Analysis of bridge failure due to Cyclone Marcia in Central Queensland using fault tree method

Over the past few years Queensland has suffered from a number of severe tropical cyclones, the most recent one being Marcia, that took place on 20th of February 2015. Damage bill of Marcia exceeded $50 million which included cost of repairing a number of damaged bridges. Failure of road infrastructure isolates communities from accessing essential services and commodities. This necessitated an urgent need to develop a systematic method of assessing the failure of the bridge component to improve the resilience of future bridges and provide base knowledge for developing emergency maintenance response. There are several methods available to investigate the bridge failure. Fault tree analysis (FTA) was selected considering its positive attributes over other methods. FTA was used to estimate the probabilities of failure of main components (Super Structure and Sub Structure) and elements of timber and concrete bridges. Secondary data (Level 1 and level 2 bridge inspection reports from the department of transport and main roads) before and after the cyclone Marcia were used in conjunction with expert consultations to construct fault trees for both timber and concrete bridges. Results indicated potential failure mechanisms and the degree of susceptibility of main components of timber and concrete bridges to cyclonic events. However, the extent of the data was not adequate to draw firm conclusions and further studies (i.e. probabilistic models) are recommended to strengthen the understanding of the complete dynamics of the bridge failure under cyclonic event

Vulnerability assessment of bridges subjected to extreme cyclonic events

Over the past few years Queensland in Australia has suffered from a number of severe tropical cyclones, the most recent one being Marcia, that took place in 2015. Damage bill of Cyclone Marcia exceeded $50 million which included cost of repairing a number of damaged road structures. Failure of road structures such as bridges isolates communities from accessing essential services and commodities. This necessitated a methodical approach to evaluate the failure of bridges to improve their resilience and provide base knowledge for developing emergency maintenance response. Although there are several methods available to evaluate the vulnerability of bridges , fault tree analysis (FTA) was selected in this study by considering its positive attributes over the other methods. FTA was used to estimate the probabilities of failure of main components (superstructure and substructure) and elements of timber and concrete bridges. Secondary data (level 1 and level 2 bridge inspection reports from Transport Main Roads in Rockhampton) before and after the Cyclone Marcia were used in conjunction with expert advice to construct fault trees for both timber and concrete bridges. Potential failure mechanisms were observed and the degree of susceptibility of main components of timber and concrete bridges to cyclonic events were evaluated. This research was based on selected bridges under specific cyclone in one region, which is a limitation of the study. Few other case study bridges subjected to cyclonic events can be used to strengthen the understanding of the complete dynamics of the bridge failure under these extreme events