• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.675-680
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• 2006

This paper deals with the flexural free vibrations of strip foundations. Based on dynamic equilibrium equations of a beam element resting on Winkler foundation, differential equations governing free vibration of strip foundation are derived, in which effects of rotatory inertia and shear deformation are included. For obtaining the natural frequencies, differential equations are solved by numerical methods. As the numerical results, relationships between natural frequencies and various strip parameters are obtained and presented in Tables and Figures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.230-235
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• 2004

This paper deals with the free vibration analysis of circular strip foundations with the variable breadth. Taking into account effects of both rotatory inertia and shear deformation, differential equations governing free vibrations of such foundations are derived. The Winkler foundation is chosen as the model of soil foundation. The breadth of strip foundation is assumed to be a linear function. The differential equations are solved numerically to calculate natural frequencies. In numerical examples, the strip foundations with the hinged-hinged, hinged-clamped. clamped-hinged and clamped-clamped end constraints are considered. The parametric studies are conducted and the lowest four frequency parameters are reported in figures as the non-dimensional forms.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.539-548
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• 2007

This paper deals with flexural-torsional free vibrations of the circular strip foundation with the variable breadth on Pasternak soil. The cross-section of the strip foundation is chosen as the rectangular one with the constant thickness and variable breadth, which is symmetrical about the mid-arc. Also, the foundation that supports the circular strip is modeled as the Pasternak soil with the shear layer. Ordinary differential equations accompanying the boundary conditions are derived. In the governing equations, the transverse, rotatory and torsional inertias are included. These equations are solved numerically and four lowest frequencies are obtained. In the numerical results, the effects of foundation parameters on frequencies are extensively investigated. It is expected that the theories and numerical results of this study can be used in the dynamic design of strip foundations.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.121-133
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• 2024

In this paper, the performance of under-foundation isolators against generally annoying train-induced vibrations was examined experimentally. The effect of foundation type on the efficacy of such isolators was investigated for the first time. To this end, laboratory models including a soil container, soil, building with three types of foundation (i.e., single, strip, and mat), and isolator layer were employed. Through various dynamic tests, the effects of foundation type, isolation frequency, and the dominant frequency of train load on the isolator's performance were studied. The results demonstrated that the vibration level in the unisolated building with the strip and mat foundation was, respectively, 29 and 38% lower than in the building with the single foundation. However, the efficacy of the isolator in the building with the single foundation was, respectively, 21 and 40% higher than in the building with the strip and mat foundation. Furthermore, a lower isolation frequency and a higher excitation frequency resulted in greater isolator efficacy. The best vibration suppression occurred when the excitation frequency was close to the floor's natural frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.703-706
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• 2005

Since soil structure interactions are one of the most important subjects in the structural/foundation engineering, much study concerning the soil structure interactions had been carried out. One of typical structures related to the soil structure interactions is the strip foundation which is basically defined as the beam or strip rested on or supported by the soils. At the present time, lack of studies on dynamic problems related to the strip foundations is still found in the literature. From these viewpoint this paper aims to theoretically investigate dynamics of the parabolic strip foundations and also to present the practical engineering data for the design purpose. Differential equations governing the free, out o plane vibrations of such strip foundations are derived, in which effects of the rotatory and torsional inertias and also shear deformation are included although the warping of the cross-section is excluded. Governing differential equations subjected to the boundary conditions of free-free end constraints are numerically solved for obtaining the natural frequencies and mode shapes by using the numerical integration technique and the numerical method of nonlinear equation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.898-901
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• 2004

Since soil-structure interactions are one of the most important subjects in the structural/foundation engineering, much study concerning the soil-structure interactions had been carried out. One of typical structures related to the soil-structure interactions is the strip foundation which is basically defined as the beam or strip rested on or supported by the soils. At the present time, lack of studies on dynamic problems related to the strip foundations is still found in the literature. From these viewpoint, this paper aims to theoretically investigate dynamics of the circular strip foundations and also to present the practical engineering data for the design purpose. Differential equations governing the free, out-of-plane vibrations of such strip foundations are derived, in which effects of the rotatory and torsional inertias and also shear deformation are included although the warping of the cross-section is excluded. Governing differential equations subjected to the boundary conditions of corresponding end constraints are numerically solved for obtaining the natural frequencies and mode shapes by using the numerical integration technique and the numerical method of non-linear equation.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.233-240
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• 1999

The laboratory tests on geogrid-reinforced sand were conducted with considering embedment effect. The relative densities of sand are 60% and 80%, respectively. The embedment depths of foundation were varied as D$\_$f/B=0, 0.5, 1.0. Based on the model test results, (u/B)$\_$cr/, BCR$\_$u/, and (b/B)$\_$cr/, were determined. The optimum depth of reinforcement was determined. The embedment depth of foundation is greatly contributed on the bearing capacity of geogrid-reinforced sand.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.202-209
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• 1996

In this paper, two dimensional vertical and comer infinite elements which can include multiple wave components to model underlying half space are developed. These elements are natural and economical to model underlying stiff half space or rock. To verify the behavior of these infinite elements, vertical, horizontal, and rocking compliances of a rigid strip foundation on a viscoelastic soil profile are analyzed and compared with those of Tzong and Penzien who used the boundary solution method. Good agreements are noticed between the two methods. The influence of material properties like Poisson's ratio, material damping, and stiffness ratio of layers as well as the influence of geometrical properties such as layer thicknesses and depth of foundation embedment are studied. Example analysis is carried out for the shaking table which is located in KIMM(Korea Institute of Machinery and Materials), and the vertical and horizontal displacements of the analysis are compared with the measured, and show good results and demonstrate the efficiency of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.548-555
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• 2005

Since soil-structure interactions are one of the most important subjects in the structural/foundation engineering, much study concerning the soil-structure interactions had been carried out. One of typical structures related to the soil-structure interactions is the strip foundation which is basically defined as the beam or strip rested on or supported by the soils. At the present time, lack of studies on dynamic problems related to the strip foundations is still found in the literature. From these viewpoint, this paper aims to theoretically investigate dynamics of the elliptic strip foundations and also to present the practical engineering data for the design purpose. Differential equations governing the free, out-of-plane vibrations of such sap foundations we derived, in which effects of the rotatory and torsional inertias and also shear deformation are included although the warping of the cross-section is excluded. Governing differential equations subjected to the boundary conditions of free-free end constraints are numerically solved for obtaining the natural frequencies and mode shapes by using the numerical integration technique and the numerical method of non-linear equation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.764-767
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• 2005

This paper deals with the flexural-torsional free vibrations of circular strip foundations with a variable breadth. The breadth of strip foundation varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing free vibrations of such foundations are derived, in which Winkler foundation is considered as the model of elastic soils. Effects of the rotatory and torsional inertias and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies. In the numerical examples, the free-free end constraint is considered. Effects of the rotatory and torsional inertias and shear parameter on the natural frequencies are reported. Parametric studies between frequency parameters and various system parameters are investigated.