A case study using finite-element software for the dynamic analysis and structural design of a machine foundation on piles in homogeneous sandy soil is reported. A parametric study was carried out to investigate the effect of the foundation geometry, the amplitude and frequency of the dynamic load, and the damping ratio. It is concluded that as the pile cap thickness increases the oscillation of displacement decreases due to material damping inherent in the concrete of the pile cap. There is a limit of the pile cap size at which its stiffness governs its dynamic response. Above this size the weight of the pile cap overrides its stiffness effect, and the additional weight leads to an increase in pile displacement. When the pile group size increases, the frequency at which maximum displacement occurs increases, and hence the system becomes more stable against resonance. In the case of changing the pile spacing, the maximum moment factor I M is always at the pile cap centre, where the load is applied. This factor increases when the pile spacing increases. The dimensionless displacement factor I z decreases markedly as the pile cap length increases, reflecting the increase in displacement with pile cap length.
Work is devoted to model and process the results of interaction between a rigid metal plate and a reinforced sand base using the software “ANSYS”.
One of the effective ways to increase the strength is the inclusion of various materials (reinforcement) in the soil below the structure. It increases the resistance of the soil to stress and shear, limits lateral deformation. Organic, synthetic, metal and stone materials are used as reinforcing elements. The studies showed that the effectiveness of the reinforcement and the bearing capacity of the reinforced ground depend on the position, length, roughness and fixity condition of the reinforcement [27].
The results of plate tests conducted in the laboratory of “soil Mechanics” of TSTU are presented. The cases of application of static and cyclic loads on reinforced and unreinforced sand base are considered. In these tests, the density of the sand base, the depth of the reinforcement element, and the initial load stage from which cycling was performed were changed. Three series of experiments were performed in a tank with rigid side walls. As the base, a fine, low-moisture, homogeneous sand was used. In the first series of experiments a stepwise increasing load was transferred to the plate at different densities. In the second series, a cyclic load was transferred to the base, with a value equal to half of the previously found ultimate load. In the third series of experiments, a reinforcing element was placed in the base at various distances from the sole of the foundation model and the load was applied both stepwise increasing static and cyclic. It is shown that the settlement during introduction of cyclic loading is from 20 to 50% of the total value. Reinforcement of the base allows you to reduce the settlement of cycling load. At the same time, there is a significant increase in the bearing capacity of the foundation and a decrease in the values of total deformations.
The article presents a comparison of the values of the soil deformability characteristics obtained at different densities of the sand base based on the results of laboratory tests3 and the results of computer modeling, using the software systems "ANSYS" and "Plaxis 3D".It was found that for loose sandy soils, at densities of 1.48 – 1.53 g/cm
3, close to experimental values of the deformation modulus were obtained using a three-dimensional finite-element model of polylinear isotropic hardening "PLAS (Miso)," in the program "ANSYS." For average density bases at ρ = 1.55 – 1.66 g/cm3 minimum differences between experimental and numerical values were obtained using the «Plaxis 3D» complex.
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