Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Dr. M. Hesham El Naggar

Abstract

Deep foundations design suffers some degrees of uncertainties. This thesis studies the behavior of defected pile group foundations installed in sand and calibrates the resistance factor of pile group foundation, utilizing a rational based system reliability analysis. This was achieved by conducting a comprehensive numerical parametric investigation using the computer program ABAQUS/Standard. The result of the parametric study showed that the presence of a defected pile in a pile group foundation causes lateral deflection of the pile cap and hence induces bending moment at the adjacent piles which affects the load distribution mechanism of the system. It was also found that the proposed resistance factor values varied from 0.31 to 0.61, 0.52 to 0.86, 0.34 to 0.63, and 0.45 to 0.96 for different design methods: Nordlund, Bluebook, β-Method, and SPT Meyerhof, respectively. The resistance factors are affected primarily by the ability of the pile cap to re-distribute the forces upon failure of one pile or more within the group.

Summary for Lay Audience

Pile foundations are structural members that are usually required to support structures when the soil at the ground surface is weak and can’t carry the loads imposed by the structure. In common practice, piles are usually made in groups and they are connected together with a thick concrete mat called the pile cap. The function for the pile cap is to connect the group piles together to ensure uniform load distribution among the piles.

Pile group foundation suffers some degrees of uncertainties that can cause some damage to one pile or more. Such damage may occur due to the existence of weakness of the soil itself or from the imperfect execution of the pile. Utilizing advanced numerical simulation and the understanding the uncertainties associated with the behavior of the pile groups foundation, this thesis investigated the effect of one or more damaged piles on the pile group foundation, and to come to conclusion whether such damage will lead to a failure of the system or it has no any significant effect?

It was found that the damage of one or more pile may not affect the pile group. The results of this research will be useful to implement a new parameter during the process of designing the project and provide a new equation to demonstrate how much stronger the system should be for a certain load ( factor of safety), and that will help cut down the expenses of the projects and minimize the usage of any extra unnecessary resources.

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