Design and construction of the South Road Superway

The South Road Superway is a new elevated highway under construction in Adelaide, Australia. When complete, the 2.8 km long structure will provide three lanes of traffic in each direction, as well as local ramps. The bridge will connect to the southern terminus of the Northern Expressway and facilitate heavy road freight movements on the main north-south route through Adelaide. The bridge superstructure consists of precast segmental concrete, built in balanced cantilever. The asymmetric, constant depth section is adapted with multiple variations to accommodate the frequently changing geometrics of the alignment. There are several features of both the architecture and construction that have led to unique design challenges. The segments are generally of constant depth, bringing a uniform appearance to the entire viaduct, with spans ranging from 50m to 85m. The expansion joints are at mid-span, and employ steel needle beams across the joints to provide continuity for moments and shear, while allowing longitudinal expansion. This is the first application of this type of joint in Australia. Piers are both architecturally interesting, and structurally challenging. In the south area both carriageways rest on a single curved, Y-shaped pier. The superstructure is monolithic with the substructure, and the top of the Y is tied together with a post-tensioned cross beam. This basic structural arrangement is carried through all of the varying roadway conditions encountered along the alignment, from the standard three-lane portion to the ramps and bifurcation areas, and into the wider four-lane box girders of the northern area.