Red Cedar State Trail - Chippewa River Bridge

Located near the small town of Dunnville and the historic Red Cedar Junction, this unusual truss bridge carries the Red Cedar State Trail over the Chippewa River. The first bridge here was a combination Howe through truss swing bridge, approached by a 126-foot and a 100-foot wooden Howe through truss spans on the north end and timber pile trestles on both ends. The bridge was set onto timber piers, and the swing span used a curved top chord. The bridge was reconstructed with a similar structure between 1892 and 1893. As trains became heavier, it was desired to replace timber truss spans with iron or steel spans. Because this was a branch line, the Milwaukee Road never gave any serious thought into purchasing a new metal bridge to install at this location. Instead, the bridge would be reconstructed in sections, using iron spans relocated from mainline bridges throughout the Midwest.

The first major reconstruction occurred in 1908, when a secondhand Whipple through truss span was rebuilt and installed to replace the swing span. At this time, two concrete piers were constructed for the bridge, likely by company forces. The bridge retained the two wooden truss spans until 1928, when the remaining truss spans would be replaced by an additional shorter secondhand truss span and two secondhand girder spans. At this time, three new concrete piers were built, and the northern 1908 concrete pier modified for the new spans. The last major rehabilitation of the bridge came in 1932 and 1935, when the trestle approaches were last upgraded, giving the bridge its present configuration. Currently, the bridge consists of a 234-foot, 10-panel, pin-connected Whipple through truss span, a 104-foot, 6-panel, pin-connected Pratt through truss span and two 84-foot deck plate girder spans. Two timber pile trestle spans approach the south end of the bridge, and twenty-four spans approach the north end of the bridge. The iron spans are set onto concrete piers, while the remainder of the bridge is supported by timber piles. The four steel spans of this bridge have unique histories, and were reused from various points in Wisconsin, Michigan and Illinois.

The 234-foot Whipple through truss span was originally fabricated in 1886 by the Morse Bridge Company as a deck truss for Bridge #U-464 across the Menominee River at Kingsford, Michigan. When that span had become too light for mainline traffic, it was replaced by the current steel arch span, and disassembled. Prior to being installed here, the span was converted to a through truss by removing the original interior bracing and floor, and constructing a new floor system at the bottom of the span. The floor system uses floorbeams which are riveted to the bottom of the vertical members. The floorbeams were likely reused from the original floorbeams of the span. The span uses two plate girders for stringers, which were likely altered from the original stringers of the span. It appears that the interior bracing was removed and reattached further up the truss members, and additional X-bracing added to create the portal and sway bracing. The upper lateral bracing does not appear to be original to the structure, and may have been reused from another span that had been scrapped. The upper lateral bracing has been attached to the top chord with plates. Empty holes on the top chord indicate that the floorbeams may have originally rested on top of the top chords. A full inventory of the alterations to this span is not currently possible, and would need to be confirmed with blueprints.

The Whipple span is heavily constructed, using a combination of V-lacing on built-up members and rolled members. The endposts and top chord use a typical design, with solid plates covering three of the four edges. The bottom chord is composed of eyebars, and the tension members of the truss also use eyebars with turnbuckles. Lower lateral bracing is comprised of slender rods, which are screwed into an end with two parallel prongs, which is pinned into the floorbeam. These pins are placed into a hole drilled into hangers which likely held the original stringers. The portal and sway bacings consist of two lattice beams, connected by an X-frame bracing. A number of cut plates are visible at the connections between the sway and portal bracing and the top chord. Because the span was originally a deck truss, the outer endposts are vertical and use a built-up design, giving the span a unique appearance. Plaques indicating the builder are visible on the top of the south endposts, likely indicating that the bridge was shortened by removing a panel from the north end.

The 104-foot Pratt through truss span was originally fabricated in 1886 for Bridge #B-256 across the Wisconsin River at Spring Green, Wisconsin.. It is unknown if this span was fabricated by a contractor, or if it was built by Milwaukee Road forces at a bridge shop. During the 1880s and early 1890s, the Milwaukee Road was known to have fabricated a number of their own spans, using raw plates and shapes to fabricate full bridge spans. Several similar spans were constructed for the four Wisconsin River bridges along the Prairie du Chein Division at Spring Green, Lone Rock and Woodman. This span uses a much shallower design than the adjacent Whipple span. The vertical members and crash bars of the span are built up using a tight V-lacing, and are considerably smaller than the members the Whipple span. The upper chord and endposts consist of a standard design, with built-up members consisting of solid plates on three sides and V-lacing on the back sides. The lower chord uses both V-laced members at the outer two panels, and eyebars for the center two panels. Initially, the floor of this span was comprised of four parallel shallow iron stringers, with timber stringers on the outside. It appears that the outermost stringers were removed when this span was relocated here. The lower lateral bracing uses a looped design, which is connected to perpendicular plates in the floorbeams. The sway bracing consists of a typical lattice beam, while the portal bracing consists of a lattice beam with decorative rosette castings at the intersections. These rosette castings were used at all spans constructed for the Wisconsin River bridges. It appears that this span had relatively minor alterations upon being relocated here.

The two 84-foot deck girder spans were originally fabricated in 1881 by the Edge Moor Bridge Works for Bridge #Z-100 across the Fox River at Elgin, Illinois. Initially, this bridge consisted of six spans, which were traditionally composed with two heavy girders and a standard interior bracing. In 1905, the bridge was rebuilt by combining the six spans into three spans, using four girders per span. These spans remained until 1928, when the doubled spans were replaced by new spans. Two spans were reused at this bridge, and the third span was reused at Bridge #Q-38. Upon relocation, it does not appear that these spans required any significant alterations, and were installed here as-is. Typical of "twinned" Milwaukee Road spans, each span consists of four girders, arranged into two sets of two. When the spans were twinned, additional bracing was installed on new hangers. Twinning spans was a common technique used by the Milwaukee Road and other railroads, as it allowed a girder which was too light for traffic to have its loading capacity doubled with only minor alterations, which could be performed in the field.

Railroads often reused steel and iron spans, as it provided a cost effective way to upgrade bridges without requiring large amounts of new material. Often, these spans became too light for mainline traffic, but were still suitable for branch line traffic. Converting a deck truss to a through truss was occasionally done by some railroads, as the alterations were somewhat difficult but were cheaper than purchasing a new span. In the case of this bridge, there may not have been any through trusses that were suitable to be reused here, and an additional pier was likely unacceptable due to the nature of the Chippewa River. Whipple trusses were used for longer spans during the 1870s and 1880s, before being superseded by larger Pratt truss variants in the 1890s. Despite the long length, the complex and indeterminate design of these spans made them unfavorable for railroad use once newer designs were developed. The Pratt truss was arguably the most common railroad truss bridge design during the late 19th Century, as it was simple, strong and economical. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. However, the timber approaches likely will need to be renewed or replaced at some point in the coming decades. Due to the iron construction of the main spans, these spans do not exhibit significant corrosion or section loss. The author has ranked this bridge as being nationally significant, due to the complex history, unique collection of spans and age.