الفهرس 
1. INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This thesis discusses the behavior of piles penetrating successive layers of strong and soft layers under the effect of the earthquake ground motion. Single pile and pile groups are studied under different earthquakes to conclude their impact on the overall behavior of them. This study is developed based on numerical analysis using the commercial finite element software PLAXIS 2D.
An extensive review is presented about the dynamic soil properties, the different methods of analysis for piles under the effect of earthquake ground motion, and the concept of Dynamic Soil-Structure Interaction (DSSI). Previous studies by different researchers are also presented and summarised. The HS-Small constitutive model is discussed in detail to put a spot on this model that is efficient in the earthquake numerical analysis. The structural elements used in the analysis are concerned with knowing how they can be simulated in the finite element analysis.
Different parametric studies are considered to better examine the behavior of the pile group. The bending moment is observed for each case and considered. The first study is based on changing the ground acceleration value to conclude their effect on the piles. The second study is based on changing the diameter of piles. The third study is based on changing the embedded depth of piles in the strong soil layer. The fourth study is based on changing the relative stiffness between the strong and soft soil layers. The fifth study is based on changing the duration of the hitting ground motion.
Based on these studies, it can be concluded that excessive bending moment is observed at the transition zone between the soft and strong soil layers. The value of this excessive bending moment varies between 30% and 100% of its static value which traditionally occurs at the upper third part of the pile. Based on this result, additional reinforcement shall be considered and added to the pile at this transition zone to resist this excessive bending moment during seismic events. It is also concluded that the reinforcement shall be extended to a depth of (5D) below the transition line, where D is the diameter of the pile.
This thesis consists of five chapters;
Chapter (1) is an introduction to the thesis and its contents.
Chapter (2) presents a literature review of the methods to study the piles under the effect of ground motion, the creation of earthquakes, and the dynamic soil properties. It also discusses the dynamic soil structure interaction (DSSI) concept and presents samples of the previous studies on piles under the effect of earthquakes.
Chapter (3) presents a detailed discussion about the HS-Small constitutive model used to simulate the soil in the numerical model to consider the effect of the earthquake. It also discusses the structure elements of the ground motion simulation used in the numerical model. Finally, it presents a verification of a case study developed by Gohl (1991) to verify the results of the numerical model with the experimental results.
Chapter (4) presents a study on the effect of earthquakes on the behavior of piles, considering the impact of changing the ground acceleration value, changing the diameter of piles, changing the embedded depth of piles in the strong soil layer, changing the relative stiffness of the soft and strong layers, and changing the period of the ground motion.
Chapter (5) presents conclusions and recommendations for further studies based on the developed research in the thesis.