CAREER: Substructure Damage Characterization for Performance-Based Earthquake Engineering

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CAREER: SUBSTRUCTURE DAMAGE CHARACTERIZATION FOR PERFORMANCE-BASED EARTHQUAKE ENGINEERING Tara C. Hutchinson Department of Civil and Environmental Engineering University of California, Irvine An extremely important yet largely unanswered question in foundation design is what constitutes satisfactory performance of the below ground portion of the foundation when subjected to earthquake loading. Observation of substructure elements following an earthquake is likely only performed if substantial movement above ground is observed, neighboring structures have unveiled foundation damage, or there are particularly vulnerable soil conditions at a site. Therefore, a thorough understanding of the severity, extent, and evolution of damage to these below ground elements is critical in the design process. In this research, I seek to better our understanding of the damage characteristics of pile foundations, with the particular application of piles embedded in liquefiable soils. While many studies have focused on characterizing the nonlinear behavior of soils, few research programs have included the nonlinear behavior of both soil and structure. My first objective is to develop the necessary experimental tools to conduct detailed damage assessment. This initial work will provide a roadmap for proper experimental procedures and thus assist me with my second objective, which is to carry out a series of experimental studies on large-scale soil-pile systems at a fundamental level. In these experiments, a phased approach is proposed, whereby the free-field soil condition is first modeled, then the pile embedded in the soil (kinematic 'test'), and finally the pile embedded in the soil supporting its mass (inertial and kinematic 'test'). This phased approach will assist in determining the relative contribution of each mode of interaction to the damage accumulated in the pile. Dense arrays of both conventional and advanced instrumentation will provide an abundance of detailed dynamic data, and allow me to carry out my third objective, which is to develop a methodology for interpreting and back-calculating soil resistance curves from these experiments. This will in turn help fulfill my fourth objective, which is to develop and evaluate a suitable numerical model of the experimental specimens and expand this model to perform sensitivity studies, thus gaining insight into the performance of a broader spectrum of soil-pile systems embedded in liquefiable soils. The results of this research will fill a vital gap in performance-based earthquake engineering of foundation systems. It will also provide sorely needed improved soil resistance functions that can be used in design practice for a refined evaluation of the performance of piles embedded in liquefiable soils. The research and educational components of this career-development plan are designed to complement and enhance each other. The education plan includes two primary approaches towards the objective of continued interaction, growth and enrichment: (1) educating the public and (2) bridging the gap between geotechnical and structural engineering. Educating the public is pursued through hands-on laboratories, interactive workshops, and web-based dissemination and outreach. Bridging the gap between geotechnical and structural engineering disciplines is pursued through curriculum enhancement, using new learning models (active learning), introducing research results into course lessons, and involving undergraduates in research projects. Bridging this gap is critical to developing a broader based understanding of the systems of civil infrastructure and its relationship with the environment, ethical and political issues. The integration of experimental and analytical work is an ideal way to ensure this research and education plan is effective in keeping students excited and promoting life long learning, thus preparing them as structural and geotechnical engineers with the fundamental knowledge to face the exciting challenges of the 21st century. This career-development plan reflects the PI's long-term goal of synthesizing geotechnical and structural engineering into performance-based engineering tangible objectives and thus reducing life and economic losses due to earthquakes. Project Summary