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in the mid 19th century suspension
bridges were collapsing all across
Europe their industrial cables frayed
during turbulent weather and snapped
under the weight of their decks so when
a German American engineer named John
Roebling proposed building the largest
and most expensive suspension bridge
ever conceived over New York's East
River city officials were understandably
skeptical but Manhattan was increasingly
overcrowded and commuters from Brooklyn
clogged the river in February of 1867
the government approved roebling's
proposal
to avoid the failures of European
bridges Roebling designed a hybrid
bridge model from suspension bridges he
incorporated large cables supported by
central pillars and anchored at each
bank this design was ideal for
supporting long decks which hung from
smaller vertical cables but roebling's
model also drew from cable-stayed
bridges these shorter structures held up
their decks with diagonal cables that
ran directly to support towers by adding
these additional cables Roebling
improved the bridges stability while
also reducing the weight on its anchor
cables similar designs had been used for
some other bridges but the scope of
roebling's plan here dwarfed them all
his new bridges deck spanned over 480
meters 1.5 times longer than any
previously built suspension bridge since
standard hemp rope would tear under the
decks fourteen thousand six hundred
eighty tons his proposal called for over
five thousand six hundred kilometers of
metal wire to create the bridges cables
to support all this weight the towers
would need to stand over 90 metres above
sea level making them the tallest
structures in the Western Hemisphere
Roebling was confident his design would
work but while surveying the site in
1869 an incoming boat crushed his foot
against the dock within a month tetanus
had claimed his life fortunately John
roebling's son Washington was also a
trained engineer and took over his
father's role
the following year construction on the
tower foundations finally began this
first step in construction was also the
most challenging building on the rocky
riverbed involved the use of a largely
untested technology pneumatic caissons
workers lowered these airtight wooden
boxes into the river where a system of
pipes pumped pressurized air in and
water out once established airlocks
allowed workers to enter the chamber and
excavate the river bottom they placed
layers of stone on top of the casein as
they dug when it finally hit the bedrock
they filled it with concrete becoming
the towers permanent foundation working
conditions in these caissons were dismal
and dangerous lit only by candles and
gas lamps the chambers caught fire
several times forcing them to be
evacuated and flooded even more
dangerous was a mysterious ailment
called the bends today we understand
this as decompression sickness but at
the time it appeared to be an
unexplainable pain or dizziness that
killed several workmen in 1872 it nearly
claimed the life of the chief engineer
Washington survived but was left
paralyzed and bedridden yet once again
the roebling's proved indomitable
Washington's wife Emily not only carried
communications between her husband and
the engineers but soon took over
day-to-day project management
unfortunately the bridges troubles were
far from over by 1877 construction was
over budget and behind schedule worse
still it turned out the bridges cable
contractor had been selling them faulty
wires this would have been a fatal flaw
if not for the abundant fail-safes
in John roebling's design after
reinforcing the cables with additional
wires they suspended the deck piece by
piece
it took 14 years the modern equivalent
of over 400 million dollars and the
life's work of three different
roebling's but when the Brooklyn Bridge
finally opened on May 24 1883 its
splendor was undeniable
today the Brooklyn Bridge still stands
atop its antique caissons supporting the
Gothic towers and intersecting cables
that frame a gateway to New York City
building bridges is cool but what about
subterranean trains how did they dig
massive tunnels under bustling cities
over a hundred fifty years ago answer
all your burning questions with this
animation on the origins of the London
Underground
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