This dissertation focuses on evaluation of seismic performance of highway network system with/without bridge retrofit and the associated socio-economic consequences in a context of probabilistic seismic risk assessment.; The methodology of this probabilistic seismic risk assessment is established by: (1) modeling seismic hazard by selecting a manageable set of probabilistic scenario earthquakes consistent with regional seismicity; (2) generating spatial distribution of the ground motion from empirical attenuation relations by considering both inter- and intra-event uncertainties; (3) modeling seismic vulnerability of bridges by fragility curves with quantified model-based uncertainty of the fragility parameters; (4) evaluating post-earthquake network performance with associated social cost measured by daily drivers' delay and opportunity cost, based on an integrated traffic assignment model considering both the reduced traffic capacity of the damaged network and the traffic demand change due to building damage; (5) simulating system restoration process by considering bridge repair process and traffic demand recovery to estimate total social cost; (6) developing system risk curve by providing system seismic risk under different levels of probabilities of being exceeded, based on the system risk distribution considering various uncertainties under each of the selected probabilistic scenario earthquakes; and (7) evaluating cost-effectiveness of bridge retrofit strategies based on economic analysis including associated bridge restoration cost, bridge retrofit cost and system social cost estimation.; The innovative approaches developed in this multidisciplinary study, such as modeling of probabilistic scenario earthquake, simulation of spatial distribution of ground motion, model-based uncertainty analysis of fragility curves, post-earthquake system restoration process simulation and cost-effectiveness evaluation of seismic retrofit, can also be applied to probabilistic seismic risk assessment of other spatially-distributed lifeline systems to aid decision-makers on optimization of seismic mitigation measures and preparedness for post-earthquake emergency response.
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