Response of Circular Machine Foundation Resting on Sandy Soil to Harmonic Excitation (original) (raw)
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Effect of mode of vibration on the response of machine foundation on sand
IOP Conference Series: Materials Science and Engineering, 2020
In this paper, the influence of the following parameters on different modes of vibration response of model footings on sand is studied: (vertical, rocking and pitching load amplitude and frequency). To achieve the objective of this study, the model footing was selected to be rectangular footing with an aspect ratio (L/B= 1.33) i.e (L= length and B= width). A physical model was manufactured to simulate a steady-state harmonic dynamic load applied at different operating frequencies with the same load amplitude (0.5 ton). A total of (9) cases was performed taking into account different parameters. The loading frequency ranged from (0.5) to (2) Hz and the footing was rectangular with an aspect ratio (L/B = 1.33). The soil type used was dry sand having a relative density of (50%). The behavior of the soil underneath the footing was examined by measuring the strain using a shaft encoder and the amplitude of displacement using a vibration meter. It was found that the change in vibration mo...
elsevier, 2022
The difficulty that arises in the design of a machine foundation is how to know the behavior of the soil at different soil conditions. Therefore, there are many indications of a need to study machine foundation on soil of different degrees of saturation, covering all the important aspects of clay soil. Experiments on machine foundation (circular and rectangular) were carried out resting on clay soil with different degrees of saturation (100 % and 60 %), in order to find the amplitude displacement of the foundation under different operating frequencies. In addition, the paper describes the vertical stress and displacements inside the soil distributed at three points under the foundation (0.5 B, B, and 2B, B is the foundation width). The experiments results showed that the effect of increasing the degree of saturation is to reduce the amplitude displacement of the foundation to about 61 %. The increase in degree of saturation of soil reduced the vertical stress by about 77 %. The change in the degree of saturation leads to significant action on displacement inside the soil. These influences depend on the distance of the point from the foundation
In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. A physical model was manufactured to simulate steady state harmonic load at different operating frequencies. The effect of relative density, depth of embedment, foundation area as well as the imposed harmonic load was investigated. It was found that the amplitude of displacement of the foundation increases with increasing the amplitude of dynamic force and operating frequency meanwhile it decreases with increasing the relative density of sand, degree of saturation, depth of embedment and contact area of footing. The maximum displacement was noticed at 33.34 to 41.67 Hz. The maximum displacement amplitude response of the foundation resting on dry sand models is more than that on the saturated sand by about 5.0 to 10 %.
Response of Different Machine Foundation Shapes Resting on Dry Sand to Dynamic Loading
Tikrit Journal of Engineering Sciences, 2020
In this paper, the effect of footing shape resting on dry sand when subjected to machine dynamic loading is experimentally investigated. A laboratory set-up was prepared to simulate the case at different operating frequencies. Nine models were tested to examine the effects of the combinations of two parameters, including different frequencies of (0.5, 1, and 2 Hz) and different footing shapes (circular, square and rectangular). The tests were conducted under a load amplitude of (0.25 ton) using sand with medium and dense relative densities corresponding to (R.D. = 50% and 80%) having unit weights of (17.04 and 17.96 kN/m3) respectively. A shaft encoder and a vibration meter were used to measure the strain and amplitude displacement, while the stress in the soil at different depths was measured using flexible pressure sensors. It was found that the shape of footing has a considerable influence on the bearing capacity of the supporting soil under dynamic loading. For instance, the str...
Analysis of machine foundation vibrations: state of the art
International Journal of Soil Dynamics and Earthquake …, 1983
The paper reviews the state-of-the-art of analysing the dynamic response of foundations subjected to machine-type loadings. Following a brief outline of the historical developments in the field, the concepts associated with the definition, physical interpretation and use of the dynamic impedance functions of foundations are elucidated and the available analytical/numerical methods for their evaluation are discussed. Groups of crucial dimensionless problem parameters related to the soil prot~ile and the foundation geometry are identified and their effects on the response are studied. Results are presented in the form of simple formulae and dimensionless graphs for both the static and dynamic parts of impedances, pertaining to surface and embedded foundations having circular, strip, rectangular or arbitrary plan shape and supported by three types of idealized soil profdes: the halfspace, the stratum-over-bedrock and the layer-over-half space. Consideration is given to the effects of inhomogeneity, anisotropy and non-linearity of soil. The various results are synthesized in a case study referring to the response of two rigid massive foundations, and practical recommendations are made on how to inexpensively predict the response of foundations supported by actual soil deposits.
Numerical Analysis of Machine Foundation Resting on Saturated Sandy Soil
ABSTRACT The behavior of machine foundation on saturated porous medium can be considered as a complicated geotechnical problem due to nature of dynamic loads and plasticity of soil which make the analysis and design of foundation subjected to dynamic loads more complex. The main criteria for safe performance of machine foundations subjected to dynamic loads are to control excessive displacements. In this paper, a dynamic analysis of strip machine foundation with multiple thicknesses is placed at the middle of the top surface of saturated sand with different states (i.e. loose, medium and dense), and vertical harmonic excitation is carried out and building up of the excess pore water pressure. The dynamic analysis is performed numerically by using finite element software, PLAXIS 2D. The soil is assumed as elastic perfectly plastic material obeys Mohr-Coulomb yield criterion. A parametric study is carried out to evaluate the dependency of machine foundation on various parameters including the amplitude and the frequency of the dynamic load. The dynamic response (displacement and excess pore water pressure) generally increases with increasing of loading amplitude, but the displacement and excess pore water pressure versus frequency are not smooth and exhibit undulations (peaks and troughs). Keywords: Machine foundation, dynamic loads, finite elements, saturated sand, elastic perfectly plastic.
A Study of Vibrating Foundation
International Journal of Research and Analytical Reviews , 2020
Improvement in manufacturing technology has provided machines of higher ratings with better tolerances and controlled behaviour. These machines give rise to considerably higher dynamic forces and thereby higher stresses and, in return, demand improved performance and safety leaving no room for failures. The project work highlights need for a better interaction between foundation designer, geotechnical engineer and machine manufacturer to ensure improved machine performance. For the study is concern the analysis is done on the machine block foundation by considering the coupling of machines attached to base frame over the foundation at top and considering the soil at bottom and the combine effect is measured in the form of amplitudes and natural frequency. Also, it discusses the elastic character of the ground and shows that foundations for reciprocating machines can be treated as spring-supported masses, the machine and foundation representing the mass, the machine and foundation representing the mass, and the ground the spring. Such elastic systems have natural periods of vibration; if the frequency of unbalanced inertia or other exciting force is near the natural frequency of the foundation, resonance will occur producing excessive vibration. To obtain the result, a problem on horizontal single cylinder reciprocating is considered, due to the functioning of the reciprocating machines unbalanced forces are developed so, the extra care has been taken in addition to static analysis i.e. the dynamic analysis has also been considered for the design of machine foundation.
Experimental Investigation for Dynamic Response of Saturated Clay Under Machine Foundation
springer , 2021
A machine foundation is considered important and because of that the foundation design under dynamic loads must be governed by serviceability limit states performance considerations rather than strength requirements. The dynamic response is carefully calculated to ensure high-quality and efficient performing for machinery. This paper presents a model for estimating the dynamical response of a machine foundation on saturated clay by experimental work. The machine is produced to simulate forced vibrations by harmonic loading at various operating frequencies. The depth influence of embedding and load frequency onmodel footings on soft clay soil is investigated. As well as, stresses and excess pore water pressure get measured at different depths in the soil below the footing. It was concluded that the maximum displacement increases as the operating frequency increases, as well as, there is an increase in the excess pore water pressure when the dynamic load increases.
A Review on the Dynamic Behaviour of Foundation Supporting Vibrating Machines
2015
In developing countries like India, vibration problems from industrial assets have been drawing attention of industrial owner and engineers since decades, world over to find ways and mean to have desired satisfactory performance of machines and to minimize failures. In the past, due importance was not given to the design of machine foundation. Simple methods of calculation were used for strength design of foundation by multiplying static loads with an estimated dynamic factor. Even with these so called excessive loads harmful effects were observed during operations. And the vibration may create problem of resonance in structure and there by damage the structure. This necessitated a research in the area of dynamics of machine foundation. At the same time, a more detailed study became urgent because of the development of machines of higher capacities. In this paper, an attempt has been made to review the new empirical methods developed for dynamic analysis and design of machine foundation. For that the past papers related to the dynamic behaviour of machine foundation has been studied and the fruitful conclusion has been made.