Risk-informed decision making for civil infrastructure subjected to single and multiple hazards

This dissertation intends to provide insight to the risk of civil infrastructure subjected to single and multiple hazards and improve communication between different stakeholders for better risk-informed decisions and efficient risk mitigation. To this end, this dissertation investigates the effects of site-specific uncertainties in soil strength and stiffness parameters on the commonly used ground motion intensity measures and the resulting engineering demand parameters of moment resisting frames of varying heights at a site in Los Angeles, California. The uncertainty in the soil strength has a more profound effect on the intensity measures than the uncertainty in the soil stiffness. Moreover, it is observed that the structure amplifies the soil uncertainty more than the seismological uncertainty. Furthermore, this dissertation evaluates the economic viability of allowing for controlled inelastic deformation of special moment resisting buildings during wind storms. This is achieved through a set of case studies involving steel buildings of varying heights made of special moment resisting frames located in three different cities in the United States of America, with different intensity levels of wind and seismic hazards. It is shown that, controlled inelastic deformation of buildings under wind load may be economically advantageous, depending upon the properties of the structures and characteristics of both hazards. Finally, this dissertation explores financial aspects of selecting retrofit strategies for an interdependent civil infrastructure system subjected to multiple hazards. A hypothetical bridge-roadway-levee system, subjected to seismic and high-water (storm surge) hazards, is analyzed and retrofit strategies for the levee and bridges of the system are evaluated in terms of risk metrics commonly used in the field of financial engineering for portfolio optimization. It is shown that an optimal retrofit strategy depends upon the risk metric(s) being used for risk evaluation. It is also quantitatively argued that various stakeholders, including the owners, policy makers, and insurance companies may perceive risks differently, use different metrics for risk evaluation, and come up with different retrofit strategies for risk mitigation of the same system.