State Boulevard Spy Run Creek Bridge

Information and Findings From DHPA Historic Bridge Survey

Statement of Significance

Seeming to have followed the rules of thumb then current, the the county engineers who designed and the noted contractor who built this bridge produced a rather standard T-beam structure.

Architectural Description

The T-shape has been used far more extensively in reinforced concrete than in metal spans. Commonly made at the bridge-site, T-beams of concrete can be adjusted to the special needs of the crossing and bonded to one another. The designer can vary the width and depth of the beam stem (the vertical part of the T) from structure to structure. Following the rule of thumb in common use during the 20s and 30s, the stem's width often approximates a third of its depth. One or two rows of steel rods reinforce the lower part of each stem for tension and bundled to reduce shearing by stirrups which interlock with the rods of the beam flanges (horizontal part of the T). The reinforcing of the flanges of one beam carries over into adjacent ones, producing a concrete slab deck integrated with the beam stems. Commonly used rules of thumb suggested that the width of each flange not exceed the width of the stem and that the flanges (or deck) be at least as deep as one-third of the stem's depth.

Allen County Engineers, A.W. Grosvenor and Orin M. Darling designed and Herman W. Tapp built this particular 40' structure. Its 13 or 14 beams are conventionally designed: their stems are about 12" wide, 36" deep, and 36" apart. The outer beams extend to carry parapet walls, reminiscent of state highway design, adn 5'10" sidewalks on each side. Altogether, the deck reaches 47'9". Concrete abutments and wingwalls support the whole structure. The deck now has an asphalt riding surface.

Other Information

Allen county engineers, A. W. Grosvenor and Orin M. Darling, designed and Herman W. Tapp built this particular reinforced, concrete T-beam structure. At the letting on 17 August 1926, Tapp's proposal at $10,395 was next to the lowest. The county "accepted" the bridge as complete at the end of July 1927. Commonly cast at the bridge-site, T-beams of concrete can be adjusted to the special needs of the crossing and bonded to one another. The designer can vary the width and depth of the beam stem from structure to structure. Following the rule of thumb in common use during the 20s and 30s, the stem's width often approximated a third of its depth. One or two rows of steel rods reinforce the lower part of each stem for tension and are bundled to reduce shearing by stirrups which interlock with the rods of the beam flanges. The reinforcing of the flanges of one beam carries over into adjacent ones, producing a concrete slab deck integrated with the beam stems. Commonly used rules of thumb suggested that the width of each flange not exceed the width of the stem and that the flanges (or deck) be at least as deep as one-third of the stem's depth. As Grosvenor noted, "These plans are similar to design of 'Concrete Girder Bridge' prepared by the Indiana State Highway Commission." The stems of the 13 beams are about a foot wide, three feet deep, and three feet apart. The outer beams are flared to carry the parapet rails with the state's standard decor of coped and bush-hammered panels. The roadway is flanked by a 5-foot and 5-inch sidewalk on each side. Seeming to have followed the rules of thumb then current, the county engineers who designed and the noted contractor who built this bridge copied state plans to produce a quite standard T-beam structure. References Butler, Fairman & Seufert, Inc., Bridge Inspection/Reinspection Report: Allen County (Indianapolis, 1973, 1977, 1981).SIECO, Inc., Bridge Reinspection Report: Allen County (Columbus, 1993, 1995). Bridge nameplate. Allen County, "Commissioners Record," 17: 112, 119, 132-133, 136, 250-251, 459. Light standards removed.

Bridge Considered Historic By Survey: Yes