Bridges

In addition to providing the southern hemisphere's largest-diameter tunnel as an alternative major Yarra River crossing to ease congestion on the 50-year-old West Gate Bridge, the West Gate Tunnel Project is also one of Australia's largest bridge projects. To the west of the tunnel, a significant proportion of the project is comprised of the brownfield environment-upgrade of the 5km long West Gate Freeway corridor between the M80 interchange and the tunnel's southern portals, with the freeway being widened from 8 to 12 lanes. The project's eastern zone consists of elevated road structures which are bookended by connections to the existing CityLink tollway and Dynon Road.

The project has required the strengthening/widening of 12 different bridge structures, including more than 40 spans of bridge superstructure and numerous substructure elements. The design load rating assessments for these structures encountered varying historic design standards and details dating from the 1950s to 2000s, which were then repurposed and transformed to meet the project performance requirements.

The modification of a variety of existing structures with different design lineage against current requirements has provided a testing ground for all manner of strengthening options, with a wide range of innovative solutions provided. The developed strengthening designs implement bespoke solutions which were customised to each of the structures, to ensure that the level of service, strength, durability, integrity and facility owner operation and maintenance criteria were achieved. Strengthening solutions adopted include carbon fibre-reinforced polymer for flexural and shear capacity, external post-tensioning, internally mounted steel rods and concrete deck overlays. This paper presents an overview of the key design / construction challenges and the lessons learnt from the implementation of these solutions. Further recommendations are provided for consideration in future widening or strengthening works.