• Geomechanics and Engineering
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• v.32 no.2
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• pp.159-177
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• 2023

In the present work, a simple and refined shear deformation theory is used to analyze the effect of visco-elastic foundation on the buckling response of exponentially-gradient sandwich plates under various boundary conditions. The proposed theory includes indeterminate integral variables kinematic with only four generalized parameters, in which no shear correction factor is used. The visco-Pasternak's foundation is taken into account by adding the influence of damping to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's foundation modulus. The four governing equations for FGM sandwich plates are derived by employing principle of virtual work. To solve the buckling problem, Galerkin's approach is utilized for FGM sandwich plates for various boundary conditions. The analytical solutions for critical buckling loads of several types of powerly graded sandwich plates resting on visco-Pasternak foundations under various boundary conditions are presented. Some numerical results are presented to indicate the effects of inhomogeneity parameter, elastic foundation type, and damping coefficient of the foundation, on the critical buckling loads.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.68-77
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• 2003

Shell structure are widely used in a variety of engineering application and mathematical solution of shell structures are available only for a few special cases. The solution of shell structure is more complicated when it has such condition as winker foundation, variable thickness and other problem. In this paper, a simple finite element method is presented for the analysis of axisymmetric several types of shell structure subjected to axisymmetric loads and having uniform and varying wall thickness on elastic foundation. The method is based on the analogy with a beam on elastic foundation (BEF), foundation stiffness matrix where the foundation modulus and beam flexural rigidity are replaced by appropriate parameters pertaining to the shell under considerations. The technique is attractive for implementation on a numerical solution by means of a computer program coded in FORTRAN language with a few elements. To demonstrate this fact, it gives good results which compare well with SAP2000.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.695-702
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• 2006

The stress distribution and the critical stresses in concrete pavements were analyzed using formulations in the transformed field domains when dual-wheel single-, tandem-, and tridem-axle loads were applied. First the accuracy of the transformed field domain analysis results was verified by comparing with the finite element analysis results. Then, the stress distribution along the longitudinal and transverse directions was investigated, and the effects of slab thickness, concrete elastic modulus, and foundation stiffness on the stress distribution were studied. The effect of the tire contact pressure related to the tire print area was also studied, and the location of the critical stress occurrence in concrete pavements was finally investigated. From this study, it was found that the critical concrete stress due to multi-axle loads became larger as the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The number of axles did not tend to affect the critical stress ratio except for a small foundation stiffness value with which the critical stress ratio became significantly larger as the number of axles increased. The critical stress location in the transverse direction tended to move into the interior as the tire contact pressure increased, the concrete elastic modulus increased, the slab thickness increased, and the foundation stiffness decreased. The critical stress location in the longitudinal direction was under the axle for single- and tandem-axle loads, but for tridem-axle loads, it tended to move under the middle axle from the outer axles as the concrete elastic modulus and/or slab thickness increased and the foundation stiffness decreased.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.179-185
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• 2004

The effect of viscous damping on stability of beam resting on an elastic foundation subjected to a dry friction force is analytically studied. The beam resting on an elastic foundation subjected to dry friction force is modeled for simplicity into a beam resting on Kelvin-Voigt type foundation subjected to distributed follower load. In particular, the effects of four boundary conditions (clamped-free, clamped-pinned, pinned-pinned, clamped-clamped) on the system stability are considered. The critical value and instability type of columns on the elastic foundation subjected to a distributed follower load is investigated by means of finite element method for four boundary conditions. The elastic foundation modulus, viscous damping coefficient and boundary conditions affect greatly both the instability type and critical load. Also, the increase of damping coefficient raises the critical flutter load (stabilizing effect) but reduces the critical divergence load (destabilizing effect).

• Structural Engineering and Mechanics
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• v.40 no.3
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• pp.373-392
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• 2011

Periodic and quasi-periodic Timoshenko beams on Pasternak foundation are investigated using the differential quadrature method. Not only band gaps in the beams but also the dynamic response of them is analyzed. Numerical results show that vibration in periodic beams can be dramatically attenuated when the exciting frequency falls into band gaps. Different from the band structures of periodic beams without foundation, the so-called critical frequency was found because of the Pasternak foundation. Its physical meaning was explained in detail and a useful formula was given to calculate the critical frequency. Additionally, a comprehensive parameter study is conducted to highlight the influence of foundation modulus on the band gaps.

• Geomechanics and Engineering
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• v.13 no.4
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• pp.601-619
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• 2017

Cantilever retaining wall movements generally depend on the intensity and duration of ground motion, the response of the soil underlying the wall, the response of the backfill, the structural rigidity, and soil-structure interaction (SSI). This paper investigates the effect of material properties on seismic response of backfill-cantilever retaining wall-soil/foundation interaction system considering SSI. The material properties varied include the modulus of elasticity, Poisson's ratio, and mass density of the wall material. A series of nonlinear time history analyses with variation of material properties of the cantilever retaining wall are carried out by using the suggested finite element model (FEM). The backfill and foundation soil are modelled as an elastoplastic medium obeying the Drucker-Prager yield criterion, and the backfill-wall interface behavior is taken into consideration by using interface elements between the wall and soil to allow for de-bonding. The viscous boundary model is used in three dimensions to consider radiational effect of the seismic waves through the soil medium. In the seismic analyses, North-South component of the ground motion recorded during August 17, 1999 Kocaeli Earthquake in Yarimca station is used. Dynamic equations of motions are solved by using Newmark's direct step-by-step integration method. The response quantities incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that while the modulus of elasticity has a considerable effect on seismic behavior of cantilever retaining wall, the Poisson's ratio and mass density of the wall material have negligible effects on seismic response.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.166-173
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• 2000

This paper describes the method of evaluating the elastic modulus of soil medium by using the Retangular Plate Loading Test. The foundaton is considered to be the elastic half-space. The stiffness matrix of elastic half space is drived using Boussinesq's analytical soulution. A numerical examples are presented to verify the validity of this procedure. Also, the numerical results are compared with those of the existing study results. The procedure proposed in this theses can be applied to the design of concrete paving resting on the elastic foundation

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.23-31
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• 2017

In the study, dynamic behavior of laminated orthotropic beams on elastic foundation is investigated. Consistent model presented here combines the finite element solution of the system with SAP2000 software and the calculation of soil parameters with MATLAB software using Modified Vlasov Model type elastic foundation. For this purpose, a computing tool is coded in MATLAB which employs Open Application Programming Interface (OAPI) feature of SAP2000 to provide two-way data flow during execution. Firstly, an example is taken from the literature to demonstrate the accuracy of the consistent FEM-Vlasov Model. Subsequently, the effects of boundary conditions, subsoil depth, elasticity modulus of subsoil, slenderness ratio, velocity of moving load and lamination scheme on the behavior of laminated orthotropic beams on elastic foundation are investigated on a new numerical example. It can be concluded that it is really convenient to use OAPI feature of SAP2000 to model this complex behavior of laminated orthotropic beams on elastic foundation under moving load.

• Journal of Applied and Pure Mathematics
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• v.5 no.5_6
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• pp.407-414
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• 2023

In this article we continue the study of smooth Picard singular integral operators that started in [2], see there chapters 10-14. This time the foundation of our research is a trigonometric Taylor's formula. We establish the convergence of our operators to the unit operator with rates via Jackson type inequalities engaging the first modulus of continuity. Of interest here is a residual appearing term. Note that our operators are not positive. Our results are pointwise and uniform.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.83-93
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• 2004

In this study. the Modified Response Displacement Method(MRDM) for seismic design of underground box-type structures is proposed. Firstly, to investigate the applicability of the conventional RDM, various parametric studies are performed according to buried depth and soil conditions. Results from the conventional RDM are compared with those of time history analysis in terms of the maximum bending moment and relative displacement. The comparison shows that the velocity response spectrum and the determination method of foundation modulus which significantly influence the accuracy of RDM should be modified. Thus, the modified velocity response spectrum and the new determination method of foundation modulus are proposed under consideration of domestic conditions. In order to demonstrate the accuracy and validity of the proposed MRDM numerical analyses are performed according to different parameters such as depth of base rock, height and width of box, buried depth and soil condition. the comparison with the results of the time history analysis verifies the feasibility of the proposed MRDM for the seismic analysis.