Probabilistic Framework for Seismic Loss Assessment of Aging Highway Bridges in Crustal and Subduction Zones

This study offers a probabilistic framework for the seismic life-cycle cost (SLCC) assessment of aging highway bridge structures in complex seismogenic zones, followed by a case-study application on a popular bridge class in Seattle (United States). The proposed framework efficiently handles the implications of differing seismic hazard scenarios (crustal and subduction earthquakes) along with time-dependent bridge deterioration mechanisms on seismic fragility and lifetime economic losses. These losses, stemming from the seismic damage-induced repair of critical bridge components, may be uncertain depending on the repair technique, availability of resources, or decision of the stakeholder. Unlike previous works that have evaluated seismic losses under a single hazard source and deterministic repair costs, this study aimed for a better approximation of the accumulated lifetime losses for aging highway bridges under simultaneous exposure to differing hazard sources, while accounting for repair uncertainties. The case-study results revealed that the SLCCs using deaggregated hazard sources incurred significantly higher contributions from subduction earthquake sources than shallow crustal earthquake sources for both as-built and aging bridge structures. Lastly, based on the proposed framework, a statistical model is proposed for easy adoptability by stakeholders and decision-makers for the SLCC computation of bridge structures in the case-study region.