Scientists sometimes get a little excited when an
experiment doesn't work the way they expect it to.
It's an opportunity to learn something new about the
world, and they can always change the expriment
a bit to try again next time.
Engineering... is a little bit different.
Desginers and engineers generally prefer to find out
something's wrong before it's built instead of after,
because engineering failures can be disasterous.
But engineering failures have
happened and, if nothing else,
they're an opportunity to learn
what not to do next time.
When it opened in 1878, Scotland's 3.2 km
Tay bridge was the longest bridge in the world.
It was so impressive that queen Victoria knighted
Thomas Bouch, the Tay bridge designer
after she took the train across it.
But on December 28, 1879, a train was
crossing the Tay bridge during a violent storm,
when the middle of the bridge collapsed.
The bridge, the train and the 60 or so people
on board crashed into the water below—
there were no survivors.
An official investigation found so many problems
with the bridge's construction and design,
that they couldn't even figure out what failed first.
But according to their report,
Bouch did just about everything wrong.
They tested a lot of the bridge's
surviving components, for example,
and found that they couldn't stand anywhere
near the pressure they were supposed to.
So the bridge would have failed eventually, anyway,
and the storm just accelerated things.
And when investigators looked at the columns
that had been holding the bridge up,
they saw that they were broken at the bottom,
so the columns might have been responsible for
the bridge's collapse.
The winds could have made the train rock as it went
along, maybe even forcing it against the bridge's walls.
If that had happened, it would have put
a lot of extra stress on those columns,
breaking them and bringing the bridge down.
Whatever the reason the Tay bridge fell,
engineers found even more problems when they looked
at some of Bouches' other projects.
Some of their components were either just
as badly-made as the ones on the Tay bridge
or they were arranged in ways that meant
they couldn't hold much weight.
Apparently, he just wasn't a very good engineer.
The Tay bridge disaster made it clear that
those projects were also ticking time bombs
and that bridge inspections had to be way more
thorough to stop these kinds of things from happening.
The other bridges were either quickly repaired...
or destroyed to prevent another disaster.
But The Tay bridge, of course, was not
the last bridge to collapse.
The Quebec bridge was set to be
the longest cantilever bridge in the world
when construction began in 1900, but it collapsed
TWICE before it eventually claimed
the title in 1917.
Cantilever bridges are made of big bulky parts that
support relatively flat sections between them.
And during construction, workers kept
noticing that some of the support pieces
were bent more than they should have been.
They were holding way more
weight than they were designed to,
partly because the bridge ended up longer
than it was originally planned to be.
But to save time and money, extra support wasn't added.
The designers hoped that the problem
could be fixed as construction went on,
but at the end of the workday on August 29, 1907,
parts of the bridge collapsed under their own weight,
killing 75 workers.
Construction resumed after investigators
figured out what happened.
Their main conclusion was that the bridge's
components just weren't strong enough.
So the bridge was rebuilt. This time
much bigger and stronger.
But, all that extra metal made it much heavier, too.
was hoisted into place in 1916 the
equipment bringing it up broke and they
plunged into the river below this time
13 people died the Quebec bridges after
was a reminder that it's important to
make sure that the thing you're building
can carry the weight you're putting on
it and it probably would not have
happened today over the last century
engineers have developed tons of new
mathematical techniques and computer
programs that probably would have caught
the first collapse long before the
bridge was built even before it opened
in nineteen forty people noticed
something strange about Washington
State's tacoma narrows bridge it moved
gentle winds could make the long
suspension bridge flex up and down by
meters at a time making it hard to drive
or even walk across the British
designers tried to keep it from bouncing
so much by installing shock absorbers
but they weren't very effective and then
about four months after it opened to the
public one of its cables snapped from
how high the bridge was bouncing a
strong wind and the other cables started
to slide around this let the bridge
start twisting back and forth instead of
bouncing and eventually the middle broke
off and fell into the water below
unlike the Tay and Quebec Bridge
disasters
there was only one fatality this time a
dog named Tubby Tacoma Narrows failed
because of something called aeroelastic
flutter when that first cable snapped
its side of the bridge fell slightly
because it was less supported then other
cables on that side pulled up like
stretched out rubber bands and the
bridge started twisting back and forth
then the wind gave each twist a little
boost so small boosts built up over the
course of the morning and eventually
twisted the bridge apart engineers
learned their lesson pretty quickly and
reinforce the bronx Whitestone bridge in
New York which is also known to flex in
the wind and that bridge is still
standing today but not all failed
construction projects has been bridges
tho the 40-story hyatt regency hotel
opened in Kansas City, Missouri in 1980
and it quickly became known for its
innovative atrium which featured three
long walkways that seemed to float in
the air the hotel called them "skywalks"
instead of being supported by pillars
each skywalk was suspended from long
rods hanging down from the ceiling the
second floor skywalk hung below the
fourth floor skywalk with the third
floor skywalk off to the side on
separate supports their unique design
made the huge atrium an ideal place to
host events and parties like the one
that the hotel hosted on july
seventeenth 1981 about 1,600 people
attended hundreds danced and talked in
the atrium while others milled around
the hotel and check out the famous
skywalks then at 7:05 p.m. two of the
skywalks suddenly collapsed without
warning a hundred and fourteen people
were killed and more than 200 were
injured making the incident the
deadliest structural collapse in US
history until 9/11 happened 20 years
later investigators found a small
last-minute change to the rods holding
the to collapsed skywalks that meant that
instead of each holding its own weight
they were linked together originally
rods went from the feeling all the way
through the fourth floor skywalk and
down to the second floor one with pieces
underneath each skywalk supporting its
immense weight but after the change the
second floor skywalk hung from the
fourth floor one so supports for the
fourth floor skywalk weren't just
holding up 129 metric ton skywalk they
were holding up two of them
it also didn't help that to save some
money the building materials themselves
weren't quite as strong as they should
have been and on the night of the party
the extra weight of a
couple dozen people standing
on the skywalks proved to be too much
what seemed like a tiny change to their
construction turned out to have terrible
consequences Manhattan Citicorp Tower
which is now just called 601 Lexington
Avenue proves that projects with
problems don't always end in disaster
the skyscraper's triangular top makes it
stand out from afar but you'd notice
something else if you were just walking
by Citicorp Tower was built on stilts
which turned out to be a problem
the stilts were built to accommodate a church
next door that essentially said they
could build a skyscraper on the property
as long as it didn't block the church so
the building's designers just decided to
start most of the tower nine stories up
they knew that such a tall building with
so little on its bottom floors could
be prone to toppling over on strong
winds so they wanted to make sure that
it could withstand even the strongest
winds blowing against its windows so
they added extra weight to the top of
the tower that moved in the opposite
direction of any lean the wind might
cause wind against the skyscraper's corners
usually just sort of slides past the
building so Citicorp Tower's designers
didn't even bother checking for them and
that probably would have been fine if
the stilts were on the corners but
because that weird thing with the church
the building's stilts are in the middle of
its sides and in 1978 about a year after the
center opened a college engineering
student figured out just how unstable
the building was calculations showed
that storms strong enough to topple the
tower hit Manhattan about every 16 years
pretty alarming the building's designers
didn't tell anyone other than the
New York City Police Department and the
Red Cross who helped them secretly work
out an evacuation plan while the
building's internal structure was
quietly but frantically improved every
night after the office workers who were
using the building went home braces that
had been bolted together during
construction were now welded steel
plates making the connections between
them stronger so Citicorp Center would
be sturdier in the wind in the end
everything turned out fine the repairs
were finished after just three months
and the only major northern hurricane of
the year missed New York City but almost no
one knew about any of this until
1995 when someone
finally spilled the beans on just how
close New York came
to having a skyscraper fall over in a
powerful storm London's Millenium Bridge
was another project with a major design
flaw that got fixed before it led to
disaster the bridge opened on June 10th
2000 as a way for pedestrians to cross the River
Thames it was touted as an engineering
accomplishment at the time a sleek new
bridge to mark London's entry into the
21st century then it promptly closed for
repairs on June 12th 2000 and no I did not say
that wrong it was open for a grand total
of three days
the problem wasn't weight or wind or
waves the bridge was plenty strong
enough to deal with everything it was
supposed to hold instead it was the
people themselves who were
unintentionally making the bridge sway
back and forth like a pendulum some sort
of random coincidence would get a wobble
started like a bunch of people randomly
stepping on the bridge on the same side
at the same time and with up to 2,000
people crossing at once that sort of
coincidence was bound to happen
sometimes
then once the wobble got started it was
easier for people to walk with that
wobble than to fight against it so many
people walking in sync made the wobble
get even bigger and soon it got so
extreme that people couldn't walk across
the bridge without grabbing the side
railings the bridge probably wasn't in
danger of failing because people would
stop walking once the wobbles got too big
and wait for them to die down before
continuing but the wobble would have
still weakened the bridge over time and
the bridge's engineers knew what happened
to Tacoma Narrows they weren't taking
any chances so they decided to close the
bridge pretty much immediately before
the wobbles started causing other
problems they spent the next two years
adding dampers all along the bridge
which absorb most of the force from
pedestrian steps to keep the bridge from
swaying the bridge re-opened in 2002 with
all the dampers firmly in place and it's
been a famous tourist attraction ever
since designers and engineers are human
and occasionally they make a mistake
that isn't caught or there's a factor
that no one anticipated sometimes like
with the Citicorp Tower and the
Millennium Bridge the issues are
fixed in time in other cases they can
lead to catastrophe but generations of
engineers have studied and learned from
these failures and there's no telling
how many potential disasters have been
avoided because of those lessons thanks
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is a suspension bridge that connects two mountain peaks
and between them is an absolutely stupefying drop of
almost 500 meters even though the bridge
is pretty remote it does
