The Significance of the SE 14th Street Bridge
Condensed from the HAER report by Richard Vidutis and James Hippen, Summer 1996
The SE 14th Street Bridge, in addition to responding to the always difficult problem of getting to the various parts of Des Moines with two major rivers joining in the center of the city, provided a necessary relief to highway traffic that had to thread its way through the center of the city. US 65 (the old Jefferson Highway) passed through Des Moines on the way from Canada to the Gulf of Mexico. The new bridge, along with its northerly companion, the SE 14th Street Viaduct over the railroad yards, kept highway traffic away from downtown, and provided imporved access to the state capitol. [Editor's Note: For another interesting Jefferson Highway bridge in Iowa, see the Lincoln Highway Colo Interchange.]
Iowa was conforming to at least two national trends in the building of this bridge. There was the choice of a continuous design and there was the assisatnce from the federal government to help relieve the unemployment brought on by the Great Depression. Shortridge Hardesty, of Waddell & Hardesty, Consulting Engineers, in reviewing the bridge engineering for the year 1936 noted that "there was a large volume of moderate-sized and small bridge work under way during the year, much of it with the aid of PWA and other federal money." Albin L. Gemeny, Senior Structural Engineer, U.S. Bureau of Public Roads, noted a year later that "there was a continuing inclination among engineers toward the use of steel, instead of concrete, for structures where these two materials were competitive." And he made another point which accurately described the SE 14th Street Bridge. Gemeny wrote that "in the field of steel bridges mulitple simple spans have almost gone into the discard. Continuous beam and girder spans are being generally adopted for intermediate lengths."
The SE 14th Street crossing built in 1936-37 was a 750' deck plate girder bridge, two 105' spans and four 135' spans. The six spans were each six girders wide. The riveted plate girders are in the order 105-135-135-135-135-105.
The bridge was a completely successful exercise in the use of continuous technology, and has lasted well to the present. Its only flaw, shared by so many bridges of that era, was that it could not forever handle the constant increase in motor traffic. Consequently, in 1971 a design was prepared to widen the bridge. This was accomplished very neatly by adding concrete corbels to the ends of the original piers, sliding the original appearance of the bridge while adding to its capacity. Today the bridge maintains its elegant efficiency in carrying traffic, and it demonstrates the high quality of bridge design construction of the 1930s.
