Assessing levels of reliability for design criteria for hurricane and storm damage risk reduction structures
In the wake of Hurricane Katrina, the U.S. Army Corps of Engineers (USACE) updated design methodologies and required factors of safety for hurricane and storm damage risk reduction system (HSDRRS) structures to incorporate lessons-learned from the system performance during Katrina and results of state-of-the-art research in storm surge modeling and foundation behavior. However, the criteria (USACE 2008) were not calibrated to a target reliability, which creates the need to understand the reliability provided by designs using those criteria, especially for pile-founded structures subject to global instability. This dissertation presents a methodology for quantifying the reliability of pile-founded structures that can be applied to hurricane risk reduction structures or more broadly to other types of pile-founded structures. The emphasis of this study is on a representative hurricane risk reduction structure designed using the new USACE criteria, for which the reliability is quantified for comparison to industry target reliabilities. A designer-friendly methodology for quantifying the reliability of hurricane risk reduction structures is presented, along with recommendations developed from a state-of-the-art review of geotechnical, hydraulic, and structural uncertainty data. This methodology utilizes commercial software and routine design methods for the development of inputs into an overarching framework that includes point estimate simulation models and event tree methods to quantify the structure’s system reliability. The methodology is used to illustrate differences in analysis results with and without accounting for variance reductions due to spatial correlation are also presented through stability and flowthrough limit states. Element reliabilities and overarching “system” reliabilities for a representative structure are quantified for hydrostatic hurricane storm surge loadings, soil loading, and dead loads. Wave loadings and impact loadings are not considered. The use of variance reductions on undrained shear strengths for point estimate simulations produced higher system reliability indices than the simulations not considering variance reductions for the stability and flowthrough limit states. Using the reduced variances, computed element and system reliabilities were above the industry target reliability indices presented in the literature.
reliability, target reliability index, unbalanced load, scale of fluctuation, hurricane storm surge, T-wall
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