Bridge, drawn wrought-iron wires were used for the cables.
Roebling opened this suspension bridge over the Ohio River between Cincinnati, Ohio, and Covington, Ky., in 1866.
The Brooklyn Bridge over the East River in New York City.
Subsequent to 1840, several wrought-iron wire bridges were built in America by Charles Ellet, John A. Roebling, Thomas M. Griffith, Edward W. Serrell and others. However, the suspension bridge was still in its infancy. It began to come of age in 1849 when Ellet spanned the Ohio at Wheeling, Virginia, with a 1,010-foot suspension span. When completed, this was the longest bridge span in the world. While it was damaged by wind in 1854, the bridge was repaired and is still in service.[1]
John Roebling had built nine suspension bridges by 1855, one of which was the 821-foot span combination highway-railroad bridge over the Niagara Falls rapids, a bridge most engineers thought doomed to failure. When Mr. Ellet’s temporary suspension bridge was built at the site in 1848, the rope for pulling the first cable across the river was pulled across by a cord flown over the gorge by a boy with his kite.[2] In December 1866, Roebling opened his recordbreaking Ohio River suspension span at Cincinnati. This structure, 1,057 feet between towers, is also still in use.[3] During the flood of 1937, this was the only highway bridge open across the Ohio between the Mississippi River and Sciotoville, Ohio.
There were at least two factors that Roebling had considered in his bridges: the quality and protection of the cable and the bracing of the structure against aerodynamic loadings. Attention to these problems, plus the other design aspects, made his bridges successes.
These major bridges, although unprecedented achievements, were only the prototype for his crowning task, the second “great bridge” of America: the Brooklyn Bridge over the East River. This bridge, its 1,595-foot main span 50 percent longer than the previous record span at Cincinnati, linked Brooklyn and Manhattan and made New York’s expansion possible. It was also the first bridge to use galvanized steel cable.
Building the East River bridge was probably the most dramatic verse in the saga of bridges. Its creator, John Roebling, died of tetanus as a result of an accident during the early stages of construction. His son, Colonel Washington Roebling, who had survived the battle of Gettysburg, was crippled by the “bends” and had to direct operations through his wife, Emily. But in 1883, 14 years after construction started, man had conquered the East River and signaled the beginning of the great age of bridge building.[4]
Two other notable suspension bridges were built over the East River at New York City around the turn of the century. The Williamsburg Bridge, built in 1903, has a 1,600-foot main span. The main span of the Manhattan Bridge, built in 1909, while 130 feet shorter, yet is considered by many as the most graceful cable arc of any of New York’s bridges.
425
