BNSF Skunk River Bridge (Wever)

Located along US Highway 61 between Wever and Burlington, this through truss bridge carries a former Chicago, Burlington & Quincy Railroad mainline over the Skunk River. The first bridge at this location was likely a wooden truss bridge, constructed when the line was first built. It is likely that this bridge was replaced by a light iron through truss bridge in the late 1880s or early 1890s. In 1910, the bridge was reconstructed with two new through truss spans and a lengthy 89-span concrete slab approach on the west (railroad south) end. The bridge remained in this configuration until 2005, when the approach spans were replaced by new concrete girder spans, giving the bridge its present configuration. Currently, the bridge consists of two 176-foot, 8-panel, pin-connected Pratt through truss spans, set onto concrete substructures. The south end is approached by a series of concrete modular girder spans, interrupted by a modern 30-foot steel stringer span over a field entrance. The approaches mainly rest on steel pile substructures, with a couple of concrete piers from the previous bridge reused. In addition, the truss spans are braced by helper bents, formed from steel piles. American Bridge Company fabricated the superstructure, and it is unclear if the substructures were constructed by an unknown contractor or by railroad company forces.

The truss spans follow a standard CB&Q design for the era, with a unique mix of pinned and riveted connections, heavy members and a standard portal bracing. The top chord and endposts are both formed from built-up box-shaped beams, with solid plates on the top and V-lacing on the bottom. The bottom chord is composed of both V-laced beams and eyebars. All vertical members are composed of V-laced beams, with the hip verticals being slightly smaller than the remaining vertical members. The diagonal members are constructed of eyebars at the outer panels and V-laced beams at the center panels. Pinned connections are used at the upper angle and first upper connection on each end, as well as the four center lower connections. The remainder of the connections are riveted and formed with large gusset plates. The floor system follows a typical design, with heavy plate girder floorbeams and heavy plate girder stringers. Both the upper and lower lateral bracing are formed from L-shaped bars. The portal bracing uses a standard X-laced beam with diagonal heel bracing, while the sway bracing uses V-laced bars with similar diagonals to the portals. The piers use a standard rounded rectangular shape, while the north abutment has short wing walls. Pratt trusses were popular for railroad use, as they were simple, strong and economical. Around the turn of the 20th Century, railroads began moving to riveted Warren spans. The CB&Q used a handful of different designs in the early 20th Century, including spans with an unusual mix of riveted and pinned connections. Since the 2005 reconstruction, the bridge has seen no significant alterations, and remains in regular use. Overall, the bridge appears to be in fair condition, with no critical defects noted. The author has ranked this bridge as being moderately significant, due to the truss design.