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Minnesota's Historic Bridges
Yellow Bank Church Campground Bridge
Description


Yellow Bank Church Campground Bridge

The Yellow Bank Church Campground Bridge is located in the northwest corner of Lac Qui Parle County along the south boundary of the Big Stone National Wildlife Refuge and adjacent to the site where church groups used to hold camp meetings. The bridge carries Township Road 76 over the Yellow Bank River just south of County Road 40 and 0.7 mile west of County Road 15. Bridge L-7744 is an iron or steel, single-span, pin-connected through truss, with a wood beam stringer approach span at each end. Its truss arrangement does not conform to any common types, although with its diagonals at varying angles it resembles the Thacher truss patented in 1881. The superstructure consists of five panels, with the middle one comprised of diagonal members in the form of an A-frame. The two panels on each end are virtually identical to the end two panels of a 19th century pin-connected Pratt truss. Another unusual feature of the bridge is the upper chord, which consists of laced paired channel sections, with the flat backs of the channels forming the top and bottom of the chord. The only vertical members in the configuration of this bridge, found in the same position of hip verticals in a Pratt truss, are paired forged eye-bars. The diagonals extending inward from these verticals are paired punched eye-bars. The diagonal members in the middle panel of the bridge, with a steeper slope than, and thus not parallel to the inclined end posts as would be typical of a Warren truss, are paired angle sections linked by batten plates. The pin connection at the apex of these two diagonal members has been replaced by a riveted joint. The lower chord is paired, punched eye-bars.

The floor is wood planks on wood beam stringers, which rest on the upper flanges of this variable depth plate girder floor beams. The floor beams are riveted to plate hangers suspended from the pins. The two middle connections for this hanger is also attached to the middle diagonals. Portal bracing is lattice between paired angle sections, with the lattice reaching down to the knee braces. Sway bracing is paired angles, top and bottom lateral bracing is round rods. The span rests on two piers, each comprised of two concrete-filled metal cylinders with plate girder strut at the top and turnbuckle cross-braces. The top of the north pier is distinctly tilted northwards. The movable end of the main span, the north end, has rollers. The south abutment is of poured concrete, the north abutment consists of wood piles with a plank retaining wall. The bridge railing is made of wood planks and probably not original.


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