Brooklyn Bridge

The Brooklyn Bridge is a hybrid cable-stayed/ suspension bridge in New York City, spanning the East River between the boroughs of Manhattan and Brooklyn. Opened on May 24, 1883, the Brooklyn Bridge was the first fixed crossing of the East River. It was also the longest suspension bridge in the world at the time of its opening, with a main span of and a deck above mean high water. The span was originally called the New York and Brooklyn Bridge or the East River Bridge but was officially renamed the Brooklyn Bridge in 1915.

Proposals for a bridge connecting Manhattan and Brooklyn were first made in the early 19th century, which eventually led to the construction of the current span, designed by John A. Roebling. The project's chief engineer, his son Washington Roebling, contributed further design work, assisted by the latter's wife, Emily Warren Roebling. Construction started in 1870, with the Tammany Hall-controlled New York Bridge Company overseeing construction, although numerous controversies and the novelty of the design prolonged the project over thirteen years. Since opening, the Brooklyn Bridge has undergone several reconfigurations, having carried horse-drawn vehicles and elevated railway lines until 1950. To alleviate increasing traffic flows, additional bridges and tunnels were built across the East River. Following gradual deterioration, the Brooklyn Bridge has been renovated several times, including in the 1950s, 1980s, and 2010s.

The Brooklyn Bridge is the southernmost of the four toll-free vehicular bridges connecting Manhattan Island and Long Island, with the Manhattan Bridge, the Williamsburg Bridge, and the Queensboro Bridge to the north. Only passenger vehicles and pedestrian and bicycle traffic are permitted. A major tourist attraction since its opening, the Brooklyn Bridge has become an icon of New York City. Over the years, the bridge has been used as the location of various stunts and performances, as well as several crimes and attacks. The Brooklyn Bridge has been designated a National Historic Landmark, a New York City landmark, and a National Historic Civil Engineering Landmark.

Description

The Brooklyn Bridge, an early example of a steel-wire suspension bridge, uses a hybrid cable-stayed/suspension bridge design, with both vertical and diagonal suspender cables. Its stone towers are neo-Gothic, with characteristic pointed arches. The New York City Department of Transportation (NYCDOT), which maintains the bridge, says that its original paint scheme was "Brooklyn Bridge Tan" and "Silver", although a writer for ''The New York Post'' states that it was originally entirely " Rawlins Red".

Deck

To provide sufficient clearance for shipping in the East River, the Brooklyn Bridge incorporates long approach viaducts on either end to raise it from low ground on both shores. Including approaches, the Brooklyn Bridge is a total of long when measured between the curbs at Park Row in Manhattan and Sands Street in Brooklyn. A separate measurement of is sometimes given; this is the distance from the curb at Centre Street in Manhattan.

Suspension span

The main span between the two suspension towers is long and wide. The bridge "elongates and contracts between the extremes of temperature from 14 to 16 inches". Navigational clearance is above mean high water (MHW). A 1909 '' Engineering Magazine'' article said that, at the center of the span, the height above MHW could fluctuate by more than due to temperature and traffic loads, while more rigid spans had a lower maximum deflection.

The side spans, between each suspension tower and each side's suspension anchorages, are long. At the time of construction, engineers had not yet discovered the aerodynamics of bridge construction, and bridge designs were not tested in wind tunnels. It was coincidental that the open truss structure supporting the deck is, by its nature, subject to fewer aerodynamic problems. This is because John Roebling designed the Brooklyn Bridge's truss system to be six to eight times as strong as he thought it needed to be. However, due to a supplier's fraudulent substitution of inferior-quality cable in the initial construction, the bridge was reappraised at the time as being only four times as strong as necessary.

The main span and side spans are supported by a structure containing six trusses running parallel to the roadway, each of which is deep. The trusses allow the Brooklyn Bridge to hold a total load of , a design consideration from when it originally carried heavier elevated trains. These trusses are held up by suspender ropes, which hang downward from each of the four main cables. Crossbeams run between the trusses at the top, and diagonal and vertical stiffening beams run on the outside and inside of each roadway.

An elevated pedestrian-only promenade runs in between the two roadways and above them. It typically runs below the level of the crossbeams, except at the areas surrounding each tower. Here, the promenade rises to just above the level of the crossbeams, connecting to a balcony that slightly overhangs the two roadways. The path is generally wide. The iron railings were produced by Janes & Kirtland, a Bronx iron foundry that also made the United States Capitol dome and the Bow Bridge in Central Park.

Approaches

Each of the side spans is reached by an approach ramp. The approach ramp from the Brooklyn side is shorter than the approach ramp from the Manhattan side. The approaches are supported by Renaissance-style arches made of masonry; the arch openings themselves were filled with brick walls, with small windows within. The approach ramp contains nine arch or iron- girder bridges across side streets in Manhattan and Brooklyn.

Underneath the Manhattan approach, a series of brick slopes or "banks" was developed into a skate park, the Brooklyn Banks, in the late 1980s. The park uses the approach's support pillars as obstacles. In the mid-2010s, the Brooklyn Banks were closed to the public because the area was being used as a storage site during the bridge's renovation. The skateboarding community has attempted to save the banks on multiple occasions; after the city destroyed the smaller banks in the 2000s, the city government agreed to keep the larger banks for skateboarding. When the NYCDOT removed the bricks from the banks in 2020, skateboarders started an online petition.

Cables

The Brooklyn Bridge contains four main cables, which descend from the tops of the suspension towers and help support the deck. Two are located to the outside of the bridge's roadways, while two are in the median of the roadways. Each main cable measures in diameter and contains 5,282 parallel, galvanized steel wires wrapped closely together in a cylindrical shape. These wires are bundled in 19 individual strands, with 278 wires to a strand. This was the first use of bundling in a suspension bridge and took several months for workers to tie together. Since the 2000s, the main cables have also supported a series of 24-watt LED lighting fixtures, referred to as "necklace lights" due to their shape.

In addition, 1,520 galvanized steel wire suspender cables hang downward from the main cables, and another 400 cable stays extend diagonally from the towers. These wires hold up the truss structure around the bridge deck.

Anchorages

Each side of the bridge contains an anchorage for the main cables. The anchorages are trapezoidal limestone structures located slightly inland of the shore, measuring at the base and at the top. Each anchorage weighs . The Manhattan anchorage rests on a foundation of bedrock while the Brooklyn anchorage rests on clay.

The anchorages both have four anchor plates, one for each of the main cables, which are located near ground level and parallel to the ground. The anchor plates measure , with a thickness of and weigh each. Each anchor plate is connected to the respective main cable by two sets of nine eyebars, each of which is about long and up to thick. The chains of eyebars curve downward from the cables toward the anchor plates, and the eyebars vary in size depending on their position.

The anchorages also contain numerous passageways and compartments. Starting in 1876, in order to fund the bridge's maintenance, the New York City government made the large vaults under the bridge's Manhattan anchorage available for rent, and they were in constant use during the early 20th century. The vaults were used to store wine, as they were kept at a consistent temperature due to a lack of air circulation. The Manhattan vault was called the "Blue Grotto" because of a shrine to the Virgin Mary next to an opening at the entrance. The vaults were closed for public use in the late 1910s and 1920s during World War I and Prohibition but were reopened thereafter. When '' New York'' magazine visited one of the cellars in 1978, it discovered a "fading inscription" on a wall reading: "Who loveth not wine, women and song, he remaineth a fool his whole life long." Leaks found within the vault's spaces necessitated repairs during the late 1980s and early 1990s. By the late 1990s, the chambers were being used to store maintenance equipment.

Towers

The bridge's two suspension towers are tall with a footprint of at the high water line. They are built of limestone, granite, and Rosendale cement. The limestone was quarried at the Clark Quarry in Essex County, New York. The granite blocks were quarried and shaped on Vinalhaven Island, Maine, under a contract with the Bodwell Granite Company, and delivered from Maine to New York by schooner. The Manhattan tower contains of masonry, while the Brooklyn tower has of masonry.

Each tower contains a pair of Gothic Revival pointed arches, through which the roadways run. The arch openings are tall and wide. The tops of the towers are located above the floor of each arch opening, while the floors of the openings are above mean water level, giving the towers a total height of above mean high water.

Caissons

The towers rest on underwater caissons made of southern yellow pine. Both caissons contain interior spaces that were used by construction workers. The Manhattan side's caisson is slightly larger, measuring and located below high water, while the Brooklyn side's caisson measures and is located below high water. The caissons were designed to hold at least the weight of the towers which would exert a pressure of when fully built, but the caissons were over-engineered for safety. During an accident on the Brooklyn side, when air pressure was lost and the partially-built towers dropped full-force down, the caisson sustained an estimated pressure of with only minor damage. Most of the timber used in the bridge's construction, including in the caissons, came from mills at Gascoigne Bluff on St. Simons Island, Georgia.

The Brooklyn side's caisson, which was built first, originally had a height of and a ceiling composed of five layers of timber, each layer tall. Ten more layers of timber were later added atop the ceiling, and the entire caisson was wrapped in tin and wood for further protection against flooding. The thickness of the caisson's sides was at both the bottom and the top. The caisson had six chambers: two each for dredging, supply shafts, and airlocks.

The caisson on the Manhattan side was slightly different because it had to be installed at a greater depth. To protect against the increased air pressure at that depth, the Manhattan caisson had 22 layers of timber on its roof, seven more than its Brooklyn counterpart had. The Manhattan caisson also had fifty -diameter pipes for sand removal, a fireproof iron-boilerplate interior, and different airlocks and communication systems.

History

Planning

Proposals for a bridge between the then-separate cities of Brooklyn and New York had been suggested as early as 1800. At the time, the only travel between the two cities was by a number of ferry lines. Engineers presented various designs, such as chain or link bridges, though these were never built because of the difficulties of constructing a high enough fixed-span bridge across the extremely busy East River. There were also proposals for tunnels under the East River, but these were considered prohibitively expensive. The current Brooklyn Bridge was conceived by German immigrant John Augustus Roebling in 1852. He had previously designed and constructed shorter suspension bridges, such as Roebling's Delaware Aqueduct in Lackawaxen, Pennsylvania, and the John A. Roebling Suspension Bridge between Cincinnati, Ohio, and Covington, Kentucky.

In February 1867, the New York State Senate passed a bill that allowed the construction of a suspension bridge from Brooklyn to Manhattan. Two months later, the New York and Brooklyn Bridge Company was incorporated with a board of directors (later converted to a board of trustees). There were twenty trustees in total: eight each appointed by the mayors of New York and Brooklyn, as well as the mayors of each city and the auditor and comptroller of Brooklyn. The company was tasked with constructing what was then known as the New York and Brooklyn Bridge. Alternatively, the span was just referred to as the "Brooklyn Bridge", a name originating in a January 25, 1867, letter to the editor sent to the '' Brooklyn Daily Eagle.'' The act of incorporation, which became law on April 16, 1867, authorized the cities of New York (now Manhattan) and Brooklyn to subscribe to $5 million in capital stock, which would fund the bridge's construction.

Roebling was subsequently named the main engineer of the work, and by September 1867, had presented a master plan. According to it, the bridge would be longer and taller than any suspension bridge previously built. It would incorporate roadways and elevated rail tracks, whose tolls and fares would provide the means to pay for the bridge's construction. It would also include a raised promenade that served as a leisurely pathway. The proposal received much acclaim in both cities, and residents predicted that the New York and Brooklyn Bridge's opening would have as much of an impact as the Suez Canal, the first transatlantic telegraph cable or the first transcontinental railroad. By early 1869, however, some individuals started to criticize the project, saying either that the bridge was too expensive, or that the construction process was too difficult.

To allay concerns about the design of the New York and Brooklyn Bridge, Roebling set up a "Bridge Party" in March 1869, where he invited engineers and members of U.S. Congress to see his other spans. Following the bridge party in April, Roebling and several engineers conducted final surveys. During the process, it was determined that the main span would have to be raised from above MHW, requiring several changes to the overall design. In June 1869, while conducting these surveys, Roebling sustained a crush injury to his foot when a ferry pinned it against a piling. After amputation of his crushed toes, he developed a tetanus infection that left him incapacitated and resulted in his death the following month. Washington Roebling, John Roebling's 32-year-old son, was then hired to fill his father's role. When the younger Roebling was hired, Tammany Hall leader William M. Tweed also became involved in the bridge's construction because, as a major landowner in New York City, he had an interest in the project's completion. The New York and Brooklyn Bridge Company—later known simply as the New York Bridge Company—was actually overseen by Tammany Hall, and it approved Roebling's plans and designated him as chief engineer of the project.

Construction

Caissons

Construction of the Brooklyn Bridge began on January 2, 1870. The first work entailed the construction of two caissons, upon which the suspension towers would be built. The Brooklyn side's caisson was built at the Webb & Bell shipyard in Greenpoint, Brooklyn, and was launched into the river on March 19, 1870. Compressed air was pumped into the caisson, and workers entered the space to dig the sediment until it sank to the bedrock. As one sixteen-year-old from Ireland, Frank Harris, described the fearful experience:

The six of us were working naked to the waist in the small iron chamber with the temperature of about 80 degrees Fahrenheit: In five minutes the sweat was pouring from us, and all the while we were standing in icy water that was only kept from rising by the terrific pressure. No wonder the headaches were blinding.

Once the caisson had reached the desired depth, it was to be filled in with vertical brick piers and concrete. However, due to the unexpectedly high concentration of large boulders atop the riverbed, the Brooklyn caisson took several months to sink to the desired depth. Furthermore, in December 1870, its timber roof caught fire, delaying construction further. The "Great Blowout", as the fire was called, delayed construction for several months, since the holes in the caisson had to be repaired. On March 6, 1871, the repairs were finished, and the caisson had reached its final depth of ; it was filled with concrete five days later. Overall, about 264 individuals were estimated to have worked in the caisson every day, but because of high worker turnover, the final total was thought to be about 2,500 men in total. In spite of this, only a few workers were paralyzed. At its final depth, the caisson's air pressure was .

The Manhattan side's caisson was the next structure to be built. To ensure that it would not catch fire like its counterpart had, the Manhattan caisson was lined with fireproof plate iron. It was launched from Webb & Bell's shipyard on May 11, 1871, and maneuvered into place that September. Due to the extreme underwater air pressure inside the much deeper Manhattan caisson, many workers became sick with "the bends"— decompression sickness—during this work, despite the incorporation of airlocks (which were believed to help with decompression sickness at the time). This condition was unknown at the time and was first called "caisson disease" by the project physician, Andrew Smith. Between January 25 and May 31, 1872, Smith treated 110 cases of decompression sickness, while three workers died from the disease. When iron probes underneath the Manhattan caisson found the bedrock to be even deeper than expected, Washington Roebling halted construction due to the increased risk of decompression sickness. After the Manhattan caisson reached a depth of with an air pressure of , Washington deemed the sandy subsoil overlying the bedrock beneath to be sufficiently firm, and subsequently infilled the caisson with concrete in July 1872.

Washington Roebling himself suffered a paralyzing injury as a result of caisson disease shortly after ground was broken for the Brooklyn tower foundation. His debilitating condition left him unable to supervise the construction in person, so he designed the caissons and other equipment from his apartment, directing "the completion of the bridge through a telescope from his bedroom." His wife, Emily Warren Roebling, not only provided written communications between her husband and the engineers on site, but also understood mathematics, calculations of catenary curves, strengths of materials, bridge specifications, and the intricacies of cable construction. She spent the next 11 years helping supervise the bridge's construction, taking over much of the chief engineer's duties, including day-to-day supervision and project management.

Towers

After the caissons were completed, piers were constructed on top of each of them upon which masonry towers would be built. The towers' construction was a complex process that took four years. Since the masonry blocks were heavy, the builders transported them to the base of the towers using a pulley system with a continuous -diameter steel wire rope, operated by steam engines at ground level. The blocks were then carried up on a timber track alongside each tower and maneuvered into the proper position using a derrick atop the towers. The blocks sometimes vibrated the ropes because of their weight, but only once did a block fall.

Construction on the suspension towers started in mid-1872, and by the time work was halted for the winter in late 1872, parts of each tower had already been built. By mid-1873, there was substantial progress on the towers' construction. The Brooklyn side's tower had reached a height of above mean high water, while the tower on the Manhattan side had reached above MHW. The arches of the Brooklyn tower were completed by August 1874. The tower was substantially finished by December 1874 with the erection of saddle plates for the main cables at the top of the tower. However, the ornamentation on the Brooklyn tower could not be completed until the Manhattan tower was finished. The last stone on the Brooklyn tower was raised in June 1875 and the Manhattan tower was completed in July 1876. The saddle plates atop both towers were also raised in July 1876. The work was dangerous: by 1876, three workers had died having fallen from the towers, while nine other workers were killed in other accidents.

In 1875, while the towers were being constructed, the project had depleted its original $5 million budget. Two bridge commissioners, one each from Brooklyn and Manhattan, petitioned New York state lawmakers to allot another $8 million for construction. Ultimately, the legislators passed a law authorizing the allotment with the condition that the cities would buy the stock of Brooklyn Bridge's private stockholders.

Work proceeded concurrently on the anchorages on each side. The Brooklyn anchorage broke ground in January 1873 and was subsequently substantially completed in August 1875. The Manhattan anchorage was built in less time, having started in May 1875, it was mostly completed in July 1876. The anchorages could not be fully completed until the main cables were spun, at which point another would be added to the height of each anchorage.

Cables

The first temporary wire was stretched between the towers on August 15, 1876, using chrome steel provided by the Chrome Steel Company of Brooklyn. The wire was then stretched back across the river, and the two ends were spliced to form a traveler, a lengthy loop of wire connecting the towers, which was driven by a steam hoisting engine at ground level. The wire was one of two that were used to create a temporary footbridge for workers while cable spinning was ongoing. The next step was to send an engineer across the completed traveler wire in a boatswain's chair slung from the wire, to ensure it was safe enough. The bridge's master mechanic, E.F. Farrington, was selected for this task, and an estimated crowd of 10,000 people on both shores watched him cross. A second traveler wire was then stretched across the span, a task that was completed by August 30. The temporary footbridge, located some above the elevation of the future deck, was completed in February 1877.

By December 1876, a steel contract for the permanent cables still had not been awarded. There was disagreement over whether the bridge's cables should use the as-yet-untested Bessemer steel or the well-proven crucible steel. Until a permanent contract was awarded, the builders ordered of wire in the interim, 10 tons each from three companies, including Washington Roebling's own steel mill in Brooklyn. In the end, it was decided to use number 8 Birmingham gauge (approximately 4 mm or 0.165 inches in diameter) crucible steel, and a request for bids was distributed, to which eight companies responded. In January 1877, a contract for crucible steel was awarded to J. Lloyd Haigh, who was associated with bridge trustee Abram Hewitt, whom Roebling distrusted.

The spinning of the wires required the manufacture of large coils of it which were galvanized but not oiled when they left the factory. The coils were delivered to a yard near the Brooklyn anchorage. There they were dipped in linseed oil, hoisted to the top of the anchorage, dried out and spliced into a single wire, and finally coated with red zinc for further galvanizing. There were thirty-two drums at the anchorage yard, eight for each of the four main cables. Each drum had a capacity of of wire. The first experimental wire for the main cables was stretched between the towers on May 29, 1877, and spinning began two weeks later. All four main cables were being strung by that July. During that time, the temporary footbridge was unofficially opened to members of the public, who could receive a visitor's pass; by August 1877 several thousand visitors from around the world had used the footbridge. The visitor passes ceased that September after a visitor had an epileptic seizure and nearly fell off.

As the wires were being spun, work also commenced on the demolition of buildings on either side of the river for the Brooklyn Bridge's approaches; this work was mostly complete by September 1877. The following month, initial contracts were awarded for the suspender wires, which would hang down from the main cables and support the deck. By May 1878, the main cables were more than two-thirds complete. However, the following month, one of the wires slipped, killing two people and injuring three others. In 1877, Hewitt wrote a letter urging against the use of Bessemer steel in the bridge's construction. Bids had been submitted for both crucible steel and Bessemer steel; John A. Roebling's Sons submitted the lowest bid for Bessemer steel, but at Hewitt's direction, the contract was awarded to Haigh.

A subsequent investigation discovered that Haigh had substituted inferior quality wire in the cables. Of eighty rings of wire that were tested, only five met standards, and it was estimated that Haigh had earned $300,000 from the deception. At this point, it was too late to replace the cables that had already been constructed. Roebling determined that the poorer wire would leave the bridge only four times as strong as necessary, rather than six to eight times as strong. The inferior-quality wire was allowed to remain and 150 extra wires were added to each cable. To avoid public controversy, Haigh was not fired, but instead was required to personally pay for higher-quality wire. The contract for the remaining wire was awarded to the John A. Roebling's Sons, and by October 5, 1878, the last of the main cables' wires went over the river.

Nearing completion

After the suspender wires had been placed, workers began erecting steel crossbeams to support the roadway as part of the bridge's overall superstructure. Construction on the bridge's superstructure started in March 1879, but, as with the cables, the trustees initially disagreed on whether the steel superstructure should be made of Bessemer or crucible steel. That July, the trustees decided to award a contract for of Bessemer steel to the Edgemoor (or Edge Moor) Iron Works, based in Philadelphia, to be delivered by 1880. The trustees later passed another resolution for another of Bessemer steel. However, by February 1880 the steel deliveries had not started. That October, the bridge trustees questioned Edgemoor's president about the delay in steel deliveries. Despite Edgemoor's assurances that the contract would be fulfilled, the deliveries still had not been completed by November 1881. Brooklyn mayor Seth Low, who became part of the board of trustees in 1882, became the chairman of a committee tasked to investigate Edgemoor's failure to fulfill the contract. When questioned, Edgemoor's president stated that the delays were the fault of another contractor, the Cambria Iron Company, who was manufacturing the eyebars for the bridge trusses; at that point, the contract was supposed to be complete by October 1882.

Further complicating the situation, Washington Roebling had failed to appear at the trustees' meeting in June 1882, since he had gone to Newport, Rhode Island. After the news media discovered this, most of the newspapers called for Roebling to be fired as chief engineer, except for the ''Daily State Gazette'' of Trenton, New Jersey

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