OVERVIEW

^[*]

Basic principles of arch construction have been known and used successfully for centuries. Magnificent stone arches constructed under the direction of engineers of the ancient Roman Empire are still in service after 2000 years, as supports for aqueducts or highways. One of the finest examples is the Pont du Gard, built as part of the water-supply system for the city of N mes, France.

Stone was the principal material for arches until about two centuries ago. In 1779, the first metal arch bridge was built. Constructed of cast iron, it carried vehicles over the valley of the Severn River at Coalbrookedale, England. The bridge is still in service but now is restricted to pedestrian traffic. Subsequently, many notable iron or steel arches were built. Included was Eads' Bridge, with three tubular steel arch spans, 502, 520, and 502 ft, over the Mississippi River at St. Louis. Though completed in 1874, it now carries large daily volumes of heavy highway traffic.

Until 1900, stone continued as a strong competitor of iron and steel. After 1900, concrete became the principal competitor of steel for shorter-span arch bridges.

Development of structural steels made it feasible to construct long-span arches economically. The 1675-ft Bayonne Bridge, between Bayonne, N.J., and Staten Island, N.Y., was completed in 1931. The 1000-ft Lewiston-Queenston Bridge over the Niagara River on the United States Canadian border was put into service in 1962. Availability of more high-strength steels...