Bridges

The Tram Grade Separation Projects Alliance is rebuilding the existing tram overpass on South Road at Glandore as part of the Tram Grade Separation Projects, to accommodate the River Torrens to Darlington (T2D) Project lowered motorway.

The new overpass main span will support two tram tracks and pedestrian walkways.

The modifications comprise a skewed network arch bridge with new Super -T spans at each end to interface with the retained sections of the existing overpass. The new section of the structure will replace five existing spans. The South Road tram stop will be also modified and updated to suit the new bridge (including lift, staircase core and piers).

The top and bottom chord of the arch will consist of fabricated box sections, with the deck supported transversely by a series of composite steel cross girders. The steel rod hangers have followed a radial set out on the top chord and are typically inclined at 55-degrees to the arch.

A network arch bridge is an ideal solution for this span due to its structurally efficient nature, with the primary action in the arch being compression rather than bending, reducing the steel consumption up to 50% from other types of arches The high stiffness of a network arch is well suited to rail applications and applies relatively small loads on the substructure which is important due to adjacent structures.
During the design stage, parametric studies were undertaken to investigate the most efficient layout of the bridge (arch height, cable layout, number of cables and angles).

The network arch span, which forms part of the new overpass, will be built 'offline' within the vacant land on the western side of South Road, north of the existing overpass. Once constructed, the new arch span will be moved into its final position on the western side of South Road using Self-Propelled Modular Transporters (SPMTs).

Temporary steelwork is added to the network arch for the SPMT move. A composite steel and reinforced concrete deck is chosen to allow quick assembly and provide more geometric certainty which is required to meet the construction timeframe and tight rail tolerances.

Continuous feedback and iterations were undertaken with other disciplines, to find a solution with track geometry that tied into the adjacent structures, whilst meeting structural and aesthetic requirements.