Damage disaggregation for seismic resilience assessment of aging bridge networks

Risk assessment of bridge networks is generally investigated considering damage and disruption caused by sudden extreme events, such as earthquakes. Nonetheless, the structural capacity of aging bridges can be progressively impaired in time due to deterioration caused by environmental stressors, which can have harmful impact on functionality and resilience of key infrastructure networks exposed to seismic hazard. This paper proposes a procedure to investigate the contribution of different damage scenarios to the probability of failing to meet a target performance measure for aging networks. The proposed approach is inspired by the disaggregation process commonly adopted in probabilistic seismic hazard analysis and is aimed at facilitating the communication to infrastructure managers and policy makers of the consequences of natural hazards. A simple road network with reinforced concrete bridges is investigated considering the exposure to chloride-induced corrosion and to a prescribed seismogenic zonation. The lifetime vulnerability of single bridges is investigated based on the assessment of time-variant seismic fragility curves associated with limit states from damage limitation up to collapse. The time-variant disaggregation of bridge network damage with respect to a resilience-based measure emphasizes the interdependencies between seismic and environmental hazards and can be adopted to inform optimal life-cycle management strategies of key transportation networks.