Fall Creek Railroad Bridge

Located in Fall Creek, this unusual truss and girder bridge carries the former Chicago, St. Paul, Minneapolis & Omaha Railway mainline across Fall Creek. Originally, the Omaha Road crossed Fall Creek about 150 feet southwest of this location, likely using a timber pile trestle. During the late 1890s and early 1900s, the Omaha Road invested significant capital into this line, replacing timber bridges with stone and steel structures. In 1898, the Omaha Road realigned the railroad, constructing a new steel and stone bridge at the present location. In 1907, the railroad was double tracked, and a second span added to the north side of the bridge, giving the structure its present configuration. Currently, the bridge consists of two distinct halves. The south half consists of a 90-foot, 7-panel, riveted modified Warren pony truss span, set onto stone abutments. The north half consists of a 90-foot deck plate girder span, also set onto stone abutments. The abutments use an elongated design, typical for larger bridges along this line. Lassig Bridge & Iron Works fabricated the truss span, while American Bridge Company fabricated the girder span. Unknown contractors constructed the stone abutments, using limestone quarried at Mankato, Minnesota.

The truss span appears to use an experimental design, combining features of Pratt, Warren and Howe trusses. In 1898, long girder spans had not yet become common for railroad use, and a through truss was likely not economical at this location. Pony trusses provided the strongest and most economical design for spans around 100 feet long. Through the 1880s and early 1890s, the Omaha Road used a standard double intersection Warren pony truss design for spans of this length. This type of span had become too light for mainline traffic by the late 1890s, and using this design with heavier members would have not been economical. Instead, it appears that the Omaha Road either designed or contracted with Lassig Bridge & Iron Works to design an alternative span, which reduced the amount of material required while not sacrificing strength. During this era, railroads and bridge fabricators were seeking to perfect a truss design using riveted connections and heavy members, which would become the new standard during the early 20th Century. The span uses a design most similar to a Warren truss, with alternating tension and compression members, and a counter at the center panel. This truss span is unique, and no other examples of this design are known to have been produced for the Omaha Road.

The truss span is heavily constructed, using a combination of rolled and built-up members. All vertical members of the truss consist of rolled construction, while the endposts, bottom chord, top chord and some diagonal members use a built-up design. The endposts and top chord use a typical built-up design, consisting of V-lacing connecting large channels. The bottom chord and diagonals use an alternative design, consisting of channels connected by plates. The floor of the truss is traditionally composed, using two stringers and floorbeams located at each joint. The stringers are constructed of I-beams, while the floorbeams are constructed of heavy plate girders. The connections consist of large gusset plates, which rivet the members together. The deck girder span is also heavily constructed, using two massive girders and an open deck. The use of two distinctly different designs parallel to one another is uncommon for railroad bridges, and represents a significant change in bridge construction in the 9 years separating the fabrication of the two spans. Overall, the bridge appears to be in fair condition, with no significant deterioration noted. The west end of the deck girder span has been braced with H-piling, forming a helper bent. It appears this bent was installed due to failing stone at the bearing points of the span. Currently, only the north track is in use, and the truss span is used for maintenance vehicles. The author has ranked this bridge as being regionally significant, due to the unique and experimental truss design used for the south track span.