Parametric Soil-Structure Modeling for Rapid Climatic Disaster Response
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Global climate changes have seemly caused acerbating impacts on coastal environments in terms of severe meteorological hazards, such as hurricanes and their induced storm surges, flooding, and heavy precipitation. Recent disasters of these types, such as HurricaneSandy, have afflicted millions in coastal communities and resulted in billion dollars of losses. Given disasters at such scales, field-based reconnaissance has become ever demanding than before. In the context of structural and geotechnical damage inspection, it calls for efficient tools that can analyze coastal structures that take a system modeling approach. Such a system approach should consider structuresthat are subjected to a combination of extreme forces and changes of boundary conditions, which may include hydrodynamic wave effects, hydraulic buoyancy, debris impact, and foundation scour. The objective of this thesis to develop a rapid tool for assessing the vulnerability of coastal structures subjected to climatic impacts. Similar tools have been widely used in Structural and Earthquake Engineering for design and loss assessment, such as the use of a fixed oscillator model characterized by a single parameter of Tn (the natural period of the structure). The direct hazardous impacts considered in this thesis are extreme hydraulic forces and local foundation scouring that may ultimately cause failure of coastal structures (i.e. collapse). The criteria of success of this tool emphasize that it should be as simple as the oscillator model in Earthquake Engineering and is parametric in terms of a few key (intrinsic) parameters to model the nonlinear behavior of a structure subjected to hydraulic storm surges and foundations scour. To precede, two research components are conducted. The first is a hypothesis-driven physical modeling experiment, in which a flume-based modeling is conducted to prove that storm surges can attack a structure by simultaneous surging and scouring. In the hydraulic flume, a generic foundation-structure system is placed and is subjected to forced vibration for probing the dynamic properties of the structure model. Test result successfully revealed the formation of foundation scour, the failure of structure, and the progressively modified dynamic characteristics of the soil-structure system. The second, based on the above flume-based evidence, is to computationally model such the failure of building systems in a reduced order subjected to the combined hazards of storm surges and foundation scour. In this thesis, Ibuild afinite-element (FE) based model using Abaqus software. In this model, the structural system response has been resolved from prototype models to simplified dimensionless model consisting of a single degree of freedom (SDOF) oscillator founded on a square foundation. The footing is embedded in near-field soil modeled using inelastic soil under an undrained condition. The two primary intrinsic parameters identified in this thesis. The first is theratio of the vertical foundation load N in comparison with the ultimate vertical capacity Nu, expressed through the ratio χ = N/Nu. The second is defined as ao = ω H / vswhere ω is the circular frequency of the fixed base structure, H is the height of superstructure and vs is the shear wave velocity. Rocking response of the (SDOF) system on nonlinear soil is examined through the general-purpose finite element software Abaqus to perform the parametric analysis, and to establish the failure mechanism of the system. Lightly loaded oscillators tend to uplift from the supporting soil whereas heavily loaded oscillators tend to accumulate settlement and soil yielding is intense. The structural response corresponding to moment-rotation settlement under monotonic loading at the mass center, under loading has been designed to output. The Python-based Abaqus scripting interface is used to realize a client-based model input, which is an extension of the Python object-oriented programming language.
Table of Contents
Impact of climate on changes in civil infrastructure -- Literature review -- Physical modeling methodology and system identification -- Soil material modeling and verification -- Parametric soil-structure modeling using Abaqus CAE -- Conclusions and future work -- Appendix A. -- Appendix B
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M.S.