This nine panel pin-connected truss bridge is a long-span pin-connected Pratt truss bridge. Typical of the long-span Pratt, this truss includes notably taller trusses and a more extensive portal and sway bracing system than the average-spanning Pratt. The bridge was originally part of a two-span truss bridge built in 1888 to carry Burlington / Fort Madison Road over Skunk River between Lee and Des Moines Counties. In 1930, one of the two spans was salvaged from a replacement projects and placed into service at this location where it has remained and is known as the Eisenhower Bridge.
The general design of the bridge was overseen by important engineer Horace B. Horton from Chicago who would later go on to form the prolific Chicago Bridge and Iron Works, a company still in existence today that would live on into the 20th and 21st centuries building not bridges, but water towers, tanks, and other industrial process equipment. The Historic Bridge Inventory states that the bridge's builder was a local contractor from Keokuk, the James B. Diver Bridge Company. However, it appears that this company's role must have been just to erect the bridge. The bridge itself was clearly manufactured by the Penn Bridge Company of Beaver Falls, Pennsylvania, something overlooked by the Historic Bridge Inventory. What evidence is there that the Penn Bridge Company was involved? Look closely at the portal bracing for the answer. The lattice is held together by little circular decorative buttons. Some of these buttons have little graphics on them. Others say PENN on them. This was something the Penn Bridge Company often put on its bridges. Another portal bracing detail that shows up on Penn Bridge Company bridges and is on this bridge are the decorative cast iron elements placed on the ends of the curved portal bracing knees. These elements are identical to those found on other Penn Bridge Company bridges. Examples of another Penn Bridge Company bridge with these details is the Clarks Mills Bridge. Wiley's Bridge is another Penn Bridge Company product with similar portal bracing.
The truss bridge is traditionally composed with a couple noteworthy exceptions. First, the top chord has v-lacing on the top instead of the vastly more common cover plate. The end post in contrast does have the cover plate. The bridge is historically and technologically distinguished for its span length (long for a pin-connected Pratt truss from this era), unusual design details, and its high level of historic integrity.
Although this bridge was closed to all traffic, the structural condition in terms of "restorability" is relatively good and restoration of such a bridge for non-motorized use would be feasible and not very difficult. Although National Bridge Inventory sufficiency ratings and bridge inspections found structural deficiencies in the bridge advanced enough that they apparently mandated bridge closure, these ratings are an extremely poor determinant of how feasible it is to restore a bridge, especially for pedestrian use. Different aspects of a bridge can lead it to be found structurally deficient. Some of those aspects may not have a large effect on how difficult it would be to restore a bridge. For instance, if members were bent or fractured in vehicular collisions or floods, this may result the bridge being found structurally deficient to the point of closure, and rightly so. However, these issues, if isolated as they often are, can be easily corrected. In contrast, if the bridge was found structurally deficient and closed as a result of massive section loss to all bottom chord connections, this problem would be more difficult (although not impossible) to correct in a restoration. HistoricBridges.org on-site inspection of the bridge found very little pack rust and section loss, even at the bottom chord connections. For this reason, the bridge should be considered a bridge that should be restored, either in place or in a new location, most likely for non-vehicular traffic.
The Eisenhower Bridge consists of the main nine panel Pratt truss and a single wooden stringer approach span.
The truss is configured as follows: Top chord: back-to-back channels with v-lacing riveted to the top and and battens riveted to the bottom. End post: back-to-back channels with battens and cover plate. Bottom chord: up-set eye bars. Verticals: back-to-back channels with v-lacing on each side. Hip verticals: up-set eye bars. Diagonal members: paired up-set eyebars. Floor beams: Riveted built-up i-beams. Sway bracing: two built up beams, each consisting of paired angles with a single row of lattice, spaced apart vertically with two rods between. Rod connections include uncommon four-pronged "claw" eyebars. Portal bracing: Two sets of built-up beams consisting of double-row lattice (including decorative lattice rivets), with rods between and curved knee bracing with same lattice design and cast iron decorative termination. Original railing: Missing. Current Railing: Two lightweight cables. Deck: traditionally configured wooden deck with running planks.
Information and Findings From Iowa's Historic Bridge Inventory
Discussion of Bridge
Located some two miles east of Milton, this long-span through truss carries a gravel-surfaced county road over the Fox River. It is comprised of a single pinned Pratt truss, which was once part of a two-span structure built between Lee and Des Moines counties in 1888. The supervisors from these two counties first met on September 7, 1887, to view the site for a proposed bridge over the Skunk River on the Burlington/Ft. Madison Road. The next day the men issued a joint resolution, stating: "We recognize the need and necessity for a bridge [here] but having lately gone to considerable expense at the Bridgeport and Augusta Bridges, we therefore deem it expedient at the present time to take definite action in this matter." The two counties dickered into 1888 over their respective shares in paying for the bridge's construction, until, finally, in June they agreed to split the cost with Des Moines County paying three-fifths and Lee County paying two-fifths. Walker's Ferry, near the river's mouth, was chosen as the crossing site, and Chicago engineer Horace B. Horton was commissioned to design the structure. He engineered two designs: one featured a single 360-foot span, the other used two 180-foot trusses, both were to be supported by iron cylinder piers. On June 28th the two boards met in joint session at Fort Madison to open competitive bids for the bridge's construction. Low bidder at $9,435, the James B. Diver Bridge Company of Keokuk was awarded the contract for the two-span design. After its completion, the Walker's Ferry Bridge carried traffic for over forty years, before it was replaced with another structure. In the spring of 1930 one of the trusses was disassembled, moved, and re-erected at this rural Van Buren County crossing to replace an 1895 structure washed out by floods. Known locally as the Eisenhower Bridge, it has since functioned in place with no further alterations.
The Pratt truss was the bridge of choice for an overwhelming majority of Iowa county road crossings in the late 19th century. Before the development of steel as a structural material around 1890, all-metal Pratts were executed in wrought or cast iron. Although thousands of iron trusses were erected throughout the state, relatively few remain in use today. The Eisenhower Bridge is distinguished among these for its well-preserved superstructure, its long span length and its association with nationally prominent bridge engineer Horace Horton. The subsequent inter-county move has compromised its locational integrity, but the truss still remains a noteworthy representative of early wagon bridge construction [adapted from Fraser 1991].
Bridge Considered Historic By Survey: Yes
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