[Narrator] In a
high-rise building.
-There was no warning.
[Narrator] At sea.
-Innocent people died.
[Narrator] In a train.
-Everything was on fire.
Everything was burning.
[Narrator] Disasters can begin
with the smallest things.
-Changing the opening
hours of a restaurant.
-The bad glue job.
-A paperwork error.
[Narrator] Now, combining the
latest research with every
available source of evidence,
experts will forensically
analyze three disasters
down to each tiny detail.
-You've really got to
think outside the box.
-You have to work your
way back and understand
each link in the chain.
[expl*si*n]
[Narrator] State-of-the-art
graphics reveal every critical
detail at every
critical moment.
-This whole disaster
could have been averted.
[Narrator]
We can dissect them.
Get inside.
Or underneath.
Freeze time.
And even reverse it.
To conduct a complete
Disaster Autopsy.
Cape Kennedy, Florida.
2:13 p.m., April 11th, 1970.
[announcer] Ignition
sequence has started.
6, 5, 4, 3, 2, 1.
[Narrator] The Saturn Five,
the most powerful rocket
in the world.
[announcer] We have commit
and we have lift-off at 2:13.
[Narrator] Apollo 13.
NASA's most infamous moonshot.
[announcer] The Saturn IV
building up to 7.6 million
pounds of thrust and it
has cleared the tower.
[Narrator] In today's money,
the Apollo project has cost
a quarter of a trillion dollars.
But it has delivered
the impossible,
putting a man on the moon.
The ten-day mission
is scheduled to be
NASA's third landing.
[announcer] We're go flight.
Looks good here.
Good flight.
[Narrator] Onboard for the
quarter-of-a-million-mile trip
are Jim Lovell, Fred Haise,
and Jack Swigert.
-This was going to be
a time of trepidation
and anxiety for their
families back home.
Jim Lovell had four children,
and Haise's wife was
seven months pregnant.
[Narrator] For two days nothing
happens to alarm the families.
It is just another
textbook NASA mission.
[Narrator] But on April 13th
-Standby.
[Narrator] At 10:08 p.m.
[Narrator] They are
200,000 miles away from Earth.
-There's been an expl*si*n and
they know they're losing power.
[Narrator] In seconds,
their spacecraft is dying.
[Maggie Aderin-Pocock]
They're losing oxygen.
They're losing water.
They're losing electricity.
They can't even
control the spacecraft.
[Narrator] The survival story
of Apollo 13's heroic crew
is well known.
Less so, is what went
wrong in the first place.
Now, using all the
available evidence,
we will piece together
the Apollo 13 mission
to answer the question.
What causes this disaster?
The first critical pieces
of evidence we have,
are the words of the
astronauts themselves.
-In 2010, 40 years after
the Apollo 13 mission,
NASA released the
transcripts of communication
between Mission Control
and the astronauts,
giving us a blow-by-blow account
of what happened
on that mission.
[Narrator] The transcripts
tell us that immediately
after the bang, the spacecraft
systems begin to collapse.
[astronaut] Houston,
we've had a problem.
A main B Bus undervolt.
[control] Roger,
main B undervolt.
[Narrator] This tells mission
control that they are rapidly
losing all electrical power.
It suggests the disaster begins
where that power is generated.
A part of the spacecraft
called the service module.
[Sophie Harker] The spacecraft
was made up of three modules
or three components.
You had the lunar module, also
known as the Aquarius module,
you then had the
command module.
And then you had
the service module.
So within the service module,
you have your engine,
you have your electrical supply,
you have your water supply,
your oxygen,
so your air, basically,
everything that you
need to keep the crew alive.
[Narrator] The electrical
power that is rapidly
disappearing should be coming
from the service module's
three fuel cells.
But the system is
disintegrating fast.
-A few minutes later,
the second power circuit
starts to fail too.
[Narrator] Within seconds, they
are fighting for their lives.
[astronaut] Jack, our O2
quantity number 2 tank
is reading zero.
Did you get that?
[control] O2 quantity
number 2 is zero.
[Narrator] They
are losing oxygen.
-Tank two is completely empty
and tank one is
rapidly depleting.
[Narrator] These oxygen tanks
are fixed to a shelf
in the service module.
They don't just provide
air to breathe,
they also supply the fuel cells.
-The fuel cell in the
service module combines
the hydrogen and the oxygen,
and it creates a
chemical reaction
that releases electrical energy.
[Narrator] It explains
the loss of power.
No oxygen, no electricity.
They are now in a fight
to simply stay alive.
They shut down their
crippled spacecraft,
which means our trail
of evidence goes cold.
[Andrew Steele]
The next few days are
an incredible survival story.
They were forced into
the lunar module, which is
normally used for landing on
the surface of the moon and
they essentially
used it as a lifeboat.
The only part of the
spacecraft where they are
able to maintain some
semblance of function and
keep themselves alive.
[Narrator] Three days later,
having survived almost
all the way home,
the crew abandon a
critical piece of evidence,
the site of the blast.
-The service module where
the expl*si*n happened
was jettisoned and it burnt
up on the Earth's atmosphere.
[Narrator] In the seconds
before it is lost forever,
the exhausted crew
grab this photograph
on high-resolution film.
[Peter Hollingsworth] As the
service module drifts away.
They look over and they can
see that one of the panels is
missing on the side
of the service module.
It's been blown
completely off.
[Narrator] This damaged
section contains both the
fuel cells and oxygen tanks.
And by expanding and
stabilizing the vital image
the crew managed to grab,
it's possible to
recover more detail.
The fuel cells are visible.
But something appears
to be missing
oxygen tank 2.
NASA telemetry shows
that tank 2 loses pressure
instantaneously at the
time of the expl*si*n.
[expl*si*n]
[Maggie Aderin-Pocock] Oxygen
is stored in liquid form.
If that container is exposed
to the vacuum of space,
you transfer from a liquid
into a gas very rapidly
with massive expansion.
This transformation from
liquid to gas has enough force
to vent the panel
out into space.
[Narrator] All the evidence
suggests the disaster is
triggered by the expl*sive
failure of oxygen tank 2.
-So, the question is,
what happened to tank 2?
[Narrator] Can any evidence
from the transcripts around
the time of the disaster
shed light on the
failure of tank 2?
[Sascha Auerbach] At 55 hours,
52 minutes, and 58 seconds
into the flight,
Mission Control
asks Jack Swigert
to stir oxygen tank number two.
[Maggie Aderin-Pocock] They
need to actually stir up the
oxygen because it has a
tendency to settle into
different layers.
Now they do this stirring by
using an in-built fan system.
[Narrator] The expl*si*n
happens just over two minutes
after Swigert is
asked to stir the tank.
And inspection of Apollo 13's
telemetry reveals an anomaly
as he flips on the fan switch.
-Three seconds after the
crew set the fan going.
There's a rise in current
and a drop in voltage,
which indicates that
there's a short circuit.
[Narrator] A short
circuit could create a spark.
But that's not enough
to cause an expl*si*n,
you also need a fuel source.
-The oxygen tanks are
mainly made of metal,
but there's something
else in there.
The wiring for the fan
and the tank heater
are covered in Teflon.
Now, Teflon is well known
for its sort of heat resistant
properties, we coat
frying pans with it.
It doesn't usually
sort of go up in flames.
[Narrator] But there's nothing
'usual' about the environment
on a spacecraft.
It can dramatically change
the properties of Teflon.
[Sophie Harker] When Teflon is
exposed to a large amount of
oxygen, which obviously it
will be in an oxygen tank,
it loses its
fire-resistant properties
and becomes very flammable.
[Narrator] And NASA has tragic
experience of the intense
fire risk of
oxygen-saturated materials.
[Sascha Auerbach] In 1967,
three astronauts tragically
lost their lives when a fire
broke out in the command module
of Apollo one, while it
was sitting on the launch pad.
The cabin was filled with
pure oxygen at 16.7 PSI
and everything caught fire.
[Narrator] Astronauts
Gus Grissom, Ed White, and
Roger Chaffee
die in seconds.
-NASA realized that when
ordinarily safe materials
become supersaturated
with oxygen,
they can burn with
incredible ferocity.
[Narrator] The short circuit
in Apollo 13's tank 2 causes
the oxygen-saturated
Teflon to ignite.
But that same Teflon
insulation should prevent
any short circuit in
the first place.
What is going on?
Analysis of pre-flight data
shows a minor anomaly in
tank 2 a month before launch.
Following a launch pad test,
engineers are unable to drain
the liquid oxygen from it.
So, they use the tank's
inbuilt heater to boil it off.
Once it has, a thermostatic
switch in the tank will
automatically
turn the heater off.
But a close look back into the
original production history of
tank 2 throws up an
unexpected anomaly.
-The tank itself was
designed to run at 28 volts.
That's the voltage you
get on the spacecraft.
But the Kennedy Space Center
ran at 65 volts.
[Narrator] NASA's records
show that the tank has been
modified to run
on both 28 volts
and 65 volts for safety.
But one vital component
is missed in the update.
-There's no record to show
that the thermostatic switch
inside tank 2 was
converted to run at 65 volts.
-If the thermostatic switch was
not upgraded to handle 65 volts,
when they connected
to the ground power,
it could have caused
the connectors to fuse.
[Narrator] Boiling off
the oxygen now becomes
a recipe for disaster.
-If the switch is fused shut and
fails to turn off the heater,
the temperatures inside the tank
could reach or exceed
1,000 degrees Fahrenheit.
-This overheating of the
tank meant that you end up
degrading the Teflon
and potentially exposing wires.
[Narrator] Exposed wires
allow the short circuit that
triggers the expl*si*n.
-This turned tank 2 into
what Commander Jim Lovell
described as a
ticking time b*mb.
[Narrator] A simple error
during the modification of
tank 2 causes the
expl*si*n on Apollo 13.
But one crucial
question remains.
-This bizarre chain of events
would never have happened
the way it did if
tank number 2 had just
drained the way it
was designed to.
So, what happened?
[expl*si*n]
[Narrator] When oxygen tank 2
explodes on Apollo 13,
200,000 miles from Earth,
Jim Lovell, Fred Haise,
and Jack Swigert
are left fighting to survive.
But NASA's records reveal
an astonishing anomaly
in the tank's history.
It wasn't meant to be in their
spaceship in the first place.
[Maggie Aderin-Pocock] That
tank 2 wasn't actually
designed for Apollo 13.
It was designed for Apollo 10.
Records show that seven months
before launch, the tank was
removed from Apollo 10 to
make space for an upgrade.
[Narrator] The paperwork also
records a minor anomaly
during the removal.
-When they tried to
crane the shelf out,
the shelf that contains
the oxygen tanks,
they had forgotten to remove
one of the bolts that
holds it in place
and the shelf drops back
two inches into place.
[Narrator] NASA tests
the tank for damage.
It gets a clean
bill of health.
But one critical piece of
evidence suggests they
may have missed something.
This photograph of Apollo 10's
service module is taken
after the incident.
When magnified sufficiently it
reveals something that isn't
recorded anywhere
in the incident log.
A repair made to the underside
of the fuel cell shelf.
-This indicates that the top
of the tank hit the shelf
above before falling down.
[Narrator] This almost
invisible mark could
explain everything.
-Impact with the shelf
and then dropping,
could have caused damage
to the internal drainpipe,
which is what prevented
the tank from draining
during the test.
The evidence suggests that that
single bolt being attached
led to the chain of events
that ultimately led to
the accident on Apollo 13.
[Narrator] Now, we have the
evidence to piece together
the Apollo 13 disaster.
[Peter Hollingsworth]
October 21st, 1968,
during the removal of the
oxygen tank from Apollo 10
a bolt is missed.
[Andrew Steele] Tank 2 hits the
shelf above and crashes down,
probably dislodging the
draining pipe inside the tank.
[Maggie Aderin-Pocock] This
fault prevents the tank from
draining properly.
[Peter Hollingsworth] When
engineers try to rectify this
problem by boiling off the
oxygen in the tank, the higher
voltage damages the
thermostatic switch,
which allows the
tank to overheat,
which damages the
Teflon insulation.
[Narrator] When Apollo 13
takes off, the service module
is an unexploded b*mb.
56 hours into the mission,
Jack Swigert turns on
the fan in tank 2.
There is a spark.
The expl*si*n destroys tank 2,
and very nearly kills
Lovell, Haise, and Swigert
200,000 miles from home.
[expl*si*n]
But by an incredible operation
on the ground and in space,
all three astronauts make it
home, exhausted, but alive.
The Apollo 13 mission
comes extraordinarily
close to catastrophe.
[Sascha Auerbach] NASA to this
day still refers to Apollo 13
as a successful failure
because of the heroic efforts
by mission control and by
the three astronauts that
brought the capsule and its
occupants home safe and sound.
[Narrator] It is an apparently
insignificant electrical error
that almost kills the crew.
Not everyone will be as lucky as
the astronauts on Apollo 13.
Las Vegas, Nevada.
The MGM Grand Hotel.
[Margaret Harris] This is the
absolute crown jewel of the
Las Vegas strip.
It cost $106 million
to build.
[Ada McVean] When it opened,
it was a really big deal.
It was one of the biggest
hotels in the entire world and
even for Vegas, it was billed
as the most luxurious,
just the best hotel around.
[Narrator] It is the pride
of the Las Vegas strip.
In November 1980.
It goes up in flames.
[Rory Hadden] There are 5,000
guests and staff in the hotel
when the fire starts,
and many of them can't
find an escape route.
[Luke Bisby] There are a lot
of people trapped on the
upper floors and they've
got nowhere to run.
[Narrator] 85 people
lose their lives.
-This becomes the deadliest
fire in the history of Nevada.
[Narrator] Now we can analyze
all the available evidence
to digitally
recreate the disaster
and answer the question
what caused this lethal fire?
The first question has to be,
where does the fire begin?
[Ada McVean] If you look at
the photographic evidence,
it's obvious that the
areas hit hardest are the
main casino floor, coffee shops,
and a restaurant
called The Deli.
The Deli is almost
completely destroyed.
[Narrator] Like the
casino and coffee shop,
The Deli is located on the
ground floor of the hotel.
And we have an eyewitness to
the start of the disaster.
[Margaret Harris] The first
indication there's anything
wrong comes at 7:05 a.m. when
a workman called Tim Connor
walks in to The Deli and
notices a flickering light.
[Narrator] According to his
testimony, he sees the shadow
of flames on the south wall
and notifies hotel security.
[Luke Bisby] We know from
official records that the
first call to the fire
department is made at 7:16 a.m.
and the first fire truck
arrives on scene just
two minutes later.
[Margaret Harris] The
firefighters get about 40 feet
into the casino when a huge
fireball rolls out of The Deli.
They go running for cover.
They can't do anything else.
[Narrator] The eyewitness
testimony and photographs of
the fire damage all point to
the fire starting around the
south wall of The Deli.
[Margaret Harris] If you look
at the plans for The Deli,
you'll see that there's a
serving station near
the south wall.
After the fire images show
that the northwest corner of
the serving station
has the most damage.
[Narrator] Something in this
corner ultimately destroys
a hotel and costs 85 lives.
What happens?
[Narrator] Fire crews
who attend the blaze
at the MGM Grand,
report that the northwest
wall of the serving station
where the fire begins
has a narrow void space.
Inside are two copper pipes
used to carry refrigerant
to and from a chilled
pastry display case.
This critical photograph
taken after the fire
shows these two copper pipes.
But it shows something
else that is vital in
understanding the disaster.
[Rory Hadden] There's also a
flexible aluminum conduit that
runs next to the copper pipes
and the evidence is around
36 inches of this has
melted or vaporized.
[Narrator] The rest of the
conduit survives the fire
which means the missing
section was subjected to
unusually intense heat.
So, this area is clearly
where the fire begins.
But what triggers it?
-These copper pipes,
they carry refrigerant,
so they should be insulated.
But after the fire, there's no
trace of insulation remaining.
It seems likely that there was
never any insulation on that
bit of the pipe.
[Rory Hadden] So now we have
an environment in which we
have two metals, the
aluminum and the copper,
touching each other in an
environment with lots of
moisture coming from
condensation on the
refrigerant pipes.
That's a perfect environment
for something that we call
galvanic corrosion.
[Margaret Harris] Basically,
the system acts like a
battery, and one of those
metals gets eaten away.
And if those two metals are
copper and aluminum, it's the
aluminum that gives way.
That's what corrodes.
[Narrator] So, it might take
years, but eventually,
the aluminum conduit in contact
with the wet copper pipe
will have eroded away.
[Margaret Harris] And that's
a big problem because inside
that conduit are
live electrical cables.
And maybe one of the pieces
of electrical cables wasn't
insulated well, maybe that
insulation got eaten away by
the copper pipe vibrating,
whatever it was, as soon as
that insulation is gone,
you're going to get a spark
and that could start a fire.
[Luke Bisby] And this is all
housed inside a casing that
makes it hard for people to
see what's going on,
on a day-to-day basis.
[Narrator] The fire starts
hidden inside a partition wall.
But small electrical
fires are not uncommon.
How does this one transform so
rapidly into such devastation?
Photographic evidence
of The D eli shows
extensive fire damage.
But only one part has
been utterly destroyed,
the ceiling.
[Rory Hadden] According to
reports from the firefighters
the ceiling is covered
in decorative tiles.
Each tile is held in place by a
blob of adhesive in each corner.
Each tile therefore has around
four ounces of adhesive and
there are 4,000
square feet of ceiling.
This results in about
1,000 pounds of adhesive
across the ceiling.
[Narrator] The problem is,
the adhesive they chose is so
flammable, it had already
been banned in some states.
-So, what we've got on
the ceiling is these
cellulose ceiling tiles, which
are flammable, and they're
held in place with an even
more flammable adhesive.
-According to witness
statements, the fire is at
first spreading about
five to ten feet per second,
and eventually it starts venting
out of The Deli and into the
main area of the casino.
The ceiling of the casino is
covered in the same tiles and
the same adhesive.
Over 100,000 square
feet of the stuff.
[Narrator] That means the
casino ceiling contains over
12 tons of highly
flammable adhesive.
But it isn't a ceiling fire
that forces firefighters back
out of the casino almost
as soon as they enter.
They report
encountering a fireball.
Where does it come from?
[Luke Bisby] You've got
foam in seating; you've got
flammable plastic coatings
on items that are perhaps
intended to look like wood.
Essentially, you have
plastic materials everywhere.
The whole décor of the
casino is flammable.
[Narrator] The burning ceiling
bakes the flammable materials
beneath it.
The perfect
conditions for a flashover.
-So as the temperatures in
the casino rise, driven by
the burning ceiling,
the materials in the
casino will
spontaneously ignite.
[Narrator] This flashover is
so powerful it blows out the
west doors of the casino.
The Deli, the coffee shop,
and the main casino
floor are obliterated.
Yet just 17 of the 85
fatalities are in these areas.
The rest die in parts of
the hotel barely touched
by the blaze.
Why?
Many of the victims were on
floors way above where the
fire breaks out,
with the majority between
the 16th and 26th floors
in corridors, stairwells,
even their rooms.
How does the fire
k*ll people so far away?
[Luke Bisby] According to
the coroner's report,
the real k*ller here
was smoke toxicity.
[Narrator] But according to
the hotel plans, it shouldn't
have been possible for the
lethal smoke to spread so far.
-They have smoke dampers which
are supposed to help contain it.
[Rory Hadden] Smoke dampers
are installed in ductwork or
perhaps voids in a building,
and they are designed that in
the event of a fire, they will
close and prevent the passage
of smoke or hot gases
throughout the building.
[Narrator] But according to
reports from fire crews,
many of the dampers are
incorrectly installed
and fail to close.
Every vertical space in
the hotel becomes a chimney
driving the toxic smoke
towards the upper floors.
The people there have
no idea what is coming.
[Ada McVean] Because it's so
early in the morning, quite a
few of the guests are still
asleep and they essentially
end up trapped in the upper
floors because of all the smoke.
[Narrator] Even the emergency
stairs become death traps.
[Luke Bisby] People who were
evacuating into the stairwells
found that once they'd
got into the stairwell,
the door had locked behind them.
And this was a security
feature that had been used to
prevent people from going
onto floors that they weren't
supposed to be on.
The consequence for the people
who are trying to evacuate the
fires, that once they find
themselves in the stairwell
potentially with smoke, they
can't turn around and go back
into the clean air.
They're trapped.
[Narrator] More than 60 people
who are nowhere near the fire
die from the deadly smoke.
The casino, restaurant,
and deli are destroyed.
But strangely, most of the
hotel is untouched by fire.
Why?
[Narrator] Just 90 minutes
after the fire at the
MGM Grand breaks out, it is
pretty much contained.
-A lot of this is due to
the quick response of
the Las Vegas Fire Department.
But there might be another
factor at play here, which is
that many areas of the
hotel have sprinkler systems.
[Narrator] But according to
the schematics, vital parts of
the disaster site have none.
-Neither The Deli nor
the casino floor were
equipped with sprinklers, and
if they had been, we might be
looking at a very
different outcome.
[Narrator] Why wouldn't
the builders have installed
sprinklers in
The Deli and casino?
-When this building was built,
it wasn't required to have
sprinklers in all areas of the
building, but nonetheless,
local papers report that
the fire marshals did
try to pressure the
builders to install them.
[Narrator] According to these
reports, a compromise is made,
where areas that are occupied
24/7, like the casino floor
and deli, are not
fitted with sprinklers.
[Ada McVean] The reasoning
behind that is that if there
are people on the floor in an
area 24 hours a day, they're
going to be able to see a fire
and respond to it very quickly
so the sprinklers
aren't necessary.
[Narrator] But looking at the
casino operation around the
time of the fire, reveals a
lethal flaw in this plan.
-At some point The Deli's
opening hours changed.
It's no longer a 24-hour
restaurant, and that means
that there's nobody there to
observe the fire when it starts.
[Narrator] And no
sprinklers to extinguish it.
[Margaret Harris] This is a
real irony because something
as small as changing the
opening hours of a restaurant
may have led to a disaster.
[Narrator] We can now go
back to the very start of the
disaster and explain the
sequence of events that
lead to the devastating fire.
-This whole thing starts
with a case of just
some poor workmanship.
They fit this chilled pastry
case, but the copper pipes
carrying the refrigerant
are too close to an
aluminum conduit.
[Narrator] After years of
corrosion, an electrical fire
starts, hidden
inside a partition wall.
Because The Deli is now closed
for the night, no one notices
the fire break out and grow.
[Margaret Harris] By 7:21 a.m.,
the fire is out of The Deli,
it's burst into the casino
and a flashover occurs.
[Narrator] The burning
plastics and ceiling create
thick plumes of toxic smoke.
Because of faulty smoke
dampers, it drives upwards
through gaps and voids.
-The smoke travels
up into the higher levels of
the building, contaminating
those areas with smoke.
[Narrator] Almost all of
the victims k*lled by
poisonous smoke are
on the upper levels.
Following the disaster,
sweeping safety changes
are rushed in across
the entire state.
-So just a few months after
the fire, the state of Nevada
changed the building regulations
and they required now that
all high-rise buildings over
55 feet would have fire
alarms and sprinkler systems.
[Narrator] That included older
buildings like the MGM Grand.
Just a year after the
disaster, it re-opens.
It is now fitted with a
fire detection system,
and sprinklers
throughout the building.
Including the
casino and The Deli.
The cause of this devastating
fire is a fault that was
out of sight inside a wall.
And fire isn't the only lethal
catastrophe caused by
faults no one can see.
Genoa, Italy.
The colossal
Ponte Morandi Bridge.
Its most iconic section is
a spectacular stay bridge.
[Luke Bisby] Each stay section
consists of a central pylon
with two stays extending
from either side
down to support
the road deck.
[Narrator] Stay bridges
have been around for
hundreds of years.
But with just two stays on
each side, this bridge is the
ultimate in minimalist design.
[Joshua Macabuag] The
Morandi Bridge was designed by
legendary architect
Riccardo Morandi,
who was professor of
civil engineering at
Rome and Florence universities.
[Narrator] The landmark
structure is a symbol of
Italy's engineering prowess.
-The Morandi Bridge
was perceived as this
masterpiece at the time.
It really changed the way
how we looked into bridges.
[thunder]
[Narrator] On
August 14th, 2018
an 820-foot section of this
engineering icon collapses.
[dramatic music playing]
More than 35 vehicles on the
bridge plummet 147 feet
to the valley floor.
43 people are k*lled.
[Andrea Sella] The collapse
shocked the people of Italy
and across the world.
How could such a marvel of
post-w*r modern engineering
fail in so spectacular a way?
[Narrator] Vital clues
could help explain
the deadly collapse.
[Luke Bisby] We have witness
reports, we have CCTV,
we have maintenance records,
then of course,
we have the original design
plans for the bridge.
[Narrator] Using this
evidence, we will digitally
reconstruct the disaster to
find out why it happened.
[Narrator] One of the
single most valuable pieces of
evidence in the collapse of
Italy's Morandi Bridge is this
footage from a security CCTV
camera on the valley floor.
By chance, it captures
the moment the
stay bridge collapses.
Zooming in and
enhancing it reveals
something extraordinary.
The roadway on the far side
of the pylon collapses first.
And the stay
supporting it is sliding down.
Which means it must have
broken away from the bridge.
Using this incredible
evidence,
we can reconstruct the
collapse, frame by frame.
[Luke Bisby] After the first
stay fails and the road deck
starts to drop, there's a
twisting force on the tower,
and an opposite stay on the
other side of the pylon fails.
And the road deck now falls
down into the river and onto
the industrial
buildings below.
This entire sequence of events
begins with the failure
of a single stay.
[Narrator] How could
the giant stay fail?
Most stay bridges use visible
cables or rods for their stays,
but Morandi
designs something that
looks completely unique.
[Luke Bisby] Morandi wanted to
achieve a particular aesthetic
where he wanted a limited
number of stay supports.
[Yasemin Aktas] So, when you
look into the Morandi Bridge.
You think that it's made
of concrete as a whole.
[Narrator] But this is
simply a clever design trick.
The cables are still there.
-All the cables are hidden
inside the concrete.
[Narrator] Beneath the
concrete covering are
52 steel stay cables.
28 of these cables are
threaded through a series of
steel tubes, and then
it's all cast in concrete.
[Luke Bisby] This allowed
steel that would otherwise be
exposed to corrosion to be
protected by the concrete,
which would be compressed
and prevent it from cracking.
And that would deliver the
aesthetic that Morandi wanted.
[Narrator] The tensioned
cables in the tubes are
secured by injecting
concrete-based glue called
grout into each steel tube.
This provides a second layer
of protection from corrosion.
It is a carefully
thought-through solution to
protect Morandi's
design from failure.
But despite that, the evidence
says a stay does fail.
-Looking at the CCTV footage,
you can see what looks
like the initial failure
in the, the southeast
stay of that pylon nine.
[Narrator] For the stay to
fail, the cables inside the
protective concrete casing
must have snapped and that
is backed up by key evidence.
[Joshua Macabuag] Now
witnesses report a dull
metallic sound as if something
has snapped or broken.
[Narrator] How could these
massive cables just break?
[Andrea Sella] When they
examine the sections of cable
inside the conduit, what they
found was about 20% corrosion.
In other words, rusting was
gradually thinning down the
steel cable until eventually,
it was no longer strong
enough to hold the load.
[Narrator] Corrosion causes
the collapse that kills
43 innocent people.
But the bridge design is
supposed to protect the cables.
How does corrosion get in?
Morandi's design was supposed
to wrap the cables in
an impenetrable
barrier of concrete.
Something clearly goes
wrong with this plan.
[Yasemin Aktas] Analysis show
us that there are large cracks
on the stays.
Which, when you examine from
up close, you see that they
are dirty, which means
that they were old cracks.
[Narrator] Other evidence
suggests that these cracks
were decades old.
[Yasemin Aktas] Maintenance
reports from as early as 1979
tell us that there were some
cracking on the stays.
[Narrator] That means
corrosive moisture may have
been penetrating through the
protective concrete barrier
for nearly 40 years.
But there is supposed to be
a second layer of defense
against corrosion, the
concrete glue known as grout
that surrounds each cable.
Why does that fail?
[Narrator] Why doesn't
the grout surrounding the
Morandi Bridge's stay cables,
protect them from
the corrosion that
leads to its collapse?
[Yasemin Aktas] The evidence
showed that there were large
gaps inside the grout that was
poured inside the steel tubing
that surrounds
the steel cables.
[Narrator] How could these
grout failures have been
formed, unseen
beneath the concrete?
-The problem with this
second line of defense
was that the waterproof grout
was quite a thick mixture,
so it couldn't flow freely.
-So, if you're trying to pump
this grout into small spaces
that's going to be quite
a hard thing to do.
[Joshua Macabuag] So, what
actually happened is that it
then left gaps or voids such
that the, the steel wasn't
completely
encased and protected.
[Narrator] Both the grout and
the concrete fail to protect
the steel cables.
But even given the failure of
both layers of protection,
the level of corrosion
is still extreme.
What caused it?
[Andrea Sella] Corrosion of
metals occur because what
they do is very slowly react
with oxygen from the air.
And in the case of steel, it's
the iron which reacts with
oxygen in the presence
of moisture and acids,
and what it does is
it produces rust,
which is much weaker
than the original metal.
[Narrator] And chemical
evidence suggests something
made this rusting process
that eats away the cables,
particularly aggressive.
-Analysis of the
corrosion in the stays
suggested that it had actually
been accelerated by an
aggressive mix of water, of
sulfates, and of chlorides.
[Narrator] Why is the
environment so corrosive?
[Luke Bisby] If we look at the
location of the bridge, we can
see that it's only one
and a half miles from the
Mediterranean Sea, and this
means there's going to be a
lot of salt in the
atmosphere, chlorides.
And when steel is exposed to
chlorides, it can cause the
steel to rust and that's
really bad if you're steel
that's making up a
stay cable in a bridge.
[Yasemin Aktas] Another issue
is that the bridge is located
on top of a, an industrial area,
which among other things,
houses some steel
recycling facilities.
And those industries release a
lot of um, airborne pollutants.
[Narrator] These
pollutants can create
highly corrosive acid rain.
The Morandi Bridge is built
in a chemically aggressive
environment that eats away
at any exposed segments of
stay cable until they snap.
[Luke Bisby] There are a
number of things that haven't
gone perfectly well with this
bridge in terms of the grout
or in terms of the corrosion
of the steel in the stays.
But there are many cable
stay bridges in the world that
suffer similar problems
and they don't fall down.
[Narrator] Is there
is something else
beyond simple
corrosion at play
in the collapse
of the Morandi Bridge?
[Luke Bisby] Cable stay
bridges, of course, were not
a new idea, and multiple cable
stay bridges existed around
the world, but often these
bridges had multiple stay
cables on them rather
than a single stay.
[Narrator] If one stay fails
on these bridges, there are
others to take up the load.
This is a critical
concept in engineering design.
It's called redundancy.
It protects you from failure.
Why doesn't the
Genoa bridge have it?
[Luke Bisby] In order to achieve
this aesthetic with few stays,
resulted in a bridge that had
essentially no redundancy.
And so, when the corrosion
of the steel occurred and the
stay failed, the
entire bridge collapsed.
[Narrator] Losing redundancy
is the price Morandi pays for
his minimalist
design aesthetic.
It proves a
catastrophic decision.
The roots of the
Morandi Bridge collapse begin
50 years before the
disaster with its concept
and construction in the 1960s.
[Joshua Macabuag] Because
Morandi wanted to emphasize a
simple aesthetic, he bundled
all of those cables together
into a single stay.
[Narrator] But the concrete
that is supposed to protect
the cables from corrosion
begins to crack after
barely a decade.
The inner grout
protection also fails.
This lets in a corrosive
chemical c*ck that eats
away at the cables.
-Eventually the cables within
the south-eastern stay
on pylon nine snapped.
[Narrator] It triggers a
devastating collapse,
that leaves 43 people dead.
[expl*si*n]
Just two years after the
Morandi Bridge collapses,
it is replaced by a new bridge.
[Luke Bisby] The Genoa
St George Bridge is not a
cable stay bridge, it's
a viaduct bridge.
And indeed, it looks like
the lessons around maintenance
might have been learned
because the new bridge is even
equipped with a series
of robots to ensure that
appropriate
maintenance is performed.
[Narrator] Hopefully, the
lessons learned from the
tragic collapse of the
Morandi Bridge will ensure
a disaster like this
never happens again.
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01x04 - Apollo 13, MGM Grand, Genoa Bridge
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Expert analysis recreates real-world disasters in 3D graphics to uncover hidden causes like paperwork errors, bad glue jobs, or changed restaurant hours.
Expert analysis recreates real-world disasters in 3D graphics to uncover hidden causes like paperwork errors, bad glue jobs, or changed restaurant hours.