Bridges

The Australian Bridge Design Standard AS 5100-2004 is currently being reviewed by Committee BD90. The new Standard AS 5100-2015 will contain improved provisions to maximise safety at bridges and structures over and under railway lines. The intent of the provisions is to avoid catastrophic failures of bridges due to loading or collision impact by derailed trains or road vehicles and to provide a ‘forgiving’ environment to minimise the probability of injury to the occupants of derailed trains. The new draft provisions being discussed by the Australian Standards BD90 Committee are considered to be leading edge in safety consistent with the Safety in Design Legislation and ‘Safe System’ philosophy. The new provisions for through-girder and truss bridges will increase safety significantly both within the bridge and on the approaches. Updated provisions for bridges over railways and underbridges include design and geometry specifications for crash walls for heavy piers and deflection walls both within the bridges and approaches. Collision simulation software may be used to assist to test proposed solutions to prove the design intent. The new provisions may be too difficult and/or costly to apply in the retrofit of existing bridges. Risk analysis may be used to determine practical improvements to safety for these structures. While the new provisions are a significant step forward to improve safety in rail infrastructure, more research and development is required to improve the provisions on an ongoing basis for maximum safety.