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Tobias Bridge

Jefferson County Bridge 30

   


Tobias Bridge

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: May 9, 2010
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Key Facts

Facility Carried / Feature Intersected
CR-1350 West Over Big Creek
Location
Rural: Jefferson County, Indiana
Construction Date and Builder / Engineer
1885 By Builder/Contractor: Indianapolis Bridge Company of Indianapolis, Indiana

Technical Facts

Rehabilitation Date
2004
Main Span Length
146.3 Feet (44.6 Meters)
Structure Length
154 Feet (46.9 Meters)
Roadway Width
13.8 Feet (4.2 Meters)
Spans
1 Main Span(s)
NBI Number
3900020

Historic Significance Rating (HSR)

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

This bridge is an example of Hoosier heritage: a Whipple truss built by the Indianapolis Bridge Company. The bridge has truly bizarre vertical members that are composed of little more that two plates with corrugation (ribbon plate) between the plates being the only form of stiffening for these plates. This design is highly unusual because paired plates like this would normally only be used for tension members, and would tend to buckle under compressive forces of compression members like a vertical. The corrugation / ribbon plate enables these plates to function as compression vertical members, however they remain very lightweight and fragile compared to more standard vertical member designs, such as back-to-back channels with v-lacing. This unique design detail gives this bridge added historic and technological significance as a rare example of an unusual approach to member composition. In addition to the unique vertical design detail, the bridge is significant as an example of an Indiana bridge builder, a rare example of a Whipple truss, and a truss bridge with an ornately decorated portal bracing that includes multiple plaques and cast iron decorative details.

Given what is essentially a shortcoming in the original design of the bridge it is hardly surprising that after serving traffic for over a century that decisions needed to be made about the bridge's future. While many agencies might look at a deteriorated bridge with these odd verticals and quickly move to demolition and replacement, Jefferson County instead hired an engineer with experience in historic bridge rehabilitation to design a rehabilitation for this bridge. Because a firm familiar with the unique aspects oif metal truss bridges was hired, Jefferson County got not only a quality rehabilitation, but one that cost far less than a demolition and replacement project would have. According to James Cooper, the 2004 rehabilitation of this bridge cost $455,000, with the estimated demolition and replacement cost being $932,000. While it might seem surprising that this bridge could be preserved for half of the cost of replacing it, this 50% cost to replace is a fairly common finding for the average aging one-lane truss bridge on a rural road, when an engineer who has experience with historic bridges is hired to do the design and/or consulting for the historic bridge rehabilitation. This bridge is an excellent example of how creative engineering can result in a rehabilitation project that provides an excellent compromise between the desire of preservationists to maintain historic integrity and the desire of owner agencies to increase safety and load limits. It demonstrates the value of finding and hiring only those engineers and consultants who have proven experience with historic bridge preservation when making decisions on a historic bridge. The rehabilitation of this bridge was designed by J. A. Barker Engineering

The creative engineering approaches employed on this bridge primarily included addressing the weak vertical members. Aware that these verticals were a main part of the historic significance of the bridge, but also recognizing that the verticals needed to be stronger, plate was welded to the outside of the vertical member plates, essentially increasing their thickness, while also retaining the original plate and corrugation on the interior. The overall appearance of the verticals were also maintained. Steel spacers were also placed between the plates near the bottom/road level to provide additional strength against possible impact damage. Another interesting approach was  to add modern steel tube for guardrail, but to then weld the original lattice railing onto these tubes in front, so that the tubes are hidden behind the top and bottom portions of the lattice railing.

The creative solutions found for the rehabilitation of this bridge may not be appropriate for another historic bridge. Each bridge and its situation is unique. However, the lesson that can be learned here and taken to other bridges is that creativity is needed to find ways to preserve historic bridges, and only by hiring creative engineers with experience with historic bridges can these win-win scenarios play out, where tax dollars were saved while at the same time preserving our transportation heritage.

Information and Findings From DHPA Historic Bridge Survey

Statement of Significance

Only about a half-dozen structures remain in Indiana of this prolific in-state firm. This one retains most of its original members including its most unusual verticals as well as its latticed guardrails.

Architectural Description

The Indianapolis Bridge Company designed this double-intersection Pratt (Whipple) through truss still seated upon its original cut stone abutments and wingwalls. The 154' span has thirteen panels bounded by unusually light intermediate verticals fabricated from rectangular bars riveted to a ribbon plate between and reinforcing pin plates above and below. Cylindrical eyebars serve as diagonals; most are doubled; those from the four central pins carry turnbuckles. U-bolted to the lower pins, girder floor beams support a timber deck with a 13'9" roadway and 14'5" of vertical clearance.

In-Depth History

M. J. Tobias and his neighbors lobbied the commissioners in 1884 to build a proper bridge across Big Creek on the long-established road between Deputy in Jefferson county and Paris on the border with Jennings county. Tobias sweetened the request by offering to "donate stone in quarry sufficient to construct all the stone work necessary for the bridge." Indeed, Deputy had established quarries which shipped stone on the Jeffersonville, Madison, and Indianapolis Railroad. In June 1884, the commissioners approved specifications for a substructure that would ultimately include nearly one thousand cubic yards of limestone. In August, James Walker of Jennings county won the contract for the stonework. The board named James D. Robertson, who lived to the south of where the bridge would be built, to superintend construction. Once Walker started excavation, he found quick-sand at the site of the north abutment. The board consequently hired H. R. Weeks, "a competent civil engineer," to resurvey the site and in September accepted the proposal Weeks and Walker worked out to place the stonework on bedrock, a decision that substantially increased the amount of excavation and masonry required for the abutments. The stonework was officially completed by April 1885 at a total cost of $4,743.37 for Walker and $481.09 for Robertson's superintendence. With the stonework done, the commissioners received bids from thirteen bridge companies for the superstructure. The board allowed each company eight minutes "to explain their plans, specifications, and bids" before accepting Plan E of the Indianapolis Bridge Company priced at $16.34 per lineal foot. David Braden, a key agent for William B. Burford, stationers from Indianapolis who had just sold Jefferson county a number of blank books, doubled as the Indianapolis Bridge Company's "General Agent" and signed a contract for the bridge builder with the commissioners. The contract called "for a wrought iron truss bridge"--"double intersection"-- of 154 feet in extreme length with a 14-ft. roadway and "iron hub guards." It also addressed "wood work," which must have involved the riding surface and the floor joists or stringers, and "painting." In late June 1885, 58,000 pounds of iron superstructure arrived at the Deputy railroad station and within two weeks the span has been erected and accepted by the county. The company received $2,516.36 for its work. The double-intersection Pratt (Whipple) through trusses stand 21 ft. tall and are subdivided into thirteen panels (@11'11"). In addition to the rod hip hangers, the interior verticals were fabricated from rectangular bars riveted together with ribbon plate between and reinforcing pin plates above and below. Cylindrical eyebars--used mostly in pairs--provide the diagonals. All but the outer three panels on each end are countered with adjustable cylindrical rods. Decorated cast-iron pieces stiffen the latticed portal struts. U-bolted to the lower pins, girder floor-beams (@ 18") support the steel stringers (@5") which replaced the timber joists in 1898; in turn, the floor-beams and stringers carry the timber deck. The trusses are lined with latticed railings. The county included the Tobias Bridge in a list of eight contracted for repainting in November 1901.


In the century before the state highway commission built a parallel highway just to its west, the Tobias Bridge accommodated the main roadway traffic between Deputy and Paris. The bridge speaks to the importance of the crossing. Its remarkably large substructure testifies to the high- quality limestone available in the area and to master regional masons. The superstructure is also special in design, fabrication, and decoration as well as remarkable for retaining all of its original cast and wrought iron members and railings. Very few, indeed, of the Indianapolis Bridge Company's structures remain. The ribbon-lacing of the interior verticals is even more rare.

It retains most of its original members. [SHPO database}

Bridge Considered Historic By Survey: Yes

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