The John Gorton Drive and Molonglo River Bridge Crossing

The Molonglo River Bridge is Australia’s largest weathering steel bridge

The Molonglo River Bridge, part of the John Gorton Drive project, is a critical piece of infrastructure linking new residential areas to the future Molonglo Town Centre. GHD and pitt&sherry, in association with COWI, were engaged by BMD to undertake the tender and detailed design for the project. The project, which includes a provision for future light rail within the alignment, will improve access around the Molonglo Valley and keep the growing town centre and the wider city moving.

Date:

July 12, 2024

Location:

Australian Capital Territory

Services:

Temporary Works Design Transport Infrastructure Design Sustainable & Circular Design

Markets:

Transport

Background

The Project includes the construction of approximately 1.7km dual carriageway, a new 200 metre long bridge over the Molonglo River, separated paths, two new signalised intersections, lighting and servicing, stormwater management, tree removal, landscape rehabilitation (including the establishment of fauna habitat), four single span pedestrian underpass bridges and associated works.

What we did

During the tender design phase, tenderers were given the opportunity to provide alternative submissions in addition to pricing the reference design. The BMD design investigated design options that increased safety, sustainability, resource efficiency through circularity, improved constructability and provided improved value for money. Key project innovations included:

Reduced the overall bridge length from 227.5m to 200m with a span arrangement 60m-80m-60m, leading to simplified and safer construction.
Integrated circular principles and a reduction in carbon due to material savings through the change from three narrow box girders to two wider box girders. This change simplified construction, provided more stable box girders and increased safety during maintenance inspections.
Incorporation of an abutment gallery, which facilitates safe access into the box girders, around the bearings, and to the expansion joints.
Provided sustainable principles by raising the road alignment by 500mm. This change resulted in a balance to the overall project cut and fill volumes and optimised the bridge grade.
Removed the stone pitching batter stabilisation at the Molonglo River Bridge abutments and replaced this with interlocking rock protection that is sustainably sourced from site.
Provided sustainable principles due to material savings by reducing the number of spherical bearings from 24, to 16.
Eliminated the need for rock anchors at the pier pad footings of the Molonglo River Bridge.

The bridge has been designed to install the girders in 80m segments by a single heavy-lift crane.

The detailed design has been delivered to a tight program in collaboration with the Contractor, BMD and regular engagement with the Principal, Transport Canberra & City Services (TCCS) and Major Projects Canberra (MPC).