Original subtitles

ANNOUNCER: This program is rated PG, and contains

ANNOUNCER: This program is rated PG, and contains

mature subject matter.

Viewer discretion is advised.

-(SIREN WAILING) -(HELICOPTER WHIRRING)

MAN: Oh, my God!

NARRATOR: An 18 story hotel comes crashing to the ground.

People are panicked. There's a lot of uncertainty.

(WOMAN SPEAKING)

MAN: Come on, get back. Get back, sir!

That tower can come down any time.

ROB: This structure comes tumbling down floor by floor.

Like a house of cards.

NARRATOR: What's behind the unexpected collapse?

This kind of thing should not be happening today.

NARRATOR: Now...

Engineers unlock the clues to the world's biggest disasters.

(GLASS CRASHING)

(TRAIN CRASHES)

(PEOPLE SCREAMING)

Find out what happens When Big Things Go Wrong.

MAN: Okay, watch it! Watch it!

These are the ultimate fears,

that keep structural engineers awake at night.

MAN: Oh, my God!

(LOUD METALLIC CREAKING)

NARRATOR: Saturday morning, 9:00 a.m.

The people of New Orleans are gearing up for a busy weekend.

Among them, artist and producer, Fallon O'Brien.

She's getting ready for her regular commute.

FALLON: So, a normal day would be to get up,

and to have a cup of coffee.

I live just around the corner from the streetcar,

so, it would, you know, take me just a few moments to... to walk to the street car.

I grabbed my normal seat.

I recall juts kind of twiddling around on my phone.

I do remember it very specifically, because there was a chill in the air.

NARRATOR: The streetcar heads toward the corner of Canal Street in North Rampart,

where a brand-new high-rise structure's being built.

The Hard Rock Hotel.

So, the Hardrock Hotel is going to be

quite a glamorous, 20-storey high-rise in downtown New Orleans.

NARRATOR: Plans for the complex include 62 condos, a 350-room hotel,

an upscale restaurant, and over 12,000 square feet of event space.

And it rises 190-feet high,

with a penthouse to top it off at 205-feet.

It's set to be a spectacular addition to New Orleans,

perfect for tourists flocking to the biggest event of the year,

Mardi Gras.

It was gonna provide so many jobs.

It was going to provide a huge boom for the tourism.

NARRATOR: The hotel should've been finished by May, 2019.

But it's now months behind schedule,

so the pressure's on to finish it.

Fallon's commute takes her past the site every morning.

FALLON: I would always look up and see the guys working.

There were hundreds of men up there.

I would look up and kind of in awe of...

Just like, wow, incredible how quickly it went up.

NARRATOR: Today seems routine.

FALLON: We got to the corner of Canal in North Rampart.

I do remember looking up briefly.

It all happened in a split second.

In the peripheral of my vision,

I just see, kind of, something falling down.

So, I look up... I see a tangle of metal.

MAN: Oh, my God!

NARRATOR: Eighteen floors come crashing down.

The building starts to crumble at the very top.

And then we have this cascade of failure,

as the floors, the concrete, pancakes from top to bottom.

MAN: Get to the back! Get to the back!

FALLON: People really, at that point were in fear for their life,

and in fear that, the building was going to just collapse right on the street car.

All that you're thinking is, "Get me as far away from this disaster as possible."

NARRATOR: Rescue services race to the scene.

(SIRENS WAILING)

(MAN SPEAKING)

The overwhelming majority of buildings are built without

any kind of failure or issues.

And this kind of thing should not be happening today.

NARRATOR: The question... what caused it, and how?

The mystery begins 14 years earlier,

in a disaster that hit New Orleans hard...

Hurricane Katrina.

August, 2005, 175 mile per hour winds

batter the Gulf of Mexico before making landfall.

Floods destroy 134,000 homes.

1,500 die.

Stormwaters overwhelm the levees protecting New Orleans.

The entire city is devastated.

DAN: In the wake of Hurricane Katrina,

a revitalization effort was required

to get people to come back into downtown,

fix the devastation and destruction, get them to spend money...

And the Hard Rock Hotel was the center of it all.

NARRATOR: And as the huge new structure takes shape,

the first clue lies in the smallest detail.

LUKE: In very broad terms,

if you wanna put up a building, you start with the foundation,

make the base of the building very stable.

And then you'll build, what is effectively the skeleton of the building.

Whether that's out of structural steelwork, or reinforced concrete.

And in case of the Hard Rock,

that was largely structural steelwork.

NARRATOR: All this steelwork must be connected.

Major structural components of large buildings are often bolted together.

It is a cheap, but very effective way of taking large pieces of steel,

and making a solid connection between them.

NARRATOR: Bolts are small components.

But they're critical

in holding the building's frame together.

If you take an individual bolt, it is seemingly quite small,

relative to the structures ahold.

But the job that it does is absolutely crucial

to the life of this building.

NARRATOR: But as investigators sift through the wreckage

of the Hard Rock Hotel Collapse,

they find something strange.

Many of the bolts on the lower floors are sheared in two.

A shear failure is where you have forces acting in opposite directions

on a piece of metal, say.

And the combination of those forces exceeds the strength of the material.

And as a result,

you get a very sudden, or catastrophic break, or failure.

NARRATOR: Footage reveals the Hard Rock collapse was indeed sudden.

So why did the bolts fail?

ROB: It could be because there weren't enough bolts used

at those junctures or connections.

Or it could be that those bolts weren't big enough. That there wasn't enough material

to have the strength needed.

Or it could be a combination of both these things.

NARRATOR: The question remains...

Are the shattered bolts the result of the collapse, or the cause of it?

In any building or machine, if a small but crucial component breaks,

it can trigger a chain-reaction...

as air-race spectators in Nevada witness.

The Reno Air Races. Billed as the world's fastest motor sport,

in 2011, thousands of people are enjoying the day's events.

In footage shot by a spectator,

a plane can be seen veering out of control.

(CRASHING)

(PEOPLE SHOUTING)

What went wrong?

DAN: The air races in Reno, Nevada feature

high-performance aircraft.

They're very, very specialized to basically

have races in the sky for people to watch.

NARRATOR: 74 year old James Leeward is piloting a P-51 Mustang,

originally built in 1944.

Named The Galloping Ghost,

it's a highly-modified former military plane.

(PLANE WHIRRING)

But mid-race, catastrophe strikes.

(PEOPLE SCREAMING)

MAN: Oh, God!

Oh, my God!

What we see is one particular airplane that's been so heavily modified,

incurs mechanical failure which causes total loss of control.

(PEOPLE SHOUTING)

So, you've got to look after the small details.

In this case, a screw failed.

NARRATOR: The screw was holding a vital part together... the trim tab.

It's essential for keeping the planes stable in flight.

Loose before takeoff,

the screw breaks once the pilot reaches high-speed.

Once that happens, you no longer have an airplane,

you more have a high-speed velocity projectile

that's gonna go wherever gravity sends it.

This malfunction, essentially of the flap,

caused the pilot effectively to lose control.

And the aircraft went into a situation where the pilot was experiencing 17Gs.

And this can cause a blackout quite quickly,

and the pilot then loses control and crashes.

(PEOPLE SCREAMING)

NARRATOR: The Mustang slams into the ground at over 400mph,

killing the pilot and 10 bystanders.

Dozens more are injured.

When we have anything that's complex and engineered

and made up of a number of parts, large and small,

often, it only takes the failure of something quite small

to start to initiate what can become a catastrophic event.

NARRATOR: But in New Orleans,

the fractured bolts of the Hard Rock Hotel

are found on the lower floors.

So, something else triggered the disaster.

But what?

(NARRATOR READING)

You've got sections of a building that are falling apart, that's catastrophic.

NARRATOR: Could more evidence to the collapse lie at the very heart of the structure?

And a tragedy at sea...

(MAN SPEAKING INDISTINCTLY)

...caused by human error.

I assumed I was about to die.

NARRATOR: When Big Things Go Wrong,

engineers have to search for answers.

(MOTOR WHIRRING)

For the New Orleans Hard Rock Hotel collapse,

should they look higher up?

2016, the framework of the Hard Rock Hotel

is rising above downtown New Orleans.

Modern high-rise construction typically is composed of

a core, which goes up first, that would be like the spine of the building.

And then the floors branch out from that.

NARRATOR: The core is the main source of strength within most high-rises.

It's made of heavy-duty reinforced concrete.

Running from the foundation to the very top,

it stabilizes the structure.

DAN: So, the core of the building is

the most important aspect, when it comes to structural integrity.

NARRATOR: As the building goes up, other components, like floors and beams, are secured,

or tied-in to it.

DAN: So, when you tie a building component

into the overall structure, what you're doing is you're creating

a strong and rigid connection,

taking a separate piece and making it a part of a whole.

And the building at the end is just one monolithic structure,

when in reality it's a bunch of really small pieces that have been tied together.

It's really important that those elements get tied in adequately

during the construction of the building.

Because otherwise,

the bits of the building that are intended to act together to support the loads

can't do so.

NARRATOR: If the pieces aren't tied in correctly,

it could mean trouble.

Combing through the rubble of the collapsed Hard Rock Hotel,

investigators find something shocking.

The initial accident investigation had issued citations,

which suggest that floors 9 through 15

on the western side of the building

were not adequately tied in to the structural frame.

DAN: This is bad, because the building is not one piece.

But now it's a collection of lose pieces that doesn't have the same strength.

This is a disaster waiting to happen.

It's difficult to tell whether or not the error was in the design itself,

or whether it was in the assembly,

or the procedure for the assembly.

But at the end of the day, it would lead to failure.

NARRATOR: Somewhere along the line, has someone made a terrible mistake?

Over 80% of all construction accidents are down to human error.

The same pattern's seen in other engineering disasters.

80% of plane crashes are caused by pilot error.

And up to 95% of all marine accidents are also due to human error.

Like this cruise from hell.

January, 2012.

Just off the Italian coast,

a huge 952-foot ship sails too close to shore.

Onboard, over 3,000 passengers,

all completely unaware of impending doom.

Suddenly, at 9:45 p.m., the ship hits rocks.

What causes this giant vessel to run aground?

Costa Concordia is an engineering monster.

The length of three football fields,

and at 170-feet tall, higher than Niagara Falls,

the ship weighs in at a massive 50,000 tons.

Its engineers have designed the boat for everything the ocean can throw at it.

ASEGUN: But it's not designed to go near an island,

where you've got rocky formations and shallow water.

NARRATOR: And that's exactly what happens.

Following departure from Rome, the captain orders a diversion.

Instead of staying on course through deep water,

he makes the fatal error of sailing close to the small island of Giglio,

reportedly to salute a former colleague on shore.

Spotting a reef on the radar, the captain orders the ship to turn.

But there's a miscommunication with the helmsman,

who steers the wrong way.

(METALLIC SCRAPING)

The Costa Concordia scrapes along the reef,

tearing a hole below waterline.

I was immediately thrown back in my seat,

as if I'd been whiplashed.

And glasses were sliding off the racks and I'm smashing into shattered glass everywhere.

The ground underneath us was violently shaking.

And there was this moment that everybody was holding their breaths,

trying out figure out what on earth was going on.

At that point, water starts to flood into the hole.

(INDISTINCT SHOUTING)

And that can easily start to short-circuit,

um, to trip breakers, and that'll cut out your electrical systems.

NARRATOR: Pumps could be used to get water out of the hull...

(INDISTINCT SHOUTING)

...but without power...

they're useless.

(INDISTINCT SHOUTING)

An hour after collision, the ship's sinking fast.

It's a fight for survival for passengers and crew.

(INDISTINCT SHOUTING)

ROSE: I looked down and I just saw thousands of people

acting like a swarm of bees,

and just running into one another.

There was screaming, shouting and it was just...

so harrowing,

because we had no idea what would happen to us.

NARRATOR: The captain escapes on one of the few working lifeboats,

leaving hundreds still onboard.

He gets off the ship before all of the other passengers get off.

Which, to me, is mind-boggling,

because you're the captain. Isn't the captain supposed to leave last?

NARRATOR: As dawn breaks, the full scale of the disaster is visible.

Thirty-two die, 157 injured.

The salvage operation will cost a staggering $2 billion.

The Costa Concordia tragedy is the result of one person making a bad decision.

But at the Hard Rock Hotel,

early reports indicate that, shockingly,

the collapse wasn't down to a single human error

but a whole catalogue of them.

NARRATOR: By fall 2019, the Hard Rock Hotel is rising up in New Orleans.

It was definitely a sight to see when I passed by in the streetcar every morning,

on my way to work.

NARRATOR: But as work begins on the 17th floor,

nobody's aware of the weaknesses below.

And this floor features the most ambitious part of the design yet.

Could it also be another piece to unravelling the puzzle?

Spread across floors 17 and 18,

a spectacular viewing gallery.

To create it, engineers use a cantilever.

Think of like pirates and walk the plank, right?

The plank is sticking out over the water.

And so that's a cantilever that sticks out.

NARRATOR: Commonly used in balcony construction,

a cantilever is a rigid structure that extends beyond the building.

It's only supported at one end,

so it has to be strong.

A cantilever is often referred to as an engineer's best friend,

because it's a very, very versatile thing that you can use to solve lots of problems.

One of the nice things of cantilevers,

especially in building construction,

is that it allows you to have unobstructed views.

LUKE: And as an architectural feature,

you can imagine this is something that many architects really want to achieve.

NARRATOR: And in the Hard Rock Hotel,

the cantilever will offer tourists a clear view of the entire city,

a huge selling point.

But there are a number of ways cantilevers can go wrong,

if they're not correctly designed.

The cantilever itself doesn't want to be there.

It wants to fall or rotate.

NARRATOR: Calculations must be precise.

DAN: Not only does the cantilever beam have to support its own weight,

but it also has to support the weight of other components that are tied into it.

NARRATOR: Because nothing else holds it up.

LUKE: Any small increase in length has significant consequences

for the overall strength of the cantilever.

Because the maximum span is intended to prevent that cantilever from collapsing.

NARRATOR: Making it longer also makes it heavier.

ROB: If you don't get the calculations of that structure correct,

that cantilever might not be able to take the weight

it's pushing down on it.

NARRATOR: When that happens, it's game over...

as shoppers in Mexico find out.

Mexico City, July 12th, 2018.

A brand new shopping mall.

It's been open just for four months,

but it's still partially under construction.

The stunning facade, held up by a cantilever,

is designed to wow shoppers.

(GLASS BREAKING)

(RUMBLING)

One of the most visually striking aspects of this structure is this

huge glass-fronted section that

appears to be sticking out from the rest of the building.

And it's sticking out because cantilevers are holding it up.

NARRATOR: On top of it, a roof garden is added.

But the planters in the garden are heavy.

It's too much.

NARRATOR: A support beam fails, and the mall is evacuated.

LUKE: Cantilever structures are very unforgiving.

Calculating the loads on any structure properly is really critical,

and if you get those loads wrong,

then there's always a chance that you might get failure.

NARRATOR: The first sign of trouble is when windows start breaking.

ASEGUN: You can't really see with the naked eye.

You don't really see the dimensions changing, but the glass knows

and it's feeling the stress of the dimensions changing.

LUKE: And then, what we see unfold is the fracture of the panes of glass

accelerates, and then suddenly the entire surface of this facade drops

down onto the street below.

NARRATOR: Thankfully, no one's hurt.

ROB: At the Hard Rock Hotel, there's also an issue with the cantilevers.

Investigators' report stated that the cantilevers on the 17th and 18th floor

exceeded the manufacturer's guidance for maximum spans.

That means that those cantilevers were too long for the weight

they were being asked to support.

NARRATOR: For now, it stays up, but it's compromised.

Another threat to this vulnerable structure...

All it will take is one push to send this house of cards tumbling down.

And there are still two more floors to be added.

Coming up... Missed warnings prove costly.

(MAN SPEAKING SPANISH)

It's very clear that something is amiss,

and something bad is about to happen, very soon.

NARRATOR: As workers in The Netherlands discover...

(WOMAN SCREAMING)

NARRATOR: When big things go wrong,

often there are warning signs.

But what happens when they're missed?

Was there a moment when the Hard Rock collapse was avoidable?

In New Orleans, construction teams are tackling the hotel's top storeys.

A critical moment comes as workers lay down concrete floors.

ROB: When you pour concrete, it starts off as a liquid,

and so, it needs time to cure and harden.

DAN: It takes time for concrete to become solid.

You have to give it sufficient time to set up and become strong.

NARRATOR: But on the Hard Rock Hotel, they're rushing to get the job completed.

While the concrete sets,

temporary supports are put in place on the floors below to help.

LUKE: As you're building, you tend to want to move

more quickly in the construction of your building,

than the concrete can gain strength.

and the way, as a contractor, that you deal with that is to prop

the concrete in the lower levels of the floor,

until it gains enough strength that you can take those props away.

NARRATOR: But according to workers on site,

temporary supports below floor 18 are taken out just three days after the pour.

If you remove these supports too soon,

the concrete isn't hard enough to support its own weight.

DAN: And what that means is, all that weight's gonna sag and droop down,

and that's not something you really, really want in a high-rise hotel.

NARRATOR: Some on the site noticed signs of trouble.

In footage shot by workers just before the collapse, the sagging is clearly visible,

and supports are bent out of shape.

The fact that it's kinked, and it's bent,

meant there's a lot of weight that's trying to come crashing down,

and there should have been more stuff kept underneath

to support that weight.

(MAN SPEAKING SPANISH)

Seeing that temporary vertical support, as bent as it is like that,

for me, would set off loud alarms bells.

(MAN SPEAKING SPANISH)

It's very clear that something is amiss,

and something bad is about to happen, very soon.

NARRATOR: Did a missed warning

lead to tragic consequences?

It happened in Holland,

when an operation to move a new bridge goes horribly wrong.

(WOMAN SCREAMING)

NARRATOR: August, 2015.

Engineers prepare to replace a section of aging bridge.

Part of the bridge deck

is being positioned and then lowered into place.

It's a bridge over a canal.

And it's these enormous cranes that are going to be doing the lifting.

NARRATOR: The cranes weigh 400 and 700 tons each,

reaching 130 feet high.

The site's in the middle of a busy residential area,

and contractors have planned the operation for months.

But they've overlooked something crucial.

The two giant cranes sit on floating barges.

Operators raise concerns about their stability before the lift.

But the job moves ahead anyway.

DAN: It's actually quite difficult as an engineer for me to watch.

You look at it and you see this doesn't look like a good scenario.

As soon as they lift, it's already kind of leaning

and then, as they slowly move, it's watching this disaster unfold in slow motion.

NARRATOR: The bridge section starts to sway.

And the barge with the smaller crane tilts.

These cranes are now reaching a point of no return.

And at some point, you can see people realize, essentially, that all is lost,

and they're now just trying to get out of the way of the impending collapse.

WOMAN: Oh!

NARRATOR: The crane breaks...

(WOMAN SCREAMING)

...and falls sideways,

setting off a domino effect.

(WOMAN SCREAMING)

NARRATOR: Miraculously, nobody dies.

(NARRATOR READING)

In New Orleans, what pushes the Hard Rock over the edge?

LUKE: A structure in this situation,

is potentially just teetering on the brink of collapse.

NARRATOR: Dawn. New Orleans.

As the sun rises over the city,

the Hard Rock Hotel approaches breaking point.

It's the weekend.

Construction teams race against the clock to finish ahead of Mardi Gras.

A large number of construction workers were working over various levels of the building,

doing various activities, right away from the top of the structure,

all the way down, to the base.

NARRATOR: On the 18th floor, the crew adds a new piece of equipment...

a scissor lift.

This is a very heavy pieces of machinery.

NARRATOR: It weighs 3,000 pounds,

and it's placed on the recently-poured concrete slabs.

My expectation, as a structural engineer,

would be that anyone who has put that scissor lift there

has thought very carefully about whether the floor slab is gonna be able to support that load

in an effective way.

NARRATOR: In the streets surrounding the hotel,

the weekend crowds are already growing.

FALLON: Even as early as 9:00, it's a busy, busy place.

So there was cars and streetcars passing by, and people in the sidewalks.

I made my way to the streetcar,

and everyone had a really nice little, sort of sprite to their step.

And the streetcar pulled up.

I grabbed my normal seat, everyone grabs their seats, and...

and we make way down Canal Street on the streetcar.

NARRATOR: Fallon's route will take her right past the Hard Rock Hotel.

She's unknowingly heading towards danger.

150 feet above her bus,

the Hard Rock is minutes from collapse.

Workers move the scissor lift to the western side of the 18th floor.

DAN: That scissor lift represented a point load on one of the upper floors,

in a position somewhere that may or may not be

mechanically as strong as it should be.

NARRATOR: On the floor directly below,

some of the temporary supports have been removed,

and the concrete isn't fully set.

If you have a floor slab that hasn't got the strength that it needs,

and you put a significant concentrated load on that floor slab,

that could lead to failure by some or other mechanism.

It's big, it's heavy, and it could push this over the edge.

NARRATOR: Fallon's streetcar reaches the Hard Rock Hotel.

Like the workers on the building,

she's unaware a chain reaction has already begun.

It's now unstoppable.

When you move the support, then the concrete might start to bend or crack.

There absolutely shouldn't be deforming in a building such as this.

FALLON: We got to the corner of Canal in North Rampart.

I do remember looking up briefly.

It all happened in a split second.

I just recall looking back down at my phone, and then hearing

what sounded just like things beginning to fall. Large, heavy concrete

and faint screams in the distance.

MAN: Oh, my God!

All of a sudden, there's a huge dust cloud, people are panicked.

(LOUD RUMBLING)

DAN: There's a lot of uncertainty.

MAN: Get to the back! Get to the back!

NARRATOR: Bystanders are in total shock.

MAN: Everybody, get back, get back!

FALLON: We got out of the streetcar pretty quickly.

You couldn't see a 100 to 200 feet in front of you.

Everything was just grey and very apocalyptic.

And people were covering their mouth, and screaming, and ducking,

and just running as fast as they can, away from the site.

(SIRENS WAILING)

NARRATOR: Bystanders are in total shock. The nightmare's only beginning.

LUKE: A structure in this situation

is potentially just teetering on the brink of some further collapse.

MAN 1: Come on, get back, get back.

MAN 2: That tower could come down any time.

Any one of those could go down.

(MAN SPEAKING)

(INDISTINCT SHOUTING)

There were these huge, like, cranes, um, that were dangling

so precariously over the building.

Nothing looked very stable at that point.

ROB: These are huge, great, big imposing machines.

They're kind of just left hanging.

They can actually come crashing down into the streets of downtown New Orleans.

It was a dangerous, very dangerous situation.

NARRATOR: Rescue is slow and painstaking.

Eventually dozens of trapped victims are recovered.

But three workers die.

FALLON: That day was...

pretty horrifying, um, on so many levels.

It was really sad and tragic, 'cause you could hear, they were crying and screaming,

and people were, you know, in tears, a mess, um,

having been bear witness to that.

NARRATOR: And now, New Orleans wants answers.

(MAN SCREAMING)

NARRATOR: When Big Things Go Wrong...

The causes can be obvious.

(MAN SPEAKING)

But for the busy city of New Orleans, the disaster comes out of nowhere.

LUKE: In a modern American city,

For a major hotel like this to literally fall out of the sky,

shows there is something very wrong here.

NARRATOR: Seen through the eyes of engineers, the clues have been building.

The lower floors...

ROB: With this hotel,

the bolts actually sheared, they snapped in two.

NARRATOR: Floors nine to fifteen...

When you have portions of the floors that aren't tied in,

these pieces of the building are almost floating in space.

NARRATOR: The cantilever on floors 16 and 17...

If you get those loads wrong, then there's always a chance that you might get failure.

NARRATOR: And too much weight on the top floor...

If you remove these supports too soon, the concrete isn't hard enough

to support its own weight.

NARRATOR: Until finally, collapse is inevitable.

DAN: The buckling of the column in that footage taken right before the accident,

it hints at what the problems are.

NARRATOR: When some of the supports are removed on floors 16 and 17,

the remaining ones become overloaded.

They buckle under the weight of recently-poured concrete,

which hasn't had time to set.

If you take the supports away from concrete that's been cast fairly recently,

then the concrete isn't strong enough to support its own weight,

and that could lead to a collapse.

NARRATOR: When more weight's added...

DAN: That scissor lift represented, kind of, like a point load

on one of the upper floors.

NARRATOR: There's no saving it.

The building starts to crumble at the very top.

ASEGUN: All it takes is one section of the structure to give way,

and it slams down on top of another structure which was not designed to hold that weight.

NARRATOR: Unable to take any more, the supports holding up the 18th floor give way...

crashing into the viewing gallery.

And now, it's kind of this domino effect that accelerates

and components just keep failing, one after another,

and the weight is transmitted to the remining members that are still standing.

NARRATOR: Weaknesses further down only make things worse.

The lower floors, not properly tied in, can't support the falling building.

DAN: You see the top floors begin to fall down on the lower floors,

causing this cascading failure of crumbling floors,

breaking material, bent steel, and then the entire front of the building rips away.

NARRATOR: The sheared bolts on the lower floors are the result of the collapse.

ASEGUN: Because they become overloaded

when all other weight of the building is transmitted, as the whole thing just falls apart.

NARRATOR: Modern buildings simply shouldn't pancake down in the way the Hard Rock does.

But it seems this structure is more house of cards than strong concrete and steel.

And anyone who's ever actually built a literal house of cards

will know that if the cards at the top of the stack fall down,

the rest of the cards are likely to follow.

NARRATOR: The consequences of this failure are tragic.

Three workers die,

30 are injured.

The site is so unstable,

it takes emergency workers ten months to retrieve one of the bodies.

There's still anger and hostility after everything that's gone on, because

the building stood for almost a year.

So, you know, it acted as this tomb.

It was this gloomy, gloomy stamp on our city.

NARRATOR: Finally, 17 months after the collapse...

(EXPLOSION)

...demolition begins.

Two building safety inspectors were suspended without pay

for allegedly falsifying reports.

But with investigations still ongoing, it's unclear who is ultimately at fault.

It sort of tore the city apart to some degree.

You know, there was lot of pointing fingers, and who was to blame.

NARRATOR: What's certain is a number of mistakes contributed to this disaster.

And since over 1,000 workers have died on US construction sites in recent years,

it's crucial to learn from them.

As buildings soar higher, the risks increase.

In reality, nothing always goes right.

Sometimes, mistakes are made.

It's the job of engineers, architects, and designers in construction projects

to make sure that if mistakes are made, they don't catastrophically

cause the entire project to fail.

The upshot of all this is, we should learn from this.

We should look back and examine what went wrong and make sure those mistake aren't made again.

MAN: Oh, my God!