Bridges

The future of bridges will be shaped by the reliability in the service life span of our older and current generation of structures. Designs and materials have changed over the years due to both lessons learnt and advances in materials. However, a significant number of older technology bridges remain in operation, including Menangle Bridge in NSW, Australia. This wrought iron structure was built in 1863 to provide a vital railway link between Sydney and Melbourne, Australia. It has been the subject of numerous investigations, testing and monitoring, due to concerns over cracking, ultimately leading to its temporary closure in 2003 – a decision highly publicised at the time. This paper discusses the most recent investigation of this infamous structure, undertaken in 2012, which included a rigorous load rating, fatigue analysis and crack investigation. The premise of the work was to allay concerns about fatigue cracking, and enable the speed restrictions over the structure to be uplifted. The investigation navigated its way through the remarkable path of the previous studies, material behaviour, effects of deterioration and alterations on the capacities and redundancies. The investigations concluded that for the first time in 10 years, the structure could operate at full track speed for current traffic, albeit with ongoing routine inspections and maintenance. This paper presents an overview of the investigation into the wrought iron connection details, and how detailed analysis of these connections has helped to remove uncertainties about its future.