Bridges

Designing and building a bridge structure within a precinct that has a high density of major utilities functioning 24/7, existing infrastructure that must remain accessible at all time and areas managed by multiple stakeholders comes with many challenges. The 19-span structure is part of the first stage of the elevated ring road within the southern precinct of Melbourne Airport and currently provides access to the Multi-level story car park.

Urban design outcomes were considered at an early stage of the reference design and an option consisting of precast segmental units was proposed which minimised the number of piers, aiming at limiting the impact on existing utilities, roads and car parks. The repetition of the span lengths required for this type of bridge structure did however not have the predicted effects. Issues raised that could not have been resolved by any other means than moving utilities. These relocations had unacceptable programme and cost implications.

The geometry was adjusted to accommodate simply supported Super T beams. The fly-over the intersection between Melrose Drive and Centre Road was proposed using a steel box girder to eliminate piers in that intersection. Following traffic management studies, it was eventually found that a pier within the intersection was possible and that the Super T structure could continue uninterrupted for the full viaduct length.

The ground conditions consisting of shallow basaltic rock were ideal for the design of pad footings for the piers. However, preference has been given to piles socketed into the basaltic rock. This type of foundation minimised the impact on the utilities running in the MLS Access Ramp corridor. Each of the piles were designed to suit the local geotechnical conditions of the sites in order to optimise the design.

The construction of the bridge structure was finalised in August 2015.