The new seven-span interchange on Interstate 95 at SR-202 in Jacksonville, Fla., is the first structure for the Florida Department of Transportation (FDOT) that uses curved precast concrete U-girder technology—and it was a resounding success.
The project involved redesigning the traffic interchange, which handles more than 220,000 vehicles per day and was in need of a significant upgrade. Designers chose precast concrete and precast concrete U-girders at the outset of the project to address the many constraints faced on the project, including tight clearance requirements, a short schedule, proximity to traffic, and the need to maintain all travel lanes open on both highways during construction.
The new bridge is composed of two units with expansion joints at each abutment and at the interior pier 5. The structure is curved on an 1100-ft radius and span lengths vary from 140 to 232 ft. The superstructure is composed of curved spliced precast concrete U-girders, post-tensioned for continuity. The longest span is just over 231 ft, with a constant-depth, curved, 84-in.-deep U-girder with a 9-in. total-depth composite cast-in-place deck.
FDOT required that all lanes remain open to traffic throughout construction, with overnight lane closures allowed, providing 6- to 8-hour windows for all construction and erection procedures that needed to occur in traffic areas.
To speed erection, the precast concrete caps were designed to support the girders during construction, eliminating the need for temporary falsework on the jobsite. The contractor also used straddle frames and strong backs supported from cantilevered girders to accommodate the sections that had to be erected over traffic.
In the midst of the project, Hurricane Matthew hit Florida with 90-mph winds. Even though construction wasn’t finished, the drop-in girders, and strongback all survived with zero damage.
The engineers believe the success of this project and proven durability of precast concrete marks the beginning of an upward trend in using this technology for flyover bridges throughout the nation.