DESIGN OF BR70 RAMP C2 STEEL-COMPOSITE BOX GIRDER BRIDGE FOR THE WEST GATE TUNNEL PROJECT IN

Nick Oehley1, Raymond Chung2, Peter Brookes3, Sasithorn Thammarak4

ABSTRACT: The West Gate Tunnel Project will be constructed over five years and provide an alternative to the in Melbourne. Opening in 2022, it will deliver a second river crossing, faster and safer travel, and will remove thousands of trucks from residential streets. The project includes widening the from 8 to 12 lanes, including express lanes between the M80 and the West Gate Bridge and reducing weaving and merging that leads to traffic congestion. Twin tunnels from the West Gate Freeway to the and the will take motorists and trucks underground, providing a more efficient freight route. It is currently one of the largest civil infrastructure undertakings in .

The West Gate Tunnel Project provides kilometres of elevated bridge structures and a wide range of complex bridge forms. One of the largest features of the east zone is the motorway to motorway CityLink Connections, where composite- steel box-girders have been selected to take advantage of the benefits the structural form provides. The long-span capability they offer reduces impacts from substructure components on existing services, buildings and carriageways, and alleviates the limits that precast girders have with span and curved alignments.

The longest (and highest) of these connections is Ramp C2, connecting CityLink Southbound to the Footscray Road viaduct, standing at 1400 m in length and up to 26.5 m in height above Footscray Road. With detailed design nearing completion, this paper will discuss the design of the ramp, outlining central aspects of the analysis and design process with a focus given to the method for steel-tonnage optimisation, the complexities of construction staging and the associated temporary works. Given recent development in local sentiment towards steel usage, a discussion on the applicability and potential for such a structural form in New Zealand will conclude the paper.

1 Senior Bridge Engineer – West Gate Tunnel Project, Aurecon-Jacobs JV. [email protected] 2 Principal Engineer / Structural Lead – West Gate Tunnel Project, Aurecon-Jacobs JV. [email protected] 3 Senior Bridge Engineer / Package Lead – West Gate Tunnel Project, Aurecon-Jacobs JV. [email protected] 4 Senior Bridge Engineer – West Gate Tunnel Project, Aurecon-Jacobs JV. [email protected]