The work and the technique: Sydney Metro Northwest, Australia

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The Sydney Metro Northwest represents the first phase of the ambitious network of metro lines of the Sydney Metro, the largest public transport work in Australia's history.
The infrastructure project consists in building the new metro line North-West of the city to connect Chatswood station with Cudgegong Road.

Works awarded to Salini Impregilo, then part of the Webuild Group, consists in designing and constructing the so called "Skytrain bridge" and other civil works that make up one of the main sections of the line.

One of the greatest engineering challenges was the span's curvature when loaded by trains and steel cables. And in particular, overcoming the significant torsional effects caused by the curvature itself. To build the viaduct, horizontal cranes were used: i.e., two 150-metre giants weighing 600 tons needed to position 1,200 prefabricated concrete segments that gave life to the viaduct.
This system represented one of the major project innovations: using the "Stage by Stage" launching technology whose kinematics are developed and implemented for the first time by Webuild on the R 881/2C of Dubai project.

The technology is based on using highly performance launching gantries and foresees the simultaneous two spans through using a bracket method for a ¼ of the span and subsequent infill and completion through the span-by-span method, which allows merging the capacity of launching spans with different lengths and over 60 metres with an extraordinary speed of execution being able to count on using the same machine. Brilliant engineering solutions made it possible to use the same machine to build a cable-stayed bridge named Skytrain, reducing to the minimum the temporary prestress quantitative.

Works on the Sydney Metro Northwest were awarded numerous international and local prizes, among which the maximum rating for sustainability assigned by the Infrastructure Sustainability Council of Australia (ISCA) in 2015 (for its design) and in 2017 (for its construction).