National self-confidence created a series of major works in steel during the first half of the twentieth century including the Bayonne Bridge (1931; a steel-arch between New York and New Jersey) and the George Washington Bridge (1931; a suspension bridge over the Hudson River in New York City), again the longest-spanning of their type then and both designed by Othmar Ammann.
Self-confidence was shaken in 1940 with the failure of the recently completed Tacoma Narrows Bridge in Washington in a relatively mild windstorm. This bridge followed the design of the George Washington Bridge by including very little deck stiffness, which led to the Tacoma collapse and to the instability of other bridges built in the 1930s such as the Golden Gate (San Francisco), the Bronx Whitestone (New York City), and the Deer Island (Maine). All of these have been subjected to considerable stiffening since 1940, but none was as narrow as the long-span Tacoma Bridge. This basic design problem was solved by Ammann in his 1964 Verrazano-Narrows Bridge (New York City) and by British designers of the Severn Road Bridge (England) in that same year.
Between 1883 and 1964 America led the world in steel-bridge design, especially with suspension bridges. Roebling's Brooklyn Bridge had diagonal stays to prevent the type of wind oscillations that destroyed the Tacoma Bridge. For the 1903 Williamsburg Bridge (New York City), the engineers did not use diagonal stays and instead designed a deep truss. This ugly design, heavily criticized, led to the lighter design of the Manhattan Bridge (1909; New York City).
In 1926 the Delaware River Bridge connected Philadelphia, Pennsylvania, and Camden, New Jersey, in time for the sesquicentennial celebration in Philadelphia. At the time it was the longest-spanning suspension bridge in the world at 1,750 feet (533 m), which Ammann exactly doubled for his George Washington Bridge.
The early twentieth century brought in reinforced-concrete bridges, of which the most prominent were arches such as the Connecticut Avenue Bridge in Washington, D.C. (1904), and the Westinghouse Bridge in Pittsburgh (1931). The latter was at the time the longest-spanning concrete bridge in the United States with a span of more than 400 feet (122 m) and represents a design that still reflected the imitative forms of ancient bridges. The towers are fake and the arcades inessential. Such extraneous effects disappear with the Russian Gulch Bridge (1940; California), America's finest of its type at the time.
In American culture, concrete bridges presented a two-part problem. First, they encouraged owners to seek architectural embellishments because concrete could be cast in the field in custom forms; second, these bridges, when built in profusion after World War II, encouraged cost-conscious engineers to create structurally inarticulate forms in standardized shapes. Thus there arose two ideas about concrete bridges. On the one hand, where owners considered beauty to be crucial, designers sought architectural ideas of decoration; on the other hand (and because of costly form work), where designers thought only of economy the results were at best bland. These conditions prevented Americans from drawing on the inspiration of the great European bridge designers Robert Maillart and Eugene Freyssinet, whose ideas focused on economy and elegance. Nevertheless, after World War II the state of California, under bridge engineer Arthur Elliot, completed a series of exceptional designs mostly using the new development, prestressed concrete. Examples of such works are the Adams Avenue overpass, the old Miramar Bridge, and the Lilac Road Bridge all just north of San Diego.
A particularly significant design is the San Mateo Creek Bridge (1970) where Elliot sculpted the high piers into a shape that the local community accepted. Surprisingly the resulting construction bid was lower than the bid on a more conventional and less elegant design. The prestressed concrete cantilever, or segmented-construction technique, developed in Germany the 1950s by Ulrich Finsterwalder, has led to many fine designs in the United States, exemplified by the bridge over the Columbia River near Portland, Oregon, in which the long-beam spans increase in depth near the supports to express the increased internal forces present there, and the vertical piers splay at their bases for the same reason.
In 1976 the state of Washington completed the Pasco-Kennewick Bridge over the Columbia River, the first major cable-stayed bridge in the United States. This European innovation has led to many elegant forms, such as the East Huntington Bridge (1985) over the Ohio River, which, like Pasco-Kennewick, was designed by Arvid Grant and the German Fritz Leonhardt. Two other examples of cable-stay bridges are the Dame Point Bridge located in Jacksonville, Florida, for which Finsterwalder served as consultant to the Howard Needles Tammen and Bergendorf firm, and the Sunshine Skyway Bridge over Tampa Bay, Florida, designed by the French engineer Jean Mueller in collaboration with Eugene Figg.
Two unusual engineering design competitions held out promise of enlivening structural engineering at the start of the twenty-first century. These competitions required strict rules and a juried decision. The state of Maryland, under its bridge engineer Earle Freedman, pioneered this process in 1989 for the U.S. Naval Academy Bridge over the Severn River. The state chose five engineering firms to compete and named a jury consisting mainly of local civic leaders, national engineering experts, and the great Swiss designer Christian Menn. Under Menn's guidance, the process followed the Swiss tradition of such design competitions. The winning bridge was designed by Tom Jenkins of the Greiner Company.
Based on this success, Maryland stimulated a second engineering design competition in collaboration with Virginia and the District of Columbia for the replacement of the rapidly deteriorating and overtaxed Woodrow Wilson Bridge carrying Interstate 95 over the Potomac River. Four designers competed and the winning design by the Parsons Transportation Group, using a form inspired by Menn, once again resulted in an aesthetically superior engineering form.
By 1964 the United States had the four longest-spanning bridges in the world (Verrazano, Golden Gate, Mackinac [Michigan], and George Washington), but by 2000 the five longest-spanning structures in the world were all in other countries. Yet in many states there had appeared smaller bridges showing the promise that engineering refinement can lead to high-quality American bridges. Nevertheless, for Americans bridges have served not only as a means of crossing bodies of water but also as inspirational monuments, evoking feelings of awe and symbolizing the highest achievements of an engineering culture.
Encyclopedia of American Studies, ed. Simon J. Bronner (Baltimore: Johns Hopkins University Press, 2015), s.v. "Bridges" (by David P. Billington), http://eas-ref.press.jhu.edu/view?aid=2 (accessed April 1, 2015).