveness
of those elevators
until they're actually used
in an emergency situation.
NARRATOR:
But there is a proven technology
that can avoid the need
for elevators by keeping
most fires from spreading.
That sprinklers have
the capacity to save lives
and buildings has been
proven time and again,
even at high-profile addresses.
A recent fire in Trump Tower,
New York,
built before sprinklers
became mandatory there,
resulted in the death
of a resident
and several
injured firefighters.
Sprinklers could've
prevented these casualties.
So why don't more
buildings have them?
JENNINGS:
The reason we don't have
sprinklers
in all tall buildings
is because the real estate
industry doesn't want
to spend the money
to put them in.
♪ ♪
NARRATOR:
The good news is
sprinklers are now mandatory
in most recently built
tall buildings.
And these have helped keep fires
and fire-related fatalities
on the decline.
But fires aren't
the only threats
to tall buildings
and their occupants.
Despite a mostly excellent
safety record...
MAN:
Everyone get back, get back.
NARRATOR:
engineering or construction
mistakes do happen.
MAN:
Oh, my God.
NARRATOR:
And when they do,
the results can be terrifying.
(people shouting)
This is San Francisco's
Millennium Tower,
a 58-story luxury condominium
that became a much
sought-after address
when it first opened
about a decade ago.
But in 2016, the news broke
that it was sinking and tilting.
REPORTER:
This 58-story downtown high rise
unexpectedly sunk 16 inches...
This golf ball
rolling down the uneven floor,
toward the direction
the building is leaning.
NARRATOR:
The revelation came
as a shock to condo owners.
HOWARD DICKSTEIN:
The building was still settling
vertically and horizontally,
and it was unclear
when that would stop.
Some people, I think, just left.
There was a concern
that the building
was about to topple over.
NARRATOR:
And in a city with
a history of earthquakes,
this was especially worrisome.
Today, the so-called "Leaning
Tower of San Francisco"
has sunk about 18 inches
on its northwest corner.
When the news broke,
Ron Hamburger,
a veteran structural engineer,
was hired by the building's
developers to find out
why the Millennium was sinking
and if it could be stopped.
RONALD HAMBURGER:
The Millennium Tower
basically is sinking
because it's a taller building
and a heavier building
than most of the other
buildings that have been
constructed in San Francisco.
It imposed greater weight
on these sand layer
that exist about
80 feet below the sidewalk.
♪ ♪
NARRATOR:
Like many cities
bordering water,
San Francisco rests
atop ancient layers
of soft sand and clay.
Whereas in New York,
a hard bedrock-type layer
called schist lies close
to the surface in many places,
so anchoring tall buildings here
is ideal.
But in San Francisco,
bedrock lies deep
below the surface.
And reaching it
with supporting piles
is difficult and expensive,
so tall buildings are often
placed on concrete mats with
piles that don't go to bedrock.
But the piles do transmit
the building's weight
through the weak
upper soil layers
to deeper, firmer layers
and the system normally
works quite well.
But for some reason,
the Millennium's extreme weight
pushed down with enough force
to compress the soil
under some of the piles,
causing the building
to settle unevenly.
The tower's owners claim a
neighboring construction project
called the Trans Bay Terminal
contributed to the uneven
settling by dewatering
the soil under the Millennium.
HAMBURGER:
Dewatering is done in order
to have a dry excavation
so that you can actually
build what you want to build.
♪ ♪
NARRATOR:
Whether the fault was
dewatering or poor engineering,
the sinking has slowed
to about a quarter inch a year
and could stop entirely.
Regardless, Ron Hamburger
is now heading up
a multi-million dollar
foundation fix that will
shore up the building
by extending the concrete
foundation mat
on the sinking corner
and adding additional
supporting piles
that go all the way to bedrock.
It is hoped that the fix
will allay public fears
about the building's stability.
♪ ♪
The Millennium saga
stands out in part
because serious mistakes in
high-profile buildings are rare.
Their engineers have
consistently produced structures
that stand straight,
can support their own weight,
and are capable of
resisting a constant threat
to any tall building...
(wind whooshing)
...the force of the wind.
Although no tall buildings of
note have ever been blown over,
another famous mistake almost
brought that frightening
prospect to New York.
When it was completed in 1977,
the now modest 59-story
Citicorp Center
was the ninth tallest
building in the world.
With its aluminum
and glass exterior,
Citicorp was among
a new generation
of lighter skyscrapers
that avoided
the expense of heavier,
masonry-clad facades,
like the Empire State Building.
But lighter buildings
can sway in the wind.
And when they do,
people inside often complain
about feeling motion sickness.
To counter the sway at Citicorp,
the building's engineer,
William LeMessurier,
had New York's first
tuned mass damper
installed near the top
of the building.
It is basically a 400-ton
block of concrete
that slides on a bed of oil.
When wind pushes against
the outside of the building,
the giant block will slide
in the direction of the sway.
Large piston-like devices
restrain the block,
absorbing the energy
and slowing its movement.
This makes the block lag
behind the moving building,
which, in effect,
counters the sway
and keeps the building steady.
Without dampers,
tall buildings like these
beanstalk-thin luxury condos
could be fairly
uncomfortable to live in.
WILLIS:
The building can't have
the reputation of having
the, kind of, proverbial
waves in the toilet,
where you can feel
the building moving,
because people then
feel uncomfortable.
They won't buy an apartment
where they feel vulnerable.
♪ ♪
NARRATOR:
Back at Citicorp,
the resourceful LeMessurier
solved another problem.
He raised the building
above the street
and placed its four major
support columns under its sides,
rather than at the corners,
as is typical.
He did this to
accommodate a church.
Not this modern one,
but an older one that
had become dilapidated.
So the church struck a deal.
They would get a new
building in exchange
for letting Citicorp
rise above it.
But some engineers were
skeptical of its radical design.
LEMESSURIER:
I got a telephone call from
a student who was assigned
to write a paper on this
building by his professor.
Professor had said there
was something funny
about this building 'cause
the columns were not
in the corners
like they ought to be.
NARRATOR:
Under the facade,
LeMessurier placed a series
of V-shaped steel braces
that channel wind
and gravity forces
diagonally to the columns.
He was confident his
radical design would work,
because computer models
and wind tunnel tests
showed that it would.
Engineers wind test
building models
to see, among other things,
if their shape produces
a dangerous phenomenon
called a vortex.
The model is bolted to a base
that contains censors underneath
and when the fans come on...
(fans click)
the censors measure
the model's response
to the air flowing around it.
BAKER:
One of the issues
with tall buildings
is called vortex shedding.
As wind goes past an object,
it'll go first to one side,
and then the other.
And when it does this,
it'll create little swirls
in the air.
NARRATOR:
Vortex shedding creates
whirlpools that lower
the air pressure
behind a building.
Now, when the wind
hits the building,
it can push it and make
it sway rhythmically,
like a child on a swing.
BAKER:
At first they kick
their feet just randomly
and the swing goes nowhere.
You have to teach them that
they have to kick their feet
at the natural
harmonics of the swing.
So in tall buildings
it's the same thing.
NARRATOR:
Buildings that gain
momentum like a swing
put dangerous pressure
on structural connections.
But changing
the building's shape
can disrupt wind forces
and stop the build-up
of vortices.
Sometimes a very small change
can be the difference
between a building being
successful or not successful.
♪ ♪
NARRATOR:
Citicorp passed its wind tests,
but about a year after
it was occupied,
LeMessurier got
a disturbing message.
One of his students
in one of his classes,
as his thesis,
comes up with a fault
in the building
under certain
circumstances of wind.
He tells Bill,
"You know, my numbers say
that the building
could fall over."
And LeMessurier says
to the student,
"Nice story, sonny,
but, uh, you know,
go check your numbers again."
♪ ♪
NARRATOR:
But LeMessurier began to wonder
if the student might be correct.
LEMESSURIER:
I pursued this and, uh,
found out...
some very awesome
and frightening facts.
NARRATOR:
He discovered that winds
striking the building
diagonally, rather than face-on,
could increase the stress
on some of the V-braces
by 40% or more.
Then he realized that
during construction,
his office had permitted
contractors to bolt
the braces together,
instead of welding them,
as he had originally specified.
He calculated that winds
in excess of 70 miles per hour,
striking the corners
of the building,
could sever
the bolted connections.
LEMESSURIER:
I came to the conclusion...
(thunder rumbling)
that a storm
which had a probability
of occurring once in 16 years,
would cause the building
to fail and collapse.
I can't live with that.
NARRATOR:
LeMessurier recommended
welding six-foot-long
steel plates on either side
of the bolted connections
to strengthen them.
This would certainly
solve the problem,
but would take weeks to finish.
So as workmen began
the arduous task...
Folks, get on
the sidewalk, please.
NARRATOR:
the city drew up emergency
evacuation plans.
HELLER:
Not only would they
evacuate the building,
but they would evacuate
the ten-square block area
around the building just in case
the building falls over...
Can you imagine?
♪ ♪
NARRATOR:
And as fate would have it,
in late August 1978,
Hurricane Ella
began heading for New York.
As its winds intensified
to over 100 miles per hour...
(thunder rumbles)
...the disaster LeMessurier
feared loomed closer.
And there was no way repairs
could be completed in time.
But instead of tracking
toward the city,
Ella veered out to sea.
HELLER:
It all, ultimately, worked out,
but it was a very
dangerous situation.
NARRATOR:
Despite the travails
of Citicorp,
tall buildings have proven
time and again that they can
successfully withstand the most
extreme weather conditions.
And they are also
engineered to withstand
another major force of nature.
(people screaming)
But when it comes
to earthquakes,
the prospects that some tall
buildings may not survive
is a very real
probability indeed.
MAN:
Here comes an earthquake!
♪ ♪
NARRATOR:
It's been over 30 years
since the 1989 Loma Prieta
earthquake in San Francisco.
(sirens blaring)
OFFICER:
Shut off the gas,
shut off electricity!
NARRATOR:
The quake caused major
damage to houses
and infrastructure near the Bay.
But the rest of the city,
including tall
buildings downtown,
escaped relatively unscathed.
That's because
the quake originated
60 miles from the city,
and more importantly,
was not another "big one."
In 1906,
a giant earthquake
on the San Andreas fault,
and devastating
fires that ensued,
basically destroyed the city.
The U.S. Geological
Survey now says
there's a 70% chance
another powerful quake
will strike the region sometime
within the next 30 years.
DAVID SCHWARTZ:
The earthquake could occur now,
it could occur in 20 years,
but it's not gonna
wait a hundred years.
NARRATOR:
There are seven major
faults in the Bay area,
with the most worrisome
being San Andreas
and the Hayward.
♪ ♪
SCHWARTZ:
We're in a parking lot
south of downtown
Hayward, California.
You can see doughnuts,
tire tracks
that kids have made.
NARRATOR:
David Schwartz, a recently
retired USGS seismologist,
has studied the Hayward
fault for years.
And as you're crossing
the parking lot,
you look down and you see
the asphalt
is sort of disturbed.
There's a little
step across it here.
There's a whole series
of cracks here.
This is the Hayward fault.
And the fault is creeping.
It's actually moving
slowly all the time.
And it produces
this type of feature.
When you come to here,
these older buildings,
this separation
expresses creep along the fault.
This building
is moving towards me,
this building is moving away.
When the fault finally decides
to move in its big earthquake,
I really wouldn't want
to be standing against
one of these buildings.
In the end,
the fault always wins.
NARRATOR:
The fault travels northwest
from the town of Hayward
through Oakland
and the Berkeley Hills,
where millions of people
live on or right next to it.
And the force of a big quake
could readily
travel across the Bay,
smack into downtown
San Francisco,
bringing with it the potential
for a major disaster.
And when this
earthquake strikes,
it's pretty clear
what types of buildings
would likely
suffer the most damage.
HAMBURGER:
The worst-performing
buildings are what we call
unreinforced masonry buildings.
These are typically either
common red brick buildings,
or sometimes stone buildings.
The masonry is quite strong,
but it's also very brittle
and under the effects
of severe ground shaking,
the masonry will
crack and crumble
and it's very common, actually,
for the walls to fall away,
creating not only a hazard
for people in the building,
but also people
outside the building.
NARRATOR:
Because masonry buildings
could be vulnerable to collapse,
it was deemed safer
to construct tall buildings
with steel frames.
LUCY JONES:
Steel seemed like
the perfect choice,
because if you push on steel
way beyond its strength,
the steel bends
instead of breaking,
and therefore you wouldn't
collapse the building.
NARRATOR:
And by the 1960s,
the preferred method
for joining the pieces
in a steel frame was
to weld them together.
What engineers call
welded steel moment frames
were deemed one
of the safest designs
for tall buildings
in California.
Oh, God, no!
NARRATOR:
That thinking would
get a severe jolt
after the 1994
Northridge earthquake.
REPORTER:
As you can see,
extensive damage here.
NARRATOR:
The 6.7 temblor struck
densely populated
suburban Los Angeles,
causing scores of deaths
and property losses
in the billions.
It also revealed a serious flaw
in supposedly safer
moment frame buildings.
HAMBURGER:
When the Northridge
earthquake occurred,
a number of these
buildings experienced
unanticipated fractures,
cracking of the steel
connections between
the beams and the columns.
NARRATOR:
Outside, most of the
buildings looked stable.
But inside, inspectors
found weld failures
and cracks in the steel.
Now the question was,
what could happen to these
steel-frame buildings
in an even stronger earthquake?
Swaminathan Krishnan
is a structural engineer
specializing in computer
simulations.
♪ ♪
After Northridge,
he modeled a specific
moment frame building
damaged in that quake
and subjected it to the force
of a stronger
San Andreas earthquake.
KRISHNAN:
In particular, we wanted to see
whether this building
would remain standing
or would it collapse.
NARRATOR:
As the big quake
begins to spread,
his program assesses its effect
on the building's frame.
This building does
fine for awhile,
you can see, you know,
that it's going back and forth
and it's coming back
and staying vertical,
but at some point,
there are several connections
that break inside
of the building
and the building
comes crashing down.
NARRATOR:
Although improved materials
and welding techniques
have made newer steel buildings
far less susceptible
to failures,
older moment frames,
including the famous
Transamerica Pyramid,
and other buildings
throughout California,
remain unfixed
and could even have become
weakened by previous quakes.
HAMBURGER:
So if a building goes
through an earthquake,
even if it is
apparently undamaged,
it's used up some
of its original
earthquake-resistant capability.
♪ ♪
KRISHNAN:
The problem is
right now there are
hundreds of tall
buildings of that kind.
They've not been opened up,
and they have not
been retrofitted.
NARRATOR:
And if a big earthquake comes...
KRISHNAN:
We are going to see
building collapses.
That is what our
modeling tells us.
NARRATOR:
A few moment framed buildings
have been retrofitted,
but a big deterrent is cost.
To remove interior walls
and ceilings
to inspect connections,
much less tear things apart
and fix those connections,
can be extremely expensive,
and may just be unnecessary.
(objects clattering)
In 1985, a powerful earthquake
struck Mexico City,
where taller buildings saw
relatively little damage,
but many mid-size,
ten-to 20-story buildings,
were tremendously damaged
or totally destroyed.
That's because
their particular height
resonated with the shockwaves
from this earthquake.
♪ ♪
HAMBURGER:
Resonance is a phenomenon
that occurs when
the natural frequency
of a structure
closely matches the natural
frequency of an exciting force.
NARRATOR:
Earthquakes send out vibrations
of various wavelengths
or frequencies.
When they reach
a cluster of buildings,
those that suffer damage
are often the ones
whose height best matches
those particular frequencies.
KRISHNAN:
When the ground
shaking has
in it high frequencies,
meaning the shaking is jarring...
it's going to go do this,
boom, boom, boom, boom.
That kind of shaking
will selectively effect
short buildings.
NARRATOR:
Whereas longer wavelengths
can cause tall buildings
to sway rhythmically.
And in extreme cases,
can collapse them.
Other factors,
such as soil conditions
or inadequate
construction materials,
can also make tall
buildings vulnerable.
But there's no factor
more important
to an earthquake's
destructive potential
than location.
JONES:
So, absolutely,
your distance from the fault
is one of the most
important things
about what shaking you receive.
NARRATOR:
In 1995, one of the most
devastating earthquakes
in the modern era
struck Kobe, Japan,
along a fault that
lay close to the city.
6,000 people died,
tens of thousands
were left homeless,
hundreds of thousands
of buildings of all sizes
were damaged or destroyed.
JONES:
There were collapsed buildings
and there were collapse
of steel-frame buildings from
the same problem with welds
that we saw in the
Northridge earthquake.
NARRATOR:
Kobe's proximity to a fault,
as well as its
large concentration
of people and buildings,
raises an obvious question.
Could this be the fate
that awaits cities
like San Francisco?
(trolley bell chimes)
IBRAHIM ALMUFTI:
I think about risk for a living.
NARRATOR:
Ibrahim Almufti...
Ibbi to his friends...
is a structural engineer who's
worried about his city's fate.
You know, I walk to work
through downtown every day,
looking up at the buildings
and I know too much, in a sense.
It is definitely possible that
a few buildings may come down
in a big earthquake.
NARRATOR:
Ibbi's goal is to engineer
a building that will be among
the safest ever built,
even reaching beyond
standard building codes.
ALMUFTI:
The building code
objective for many years has
always been life safety,
to protect it against
full collapse.
NARRATOR:
Recent earthquakes
in Christchurch, New Zealand,
demonstrate the flaw
in life safety codes.
Many heavily impacted
buildings did not collapse,
and therefore saved lives,
but most were
so severely damaged,
they could not be reoccupied
and had to be torn down,
which has depopulated the city
and derailed it economically.
ALMUFTI:
And actually, Christchurch,
you could argue,
is still recovering
from that earthquake
ten years ago.
And so, I always
ask the question,
are we as engineers bringing
our knowledge to bear
on designing these buildings
to be more resilient
and allowing these
cities to recover
more quickly
after big earthquakes?
NARRATOR:
San Francisco city
administrator Naomi Kelly
is hoping to make
tall building resiliency
one of the city's
top priorities.
KELLY:
Downtown San Francisco
is our economic engine
for the city.
We have now 62 tall buildings.
♪ ♪
Many more people
are living downtown.
And so we're now looking
at not just the building codes
where the building's
good enough for you
to get out the building,
but how do we make our buildings
more resilient
and how fast can
we reoccupy those buildings.
Most folks want to not only
just survive the earthquake,
but they want to get
back into their home,
or office building
as soon as possible.
(telephone ringing)
NARRATOR:
And that's exactly what Ibbi
and the engineering team
for 181 Fremont set out to do.
They're triangulating, right?
All of those forces...
NARRATOR:
Located near the Millennium
and Salesforce Towers,
181 Fremont is 56 stories tall,
slim, and angular.
The visionary structure owes
its design to Jeffrey Heller.
As a young architect,
Heller had gone
to Armenia in 1988,
where he saw first-hand
the devastation inflicted
by a huge earthquake.
HELLER:
What really got me was the level
of desolation and devastation.
What we saw was,
in the town of Spitak,
which was the epicenter
of the earthquake.
A city of 25,000, gone.
Nothing left.
♪ ♪
NARRATOR:
Over the years,
Heller designed several
earthquake-resistant buildings,
but 181 was, for him,
the commission of a lifetime.
The building had to be great,
or at least the best I could do.
♪ ♪
181 is 800 feet tall,
two thirds of it is office,
about 45 floors,
and then the top one third
is residential.
NARRATOR:
The views from inside
the upper floor apartments
are nothing less
than spectacular.
As are the appointments
in its luxurious penthouses.
Architecturally, the building's
most defining feature
is its striking exoskeleton,
with long braces that help
support the entire building,
thereby opening up
interior spaces.
HELLER:
It leaves the interior
of the building completely free,
up to the core,
of any vertical support at all.
NARRATOR:
The exoskeleton is key
to the building's ability
to manage earthquake
and wind forces.
ALMUFTI:
So if you look at the building
from the outside,
you'll see these diagonals that
are connected to the columns,
and at the corner connection,
we've introduced dampers
on the ends of the braces
that basically act
as giant shock absorbers.
NARRATOR:
As the building flexes,
the middle brace
stretches or shortens.
When it does, secondary braces
activate the dampers
that compress
and stretch like springs,
absorbing energy
and channeling the force
of these movements
to the main columns.
At the base of the columns,
we see they can lift up
incrementally,
so in an earthquake,
the building acts
as Ibbi notes, like
a skier with ski poles.
ALMUFTI:
And so you've got these columns
that are acting like ski poles,
in a sense,
and some lift up
and you've got more pressure
on this one
to stabilize yourself,
and as you go this way,
same thing.
NARRATOR:
The overall design is so unique,
it earned 181 a first.
ALMUFTI:
We actually received the world's
first
REDI gold rating,
which means that we've
designed it in a certain way
such that building occupants can
get back and use the building
almost immediately
after a very big shake.
♪ ♪
NARRATOR:
This is something some
seismic experts
have been advocating for.
JONES:
We are trying to change
the building code
to say,
"Life safety is not enough."
We need functional recovery,
meaning I can recover
the function of the building
in a reasonable amount of time.
NARRATOR:
But resiliency features
like those on 181
can be expensive,
so until they are
mandated in building codes,
getting developers
to incorporate them
may be a challenge.
HAMBURGER:
It would be wonderful
if American building owners
and developers wanted
to provide society
buildings that
were more resilient,
but for the present,
it seems it will take
government to force that...
or an earthquake.
If we had a major earthquake
and it caused
catastrophic damage,
damage similar to what
New Orleans saw in Katrina,
that might be enough
to change society's attitudes
and foster an era when
we do indeed develop
more resilient construction.
♪ ♪
NARRATOR:
If we have the will
to apply lessons learned,
tall buildings will
continue to become better
at withstanding earthquakes,
wind, or fire.
And this is certainly critical,
since going up is just
about the only solution
to urban population density.
But beside becoming safer,
what else could
tall buildings become?
What other considerations
might go into
their planning and design?
For decades,
visionary thinkers have proposed
making tall buildings more like
eco-friendly vertical villages.
Although some of these designs
are, well, a little bizarre,
they generally
promote light-filled,
open, communal spaces
that can make buildings
more people-friendly.
And today, some designers
are reaching for that vision
with a less fantastic,
but still vibrantly creative
tall building environment.
This bustling atrium is office
central for Bloomberg LP,
the global business, financial,
and communications giant.
The first thing you notice
in this building
is all the stairs...
and people constantly
on the move.
The elevators stop
on every floor,
only for disabled people.
For everyone else...
MICHAEL BARRY:
The elevators,
in fact, only stop on
nine out of the 25 floors
that we occupy.
♪ ♪
NARRATOR:
The stair-stepping helps
promote employee fitness
and is just one of
the out-of-the-box concepts
in this building's
overall design.
The offices are in the lower
half of a tall residential tower
and in a smaller building
connected to the tower
by a dramatically curved,
multi-use space.
Its lead architect
is Rafael Pelli.
PELLI:
There's a theatrical quality
that I hadn't anticipated
as much as, as it truly is.
NARRATOR:
In addition to this active,
light-filled atrium,
the rest of the offices
are also atypical.
PELLI:
The company wanted
a different model
for organizing office
buildings than the traditional,
historical one where you stack
a bunch of very isolated
units on many, many floors,
making a very
siloed environment.
♪ ♪
Instead of that,
they wanted fewer floors,
very big floors, all connected
around a central space.
NARRATOR:
That central space is called,
"the pantry,"
for obvious reasons.
It looks more like a public
space than a corporate office.
The openness and informality
clearly encourages
employees to meet
and exchange ideas.
KAREN TOULON:
You'll be grabbing a cup
of coffee
and you'll see ten people that
you need to catch up with.
And it's a great way
of getting work done.
♪ ♪
BETH MAZZEO:
"Oh I haven't seen you in
so long, we need to catch up.
"I got something
I need to tell ya.
"And, by the way do you
have five minutes now,
'cause we'll grab a coffee
stand around one of the pods."
PELLI:
We wanted the sixth floor
central space to be
the beating heart of what
Bloomberg wanted to be.
NARRATOR:
There are no
closed-door offices here.
Meeting rooms have glass walls.
PELLI:
So it was all done
to be transparent,
everybody could
see what's going on.
NARRATOR:
As part of what the company
calls its Fitwel program,
beside all the stairs,
there are several outdoor decks
where people can get fresh air.
And keeping with its green
buildings initiative...
near JFK Airport in Queens,
the company has
financed a solar array
that generates over
a million and a half kilowatts
of sustainable energy a year.
♪ ♪
That's about five percent
of its power use.
Many of the concepts,
like encouraging bike riding,
as well as the free snacks,
and open interior spaces,
are not new.
They're borrowed from Silicon
Valley companies like Google.
But these companies
are in low-rise buildings,
in roomy, open spaces,
whereas incorporating
these design considerations
in a tall building environment
breaks the mold on how these
buildings can be reimagined.
SIMMONS:
The energy,
the environment,
it's just an amazing building.
♪ ♪
NARRATOR:
As more and more skyscrapers...
office and residential...
come to dominate our cities,
ultimately what will
this mean for our future?
WILLIS:
I think the skyscraper makes
sense in the future of the city
because it does
use land efficiently
and that's a more sustainable
way to live on the land.
It's a smarter way
to build a future city
that consumes less energy,
that accommodates
the lifestyle amenities
for many more people than
if we have to spread out.
WOOD:
Tall buildings are
a huge part of the answer
to the challenges
that face us today...
social, economic,
climate change,
urbanization,
population growth...
But they are only
several baby steps
along the path
they need to tread
to truly deliver
on that potential.
The buildings need
to do the very best
that they can do if we want to
carry on living on this planet.
♪ ♪
ALOK PATEL:
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behind the news
with the "NOVA Now" podcast.
or wherever you find your
favorite podcasts.
ANNOUNCER:
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♪ ♪
♪ ♪