Red Bridge, Spanning North Benson Creek, Frankfort

Source document Quoted word for word from HAER KY,37-FRAFO.V,1-. Not written, edited or summarised by this site.

Jayne C. Henderson Edited and Transmitted by: Paul Hawke Historian Southeast Regional Office National Park Service Atlanta, Georgia t Red Bridge (Kentucky Route 100E Bridge) HAER No. (Page 2) The Red Eridge (Kentucky Route Bridge) over Benson Creek in Franklin County is eligible for the National Register of Historic Places as a structure of State and local iinportance. It possesses integrity of location, design, setting, materials, workmanship, and embodies the distinctive characteristics of a type period and method of construction. Built in Red Eridge is a rare survivor of a standard bridge design, constructed in the late century. Presently under State ownership, Red Bridge is a 150 foot long, single truss, one lane, metal bridge.

The structure was given a Structural Inventory Appraisal rating of 27 points out of a possible 100 points, and was determined structurally deficient and functionally obsolete. In Red Bridge was replaced with a new bridge structure, and plans for the removal of the historic structure are now underway. Eistoric Red Bridge, part of Kentucky Route in west central Franklin County, crosses the south fork of Benson Creek. The route is a two-lane secondary road which extends north from Frankfort, the county seat of Franklin County. Frankfort, located in north central Kentucky, is bisected north to south by the Kentucky River, into which Benson Creek empties.

The Eenson Creek community, of which Red Bridge is a part, is a colesive, rural area adjacent to the historic site of Conway Mills and picturesque Benson Falls. The bridge itself serves as a local point for the community, and the artistic and recreational activities which it sponsors. Red Bridge is a 151 foot long pin-connected Pratt through truss, constructed in Built by the King Bridge Company of Cleveland, Ohio, it is an unusually good example of a standard bridge design popular during the late century. The bridge is a tall, elegant, simple truss with star pattern cutouts in the portal bracing. Due to its construction date, Red Bridge is probably of steel construction material.

The Pratt through truss was patented in by Thomas and Caleb Fratt and utilized wooden compression posts and wrought iron tension members. Soon, however, all members were constructed of metal, first cast and wrought iron, then steel. This truss, capable of larger spans which would bear greater loads is the oldest and most common truss type. On all truss spans, the end posts and top chord act in compression, with the bottom chord in tension. In a truss, unlike a rigid arch, at least one bearing point at the abutment must be able to expand or move. In the Pratt truss, the vertical between the end posts go into compression to keep the top chord from collapsing, and the diagonals act in tension to support the deck when a load first enters the bridge. Red Bridge (Kentucky Route Bridge) HAER No.

{Page 3) Pratt trusses have both diagonals and counters in the web system acting in tension. Inclined members that are not parallel to the nearest end posts are called diagonals. Inclined members parallel to the nearest end posts are called counters. Diagonals support the dead load of bridge weight and the live load of the bridge. Counters always intersect with a diagonal between two panel points (or floor beams) of the bridge. The compression members of a Pratt truss must be rigid and of sturdy construction. The main compression member on Red Bridge, the top chord, inclined end posts and intermediate posts are all composed of two channels, cover plate and lacing bars.

The main tension members are as follows: bottom chord is two rectilinear, die-forged eyebars; hip verticals are two square eyebars, loop welded at top chord and die-forged at bottom chord and welded to floor beams; diagonals are two die-forged, rectilinear eyebars, with one square eyebar with a loop welded sleevenut; counters are square eyebars with a loop welded sleevenut. All panel points are pin-connected. The floor system consists of rolled I-beams with floor beam hangers supporting a wood deck. The substructure is composed of two rough cut stone abutments. t