Bridging San Francisco Bay (1937)

Heat. Heat. Heat. Heat. San Francisco, metropolis of the West, seapport of the Pacific, glories in its calm, landlocked bay. As far back as 1856, men dreamed of linking the city of San Francisco with the east shore of the bay. The steady growth of San Francisco and the Oakland area emphasized the need of communication. As the years passed, many proposals were made, but it remained for modern science and engineering to overcome almost insurmountable obstacles and make the dream come true. Today, there towers over San Francisco Bay, a realization of the century old dream. A sixlane double-deck bridge 8 mi long connecting San Francisco with the Oakland Berkeley area. spanning the largest major navigable body of water ever bridged. The West Bay crossing is a twin suspension bridge with an anchorage in San Francisco, a central anchorage, and another anchorage on Yerba Buena Island. This twin suspension span is the largest of its kind in the world and crosses nearly 2 mi of deep water. A tunnel through the island connects it to a cantal lever span on the east side which in turn is connected to the east shore of the bay by a number of through truss and deck truss type spans. [Music] Building the cantal lever and suspension sections was a challenge to American ingenuity. A novel method of sinking the foundations was employed. Steel cutting edges towed to location between working docks were built up with hollow steel cylinders. [Music] Wooden walls. The work walls encased the cylinders. New units were added at the top as quesan sinking progressed. This cross-section diagram shows the quesan in position between two working docks. Air pressure was maintained in the cylinders to control the sinking as concrete was poured into the spaces between them. On reaching bedrock, the mud was scooped from the cylinders and replaced by a 30-foot concrete seal. [Music] Thus were built the deepest foundations ever undertaken, some as deep as 242 ft. On these unique foundations, concrete bases were built to receive the superructure. [Music] The huge steel towers rose like magic. After years of planning, the visions and blueprints of the engineers took physical shape under the skilled hands of the men of action. The bridgemen, long experienced in this hazardous business, went about their work, sometimes in precarious positions, expertly guiding the steel into place. Some sections weighed as much as 79 tons. [Music] All the steel sections were fabricated at American Bridge Company's plants at Gary, Indiana and Ambridge, Pennsylvania. [Music] Looking toward San Francisco from the center anchorage in the West Bay, two of the 500 ft towers for the suspension bridge can be seen. Looking in the opposite direction, past the other pair of towers, we see Yerba Buena Island with a great east and west bay sections of the bridge are connected by a tunnel. This tunnel, 63 ft wide and nearly as high, has the largest crosssection of any tunnel in the world. [Music] Let's cross to the other end of the tunnel for a glimpse at the East Bay section. Two mighty peers will support the massive steel towers for the 1400 ft can lever span and its two 520 ft anchor arms. [Music] High above the waters of the bay, the fabricated steel sections swing into place with infinite care and precision. Building the third longest cantal ever span in the world, the longest in the United States, was the bridgeman's toughest job. [Music] [Applause] The last mighty section in the 40 million pound can cattle lever structure fitted perfectly into position. Surprising to the laymen, but expected by the engineers. The remainder of the East Bay crossing to Oakland consisted of through truss and decktype spans. Back on Yerba Buuena Island, work is being completed on the cable anchorage for the second of the West Bay twin suspension spans. Steel eye bars and a wedge-shaped mass of concrete have been firmly embedded in the rock of the island. More eyebars sunk deep in 130,000 tons of concrete in San Francisco's Rencon Hill form the western anchorage. The 340,000 ton center pier with its steel A-frame and eye bars is ready to serve as a common cable anchorage for the twin suspension spans. While signs and sentinel launches keep bay traffic away from danger, the capwalk ropes are drawn into place. A huge reel of USS American Tiger brand wire rope at a tower base feeds out above the water toward the center anchorage, 1160 ft away. [Music] on the tower 500 ft above the water. Bridgemen adjust and secure the wire rope to provide a firm safe footing for the bridgemen. A special type of catwalk was designed. USS Cyclone chainlink fence was chosen for its lightweight, low wind resistance, and great strength. This bundle of cyclone fence will cover a distance of 100 ft. When sufficient flooring had been placed to reach the next tower, it was stretched into position. This job calls for iron nerves for the bridgemen ride the catwalk during the stretching operation. But after the precarious footing during tower erection, this 10-ft catwalk was a cinch. [Music] Fun, but with a serious purpose. To keep the wire mesh sliding freely as it is stretched over the steel ropes. San Francisco Bay looked like this from the catwalk. Far below the old ferry boats plow solidly along. Soon to be replaced by trains of electric cars, automobiles and trucks rolling in an endless stream across the bridge that soarses above. At dinnertime, the bridgemen lose no time hitting for home. A run along the catwalk to wet the appetite, then the skyide and down the escalator. Helter Skelter. [Music] It's a hard, dangerous job that of the bridgeman, but he loves it. [Music] With catwalks in position, the spectacular job of cable spinning is about to begin. Giant reels of special bridge wire supplied by American Steel and Wire Company rise majestically to the top of the anchorages. [Music] These huge reels, each carrying 60 m of wire, were assembled at the nearby Columbia Steel Company warehouse. High above the water, the spinning wheels begin to travel. 18,000 tons of galvanized wire will be used to bind together two neighbor cities, Oakland and San Francisco. This cable will consist of 37 strands, each made up of 472 galvanized steel wires as thick as a lead pencil. In making a cable of this size, the individual wires are not twisted in any way, but laid parallel for the entire length of the bridge. From San Francisco to the center anchorage, more than a mile away, and from there to Yerba Buena Island, nearly another mile away, the spinning wheels work with everinccreasing speed. This model will illustrate the principle of cable spinning. [Music] The end of the wire is anchored temporarily and passed around the strand shoe. Then the spinning wheel takes the loop across to the other side. There it's removed from the spinning wheel and looped around that strand shoe. This is repeated until a sufficient number of wires have been laid. Then the wire is cut and spliced to the beginning end. [Music] Day and night spinning continues down plunge the spinning wheels toward the island anchorage. there. Bridgeman removed the wire and rethread the wheel. [Music] Four cable wires are placed on every trip. Let her go. >> The end of a coil of wire is joined to the beginning of the next coil by means of a turnbuckle type splice. Each wire is beveled so that when they're drawn together by the turnbuckle sleeve, the ends fit snugly. The two wires are gripped in separate vices as a workman draws them up with a wrench applied to the turnbuckle sleeve. The beveled ends form a lock and will not become loose unless they are again placed in vices and unscrewed with a wrench. [Music] Two spinning wheels operate on each hauling rope. Halfway between the anchorages, they meet and pass. A clanking cowbell warns the Bridgeman of the Wheel's approach as it continues to spin its web of steel against the sky far above the traffic of the bay. When spinning was completed, the compactor went into action. Six 75ton jacks in this machine squeeze and bind the strands into a mighty cable 28 and 3/4 in in diameter. Special steel castings are spaced at intervals along the cable. Each carries two pairs of steel suspender ropes cut to length and pre-stressed to support the bridge deck. [Music] Barges controlled by radio phones carry the massive pre-fabricated truss units, some weighing 200 tons. out into the bay to be hoisted into place by traveler cranes. [Music] Soon, hundreds of sections had been guided accurately into place in the structure. An amazing example of coordinated engineering, manufacturing, fabrication, and transportation. The work of the bridgemen is completed. The rugged men of steel are ready to move on to the next job, wherever it may be, of drawing together the people of the world. When they leave, the romance of bridge building leaves with them. These men of skill and courage are the adventurers whose work and sweat and toil have constructed a mighty edifice, woven a web of dreams into a web of steel. [Music]