Design-Build Replacement Bridge for St. George Island Protects the Environment and Ensures Durability

摘要

A 4.1 mile (6.6 km) long, precast, prestressed concrete replacement bridge, belonging to the Florida Department of Transportation (FDOT), was built to provide mainland access to the barrier island of St. George in the Gulf of Mexico. The $73.4 million bridge is needed to accommodate sensitive environmental restrictions and must provide a 75-year service life with quality production and erection processes for a 10-year warranty from the design-build team. At the time of construction, the two-lane St. George Island Bridge was the single largest design-build project undertaken by the FDOT, and when completed in 2004, the 1180 ft (360 m) long, five-span continuous channel span was the longest spliced girder crossing in the United States. In this article, the authors discuss the major advantages of the design-build approach, the innovative concepts used in the project - including spun-cast cylindrical piles, a new precast concrete bent cap-to-pile connection, stay-in-place precast concrete footing forms, and bulb tee girders - and how precast concrete design ingenuity led to rapid construction and maximum span lengths while protecting the marine ecosystem.