Bridges

The Regional Growth NSW Development Corporation (RGDC) is currently delivering the first Special Activation Precinct (SAP) in Parkes to provide opportunities for investment, business development and employment growth for new and existing industries in the Central West. The Parkes Special Activation Precinct Enabling Works is currently being delivered by the RGDC and their construction partner, Fulton Hogan and their designer, Cardno. The enabling works include an upgrade to 7.3 km of Brolgan Road, two ARTC rail overbridges, Reinforced Soil Wall (RSW) approach structure, intersection improvements, and utilities.

The Bridge Over Parkes to Narromine Rail Line at 449.850km is a grade separated crossing of Brolgan Road over the existing rail line owned and maintained by ARTC. The horizontal road alignment is straight and the vertical alignment is on a crest curve with a high point positioned on the bridge structure itself. The single span steel composite bridge is approximately 53.7 metres long, crossing the railway at a skew of approximately 55 degrees.

The bridge abutments are formed of four piles and a 1200mm diameter pile extension through a RS wall embankment and a reinforced concrete headstock. Piles are founded on the underlying rock stratum, through the RSW fill, with the pile extensions designed to be constructed with a permanent isolation gap between the pile and the RSW. The superstructure will be formed of 4 No. 2300 millimetre deep weathering steel trough girders supported on spherical bearings. The steel trough girders are overlain with a minimum of 250 millimetre thick deck. Cross bracing is provided between the girders the quarter point of the span approximately. Steel plate diaphragms are provided at the ends of the span. Weathering high strength structural bolting is used all connections. The paper will discuss the main design features of the bridge, including its construction over the existing ARTC rail line, geometry constraints and its effects on the articulation. Additionally, the design considerations for substructure structural elements and end cross girders of the highly skewed bridges will be presented. It will also present the application of a buried RSW behind the abutments, as an innovation developed by the project team.