Bridges

The Warringah Freeway Upgrade (WFU) in Sydney is a critical enabling works project for the current Western Harbour Tunnel project. The Warringah Freeway corridor is of critical importance due to its role in providing access for the three Harbour crossings, as well as providing the primary bus corridor to and from the CBD. The project will optimise the corridor, improving connectivity, performance and safety by reconfiguring access arrangements, lane configurations and wayfinding improvements.

Two existing pedestrian bridges that span across the Warringah Freeway from Falcon Street North Sydney to Merlin Street, Neutral Bay and from Ridge Street North Sydney to Alfred Street North, were required to be replaced to accommodate the changes in the road configurations for the upgrade. The new pedestrian bridges will include a dedicated pedestrian footpath and bicycle lanes, providing safer, improved walking and cycling journeys. Both new shared user path bridges consist of a 1550mm deep single cell steel box girder with composite cast-in-situ concrete decks. The Falcon Street pedestrian bridge is on a horizontal curve and has an overall deck length of 187.23 m comprising of four spans. The Ridge Street Bridge is a two-span straight bridge with an overall length of 94 m, excluding access ramps and a lift to Alfred Street.

The bridges are being constructed over the busiest section of road in Sydney. To minimise the disruption of the Warringah Freeway Road users and reduce the site work, it was proposed to install most of the fittings that include safety screens, drainage pipes and cables before lifting.

This paper describes the challenges encountered during the design and construction of the bridges. with a particular focus on the integration of the permanent and temporary designs required to assemble the bridges and the importance of the construction staging for the optimisation of both designs.