Auction Road Bridge
Structural Precast Elements:
The key details of the precast concrete arches are:
• Max. height of 11’-7 1/2”
• Top Chord: 1’-8” x 2’-0”
• Bot. Chord: 1’-8” x 2’-7”
• Vert. & Diagonals: 1’-0” x 1’-1”
• Weight: 47 tons/arch
• Reinforcing: 25,000 pounds of reinforcing and temporary post-tensioning strands
• Post-tensioning strands used for lifting and transportation only; released after final erection.
• Form tolerances set to 1/16” max. using survey and control equipment
• Modified concrete mix design with reduced aggregate size to assure concrete consolidation
The existing 58’ simple span reinforced concrete tied-through arch bridge over Big Chickies Creek in Lancaster County, Pennsylvania was one of only four left of its kind in Pennsylvania. The County of Lancaster contracted with the designer to design the replacement structure with specific instructions to develop a context sensitive design that reflected the distinctive architectural and historical features of the National Register eligible bridge. Originally designed by prominent Lancaster County engineer Frank Shaw in 1916 and put into service in 1922, this reinforced concrete tied through arch bridge is modeled after the patented rainbow arch bridge design of James H. Marsh, only slightly changing the design by adding diagonal truss chords.
The design for the replacement bridge consisted of precast concrete tied through arches and a cast-in-place concrete deck. The designer coordinated efforts with contractors and precast fabricators from the preliminary design stage through fabrication to address concerns with construction, fabrication and transportation of the arches.
Context sensitive design for this structure meant incorporating the same significant architectural and historical details of the original tied through arch bridge in the new structure. To achieve the County’s goal of having a context sensitive structure, the designer designed the concrete arches as precast concrete members with a compressive strength of 8,000 psi. The final typical section of the bridge resulted in an out-to-out width of 34’-4” with two 1’-8” wide precast concrete arches matching the increased span length of 70’.
The use of precast concrete for the arches incorporated modern design and fabrication techniques allowing all benchmarks to be met. Lancaster County’s rich heritage of historic bridges remains in tact with a new bridge that will serve the community – both in form and function – for as many years as Frank Shaw’s original 1916 structure.