Bridges

The M1 Pacific Motorway extension to Raymond Terrace project is one of the last remaining major upgrades required to complete a free-flowing dual carriageway route between Sydney and Brisbane. The project connects the existing M1 Pacific Motorway at Black Hill and the Pacific Highway at Raymond Terrace. The southern section of the project involves building approximately 10 kilometres of dual carriage motorway improving travel time and road network efficiency for freight and commuters at the key junction of M1 Pacific Motorway, the New England Highway, and the Pacific Highway Tomago intersection. It will provide improved route reliability in relation to congestion reduction, flood immunity and high demand holiday peak travel.

As part of the project a new bridge is required to span the Old Punt Road interchange at Tomago. The bridge is a single span structure comprised of eight post-tensioned Bulb-T girders acting compositely with a cast in-situ concrete deck.

This paper presents the main considerations for the design and construction of the bridge at 50-metre overall span length and 45 degree skew alignment. The use of precast concrete Bulb-T girders with buttress type reinforced soil walls was adopted as the most optimal solution. Limitations on the handling of the girders within the precast yard necessitated the casting, transporting and erecting of two girder segments with post-tensioned stitch connections. This innovative solution is presented in detail including the construction requirements and constraints through each stage, and the investigation of longitudinal cracking of the concrete deck between girders due to creep and shrinkage. Other key design features are presented including the urban design integration, particularly on the reinforced soil walls and the maintenance access provisions.

At the time of writing, the design is complete and construction is ongoing.