Risk-informed decision for civil infrastructure exposed to natural hazards: sharing risk across multiple generations
Lee, Ji Yun
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Civil infrastructure facilities play a central role in the economic, social and political health of modern society and their safety, integrity and functionality must be maintained at manageable cost over their service lives through design and periodic maintenance. Hurricanes and tropical cyclones, tornadoes, earthquakes and floods are paramount among the potentially devastating and costly natural disasters impacting civil infrastructure. Even larger losses may occur in the future, given the population growth and economic development accompanying urbanization in potentially hazardous areas of the world. Moreover, in recent years, the effects that global climate change might have on both the frequency and severity of extreme events from natural hazards and their effect on civil infrastructure facilities have become a major concern for decision makers. Potential influences of climate change on civil infrastructure are even greater for certain facilities with service periods of 100 years or more, which are substantially longer than those previously considered in life-cycle engineering and may extend across multiple generations. Customary risk-informed decision frameworks may not be applicable to such long-term event horizons, because they tend to devalue the importance of current decisions for future generations, causing an ethical and moral dilemma for current decision-makers. Thus, intergenerational risk-informed decision frameworks that consider facility performance over service periods well in excess of 100 years and extend across multiple generations must be developed. This dissertation addresses risk-informed decision-making for civil infrastructure exposed to natural hazards, with a particular focus on the equitable transfer of risk across multiple generations. Risk-informed decision tools applied to extended service periods require careful modifications to current life-cycle engineering analysis methods to account for values and decision preferences of both current and future generations and to achieve decisions that will be sustainable in the long term. The methodology for supporting equitable and socio-economical sustainable decisions regarding long-term public safety incorporates two essential ingredients of such decisions: global climate change effect on stochastic models of extreme events from natural hazards and intergenerational discounting methods for equitable risk-sharing. Several specific civil infrastructure applications are investigated: a levee situated in a flood-prone city; an existing dam built in a strong earthquake-prone area; and a special moment resisting steel frame building designed to withstand hurricanes in Miami, FL. These investigations have led to the conclusion that risks can and should be shared across multiple generations; that the proposed intergenerational decision methods can achieve goals of intergenerational equity and sustainability in engineering decision-making that are reflective of the welfare and aspirations of both current and future generations; and that intergenerational equity can be achieved at reasonable cost.