Bridges

Twin 112 metre-long bridges have been designed with superstructures comprising fabricated steel I girders composite with a cast-in-place deck slab. These are to be constructed in the approach and launched over Australia’s second busiest railway line. The line consists of six tracks, four of which carry coal between the mines and the sea port, and two of which carry intercity passenger and freight traffic. Any interruption to the service of this railway, apart from maintenance, is not permitted due to the high cost to productivity. Another constraint on the site was the road alignment requirement to have the bridges on a 45 degree skew. There was also significant predicted settlement due to the construction of the bridge approach embankment. These constraints presented unique challenges to the design and construction method. Many bridge options were investigated at the design stage and the most appropriate solution for final design was twin bridges with launched composite steel and concrete superstructures. Each superstructure was designed to be launched with a maximum cantilever length of 53.5 metres during one of the few short scheduled railway maintenance closures available per year.