Published works

In recent years, frequencies of flood events in Australia have increased. It is noted that flood events cause the most damage to infrastructure compared to any other natural hazards in the world. Road bridges are lifeline structures with a pre and post disaster critical functionality. Failure or damage of bridges during an extreme flood event can have severe consequences to the community as well as road authorities and emergency services. Currently a major gap in knowledge is the ability to evaluate the vulnerability of bridge structures using a methodology which captures the variability of the event intensities and the variability of the structural capacity. The research presented here addresses this knowledge gap.

Research commenced with a comprehensive literature review covering review of major bridge design codes in the world, literature on flood loading, vulnerability modelling of bridges and numerical modelling approaches to simulate bridges under natural hazards. Damage indices proposed by researchers to depict the levels of damage to structures are also noted.

A comprehensive analysis of case studies of failure of bridges under flood loading under the 2011 and 2013 floods in Queensland and Victoria was undertaken to establish the major failure mode of bridges under flood loading. This identified that failure of girder and deck of concrete girder bridges, which constitute more than 60% of the bridge network, is a common case study to investigate. Two bridges were selected for analysis and the outcome was used to establish the vulnerability modelling methodology.

A deterministic analysis of the selected structures was undertaken under variable flood loading to establish the analysis methodology using ABAQUS software. The loading configuration considered covered flood, log impact and debris impact. This analysis demonstrated that Kapernicks Bridge would fail at a flood velocity of 3.71m/s which closely agrees with the recorded flood velocity as well. Understanding the limitations of the deterministic analysis where the variability of flood loading and the variability of structural capacity cannot be accounted for, a probabilistic fragility analysis was undertaken to establish the probability of failure of the bridges.

Probability distribution was established for flood velocity as well as the structural section capacity. Fragility curves were derived for concrete girder bridges using the developed methodology.

The methodology developed is applicable for any bridge structure when the flood loading distribution for the location of the bridge can be established.

Contribution to the existing knowledge from this research has been the methodology developed to quantify vulnerability of road infrastructure exposed to flood hazard that would assist evaluate damage state for bridge structures. Emergency Management could use this damage state to assess evacuation routes while Road Authority could make decisions on strengthening the bridge structure.

A sensitivity analysis was undertaken to explore the effect of span of the bridge and also increase in flood frequency on the probability of failure.

A method to derive damage indices which can be used by bridge engineers for decision making has been demonstrated.