IN-75 Bridge

Information and Findings From DHPA Historic Bridge Survey

Statement of Significance

R. L. Schutt of Indianapolis, Indiana, won an $118,373.20 contract in July 1947 to build a two-span, state-design structure consisting of a 61-ft. 6-in. I-beam approach and a 175-ft. Parker through-truss upon a concrete substructure. The bridge was officially not completed until the beginning of March, 1948. The ISHC used a revised version of its fifth-generation standard plan #1551 for a 175-ft., riveted, Parker through-truss span with a 28-ft. roadway plus a pair of 2-ft. walks also inside the trusses. Truss depth varied from 23 ft. at the portal to 34 ft. 4 in. at midspan. Each truss carried eight panels, the outer two at 20 ft. 3 in. and the inner four at 23 ft. 6 in. Every top chord member is differently sloped; none is parallel with the lower chord; and all were fabricated from a pair of 15- in. channels (@40# for the endposts, third, and fourth panels, and @53.9# for the second). For the lower chord, 10-in. I-beams grow in weight from the outer panels (@66#) to the inner-most one (@100#). The state used rolled I-beams in some truss web members. The verticals or posts consist of two forms and weights: the hip and the fourth are 10-in. I-beams (@33#); the second and third are fabricated from a pair of laced 10-in. channels (@15.3#). To protect the quite-tall trusses against wind and vehicle-induced stress, substantial latticed struts and heavy upper sway framing buttress the verticals above 15 ft. of roadway clearance. The portals used latticed sections, too. While a 10-in. I-beam (@37#) provided the second-panel diagonal, the others used a pair of laced 10-in. channels (@15.3#). None of the panels was countered. The ISHC prescribed 33-in. I floor-beams (@200#) riveted to the verticals above the lower chord. Ten rows of rolled I-beam stringers attached to the floor-beams' sides varied in depth and weight by placement. The 20-ft. panels used 16-in. Is; the 23-ft. 6-in. ones relied on 18-in Is. Outside stringers were lighter than inner ones. Weights varied on 20-ft. panels from 36 lbs. (outer) to 50 lbs (inner); on the 23-ft. panels from 50 lbs to 55 lbs. Together, the floor-beams and the stringers carry the concrete deck. Angles supply each lower sway-bracing member. Tube-channel-and- post rails lined the inner sides of the trusses, and coped concrete approach rails with bush- hammered panels funneled traffic into the spans. This bridge provides one of several extant--and certainly one of the latest--examples of this fifth-generation standard plan for a fairly-long through-truss span. The trusses retain their original members. The metal guardrails and the concrete approach ones remain. The concrete deck has been replaced.

Other Information

References Indiana State Highway Commission, Structure, #75-J-3653; Contract, #2814; Superstructure Standard, #1551.

Bridge Considered Historic By Survey: Yes