الفهرس 
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Abstract
This thesis investigates different aspects related to the problem of structural damage induced by varied ground conditions. Two main cases for the varied conditions are considered in this research. The first case addressed the effect of structures resting partially on compacted soil with Emin and partially on natural formation with Emax. Emin is representing the output of the normal compaction results (i.e., Ecompacted soil ≈ 300 kg/cm2), and Emax is representing the highest expected Young’s modulus for very dense sandy soil (E ≈ 1000 kg/cm2). The second case investigated the effect of ground movements of MSE wall on the structures that are partially resting on it.
6.2 Summary
Review of the previous studies concerning the topic of this research shows the following:
1. The variation in soil conditions below the foundation would result in differential movements and would negatively affect the performance of the structure and could cause damage.
2. Rigidity of the skeleton of the structure resists the differential settlement caused by the different foundation soil conditions.
3. Rigidity of the ground beams enhances the performance of the structures and reduces the stresses in the structural elements of the upper floors.
4. The location of structure with respect to the fill area of the retaining structure (partially on fill and cut, totally on fill, or totally on cut) should be considered in the structural analysis.
5. In case of necessity of construction on soil with varied conditions, differential settlement would occur. Distortion could be avoided by increasing the rigidity of the structure and its foundation.
6. Infill brick walls could increase the rigidity of the structure. However, cracking in brick walls decreases the stiffness of the bricks significantly.
7. Angular distortion could express the caused damage of structures induced by differential settlement.
8. Number of stories, the ratio between length and height of building (L/H), ratio between bending stiffness and shear stiffness (E/G), statical system of structure (Masonry walls or RC frame structure or RC frame structure with infilled brick walls), and existence of openings in the brick walls affect significantly on the structural performance.
A parametric study using three-dimensional finite element analysis was developed to investigate the impact of the foundations and the floor beams on the performance of RC structures in residential buildings to resist the varied ground conditions. The parametric study investigated most common cases including:
1) Structures supported partially on sand of different relative densities, and
2) Structures founded near to MSE wall facings.
Structural distress associated with ground movement was concluded for the first case, and the relationships between that distress and ground beams rigidities were outlined. The results were presented to be considered in the design of the structure foundation to determine the suitable depth of ground beams to minimize structural damage. For the second case, the performance of MSE wall supporting a structure was addressed. An additional parametric study was performed to determine the recommended distance required for the building to set back from MSE wall face for different fill properties.
6.3 Conclusions
Based on the results obtained from the presented study, the following conclusions could be drawn for residential low-rise buildings:
1. The flexural rigidity of the foundation increases the rigidity of the whole structure, which transforms the differential settlement and structure distortion to tilting.
2. Ground beams with lowest moment of inertia (I) of 40cm height
(≈Span/10-12) which is commonly adopted in low-rise residential buildings were found to be the minimum to control structure distortion if the ratio of Young’s modulus of two soils (Emin/Emax) is more than 0.50, without considering any additional settlement due to another condition often operation, i.e., wetting of the sandy soil as an example.
3. Highly rigid Ground beam (100I) could prevent structure damage at Emin/Emax equal to or more than 0.10.
4. For Emin/Emax less than 0.30, the shear deformation of the structure is the controlling mode of deformation. Nevertheless, the bending mode of deformation controls at Emin/Emax more than 0.30.
5. The maximum settlement below the structure is almost the same, regardless of the stiffness variation of ground beams, i.e., the stiffness of the ground beams does not significantly affect the overall settlement of the foundations.
6. The ground beams and lower floors beams are more susceptible to damage than the higher floors and that damage increased with decreasing the ratio of Emin/Emax.
7. The bending moments on upper floor beams decreased with increasing the ground beams rigidity at the same ratio of Emin/Emax. It is worth noting that the results are presenting no additional settlement upon wetting after operation.
8. The ratio of Mff/Mt (Bending moment on first floor beams / Bending moment on ground beams) for Emin/Emax less than 0.30 equaled 0.75 times the case with Emin/Emax of 1.00. This value was found to be 0.5 and 0.4 for Msf/Mt (Bending moment on second floor beams / Bending moment on ground beams) and Mtf/Mt (Bending moment on third floor beams / Bending moment on ground beams), respectively.
9. For Emin/Emax values from 0.30 to 0.80, the ratios of Mff/Mt, Msf/Mt, and Mtf/Mt were the same and equaled to 0.80 times the case with Emin/Emax of 1.00.
10. The ratio between the lateral deformation of MSE wall at the top and the maximum value at the mid-height was found to be in the range of 0.60 (without considering the effect of structure loads).
11. The ratio between the maximum vertical settlement behind MSE wall and the maximum lateral deformation of the wall is about 0.7 (without effect of structure loads).
12. Due to structure load, the ratio between the maximum settlement below the structure and the maximum lateral deformation of the wall is about 0.60 for wall height 10m, and 15m.
13. There is no fixed relation between the angular distortion of the structure and the MSE wall height at the same ratio of setback distance of structure from wall edge to wall height (Y/H).
14. The ratio between the distance from the structure edge to natural soil area (X) and the structure length (L) is impacting the structural behavior and should be considered in the detailed design. (X/L) value of 0.4 was found to represent the maximum value to prevent high distress on the structure.
6.4 Recommendations for Further Studies
The following topics are recommended as an extension to the present work:
1. Study the effect of other retaining walls structures types on the performance of nearby structures.
2. The performance of high-rise buildings resting on varied ground conditions.
3. The effect of ground slopes on the performance of nearby structures.
4. Study the effect of varied ground conditions on several types of structures with varied spacings between columns.