the genius of a suspension bridge is
that you can hang the bridge from above
but then of course that raises a whole
new set of challenges how do you hang a
bridge from above well you have to begin
with towers Engineers use huge towers on
either end of the bridge to suspend a
flat roadway from
arcing cables which are encased in 60000
ton stone blocks called a garages on
either Shore smaller cables called
suspenders hang down from the main
cables and hold up the roadway the heavy
weight of the road pulls down on the
cables but the Anchorage’s keep the
cables pulled taut holding the road up
the combined forces push down on the
towers compressing them into a solid
rigid mass
since the towers cables and Anchorage’s
do all the work of holding up the
roadway additional pillars underneath
aren’t needed keeping the river clear
it’s an ingenious way to make a bridge
and it also sort of seems to defy nature
because there doesn’t seem to be any way
that it’s being held up before now no
one has dared used these engineering
Marvel’s to cross a river this wide the
Brooklyn bridges center span will need
to be over 1500 feet 50 percent longer
than any suspension bridge ever built
connecting City Hall in Manhattan with
downtown Brooklyn it seems like an
impossible job but one man in America is
up to the challenge a civil engineer
named John Augustus Roebling even at one
of the river’s narrowest points the
bridge will require a center span that
will stretch a staggering fifteen
hundred ninety five and a half feet
he will need 14,000 miles of wire to
make the four main cables it hangs from
to hold all that up he designs towers of
stone taller than almost every building
in the city but then tragedy strikes in
1869 while making final sightings for
the bridge roebling’s foot is crushed by
a ferry slamming into its slip his toes
are amputated and he dies soon after of
an infection
one of the largest engineering projects
ever attempted is internally
but salvation is found close to home his
son Washington Roebling must take his
father’s place as chief engineer finally
the massive effort is ready to begin on
January 3rd 1870 the first of a
workforce that would reach nearly 1,000
men report to duty their first challenge
is to erect the massive gothic arches
that will one day become one of the
bridges most iconic features but their
foundations must rest on solid ground at
river bottom to be sturdy
that means Robley must somehow send men
up to 80 feet underwater to dig away the
riverbed down to bedrock Roebling turns
to a risky new device an open bottom
blocks of wood and iron called a caisson
pneumatic caissons are basically large
boxes that are placed upside down so
that what would normally be the bottom
of the boxes up at the top and the open
bottom is facing down into the water
sunk to the bottom of the river highly
pressurized air is pumped into the open
area forcing the water out men climb
inside through airlocks to work in the
craft pressurized space some compare it
to hell unbearably hot and humid
in danger from both fire and drought men
spend a year toiling in these case odds
digging away at a rate of more than a
foot per day at the riverbed beneath
them it was a challenge like no one had
ever taken on before every day they
would go down there through airlocks and
gave with picks and shovels and slowly
but surely go down through the riverbed
down to bedrock
but the pressurized air that keeps the
water out also leads to a mysterious
sickness
that you can hang the bridge from above
but then of course that raises a whole
new set of challenges how do you hang a
bridge from above well you have to begin
with towers Engineers use huge towers on
either end of the bridge to suspend a
flat roadway from
arcing cables which are encased in 60000
ton stone blocks called a garages on
either Shore smaller cables called
suspenders hang down from the main
cables and hold up the roadway the heavy
weight of the road pulls down on the
cables but the Anchorage’s keep the
cables pulled taut holding the road up
the combined forces push down on the
towers compressing them into a solid
rigid mass
since the towers cables and Anchorage’s
do all the work of holding up the
roadway additional pillars underneath
aren’t needed keeping the river clear
it’s an ingenious way to make a bridge
and it also sort of seems to defy nature
because there doesn’t seem to be any way
that it’s being held up before now no
one has dared used these engineering
Marvel’s to cross a river this wide the
Brooklyn bridges center span will need
to be over 1500 feet 50 percent longer
than any suspension bridge ever built
connecting City Hall in Manhattan with
downtown Brooklyn it seems like an
impossible job but one man in America is
up to the challenge a civil engineer
named John Augustus Roebling even at one
of the river’s narrowest points the
bridge will require a center span that
will stretch a staggering fifteen
hundred ninety five and a half feet
he will need 14,000 miles of wire to
make the four main cables it hangs from
to hold all that up he designs towers of
stone taller than almost every building
in the city but then tragedy strikes in
1869 while making final sightings for
the bridge roebling’s foot is crushed by
a ferry slamming into its slip his toes
are amputated and he dies soon after of
an infection
one of the largest engineering projects
ever attempted is internally
but salvation is found close to home his
son Washington Roebling must take his
father’s place as chief engineer finally
the massive effort is ready to begin on
January 3rd 1870 the first of a
workforce that would reach nearly 1,000
men report to duty their first challenge
is to erect the massive gothic arches
that will one day become one of the
bridges most iconic features but their
foundations must rest on solid ground at
river bottom to be sturdy
that means Robley must somehow send men
up to 80 feet underwater to dig away the
riverbed down to bedrock Roebling turns
to a risky new device an open bottom
blocks of wood and iron called a caisson
pneumatic caissons are basically large
boxes that are placed upside down so
that what would normally be the bottom
of the boxes up at the top and the open
bottom is facing down into the water
sunk to the bottom of the river highly
pressurized air is pumped into the open
area forcing the water out men climb
inside through airlocks to work in the
craft pressurized space some compare it
to hell unbearably hot and humid
in danger from both fire and drought men
spend a year toiling in these case odds
digging away at a rate of more than a
foot per day at the riverbed beneath
them it was a challenge like no one had
ever taken on before every day they
would go down there through airlocks and
gave with picks and shovels and slowly
but surely go down through the riverbed
down to bedrock
but the pressurized air that keeps the
water out also leads to a mysterious
sickness
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