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Dissertation
Development of Viscoelastic PML and Deconvolution of Input Motion at Depth for Soil-Structure Interaction: Application to Dams
Doctor of Philosophy (Ph.D.), Drexel University
Jul 2019
DOI:
https://doi.org/10.17918/00000100
Abstract
The numerical modeling of Soil-Structure-Interaction (SSI) is one of the most challenging issues in structural earthquake engineering. Due to the computational cost and complexity of SSI analyses, some simplifications and assumptions have to be made to the real system so that the numerical modeling becomes more tractable. Certainly, such simplifications and assumptions impose uncertainties on the results. This research study examines the limitations of commonly made simplifications and assumptions in the numerical evaluation of structures considering SSI effects, and improves the reliability and accuracy of SSI analyses by developing new analytical and computational approaches. As an example application, a comprehensive model of a dam-foundation system is developed for the seismic response evaluation of concrete gravity dams. To improve the accuracy of SSI analyses a new deconvolution process, the phase-amplitude modification procedure, is proposed to deconvolve both horizontal and vertical target (design) surface ground motions in multi-layered, equivalent-linear viscoelastic media for use in finite element time-domain structural analyses. It is shown that the approach can accurately estimate the seismic excitations at depth of soil profiles. In addition, a viscoelastic Perfectly Matched Layer (PML) formulation with Rayleigh-type damping is developed and implemented in ABAQUS/Standard by merging it with a User-Defined Element (UEL) subroutine in Fortran90. The performance of the viscoelastic PML vs. the commonly-used viscous Absorbing Boundary Conditions (ABCs) is examined through numerical examples under different types of dynamic excitations including uniform and spatially variable seismic ground motions. The numerical results highlight the excellent performance of the PML approach to model the unbounded domain under all types of excitations. The proposed numerical models are implemented in the finite element seismic evaluation of a concrete gravity dams, and the results are compared to the simplified dam-foundation models that are being used widely by both academicians and practitioners. It is shown that the use of the massless foundation model as well as the massed foundation model with viscous-type ABCs can lead to substantial errors in the dynamic response of concrete dams. This is the first study ever that rigorously evaluates the effect of foundation modeling on the dam response under uniform and spatially variable excitations.
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Details
- Title
- Development of Viscoelastic PML and Deconvolution of Input Motion at Depth for Soil-Structure Interaction
- Creators
- Masoud Khazaei Poul
- Contributors
- Aspasia Zerva (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xii, 156 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Civil (and Architectural) Engineering [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991014695144904721