Bridges

Sydney Gateway is a road and rail project to cater for forecast growth in passengers and freight through Sydney Airport and Port Botany. The project comprises road (Stages 1 & 3) and rail (Botany Rail Duplication Stage 2, delivered separately by ARTC). The Sydney Gateway road project completes the missing links in the motorway network, and will improve traffic flow and reduce travel times. The project is located in a highly developed brownfield environment, with adjacent road, rail, pedestrian, air transport, water and miscellaneous utility infrastructure.

Two Bridges on Qantas Drive over Port Botany Rail Line and Alexandra Canal, a 8 span continuous composite steel box girder bridge with a total length of 369m, happens to slot in amongst nearly every form of constraint listed. Road, rail, pedestrian and water infrastructure governed pier set-out, requiring high and variable skews. In addition to horizontal restraints, the allowable bridge depth was squeezed between vertical clearance requirements from the Airport Object Limitation Surface (OLS) and rail / road clearance envelopes governing available span/depth ratios for the superstructure. To address these constraints, the design team adopted a range of innovative engineering techniques. This paper will focus on the restricted geometry of the site, and how the use of precast permanent formwork for blade piers adjacent to and within the rail corridor, weathering steel composite superstructure, and construction methodology including the use of SPMT installation for the main span over the Alexandra canal which were adopted to satisfy the various constraints in addition to contractual, design and stakeholder requirements.