Design excellence and innovation for the Bruce Highway (Cooroy to Curra), Section D (Gympie Bypass)

This major transport corridor enhances connectivity between the Sunshine Coast, Gympie, Maryborough and regional centres while supporting freight movement along Australia’s east coast. The Gympie Bypass, or Section D, is the final section from Woondum (south of Gympie) to Curra, and is a critical part of the 15-year upgrade, improving safety, flood resilience, capacity and freight efficiencies. Spanning 26 kilometres, Section D incorporates a new four-lane highway, three interchanges, 42 bridges at 23 locations, with the impressive Six Mile Creek Bridge.

The Six Mile Creek Bridge presented a complex engineering challenge due to its location within a flood-prone and environmentally sensitive landscape. Given the scale of the bridge, at 255 metres-long, and the project, the bridge structure needed large spans while minimising environmental disruptions and impacts, and ensuring long-term structural resilience. A variety of structural options were assessed in collaboration with TMR, with the intent of maintaining construction consistency with the broader project and avoiding the introduction of additional complexities such as on-site post-tensioning or extensive steel structures. Achieving this required a design that balanced technical innovation, value engineering, and construction efficiency while adhering to the broader project’s requirements. Additionally, given the project’s scale, standardisation of components was critical to streamline construction, reduce costs and maintain consistency across the 26-kilometres and multiple bridge locations.

GHD developed a comprehensive design strategy incorporating a combination of continuous deck systems, supported Super T girders, and pre-cast reinforced concrete elements for the 255-metre bridge. This integral bridge design approach ensured efficiency in production, installation, also benefiting the long-term maintenance of this road infrastructure asset.

A key aspect of the engineering solution was the placement of 92 girders, the longest measuring approximately 38 metres and weighing 115 tonnes. Standardisation played a crucial role in constructability and project efficiencies. GHD developed standard drawings for 1,200 Super T girders, restraint blocks, barriers and wingwalls, providing consistency throughout the design and construction phases. This standardisation facilitated smoother procurement, installation and asset management across all 42 bridge locations within Section D.

Value engineering also contributed to significant cost and material savings. A detailed review of all bridges resulted in optimised span configurations, eliminating redundant structures and reducing overall bridge lengths while maintaining performance. Collaboration was central to success, with GHD working closely with delivery partners including KBR, Beilby Holdings, BMD Group Joint Venture and CPB Contractors. This partnership enabled the refinement of construction sequencing, ensuring efficient crane-based installation methods aligned with project requirements and contractor preferences.

From the initial planning and design phases, through to construction administration with the delivery partners, GHD’s involvement has been deeply embedded in delivering the Bruce Highway Cooroy to Curra program of works. A standout feature of the project is the Six Mile Creek Bridge, where innovative engineering solutions were implemented to optimise performance, minimise environmental impact, and support effective long-term asset management.

The Six Mile Creek Bridge exemplifies intelligent design and collaboration in large-scale infrastructure projects. By pushing conventional bridge forms to their limits before introducing more complex solutions, the project achieved a durable and cost-effective outcome in a flood-prone and environmentally sensitive landscape.

The completion of the Cooroy to Curra project, particularly the Gympie Bypass and Six Mile Creek Bridge, delivers significant benefits to Queensland’s transport network with improved road safety, reduced travel times, and efficient regional freight routes, this section of the Bruce Highway fosters economic growth, improved connectivity and delivers long-term community benefits for the region. Furthermore, the innovative engineering and industry collaboration showcased in this project sets new benchmarks for future infrastructure developments while demonstrating how strategic design and teamwork can drive excellence in structural bridge design, road infrastructure and transport solutions while delivering a lasting legacy.