Indianapolis Boulevard Bridge

Information and Findings From DHPA Historic Bridge Survey

Description of Bridge

A year after the ISHC had an overpass of two railroads built in Lake County (#1030), it contracted for an even more complex railroad overpass. This one involved eighteen spans on a 19-degree skew, carrying a 40-ft. roadway, 6-ft. sidewalks outside the trusses, and a metal stairway to the rail yard. In December 1935, E. J. Albrecht of Chicago, Illinois, successfully bid $590,512.92 to build the overpass on concrete bents and abutments. From North to South, the structure consisted of nine reinforced-concrete T-beam spans (8@42'1"; 1@41') which then flanked nine steel Parker through-truss spans. Each outer steel span had one truss of 171 ft. 6 in. and one truss of 186 ft. 8 in. to accommodate the skew and sandwiched between them a 171 ft. 6 in. span, three 245 ft. 6 in. spans, and three 171 ft. 6 in. spans. Albrecht officially completed his work by mid-September 1937.

The state's design task was not an easy one. The very substantial rail yard required both a very long and, given some raised rails or humps to facilitate classification, more than average vertical clearance. The yard, though, was located in the city of East Chicago which limited the state's ability to shift or to elevate the roadway ahead of the bridge easily. As a result, the bridge had to be skewed considerably, and it had to accommodate within the structure much of the vertical rise needed to clear the rail yard--in all, 744 ft. of vertical curve. The first four trussed-spans from the North inclined up; the next five to the South angled downward. The wider than average roadway appropriate for an urban setting also complicated the design of the trusses. No state standard addressed all or even most of these special conditions. The state engineers met the challenges with some mixture of structural types and a combination of unusual trussed-span lengths. To handle the 19-degrees of skew settled upon, the state engineers had to offset the trusses of each span by approximately the length of an end panel. For the internal spans, this resulted in trading off a panel at each end with the adjacent span. The end spans, however, required trusses of different length, since there was no span beyond the abutment from which to borrow a panel. Thus each end-span had one truss of 171 ft. 6 in. and one of 186 ft. 8 in. Panel lengths varied from span to span. End panels tended to be shorter than central ones, although there seemed to be no consistent standard by span-length or panel-position. End panels ranged from 13 ft. 10 in. to 18 ft. 10 in. on the shorter spans, and from 15 ft. 8 in. to 22 ft. 5 in. on the longer ones. Most center panels on the shorter spans were 23 ft. 9 in. long and on the longer ones at 26 ft. 6 in. With one truss of each outer span made one panel longer than the other, the trusses of every other span were offset. Where the offset operated, those members which crossed from one truss to another-- struts, sway frames, and floor-beams--were tied between verticals of different panels within a span and inevitably skipped one hip vertical. At the ends of the spans, the portals and the floor-beams between the endposts necessarily accommodated the skew and left a different distance from the previous frame or floor beam at each side. Hence the decision noted above to shorten the outer panels over the inner ones and thereby to contain the varied distance between members at span- end to manageable lengths. Truss depth varied by place in the span, span-length, and--given the skew and vertical curve-- location in the structure. At the portals, shorter spans (171'-186') varied from 20 ft. 6 in. to 27 ft. 10 in., and longer ones (245') ranged from 21 ft. to 30 ft. At midspan, the variation depended entirely upon truss-length: the shorter at 35 ft.; the longer at 44 ft. 6 in. All top chord members are differently sloped, and only in the nine-panel length is the center panel's member parallel with the lower chord. In the shorter spans, all top chord members are fabricated from a cover plate, lattice bars, and a pair of 18-in. channels generally increasing in weight from the endposts to the more central members, sometimes by riveting plates to the channels' webs. The longer spans relied on fabricated rather than rolled channels, using 26-in. plates and angles to provide unusually heavy members. The lower chord's members differ by span length. The shorter ones rely on a pair of rolled 15-in. channels growing in weight toward midspan, sometimes by the addition of stiffening plates. The longer spans call for crafted channels made from 24-in. plates and angles, stiffened in all except the outer two panels on each end with a second set of plates added to the channel web. The size and design of web members also often varied by span length. The verticals of both the shorter and the long spans were alike in format, except that the latter were somewhat heavier. They all generally used a pair of laced 12-in. channels, except for the hip vertical which depended upon a rolled 12-in. I-beam. Substantial latticed struts and heavy upper sway framing placed above 15 ft. of roadway clearance buttress the quite-tall trusses against wind and vehicle-induced stress. Like the upper bracing, the portals rely on latticed sections. The diagonals of the shorter spans were made from a pair of 12-in. channels dropping in weight from the outer (@40#) to the inner (@20.7#) panels. The long spans used a pair of 15-in. channels with tie-plates for the outer diagonals and crafted channels laced together for the inner ones. None of the spans used counterbracing. For its floor-beams, the state required 48-in. deep crafted girders, in turn to be riveted to the verticals above the lower chord in each span. Arranged in nine rows, the rolled I stringers vary considerably depending largely upon the panel length each needed to accommodate. They range from 13 in. to 24 in. depths and from weights of 53 lbs. to 83 lbs. All are attached to the floor-beams' sides. Together, the floor-beams and the stringers carry the concrete deck. A pair of angles supplies each lower sway bracing member. A pair of channels and posts line each truss as guardrails, and coped concrete approach rails with bush-hammered panels guide traffic into and out of the approach spans. Brackets added to the floor-beams and verticals carry the sidewalks and steel handrails outside each truss. A metal stairway located on the East about midway along the bridge accommodated pedestrian passage to and from the rail yard.

The requirements of this location forced the state engineers to move well beyond their standard plans for parts of the Parker through-truss design. In this, they are among the more notable design difficulties addressed by the ISHC and produced some of the state's longest trussed spans. While the trusses remain and retain their original members, the concrete deck has been replaced. The reinforced concrete T-beam approaches have also all been replaced with prestressed concrete I-beam spans, most of which are somewhat longer than the originals. The coped concrete approach rails were ripped out with the T-beams. [HABS/HAER card]

1949: Concrete Floor Repaired
1964: New Concrete Filled Steel-Grate Floor
1973: Concrete Deck Repaired
1983: T-Beam Superstructure Replaced with Prestressed I-Beams; New Aluminum Rails and Lights [SHPO database]

Bridge Considered Historic By Survey: Yes