الفهرس 
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Abstract
This thesis presents a nonlinear three dimensional analysis of grid beam foundation. Which the foundation consists of a combination of crossed grid beams loaded at the intersected beams sections and transmits the load along its beam to the soil. The main objective of this thesis is to study the grid beam foundation as a special economic shallow foundation shape.
The study is performed using Abaqus/Cae V. 6.9 finite element program and includes two main grades. The first grade presents evaluating the ultimate and the allowable bearing capacity of that foundation shape numerically and by the approximated equations, then a comparison between the two methods are presented. And it’s clear from the results that there is no approximated equations can analyze this type of foundation. A parametric study for the grid beam foundation is presented in the second study grade. This study covers the factors which affecting the grid beam foundation behavior. These factors are observed through study the contact stress, the settlement along the grid beam elements, the horizontal and the vertical stress distribution in the soil profile. The main factors of the parametric study are the grid foundation rigidity, the ratio between columns spacing (B: L), the superstructure loading level, the deformation analysis used types, the material modeling used type, and the loading assignment technique. This study shows that the foundation shape affects the interference of the shear zones under the foundation parts by increasing its performance as well as its bearing capacity. By the decreasing of the grid beam stiffness and by the increasing of the ratio (B: L), the Grid beam foundation becomes more flexible, the relative settlement increases and the contact stresses concentrates under the grid foundation center.
There is adequate grid beam foundation geometry for every loaded area. This adequate design depends on the soil type, the super structure loading level and the arrangement of the superstructure loaded positions. All this points give the Grid Foundation recommended study more interest as economic, safe and suitable foundation type to be founded on the weak soil layers.