The challenge for this concrete arch bridge rehabilitation was to widen the bridge while maintaining the original arch and historic character. Solution was to “hide” a new bridge inside an excavated area of the existing bridge without transferring any of the new loads onto the existing arch.
The unique design utilized precast, prestressed concrete box beams. Because the existing bridge was approximately 21’-0” wide and the new bridge is 32’-0”wide, the new deck cantilevers approximately 5’-6” outside of the existing spandrel walls on each side of the bridge. The beams had to have significant flexural strength, shear capacity, and relatively shallow depth in order to clear the crown of the existing arch rings and minimize the height the roadway profile grade would need to be raised. In addition, the new bridge needed to be opened before the local schools were back in session. Use of prestressed deck panels sped up the erection process and eliminated the need for support framework in the creek.