The towers were to serve two very fundamental purposes. They would bear the weight of four enormous cables, and they would hold both the cables and the roadway of the bridge high enough so they would not interfere with traffic on the river. Were the two cities at higher elevations, were they set on cliffs, or palisades such as those along the New Jersey side of the Hudson, for example, such lofty steelwork would not be necessary. As it was, however, only very tall towers could make up for what nature had failed to provide, if there was to be the desired clearance for sailing ships.
And as the mass of the anchorages had to be sufficient to offset the pull of the cables, where they were secured on land, so the mass of the towers, whatever their height, had to be sufficient to withstand the colossal downward pressure of the cables as they passed over the tops of the towers.
Original cross-section of the roadway on the Brooklyn Bridge. To commemorate this occasion, and to demonstrate the integrity of the wire rope, master mechanic Farrington crossed the East River riding on a boatswain's chair tied to the rope. More on the suspension wire and cable system from McCullough: The suspended roadway's great "river span" was to be held between the towers by the four immense cables, two outer ones and two near the middle of the bridge floor. These cables would be as much as fifteen inches in diameter, and each would hang over the river in what is known as a catenary curve, that perfect natural form taken by any rope or cable suspended from two points, which in this case were the summits of the two stone towers.
At the bottom of the curve each cable would join with the river span, at the center of the span. But along all the cables, vertical "suspenders," wire ropes about as thick as a pick handle, would be strung like harp strings down to the bridge floor.
And across those would run a pattern of diagonal stays, hundreds of heavy wire ropes that would radiate down from the towers and secure at various points along the bridge floor, both in the direction of the land and toward the center of the river span. The wire rope for the suspenders and stays was to be of the kind manufactured by Roebling at his Trenton wire works. It was to be made in the same way as ordinary hemp wire rope, that is, with hundreds of fine wires twisted to form a rope. The cables, however, would be made of wire about as thick as a lead pencil, with thousands of wires to a cable, all "laid up" straight, parallel to one another, and then wrapped with an outer skin of soft wire, the way the base strings of a piano are wrapped.
Deviating from tradition, Roebling introduced the use of steel, which he called "the metal of the future," for the four cables. At the time, steel was being used for construction of the railroads, but its use had not yet been used for major structures such as bridges. Until the Brooklyn Bridge was constructed, iron wire was used for suspension cables. Roebling defended his use of steel wire in an article in The American Railroad Journal , discussing the weaknesses of earlier iron-wire and chain suspension bridges and their vulnerability to destructive oscillation caused by high winds.
In February , not long after the temporary footbridge was finished, work began on spinning the four cables at the Manhattan and Brooklyn anchorages. The four steel cables, which could each hold 11, tons, connect the anchorages with the Manhattan and Brooklyn towers, where the cables pass over saddles within the towers. Once the spinning of the four main cables was completed in October , workmen strung wire ropes from the cables down to the bridge floor. More than 14, miles of wire were used for the suspender ropes. After the suspending ropes and deck beams were in place, the diagonal stays were installed.
The long river span passes the tower arches at an elevation of feet, gradually rising to feet above the East River at mid-span to accommodate passage of even the tallest ships. The foot clearance soon became the standard for bridge construction. Because of the elevation of the span above the East River and the relatively low-lying shores, the rest of the bridge, sloping down to ground level, had to extend quite far inland on both sides of the river to provide an easy three and one-quarter percent grade.
Roebling designed the Brooklyn Bridge to have a load capacity of 18, tons. He planned to run two elevated railroad tracks, which were to connect to elevated railroad systems in New York and Brooklyn, down the center of the bridge.
On either side of the tracks, he designed four lanes - two lanes on two outer roadways - for use by carriages and horseback riders. Directly over the tracks, he provided an elevated promenade for pedestrians and bicyclists. To support the load, and to protect the span from high winds and vibrations, deep stiffening trusses were constructed. Indeed, construction was delayed because Roebling had to redesign the trusses for the heavier trains of the day. Construction of the bridge understructure, the stiffening trusses, and the roadway began in March , and continued for four more years.
The 1,foot main span would be the longest for any suspension bridge in the world, and would be more than feet longer than John Roebling's Cincinnati-Covington Bridge. First, two terminal buildings, complete with ornate ironwork and plate-glass windows, were to be constructed at the Manhattan and Brooklyn ends of the bridge.
Second, seventy blue-white, electric arc lamps were to be installed along the promenade at intervals of about one hundred feet. Roebling gave these last details his full attention. Even before it opened, the Brooklyn Bridge had become a symbol of not only of the greatness of New York, but also of American ingenuity. While the engineering feat of crossing the East River was spectacular, what impressed people most was the overall arc of the bridge when they saw it from the river. An editor from Scientific American remarked the following: The bridge is a marvel of beauty viewed from the level of the river.
In looking at its vast stretch, not only over the river between the towers, but also over the inhabited, busy city shore, it appears to have a character of its own far above the drudgeries of the lower business levels. Emily Roebling was given the first ride over the completed bridge with a rooster, a symbol of victory, in her lap. After the opening ceremony, anyone with a penny for the toll could cross the Brooklyn Bridge. On the first day, the bridge carried trolley lines, horse-drawn vehicles, and even livestock.
That evening, one man crossing the bridge penned the following: As the sun went down the scene from the bridge was beautiful. It had been a perfect day. Up and down on either side of New York the bright blue water lay gently rippling, while to the south it merged into the great bay and disappeared toward the sea.
The vast cities spread away on both sides. Beyond rolled the hilly country until it was lost in the mists of the sky. All up and down the harbor, the shipping, piers and buildings were still gaily decorated. On the housetops of both Brooklyn and New York were multitudes of people. The great buildings in New York loomed up black as ink against the brilliant background of the sky. The New York bridge pier looked somber and gloomy as night.
But in Brooklyn, the blaze of the dying sun bathed everything gold. Gradually the gold melted away, leaving the heavens cloudless. The sky was a light blue in the west, but grew darker as it rose, until it sank behind Brooklyn in a deep-sea blue. Slowly the extremities of the twin cities began to grow indistinct. The towers of Brooklyn lost their golden hue.
The History and Photography of the Brooklyn Bridge
They seemed to sink slowly into the city itself. In New York, the outlines of the huge buildings became wavering and indistinct. Then one by one, the series of electric lights on the bridge leaped up until the chain was made from Brooklyn to New York. Dot by dot, flashes of electric light sprang up in the upper part of New York. The two great burners at Madison and Union Squares flared up, and the dome of the Post Office in New York set a circlet of diamonds out against the relief of the sky.
The streets of the two cities sparkled into life like the jets on a limitless theatrical chandelier, and the windows of the houses popped into notice hundreds at a time. Long strings of lanterns were run over the rigging of the shipping in the harbor, and red and green port and starboard lights seemed numberless.
The steamers sped on the water, leaving long ripples of white foam, which glistened in the light like silver.
Brooklyn Bridge – Mytek Digital
However, amid the novelty, there was tragedy. On Memorial Day, , a woman who was walking up the steps of the Manhattan side tripped, and her female companion screamed.
The scream triggered off a rumor that the bridge was about to collapse. In the panic and resulting crush, 12 people were killed and 35 others were seriously injured. The Brooklyn Bridge and the Lower Manhattan skyline in Ten years after the bridge opened, the city of Brooklyn annexed adjoining towns until it encompassed all of Kings County. That year, the roadway was configured to allow trolleys and automobiles to travel in the outer lanes.
By , the penny toll on the Brooklyn Bridge was removed after the City of New York passed a law prohibiting the use of tolls to finance construction and maintenance of its bridges. In , the elevated railroad trains that ran along the interior of the bridge ceased operation, and soon thereafter, the trolley lines ended service. More from nycroads. A decade later, when the trolleys stopped running, the elevated tracks were removed, and the roadways were rebuilt.
Between and , noted bridge engineer David Steinman oversaw a comprehensive reconstruction project that saw the inner and outer trusses strengthened, new horizontal stays installed between the four main cables, the railroad and trolley tracks removed, the roadways widened from two lanes to three lanes in each direction, and new approach ramps constructed.