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Big Apple Bridges | Bridges of NYC

00:00:09the genius of a suspension bridge is

00:00:12that you can hang the bridge from above

00:00:14but then of course that raises a whole

00:00:16new set of challenges how do you hang a

00:00:17bridge from above well you have to begin

00:00:21with towers Engineers use huge towers on

00:00:25either end of the bridge to suspend a

00:00:27flat roadway from

00:00:28arcing cables which are encased in 60000

00:00:31ton stone blocks called a garages on

00:00:33either Shore smaller cables called

00:00:36suspenders hang down from the main

00:00:39cables and hold up the roadway the heavy

00:00:41weight of the road pulls down on the

00:00:43cables but the Anchorage’s keep the

00:00:46cables pulled taut holding the road up

00:00:48the combined forces push down on the

00:00:51towers compressing them into a solid

00:00:53rigid mass

00:00:57since the towers cables and Anchorage’s

00:00:59do all the work of holding up the

00:01:01roadway additional pillars underneath

00:01:03aren’t needed keeping the river clear

00:01:06it’s an ingenious way to make a bridge

00:01:09and it also sort of seems to defy nature

00:01:11because there doesn’t seem to be any way

00:01:13that it’s being held up before now no

00:01:16one has dared used these engineering

00:01:18Marvel’s to cross a river this wide the

00:01:21Brooklyn bridges center span will need

00:01:22to be over 1500 feet 50 percent longer

00:01:26than any suspension bridge ever built

00:01:28connecting City Hall in Manhattan with

00:01:31downtown Brooklyn it seems like an

00:01:33impossible job but one man in America is

00:01:36up to the challenge a civil engineer

00:01:39named John Augustus Roebling even at one

00:01:43of the river’s narrowest points the

00:01:45bridge will require a center span that

00:01:47will stretch a staggering fifteen

00:01:48hundred ninety five and a half feet

00:01:52he will need 14,000 miles of wire to

00:01:55make the four main cables it hangs from

00:01:57to hold all that up he designs towers of

00:02:01stone taller than almost every building

00:02:04in the city but then tragedy strikes in

00:02:091869 while making final sightings for

00:02:12the bridge roebling’s foot is crushed by

00:02:14a ferry slamming into its slip his toes

00:02:18are amputated and he dies soon after of

00:02:22an infection

00:02:24one of the largest engineering projects

00:02:26ever attempted is internally

00:02:29but salvation is found close to home his

00:02:33son Washington Roebling must take his

00:02:36father’s place as chief engineer finally

00:02:40the massive effort is ready to begin on

00:02:42January 3rd 1870 the first of a

00:02:46workforce that would reach nearly 1,000

00:02:48men report to duty their first challenge

00:02:52is to erect the massive gothic arches

00:02:54that will one day become one of the

00:02:56bridges most iconic features but their

00:03:00foundations must rest on solid ground at

00:03:02river bottom to be sturdy

00:03:04that means Robley must somehow send men

00:03:07up to 80 feet underwater to dig away the

00:03:10riverbed down to bedrock Roebling turns

00:03:13to a risky new device an open bottom

00:03:17blocks of wood and iron called a caisson

00:03:20pneumatic caissons are basically large

00:03:24boxes that are placed upside down so

00:03:28that what would normally be the bottom

00:03:29of the boxes up at the top and the open

00:03:31bottom is facing down into the water

00:03:34sunk to the bottom of the river highly

00:03:36pressurized air is pumped into the open

00:03:38area forcing the water out men climb

00:03:42inside through airlocks to work in the

00:03:44craft pressurized space some compare it

00:03:48to hell unbearably hot and humid

00:03:51in danger from both fire and drought men

00:03:56spend a year toiling in these case odds

00:03:59digging away at a rate of more than a

00:04:01foot per day at the riverbed beneath

00:04:03them it was a challenge like no one had

00:04:06ever taken on before every day they

00:04:08would go down there through airlocks and

00:04:10gave with picks and shovels and slowly

00:04:13but surely go down through the riverbed

00:04:15down to bedrock

00:04:18but the pressurized air that keeps the

00:04:20water out also leads to a mysterious