Bridges

The Karel Avenue Upgrade Project delivered by Main Roads Western Australia and constructed by Georgiou Group, aimed to improve traffic mobility and accommodate future developments in the area. Part of the project, completed in 2021, comprised the design and construction of the Karel Avenue Bridge no.1595A over the Thornlie to Cockburn rail line. The new bridge was required to widen the road to a double lane carriageway and to accommodate two future rail lines underneath.

This brownfield project presented several challenges, such as space limitations due to the existing structure and complex construction staging to retain traffic flow, meaning the bridge was constructed in stages with multiple stitch pours to control the differential deflection between stages. The bridge was built using a 'top-down' system to reduce construction footprint, costs and minimise disruptions to road and rail traffic.

The substructures were constructed around partially retained existing abutments. Since the existing south abutment was retained, the new bridge span was lengthened to reduce the risk of damaging the existing Mechanical Stabilised Earth wall during piling. The existing north abutment was de-constructed and replaced with piles integrated with shotcrete facing. The new north abutment utilised a deadman anchor system with sheet-piling as an efficient design to retain the significant height of soil behind the abutment.

This paper discusses the engineering solutions adopted in the design of the new bridge to reduce road and rail traffic disruptions and to retain the south abutment of the existing bridge without impacting its stability.