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Investigation of the Seismic Behavior of the Soil-Pile System with Three-Dimensional Nonlinear Modeling

Afsaneh Borzeshi, Sajjad | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56839 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadi, Mohammad Mehdi
  7. Abstract:
  8. A large number of structures and substructures, such as piles, have damaged or even yielded the entire structure during seismic loading. The kinematic interaction of piles under seismic loading has been widely studied from analytical, experimental, and numerical perspectives. In numerical modeling, most existing literature relies on simplified approaches to describe the soil-pile interaction, which leads to the need for more reliable and comprehensive research. In this research, the seismic response of the soil-pile system was investigated through a fully nonlinear three-dimensional numerical analysis in the time domain using the FLAC3D program. This model simulates the dependence of soil strength and stiffness on the stress level and nonlinear behavior of soil under cyclic loading. The Mohr-Coulomb constitutive model was used to describe the mechanical behavior of the soil with additional hysteretic damping to match the dynamic behavior. In the framework of a parametric study, the effects of loading frequency on the response of the soil-pile system under seismic loading were investigated. The results showed that the response of the soil-pile system and the characteristics of the soil as well as the mode of system natural frequency are strongly influenced by the frequency of seismic loading. So that as the loading frequency approaches the natural frequency of the system, the bending moment increases along the length of a pile. While when the loading frequency reaches a threshold value far from the fundamental frequency of the system, the effect of the loading frequency on the response of the soil-pile system becomes insignificant. In addition, it was found that the piles under seismic loading can be divided into "short" and "long" categories based on their bending moment diagram. The measure of a "long" or "short" pile depends not only on the length-to-diameter ratio but also on the loading frequency. Finally, a practical relationship was presented to calculate the bending moment along the length of the pile based on the soil, pile, and seismic load parameters
  9. Keywords:
  10. Soil-Pile Interaction ; Bending Moment ; Numerical Analysis ; Pile Seismic Response ; FLAC Software ; Load Frequency ; Nonlinear Modeling ; Seismic Behavior

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