The $175 million Iron Cove Bridge duplication has been designed to improve peak hour travel times along one of Sydney’s busiest roads. ARC’s experienced team of engineers, schedulers and bar processors used extensive 3D modelling and prefabricated the headstock offsite to overcome buildability issues and minimise safety risks.
The Iron Cove Bridge spans the Parramatta River connecting Parramatta and Sydney central business districts along Victoria Road one of Sydney’s busiest roads.
In April 2009, the NSW Government announced the construction of a second bridge over Iron Cove as part of the Inner West Busway along Victoria Road. The new bridge was opened to traffic on 28 January 2011.
Located on the western side of the existing bridge, the new bridge has a priority bus lane in the morning peak to improve travel times for about 200,000 commuters by up to 18 minutes. Outside of morning peak periods, it now includes three lanes for westbound traffic. There is also be a 4.3-metre wide shared-use path constructed on the existing bridge to link the Bay Run in Drummoyne and Rozelle to provide an efficient and safe link for pedestrians and cyclists.
The new bridge is now dedicated to westbound vehicles while the existing Iron Cove Bridge carries citybound traffic, a full-time bus lane and the cyclist and pedestrian path.
The $175 million project included 10 piers to support the bridge and eight concrete bridge segments, which were built onsite and launched towards the abutment in Drummoyne. Precast concrete Super T beams were lifted into place in Drummoyne and Rozelle to complete the main bridge structure.
ARC manufactured and supplied 2,100 tons of reinforcing steel for the bridge piers, deck and foundation cages at its mills in Victoria and New South Wales. A significant amount of accessories were also supplied by ARC to the project.
One of the most complex parts of the project for ARC was prefabricating the Pier 9 headstock offsite. Approximately 500 steel bars and fitments were manufactured for this headstock, assembled at ARC’s St Marys factory and delivered as one unit, ready to be positioned over the existing pier. Each steel bar was detailed and positioned with the aid of 3D computer modelling.
The Pier 9 headstock was one of the last substantial pours to be made on the bridge. It had very limited access for steel fixing and, at 16 metres long, included N36 bars 15 metres long. These bars alone weighed nearly 2 tons. The headstock was built on its ‘side’ with the 15-metre bars placed in rack supports at predetermined heights and the N24 fitments then slid over the bars and finally positioned.
“What made this process awkward and sometimes slow was the safe supporting of the 15-metre bars, while the varying sets of fitments, up to 30kg each, were manoeuvred over and located. All the fitments had unique locations and were sorted and tack welded, prior to installation,” says Peter Connell, ARC’s scheduling engineer for the project.
ARC also manufactured the pilecap starter bar cages. This resolved a number of buildability issues on site, with the cages essentially setting the alignment for the raking piers. The cages were large and geometrically challenging, requiring extensive use of 3D modelling.
“By prefabricating offsite, we reduced the amount of work that needed to be carried out at heights, and in very awkward locations, and therefore minimised risk, shortened the construction time, and reduced crane lifts and costs,” says Connell.
ARC also carried out an in-house comprehensive Job Safety Analysis to ensure that the prefabrication methodology was safe and risk free.
The heritage-listed Iron Cove Bridge is not the only iconic structure ARC has worked on. Other key ARC projects include the first Gateway Bridge, Brisbane’s Goodwill Bridge, Melbourne’s Westgate Bridge, Snowy Mountain Hydroelectricity project, Gladstone Alumina Refinery, the Sydney Opera House, Sydney Harbour Bridge, MCG, Melbourne Crown Casino, Sydney Olympic Stadium and Hobart’s Tasman Bridge.