Non-linear dynamic analyses (NDAs) are widely used in engineering practice to evaluate the seismic performance of geotechnical structures affected by liquefaction or cyclic softening. NDAs can provide an improved basis for estimating deformations over simplified methods that do not account for dynamics or are limited to idealized geometries or conditions. However, the quality of results from an NDA study depend on several technical and nontechnical factors, including – amongst others– the selection and calibration of the constitutive models, the limitations of the numerical modeling procedures, the quality of the site characterization work, and the selection of the input ground motions.
The first part of this presentation will focus on the development and calibration of two advanced constitutive models for sands, and clays and plastic silts (PM4Sand and PM4Silt respectively). The two models were developed for earthquake engineering applications aiming at capturing the broad range of responses indicated by the body of data collected through the years. In its second part, this presentation will focus on the numerical simulation of a case history from the 1994 Northridge earthquake, where significant earthquake-induced ground deformations were observed. The availability of soil, ground motion, and post-earthquake damage records, will be presented and utilized as a validation basis of NDAs involving state-of-the-art set of numerical modeling procedures: (1) the geotechnical characterization of interbedded soils; (2) the use of FLAC to perform nonlinear deformation analyses, and TPROGS to simulate interbedded soil deposits conditioned on field data and consistent with geological facies; and (3) the use of PM4Sand and PM4Silt for sand- and clay-like soils respectively. Uncertainties associated with soil profiles and ground input motions are accounted for by using suites of possible realizations. NDA results are in good agreement with observed ground deformation patterns and measured horizontal displacements.
Katerina Ziotopoulou joined the Department of Civil and Environmental Engineering at University of California at Davis in August of 2016. Prior to this appointment, she was an Assistant Professor at the Charles E. Via Jr. Department of Civil and Environmental Engineering at Virginia Tech for two years. She received her PhD and MS degrees in Civil Engineering from the University of California at Davis, and her undergraduate Diploma degree in Civil Engineering from the National Technical University of Athens, Greece. Currently, her research focuses on the numerically and experimentally studying ground failure due to liquefaction during earthquakes and its mitigation. Her goals are to: (a) improve our understanding of the response of liquefiable soil-structure systems, (b) perform reliable numerical simulations, and develop and deliver usable numerical simulation tools, and through these (c) facilitate advances in the performance-based design across a range of geosystems. Her work is currently funded by the National Science Foundation, the Center for Biomediated and Bioinspired Geotechnics, the Transportation Research Board, and Caltrans. In parallel, she is also working on developing mentoring practices and tools focused on promoting and supporting underrepresented groups.