The mechanical behaviour of partially saturated soils can be very different from that of fully saturated soils. It has long been established that for such soils, changes in suction do not have the same effect as changes in the applied stresses, and consequently the effective stress principle is not applicable. A procedure was proposed to define the soil water characteristic curve. Then this relation is converted to relation correlating the void ratio and matric suction. The slope of the latter relation can be used to define the H-modulus function. This procedure is utilized in the finite element analysis of a footing on unsaturated coarse grained soil to investigate its bearing capacity. The finite element results demonstrated that there is a significant increase in the bearing capacity of the footing due to the contribution of matric suction in the range 0 to 6 kPa for the tested compacted, coarse-grained soil. The ultimate pressure increases from about 120 kPa when the soil is fully saturated to about 570 kPa when the degree of saturation becomes 90%. This means that an increase in the bearing capacity of about 375% may be obtained when the soil is changed from fully saturated to partially saturated at a degree of saturation of 90%. This development in the bearing capacity may exceed 600% when the degree of saturation decreases to 58%.
This paper includes an analysis to asses the behavior of stone columns using the finite element method and to provide bases and information helping geotechnical engineers to design foundations resting on weak soils reinforced with stone column. The axisymmetric quadrilateral element is adopted in the finite element program to simulate the soft soil and the stone column while the one-dimensional element is used to simulate the soft soil and the stone column-soil interface. The nonlinear inelastic stress-dependent model is used to simulate the behavior of the soil and the interface throughout the incremental loading stages adopting nonlinear parameters obtained from triaxial and direct shear stress. The analysis is carried first on a selected basic problem, to clarify the nonlinear of the column, in which a selected geometry, boundary condition, and material properties for both soil and interface as chosen. The rest of the analysis is grouped into the effect of some of the parameters concerning the geometry of the stone column and the material of column and adjacent soil are investigated. It was found that the increase in stone column length and in relative stiffness of stone column material to soil play an important role in increasing ultimate capacity of the stone column and in reducing settlements.
In the present paper, a one-dimensional finite element model for the analysis of composite beams of partial interaction is constructed. This model was verified against some analytical results available in the literature and achieved very good agreement with the natural frequencies and the time histories it was compared to. Then it was utilised to analyse partial interaction composite beams under the effect of uniform step loads and provided important information about the expected dynamic amplification factors, which turned out to be particularly high, and the effects of the linear stiffness ratio of the interface and the boundary conditions of the lower layer of the beam. The results, in particular, showed that even for extreme cases the orders of magnitude of the slip and the corresponding uplift remain the same. This pointed out an important finding that the uplift in the researched context, at least, is not negligible as it is widely assumed in the literature.
In this study, eight rectangular reinforced concrete beams strengthened by bottom steel plates firmly interconnected to them by headed-stud shear connectors are manufactured using self compacting concrete and tested up to failure under two point loads to demonstrate the effect of steel-plate thicknesses, lengths, and the shear-connector distributions on the behavior, ductility and strength of this type of beams. A trial mix conforming to the EFNARC Constraints had been successfully carried out to satisfy the three fresh tests of SCC, these tests are flowability, passing ability and segregation resistance. The results show that there is a substantial improvement in the flexural resistance, increasing the flexural stiffness and decreasing the ductility ratio due to thickening steel plate, On contrary, increasing the spacing between shear connectors to 50% had slight effect on the flexural resistance, but subsequent increase of their spacing to 100% had seriously lowered that resistance, The spacing between shear connectors has a primary effect on the average flexural stiffness and ductility ratio. In regard to the steel plate length, its shortening has reduced the flexural resistance significantly, decreased the average flexural stiffness and had increased the ductility ratio. The experimentally determined ultimate flexural strength had been compared with its corresponding one computed by the "Strength Method" using ACI requirements where high agreement gained between them due to the nearly perfect interaction provided by SCC. The eight composite beams had also been analyzed by the non-linear three dimensional Finite Element Analysis employing ANSYS program (release 12.1),where high agreement is achieved compared with experimental results.