Multi-hazard probabilistic risk assessment of bridge networks in cold regions

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Recent natural and man-made disasters have highlighted the vulnerability of civil infrastructures to extreme events and the resulting severe social and economic disruption to the affected communities. To address this issue, engineers are moving towards probabilistic risk assessment methods to better account for the uncertainties inherent to bridge life-cycles. Also, due to climate change, Highway bridges in Canada are experiencing increased magnitudes and frequencies of natural hazards such as flooding, ice impact and foundation scours. Even though engineers and decision-makers have over the years adopted more sophisticated methods for the analysis and evaluation of bridges, the use of probabilistic methods has been limited to the analysis of few bridge components. As a consequence, it is still not clear how changes in the characteristics of other key bridge elements affect the overall performance and safety of these structures. This lack of knowledge is even more emphasised when bridges are subject to multiple hazards. The overall objective of my research program is to reduce this gap by assessing the overall performance of typical highway bridges and the consequences of failure for three of the most common bridge hazards, which are overloading, impact and scour. Worldwide, these three hazards combined account for about 90% of all bridge failures. In particular, in cold regions like Canada, the effect of scour on bridge foundations is even more accentuated due to freezing cycles and ice jams. Water freezing, due to natural seasonality and climate change, also increases the risk of flooding with higher chances of bridge failure by impact of debris and increased water pressure. Furthermore, if we consider that in Canada about 45% of bridges have already reached their life expectancy and that the overall budget for maintenance and rehabilitation only covers about 59% of the estimated cost, addressing the safety of highway bridges with a probabilistic risk-based approach is the only viable alternative for the optimal allocation of these economic resources at a local and national network levels. The short-term goals of my research program will be to develop computationally efficient assessment tools for the risk of highway bridges using a scenario-based approach for the aforementioned hazards. Second, social and economic consequences of bridge failure will be evaluated considering key characteristics of the Canadian highway network and urban developments. The long-term goal of my research is to develop a framework to support decision-making processes that will address all bridge hazards. An immediate benefit to society of this research program is the training of highly qualified personnel. Under my supervision, both students and practising engineers will gain state-of-the-art skills in the area of probabilistic risk assessment of bridges offering new valuable expertise to Canadian groups, like SNC-Lavalin, Stantec and Manitoba Infrastructure.