Original subtitles

[Narrator] Construction. Heavy machinery.

Tight schedules. Millions at stake.

What could go wrong?

Everything.

Whether it's faulty equipment, poor design, human error...

or just bad luck...

These are...

Construction Fails.

In this episode...

In Miami - a brand new bridge

hailed as the first of its kind, becomes the worst of its kind.

Electricity, when the power grid fails...

Things go off with a bang!

Cement trucks...

These heavyweight haulers make light work of a dirty job...

so long as they make it to the construction site.

Boston's big dig - a mega tunnel project with mega fails.

On March 15, 2018, traffic was moving briskly

under the brand new Florida International University

pedestrian bridge.

Suddenly the bridge collapsed,

crushing the cars below.

But, there had been warnings.

Multiple, glaring signs of a looming breakdown.

The instant the structure gave way,

there was even a repair crew on the bridge.

One worker fell to his death.

Five motorists were killed by falling debris.

Ten more were injured.

Was it preventable?

It didn't take much investigation to determine

that the bridge was doomed to fall.

The pedestrian bridge had been commissioned

to link the university and the town of Sweetwater.

Up to 3000 students a day would be able to cross over

the busy 7-lane highway below.

The fifty three metre bridge was supposed to set the standard

for a new kind of construction,

employing advances in techniques and materials

that would make the build faster,

more efficient and higher quality.

It was supposed to be safer.

So, what went wrong?

In a standard cable-stayed bridge,

the towers and cable distribute the load,

and although the Miami footbridge

had the same distinctive fan-like silhouette,

the cables were not shouldering the weight.

Instead, the 950-ton deck was supported

by a series of concrete trusses.

The vertical trusses keep the bridge in compression

and the diagonal ones in tension.

Keeping the bridge stable by having it push in on itself.

The engineers also used a newer manufacturing technique

called Post Tensioning.

Unlike the traditional method of pouring concrete

around a rebar skeleton,

to prevent it from sagging and cracking

under its own weight,

post tensioning uses pre-formed concrete slabs

that come with pre-drilled holes.

Then, steel bars are inserted into the holes.

Once the slab is placed in position,

nuts on either side of the surface

are tightened to squeeze the slab.

Which strengthens and compresses the concrete.

Lighter. Faster. Cost-effective.

And in the case of the pedestrian bridge,

a fatal mistake.

In constructions like these, redundancies are often built in

to protect against a catastrophic failure,

but in this case they were not.

The 12 concrete "truss members"

were non redundant.

Meaning when one truss failed, they all failed.

The pedestrian bridge assembly was hailed

as a "first of its kind".

The engineers used a modular approach to construct

and install called Accelerated Bridge Construction -

or ABC.

Instead of bridge construction taking months or years,

it can take days, even hours, to do the same job.

The bridge components are preconstructed offsite,

then transported into position.

This advancement in bridge building is touted as a cheaper,

higher quality and safer method of construction.

And it might have been - had it been done correctly.

Moving day.

The 53 metre span was hoisted onto the jacks

to begin the trek to the bridge site.

But when the transport crew mapped out the route,

they discovered a curbstone on the north side of the road -

directly in their way.

So instead of carrying the load at each end,

they opted to shift the left jack

closer to the centre of the bridge

so as to clear the obstruction.

This put tonnes of stress on the concrete trusses

on the left side of the bridge -

which caused bending in the steel bars.

The plan was to tighten the bolts on the bars

once the bridge was lifted into place,

which they hoped would compress and fortify the trusses.

The bridge opened on March 10th.

Almost immediately, cracks began forming

around those same truss joints on the left side.

And it got worse.

Minute by minute, hour by hour, day by day.

Over the five days the bridge stayed up

those spreading cracks were a clear sign

of imminent failure.

But instead of closing the road to traffic

while the repairs took place, the bridge remained open,

and traffic continued to flow.

As vehicles circulated below, a crew was dispatched

to tighten the post-tension rods

on the left side of the bridge.

But it was already too damaged from transporting

the unsupported load and too late to do any good.

While they were attempting to repair the bridge -

the walkway collapsed.

950 tons of concrete came apart, dropping onto the highway below.

The bridge that had been designed to offer students

safe passage between the campus and the town

had been called "the first of its kind".

Instead, it will be remembered as the worst of its kind.

Cement trucks are heavyweight haulers.

But calling them cement mixers is misleading.

They actually mix concrete.

Cement is just one ingredient -

it's the muddy paste that binds sand and gravel together

to make concrete.

These trucks carry, mix and pour concrete -

the foundation of every building.

But to do their job on the construction site -

they have to get to the construction site.

And they don't always make it.

Some modern cement trucks are equipped

with separate water, cement and aggregate tanks -

which automatically mix together as they approach the site.

But they forgot the rear-view mirror option on this one.

So, the driver is using his phone to back up his vehicle.

Unless he's just taking a selfie of his truck.

They're still working the bugs out

on the self-driving cement truck.

Things like steering.

And stopping.

The drum on the back revolves

to keep the concrete from setting.

But it's better if just the drum spins...

not the whole truck.

Most cement trucks are equipped with air brakes.

Although in this case, they don't seem to be working.

Unless the idea is to actually take to the air.

If you've ever wondered who would win

in a fight between a tanker and a cement truck

here's your answer.

Because cement trucks are heavy.

Most have extra axles to distribute the weight

when crossing bridges.

This one didn't.

A fully loaded cement truck can weigh 33 tons.

That's almost the same as a two-story house.

The concrete spinning in a cement truck

is actually on a time limit.

After 90 minutes it starts to harden.

And solid concrete doesn't pour too well.

So, it makes sense that these trucks are in a hurry.

And nothing's going to get in their way.

Although it's hard to tell if these road hogs

are racing against time or each other.

But if their mission was to turn their trucks

into battering rams

and the highway into a demolition derby,

they're both winners.

This driver decided the best way to beat the traffic

was to drive on the wrong side of the road.

Because when you're this big, there is no wrong side.

This three metre-wide truck gets through

a two-metre gap by making the narrow space....

wider.

While these truck drivers are breaking

all sorts of traffic laws,

they're fine practitioners of Newton's first Law of Motion -

which says, "an object in motion will stay in motion."

And the bigger that object is,

the more things you need to stop it.

Like cars.

And light poles.

And trees.

So, if you're sharing the road with a cement truck

maybe take a detour.

Or you may end up leaving your prints in concrete.

Boston's Big Dig project was the most expensive

highway development in U.S. history.

It broke ground in 1991 and was not completed

until 2007.

The challenges were enormous:

Tunnelling through the dense downtown

without hampering the existing subway tunnels

and tunneling under the harbour.

The multi-lane highway also had to pass under

South Station's seven railway tracks,

which carries over 40,000 commuters

on 400 trains per day.

The city even had to plan for the millions of rats

who would be left homeless.

But its darkest hour came on July 10th, 2006.

Deep within the Four Point Channel tunnel,

24 tonnes of concrete and debris collapsed onto the road.

A car was crushed.

The driver was injured.

The passenger was killed.

The collapse shut the key traffic artery

for almost a year.

So, what went wrong?

From day one the project was plagued with problems:

delays, spiralling costs and leaks.

As far back as 1997 officials knew of leaks

in the ceilings and walls.

This caused extensive water damage to the steel supports

and overloaded drainage systems.

Many of the leaks were caused by subcontractors

failing to remove gravel and other debris

before pouring concrete.

A report in 2004 revealed

that the $14.6 billion tunnel system

was riddled with more than 400 leaks.

Leaks are bad enough, but the tunnel passed

beneath the saltwater of Boston Harbor.

Salt-accelerated corrosion had already caused

light fixtures to fail.

Had it also affected steel reinforcements

holding the tunnel ceiling in place?

Was saltwater the problem?

Or was it a fundamental error in the tunnel's construction?

How a tunnel is built depends on what it's going through...

and what it's going under.

Water and rocks are heavy!

The deeper the tunnel,

the greater the pressure from above.

This creates tensile stress.

Tensile means under tension.

This is vitally important when building a tunnel

as the ultimate tensile strength is the maximum stress

is can stand before it collapses.

Was the ultimate tensile strength exceeded in Boston?

Or was the cause more sinister - even criminal?

In 2005 police found evidence

that the largest concrete supplier

for the underground portions of the project

had delivered sub-standard concrete.

In the end, it turned out none of these factors was to blame.

After a lengthy investigation,

the National Transportation Safety Board

determined that the cause of the tragedy was epoxy glue.

Investigators found a lack of understanding

in the construction industry

about how ceiling adhesive would perform long term.

In the case of the Big Dig, the epoxy slowly deformed

and fractured over time,

causing anchors supporting 20 concrete ceiling panels

to give way.

The costliest public works project in U.S. history

suffered from leaks, substandard materials

and poor construction.

But in the end, this terrible incident

was caused by a five-dollar tube of adhesive.

We take it for granted.

We flip a switch.

The lights come on.

Our homes are heated.

Our food is kept cool.

Everything from the water supply to traffic lights...

to the screen you're watching right now,

is powered by electricity.

But what happens when electricity disappears?

When infrastructure fails, construction can fail.

The first indication of a power outage

may be when the lights go out.

Even when the power returns, there are still dangers.

The electrical surge can damage equipment,

and even cause it to explode.

When too much electricity flows through an appliance at once,

it can overheat, break down...

or even catch fire.

The power grid is smart,

designed to prevent catastrophes like these.

It's constantly adjusting for supply and demand.

And it should act as a failsafe,

triggering circuit breakers and rerouting electricity

when there are faults in the line.

The grid is a complex distribution system

that directs and delivers power across the country.

It sends a current to a substation,

where transformers bring the dangerous high voltage down,

then it feeds to a final transformer

in your neighbourhood that further reduces the voltage

to make it safe for home use.

Alaska and Northern Canada have their own power grids.

While most of the US and Canada share only a handful.

They work independently, but they also interconnect.

Which is how a power failure originating in northern Ohio

in August 2003 -

caused a cascading series of blackouts

that stretched for a thousand kilometres.

The largest power outage in North American history

left more than 50 million people in Canada

and the United States without electricity.

While some embraced the situation,

for others, it was mayhem.

The infrastructure fell apart - Flights were cancelled,

trains and subways were evacuated,

and sales were cash only.

So, what went wrong?

Weather can have a considerable effect on the power supply -

high winds or ice accumulation frequently down power lines.

Lightning strikes can set them on fire.

Had that been the problem?

Power lines are not insulated.

That would make them too heavy.

So, they're placed high in the air and spaced far apart

to avoid high voltage electricity

arcing from an exposed wire

to whatever conductive material is closest.

Could a burnt out cable

have left 50 million people powerless?

The current in a damaged wire will take to the air

looking for a conductor.

That's when sparks fly.

These arc flashes ionize the air

putting nearby buildings at risk.

They can detonate metal, trigger electrical fires

and even cause explosions.

[Voice] Oh! I got that on video!

Large power fails are the result of a small single event

that gradually leads to cascading outages

that eventually collapses the entire system.

And one of the most common culprits for these power cuts...

Trees.

Trees are a danger to many constructions,

not just power lines.

In 2003 the culprit was indeed revealed to be trees.

A single high voltage line in northern Ohio

brushed against some overgrown trees and shut down.

This one incident rippled through the grid

with catastrophic consequences.

We may think of power outages as an inconvenience,

but when our infrastructure fails,

our structures can fail too.

our structures can fail too.

All work and no play makes for a dull day.

After all, what's a construction site

but a big sandbox?

You've got toys. You've got blocks.

You've got mates.

It's fun time!

Instead of working, this guy's working out.

Which is why his career is going nowhere fast.

After a hot day of sweating it out on the site,

it's time for a little good clean fun.

Either this worker is being treated to a dip in the digger,

or the constructing crew

just fished out a drowning victim.

This truck didn't come with air conditioning -

but it does have other options.

Construction work can be exhausting.

This fellow hasn't even started his shift

and already needs a nap.

But if you fall asleep on the job...

You're defenceless against pranksters.

Later he's going to wonder if he was dreaming of lobster.

Dominos is a game of chance.

Either they'll wake him up or put him in a much deeper sleep.

Back to work.

With a major headache.

This is what happens when you sit down on the job.

Not every construction job comes with a dental plan.

But this one does.

And you don't even have to make an appointment.

Or use an actual dentist.

The dude's figured out how to balance work and play.

Shovel? What's a shovel?

These two trick riders demonstrate the difference

between a pump truck...

This daredevil's tight rope walk may not seem dangerous...

...but it still managed to hurt the area

where he does most of his thinking.

It's safe to say whatever stunt

this worker was trying to pull off flopped.

If this rodeo clown stays on for 10 seconds,

he gets a trophy.

If he stays on for 10 minutes, he gets fired.

Music is a great way to boost crew morale.

Sparky here is rocking out on his Heavy Metal guitar.

And these guys are working up a production of Dirty Dancing.

Although they might need a crane to get this Baby

off the ground.

If you're stuck on the tarmac, you can watch this ground crew

compete in an exciting new spectator sport.

It's not clear if the game has already begun

or if they're flipping a cone to see who goes first.

We have a winner.

If you wondered how to get ahead in the construction game,

watch carefully.

Last man standing gets to be foreman.

So why spend your workday working

when you can play it away?

Just make sure the boss is playing along,

or you may find yourself on permanent vacation.

♪ ♪