An old, deteriorating trestle bridge above an historic trail in Tallahassee, FL, was scheduled for replacement. Orange Avenue Bridge sits above the intersecting bike and pedestrian trail portions of St. Marks Trail. Replacing the 60 ft (18.3 m) bridge would be straightforward in most circumstances. But this short-span bridge construction project faced a number of challenges.
With a bike path and a pedestrian trail directly below the bridge, there was little room to excavate support walls. And timing was critical, as the road serves an elementary school and is in frequent use most of the year. In addition, the Florida Department of Transportation (FDOT) had a limited budget for the replacement project.
Once school was out and summer recess underway, the road was closed so construction could begin. The old bridge was removed and excavation for the new support walls began. A proprietary concrete block retaining wall system was specified for its near vertical batter, which helped alleviate the space restriction issue and also allowed for a much wider passageway for the trail below the bridge.
Speeding up construction time through completion was a high priority for this project. The concrete block face walls are dry stacked, and as a result, the abutment walls were rapidly erected and ready to support the superstructure. With dry-stacking there was no cure time required, meaning that the abutment wall construction was not interrupted at various courses and so installation progressed ahead of schedule. The abutment walls were 18 ftt high (5.5 m), with acute angles that necessitated special cuts in the block, along with rebar reinforcements at the corners and on the sides. To prevent the corners from separating, block cores were filled with grout, from top to bottom. The Orange Avenue Bridge opened to traffic 23 days ahead of schedule.