Description
A Master of Science thesis in Civil Engineering by Pouya Partazian entitled, "Finite Element- Based Parametric Analysis of Mat Foundations," submitted in April 2016. Thesis advisor is Dr. Magdi El-Emam and thesis co-advisor is Dr. Sami Tabsh. Soft and hard copy available.
Abstract
Raft or mat foundation is a thick reinforced concrete slab covering the entire contact area of the structure and supporting heavy loads from superstructure to a large area of soil. This type of foundation is employed in scenarios where the column loads are not distributed evenly, level of the structure is lower than the ground water table, and soil is prone to differential settlement. A literature review showed that there is lack of parametric studies on the subject. This study is aimed at using finite element method to investigate the behaviour of mat foundations under gravity loads. The analysis considers mat foundations with different plan dimensions, thicknesses, soil modulus of subgrade reaction, concrete Poisson ratios, modulus of elasticity, panel aspect ratios, number of bays, and load eccentricities. Effect of these design parameters on the maximum and minimum soil bearing pressure below the mat foundation, as well as on the maximum positive and negative bending moment, and shear within the mat will be determined. Result of this study showed that the rigidity of the mat in comparison to the stiffness of the supporting soil is the main parameter that affects the soil bearing pressure and internal forces within the mat. Rigid mats have somewhat uniform soil bearing pressure underneath them, whereas flexible mats have more bearing pressure under the columns than elsewhere. For symmetrically loaded mats subjected to column loads in proportion to their tributary areas, the maximum soil bearing pressure was observed below the corner columns, while the minimum soil pressure occurred within the middle region of central panel. The maximum positive bending moment was found below the interior column closest to the edge, whereas the maximum negative moment was located mid-way between the edge and first interior columns. Location of the maximum shear always happened to be at the face of the edge column nearest to the corner column. Most important parameters that affects the soil bearing pressure, bending moments and shears are mat thickness, soil modulus of subgrade reaction and the distance between columns and eccentricity of the total load with respect to the centroid of the mat.