Bridges

Cover of Design of the New Shared Use Path Bridge over the Maribyrnong River Using Weathering Steel
Design of the New Shared Use Path Bridge over the Maribyrnong River Using Weathering Steel
  • Publication no: ABC2017-138-17
  • Published: 26 April 2017

To improve the amenity for cyclists and pedestrians travelling on Melbourne’s second busiest cycle path, a new Shared Use Path (SUP) Bridge has been designed to provide a new and improved crossing of the Maribyrnong River. This new 190 m long and 4.5 m wide bridge will replace the existing narrow SUP on the adjacent Shepherd’s Road Bridge, which is being widened and strengthened to support increased freight movements to the Port of Melbourne as part of the West Gate Distributor – Stage One Project.

The SUP bridge has been designed through a collaboration of engineers and architects to provide a structure that complements and enhances the industrial and maritime character of the local area. To this end, weathering steel was used to construct the twin curved steel I girders that represent the main structural element supporting the bridge deck.

Weathering steel has been used extensively in Europe, North America and New Zealand for many years as the primary structural element, whereas within Australia, weathering steel is largely limited to cladding or architectural features. There exists only one other bridge within Australia where weathering steel is used as the primary structural element, the Lotterywest Federation Walkway pedestrian bridge in Kings Park, Perth.

Weathering steel is a high strength low alloy steel that in suitable environments, forms a protective rust ‘patina’ that inhibits further corrosion. This paper will outline the benefits of using weathering steel for primary structural elements, including reduced ongoing maintenance and reduced construction time and cost. However, weathering steel is not without its limitations, and specific detailing that was adopted for the bridge will be discussed along with specific welding requirements that were considered. To facilitate the design of the bridge using weathering steel, the HERA Report R4-97 "New Zealand Weathering Steel Guide for Bridges" was adopted and the paper will outline the suitability of this document for use in the Australian context.