00:00THE END
00:49San Francisco, metropolis of the west, seaport of the Pacific, glories in its calm, landlocked bay.
01:00As far back as 1856, men dreamed of linking the city of San Francisco with the east shore of the
01:06bay.
01:07The steady growth of San Francisco and the Oakland area emphasized the need of communication.
01:14As the years passed, many proposals were made, but it remained for modern science and engineering to overcome almost insurmountable
01:24obstacles and make the dream come true.
01:28Today, there are towers over San Francisco Bay, a realization of the century-old dream.
01:35A six-lane double-deck bridge, eight miles long, connecting San Francisco with the Oakland-Berkeley area, spanning the largest
01:44major navigable body of water ever bridged.
01:50The west bay crossing is a twin suspension bridge with an anchorage in San Francisco, a central anchorage, and another
01:59anchorage on Yerba Buena Island.
02:03This twin suspension span is the largest of its kind in the world and crosses nearly two miles of deep
02:10water.
02:13A tunnel through the island connects it to a cantilever span on the east side, which in turn is connected
02:21to the east shore of the bay by a number of through-trusts and deck-trust-type spans.
02:29Building the cantilever and suspension sections was a challenge to American ingenuity.
02:37A novel method of sinking the foundations was employed.
02:43Steel cutting edges, towed to location between working docks, were built up with hollow steel cylinders.
02:56Wooden walls, the work walls, encased the cylinders.
03:01New units were added at the top as caisson sinking progressed.
03:05This cross-section diagram shows the caisson in position between two working docks.
03:11Air pressure was maintained in the cylinders to control the sinking as concrete was poured into the spaces between them.
03:19On reaching bedrock, the mud was scooped from the cylinders and replaced by a 30-foot concrete seal.
03:32Thus were built the deepest foundations ever undertaken, some as deep as 242 feet.
03:40On these unique foundations, concrete bases were built to receive the superstructure.
03:46The huge steel towers rose like magic.
03:49After years of planning, the visions and blueprints of the engineers took physical shape under the skilled hands of the
03:56men of action.
04:00The bridge men, long experienced in this hazardous business, went about their work, sometimes in precarious positions, expertly guiding the
04:09steel into place.
04:10Some sections weighed as much as 79 tons.
04:24All the steel sections were fabricated at American Bridge Company's plants at Gary, Indiana and Ambridge, Pennsylvania.
04:32That clear there was only one of the biggest named
04:40...
04:45...
04:46...
05:06Looking towards San Francisco from the center anchorage in the West Bay, two of the 500-foot
05:11towers for the suspension bridge can be seen. Looking in the opposite direction past the
05:17other pair of towers, we see Yerba Buena Island, where the great East and West Bay sections
05:23of the bridge are connected by a tunnel. This tunnel, 63 feet wide and nearly as high, has
05:31the largest cross section of any tunnel in the world.
05:38Let's cross to the other end of the tunnel for a glimpse at the East Bay section. Two
05:44mighty piers will support the massive steel towers for the 1,400-foot cantilever span and
05:50its two 520-foot anchor arms.
06:05High above the waters of the bay, the fabricated steel sections swing into place with infinite
06:11care and precision. Building the third longest cantilever span in the world, the longest in
06:18the United States was the bridge men's toughest job.
06:46The last mighty section in the 40 million pound cantilever structure fitted perfectly in the
06:51world. The last mighty section in the 40 million pound cantilever structure fitted perfectly in the
06:51position, surprising to the laymen what expected by the engineers. The remainder of the East Bay crossing
06:59to Oakland consisted of through truss and deck type spans. Back on Yerba Buena Island, work is being completed
07:07on the cable anchorage for the second of the West Bay twin suspension spans. Steel eye bars and a wedge
07:14-shaped
07:14mass of concrete have been firmly embedded in the rock of the island. More eye bars sunk deep in 130
07:21,000 tons
07:22of concrete in San Francisco's Rincon Hill form the western anchorage. The 340,000 ton center pier with its steel
07:31A-frame and
07:31side bars is ready to serve as a common cable anchorage for the twin suspension spans. While signs and
07:38sentinel launches keep bay traffic away from danger, the catwalk ropes are drawn into place. A huge reel of
07:46USS American Tiger brand wire rope at a tower base feeds out above the water toward the center anchorage,
07:531,160 feet away. On the tower, 500 feet above the water, bridgemen adjust and secure the wire rope. To
08:22provide a firm
08:23safe footing, safe footing for the bridgemen, a special type of catwalk was designed. USS Cyclone
08:30chain-link fence was chosen for its light weight, low wind resistance and great strength. This bundle of
08:38cyclone fence will cover a distance of 100 feet.
08:49When sufficient flooring had been placed to reach the next tower, it was stretched into position. This job calls for
08:59iron nerves for the bridgemen ride the catwalk during the stretching operation. But after the precarious footing during
09:07tower erection, this 10-foot catwalk was a cinch. Fun, but with a serious purpose, to keep the wire mesh
09:23sliding freely as it is stretched over the steel rope. San Francisco Bay looked like this from the catwalk. Far
09:33below, the old ferry boat plows
09:34solidly along, soon to be replaced by trains of electric cars, automobiles and trucks, rolling in an endless stream across
09:43the bridge that soars above.
09:50At dinnertime, the bridgemen lose no time hitting for home. A run along the catwalk to whet the appetite, then
09:58the sky ride, and down the escalator helter-skelter.
10:04It's a hard, dangerous job, that of the bridgeman, but he loves it. With catwalks in position, the spectacular job
10:16of cable spinning is about to begin. Giant reels of special bridge wire, supplied by American Steel and Wire Company,
10:24rise majestically to the top of the anchorages.
10:30These huge reels, each carrying 60 miles of wire, were assembled at the nearby Columbia Steel Company warehouse. High above
10:40the water, the spinning wheels begin to travel.
10:4318,000 tons of galvanized wire will be used to bind together two neighbor cities, Oakland and San Francisco. This
10:55cable will consist of 37 strands, each made up of 472 galvanized steel wires as thick as a lead pencil.
11:03In making a cable of this size, the individual wires are not twisted in any way, but laid parallel for
11:10the entire length of the bridge.
11:12From San Francisco to the center anchorage, more than a mile away, and from there to Yerba Buena Island, nearly
11:17another mile away, the spinning wheels work with ever-increasing speed.
11:23This model will illustrate the principle of cable spinning. The end of the wire is anchored temporarily and passed around
11:33the strand shoe.
11:37Then, the spinning wheel takes the loop across to the other side. There, it's removed from the spinning wheel and
11:45looped around that strand shoe.
11:49This is repeated until a sufficient number of wires have been laid. Then, the wire is cut and spliced to
11:58the beginning end.
12:08Day and night, spinning continues. Down plunged the spinning wheels toward the island anchorage.
12:21There, Bridgeman removed the wire and rethread the wheel.
12:41Four cable wires are placed on every trip.
12:45Let her go!
12:51The end of a coil of wire is joined to the beginning of the next coil,
12:55by means of a turnbuckle type splice. Each wire is beveled, so that when they are drawn together by the
13:02turnbuckle sleeve, the ends fit snugly.
13:05The two wires are gripped in separate vices, as a workman draws them up with a wrench applied to the
13:11turnbuckle sleeve.
13:13The beveled ends form a lock, and will not become loose, unless they are again placed in vices and unscrewed
13:20with a wrench.
13:25Two spinning wheels operate on each hauling rope. Halfway between the anchorages, they meet and pass.
13:34A clanking cowbell warns the bridgeman of the wheel's approach, as it continues to spin its web of steel against
13:42the sky, far above the traffic of the bay.
14:04When spinning was completed, the compactor went into action.
14:08Six 75-ton jacks in this machine squeeze and bind the strands into a mighty cable 28 ¾ inches in
14:18diameter.
14:28Special steel castings are spaced at intervals along the cable. Each carries two pairs of steel suspender ropes, cut to
14:37length and pre-stressed to support the bridge deck.
14:45Barges controlled by radio phones carry the massive prefabricated truss units, some weighing 200 tons, out into the bay to
14:54be hoisted into place by traveler trains.
15:00Barges controlled by radio, before crossing the edge of the bay to be hoisted with the bay to be hoisted
15:04with a different vessel,
15:05with a little bit of a trick.
15:18Barges controlled by radio, the flat-like ball from the bay to be hoisted with an important wall.
15:24Barges controlled by radio, the inside and of the bay to be hoisted with a tiny band.
15:39Soon, hundreds of sections had been guided accurately into place in the structure.
15:44An amazing example of coordinated engineering, manufacturing, fabrication, and transportation.
15:55The work of the bridge men is completed.
15:58The rugged men of steel are ready to move on to the next job, wherever it may be, of drawing
16:04together the people of the world.
16:07When they leave, the romance of bridge building leaves with them.
16:12These men of skill and courage are the adventurers whose work and sweat and toil have constructed
16:20a mighty edifice, woven a web of dreams into a web of steel.
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