The LeJeune Flyover
The LeJeune Flyover was built to ease traffic congestion leaving the Miami Airport going westbound to the City of Hialeah. Approximately 33 feet wide and 262 feet long, the superstructure is supported on two piers and consists of a twin, steel box girder bridge with an 8 inch cast-in-place composite deck.
A few months after the bridge deck was constructed, cracks resulting from construction loads were discovered. Horizontal cracks uniformly spaced at about 12 to 18 inches were observed on Pier Two. “V” shaped cracks also were discovered in the pier cap of Pier Two and Pier Three. The Florida Department of Transportation concluded that these cracks would continue to deteriorate over the years and, ultimately, cause long-term maintenance issues. To ensure a minimum service life of 75 years, it was necessary to repair the cracks immediately with minimal impact on the aesthetics of the structure, the budget and the schedule. The repair also had to take into account the moderately aggressive environment over which the bridge was constructed.
Upon review of the details in the as-built construction documents, it was determined that the horizontal cracks on Pier Two were caused by a rebar detailing error. The vertical reinforcing steel in the column was not properly lapspliced with the top steel in the pier cap thereby causing horizontal cracks. The “V” shaped cracks in the pier cap were caused by insufficient top reinforcing bars. This situation also was the case for Pier Three, which had insufficient reinforcing steel in the pier cap.
To meet the goal of minimizing the repair time and meet the need for a corrosion resistant solution, the repair team recommended that post-tensioning tendons be placed into vertically drilled holes and encased in concrete after stressing. This would replace the vertical reinforcement in the pier and close the horizontal cracks. Horizontal post-tensioning was proposed to reinforce the pier caps for Piers Two and Three. To enhance durability and improve aesthetics, it was decided to encase the post-tensioning tendons in concrete.
The LeJeune Flyover Project presented a unique set of client objectives. Before the project began, the road had been under construction for nearly two years, so it was critical that the repair work be completed in a timely fashion with minimal impact. A turnkey solution that included repair design services, labor resources and shop drawings was designed to fulfill all client objectives. Repairs were delivered using the most cost-effective solution, were completed in four weeks and allowed the Flyover to open ahead of schedule.