Plans for a new wire cable suspension bridge between Canal Street and Flatbush Avenue were completed by Richard S. Buck and approved in November 1899. An alumnus of Rensselaer Polytechnic Institute, Buck served as an assistant to Lefferts L. Buck on two arch bridges across the Niagara River and was the chief engineer of the Queenston-Lewiston Bridge, a suspension bridge near Niagara Falls. Buck's design included a 1,465-foot (447 m) long main span carrying eight railroad tracks on two levels, a 35-foot (11 m) wide carriageway, and 12-foot (3.7 m) wide walkways on both edges.
Although construction contracts were awarded for the tower foundations in 1901 and preparations were being made to begin work on the new bridge, the mayoral election that fall brought about a change in the administration of the Bridge Department. Gustav Lindenthal, the newly appointed commissioner, decided to radically change the design to use stiffened eye-bar chains to make its appearance more aesthetically pleasing. Born in Austria, Lindenthal emigrated to the United States in 1874 and designed several bridges in Pittsburgh, including the Smithfield Street Bridge, and would later design the Hell Gate Bridge in New York City.
Lindenthal's redesign of the Manhattan Bridge and the attempt to use eye bar chains in lieu of wire cables made it the most debated bridge in the technical journals and newspapers of the time, including Transactions of the American Society of Civil Engineers. No such structure of this magnitude had ever been built and new methods of construction would be required along with types of eye-bars that had never been fabricated before. Although in 1903 a panel of prominent engineers selected by Mayor Seth Low and the Art Commission both endorsed Lindenthal's design, approval for funding was rejected on two occasions by the Board of Aldermen.
Mayor George McClellan Jr. took office in January 1904 and appointed George Best as the new Commissioner of Bridges, replacing Lindenthal. The change in administration resulted in Othniel Foster Nichols becoming the department's chief engineer (who had been fired after Lindenthal became commissioner) and Richard S. Buck returning as a consulting engineer (who had resigned in May 1902 after Lindenthal scrapped his original design for the bridge).
The new administration quickly discarded Lindenthal's plans to use eye-bars and returned to a traditional design utilizing wire cables, as the uncertainties involved in constructing the eye-bar design would likely further delay the opening of the bridge, increasing congestion at the other lower East River crossings. The new design also needed to adapt to the locations of the tower foundations then under construction (which had been advanced under Lindenthal's design) and also incorporate architectural details to meet the approval of the Art Commission (which came into existence in 1902, after the original plans for the bridge were completed).
The third design for the Manhattan Bridge—the one eventually approved and constructed—was the first to use Josef Melan's deflection theory for the stiffening of the deck. Leon Moisseiff, the earliest proponent of this method in the United States, prepared the calculations under the supervision of O. F. Nichols, a classmate of Richard S. Buck at RPI that was the assistant engineer on the Williamsburg Bridge under Lefferts L. Buck. Born in Russia, Moiessiff came to America in 1891 and earned a civil engineering degree from Columbia University, later serving as an assistant engineer on the Benjamin Franklin Bridge, a consultant on the Golden Gate Bridge, and the lead engineer on the Tacoma Narrows Bridge.
Moisseiff's pioneering use of the deflection theory (as opposed to the more conservative elastic theory) resulted in a much lighter and shallower stiffening truss, reducing the amount of materials that were required in construction. As the first suspension bridge to use the deflection theory, it is considered to be the forerunner of modern suspension bridges and served as the model for the major long-span suspension bridges built in the first half of the twentieth century. The Manhattan Bridge contains four parallel stiffening trusses, each below a main cable, and was the first suspension bridge to utilize a Warren truss in its design.
On December 31, 1909, the last day of Mayor McClennan's term in office, the Manhattan Bridge opened to the public – although it was not completely finished and vehicular traffic had to cross the bridge on temporary wooden planks laid over the deck. The first pedestrian walkway on one side of the bridge opened in July 1910 and the first trains began running across the bridge in September 1912. Completed at a cost of $31 million, the Manhattan Bridge was the third longest suspension bridge in the world from 1909-1924 with a main span of 1,470 feet (448 m). Its four 21-inch (53 cm) diameter cables were the largest in the world when spun.
The Manhattan Bridge pioneered the use "two-dimensional" slender steel towers, which are 322 feet (98 m) high, and was the earliest bridge to incorporate nickel steel to a large extent in construction. Unlike the Williamsburg Bridge, which had four columns in each of its steel towers, the towers of the Manhattan Bridge were only braced in two directions. This allowed the towers to flex, reducing bending moments and requiring smaller foundations under the towers. A total of 42,000 tons (38,000 t) of nickel steel (which is lighter and stronger than carbon steel) was used in the bridge's superstructure.
The New York City-based architecture firm of Carrère and Hastings designed the impressive arch and colonnade plaza on the Manhattan approach to the bridge near the intersection of the Bowery and Canal Street. The 73-foot (22 m) high arch was modeled after Porte Saint-Denis in Paris and the elliptical colonnade was inspired by Saint Peter's Square in Vatican City; the Manhattan plaza opened in 1916 and was designated as a New York City Landmark in 1975. Carrère and Hastings also designed the masonry anchorages and plaza on the Brooklyn approach.
Essentially planned in the horse and buggy era, the Manhattan Bridge originally carried eight railway tracks—four streetcar tracks and four rapid transit tracks. The rapid transit tracks were first intended for elevated trains, but instead they were used by heavier subway trains. The placement of the subway tracks on the outer part of the bridge caused severe torsional stresses, requiring the need for an extensive rehabilitation in the end of the twentieth century. Today, the Manhattan Bridge carries a third of a million passengers in nearly 1,000 subway trains each day, making it the busiest public transit crossing into Manhattan.
The Manhattan Bridge was designated as a National Historic Civil Engineering Landmark by ASCE in 2009, the year of its centennial anniversary. A bronze plaque is installed on the pedestrian walkway at the Brooklyn end of the bridge, near the intersection of Jay Street and Sands Street.
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