Historic Bridges of Iowa
||concrete through girder|
||remains in use|
Click to view larger image
300th Avenue over Ames Creek, 2 miles northeast of DeWitt, Section 4/5, T81N-R4E (DeWitt township)
The Clinton County Board of Supervisors in 1912 contracted with local builder J.A. Kane for a concrete bridge in De Witt township. Designed by the county engineer, the medium-span structure carried a section-line road over Ames Creek about two miles northeast of the town of De Witt, in the southern part of the county. The Charlotte, Iowa, contractor completed the Ames Creek Bridge that year for a total cost of $2,154. Consisting of a poured-in-place concrete through girder, the structure consumed some 11,000 pounds of reinforcing steel and 157 cubic yards of concrete; its concrete abutments and wingwalls required almost 125 cubic yards of excavation. The ornamentation was typically minimal, with simply formed recessed panels on the girder faces and angled haunches at the girder/abutment juncture. The Ames Creek Bridge has carried county-road traffic since its completion, and it remains in place in unaltered and well-preserved condition.
When the Iowa State Highway Commission began developing standard bridge plans in 1913, it first concentrated on concrete culverts and short-span steel structures. The only concrete bridge type of note developed in the commission's first year was the I-Series through girder, which carried the roadway deck between two thickened concrete guardrails that also functioned as girders. Concrete through girders were soon built in abundance throughout the state, using ISHC's I-Series standard. But many of the counties had begun building concrete bridges--primarily concrete slabs and filled spandrel arches--on their own before the distribution of standards by the highway commission. Few of these pre-ISHC structures employed through girders, however, and only the Ames Creek Bridge is known to have survived to the present. It is therefore an important and well-preserved, early example of concrete bridge design undertaken before the codification of standards by the state highway commission [adapted from Fraser 1990].