Special-Design Precast Concrete Beams for Sidney Lanier Bridge Replacement Project

Abstract

The Sidney Lanier Bridge Replacement Project is a $100 million undertaking in Brunswick, Georgia, that will lead to the replacement of an existing 40-year-old steel lift-span structure. The approach bridges that lead to the project’s main-span unit consist of 16 spans of 54.9-m (180-ft), special-design, precast concrete beams as well as 14 spans of 36.6-m (120-ft) Type V AASHTO girders. The special-design beams are 2.3 m (7.5 ft) deep, are erected as simply supported members and are then made into two-span continuous units by longitudinal posttensioning, and are rigidly connected transversely with cast-in-place diaphragms. The riding surface is a cast-in-place concrete deck constructed on stay-in-place metal forms. The 54.9-m (180-ft) beams, supported by hollow tapered concrete piers with hammerhead caps, are founded on 1.2-m (48-in.) drilled shafts. Wet-hole construction methods with bentonite slurry were required for the drilled shafts. The bridge piers are over land and water, and large cofferdams were required to facilitate construction. Additionally, the sizes of the cast-in-place footings and hammerhead pier caps required mass concrete thermal considerations. The approach bridges lead to the main-span portion of the project, which will be a 762-m (2,500-ft) concrete, cable-stayed unit with a 381-m (1,250-ft) center span. The design, casting, and erection of these beams, and construction of the substructure, posed many challenges to the Georgia Department of Transportation designers and contractors. These beams are among the longest erected in Georgia.