Fragility of bridges exposed to multiple hazards and impact on transport network resilience

Transportation infrastructure is a pylon for the society and economy, enabling the services and transportation of goods and people, under normal and emergency circumstances. Bridges act as bottlenecks within road and rail networks, since bridges are crunch points along the network system. Their failures due to multiple natural hazards (e.g. floods, earthquakes, tsunami or ground movements) may cause disproportionate losses, which are expected to be exacerbated due to climate change. Thus, pinpointing the vulnerabilities and quantifying bridge resilience within transportation networks is of paramount importance in the context of natural hazards. However, reliable quantification of risk and resilience of bridges is not yet available, as engineering judgment dominates quantitative assessments. This paper describes an integrated framework for the development of numerical fragility functions and the resilience assessment of bridges subjected to multiple hazards. The framework is applied to obtain the fragility of a representative bridge exposed to flood-induced scour followed by an earthquake. The resulting fragility functions are essential to evaluate direct losses due to multiple hazards, i.e. physical damage, as a means to deliver the Quantitative Risk Assessment (QRA) of the exposed bridges and networks. The framework is extended to the transport network level exposed to multiple hazards, providing a mean for allocating the resources reasonably toward efficient management and consequence analysis