The report captures the major failure modes of bridges under exposure to potential natural hazards in Australia: flood, bushfire and earthquake.
Attributes of bridge structures which influence failure and the typical levels of natural hazards experienced in Australia are explored. Case studies on analysis of failure of bridges have been presented which can provide input to vulnerability modelling of the bridge structures. Analysis of case studies and literature indicated that the most common failure mechanisms of bridge structures under flood is scour, debris loading and damage to approach roads. Failure mechanisms of bridges due to bushfire are significantly affected by the construction material of bridge components. Major mechanisms of failure in reinforced concrete structures is observed to be the spalling of concrete, failure due to reduction in strength and elastic modulus of concrete and yielding of reinforcing steel. In steel bridges, when temperatures rise above 400 degrees Celsius, a rapid reduction in strength of members could lead to failure. Failure mechanisms of the bridges due to earthquake are explored using analytical methods and fragility curves have been developed using finite element modeling of a bridge structure. Deck joints have been observed to be the most vulnerable elements of girder bridges in Australia under earthquake loading. The generic methodology developed will be applied to other structural forms in future.