• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.153-164
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• 2015

The methods of design of mat foundation may be classified as the rigid method and the flexible method according to the assumptions used. In the rigid method, the mat is assumed to be infinitely rigid and the contact pressure is assumed planar distribution. However, the contact pressure is not planar but curved surface because the real mat is not rigid. Therefore, it is not precise to analyze the mat foundation using the rigid method, and so there is no choice but to accept an error. On the other hand, in the flexible method, the mat is considered as the plate on the elastic foundation. This elastic plate theory is for the infinite plate acting a concentrated load on the elastic foundation. However, the functions for the moment, shear, and the deflection by the flexible method are very complex, there are many difficulties for the designer to use them. Also, it is impossible to use the design aid figures as a substitute of the complex functions, because they do not cover the values at the critical sections for the moment and shear. Therefore, in this research, the simplified functions for the moment, shear, and the deflection are proposed by regression analysis for an designer to use easily the flexible method. The simplified functions are very accurate and very ease to use.

• Structural Engineering and Mechanics
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• v.48 no.4
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• pp.455-466
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• 2013

In recent years, many countries have added railway noise to the issues covered by noise regulations. It is known that the rail is the dominant source of rolling noise at frequency range of 500Hz-2000Hz for the conventional speeds (<160km/h). One of the effective ways to reduce noise from railway track is using a rail vibration absorber. To study the acoustic performance of rail absorber, the decay rates of vibration have long been used by researcher. In this paper, A FE model of a periodic supported rail with infinite element in ABAQUS is developed to study the acoustic performance of the rail absorber. To compute the decay rates, acceleration responses along the rail transferred to MATLAB to obtain response levels in frequency domain and then by processing the response levels, the decay rates obtained for each1/3octav band. Continous rail absorber is represented by a steel layer and an elastomer layer. The decay rates for conventional rail and rail with one-side absorber and also, the rail with two side absorber are obtained and compared. Then, to improve the system of rail absorber, a steel plate with elastomer layer is added to bottom of the rail foot. The vertical decay rate results show that the decay rate of rail vibration along the track is significantly increased around the tuned frequency of the absorber and thus the rail vibration energy is substantially reduced in the corresponding frequency region and also effective in rail noise reduction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2223-2233
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• 1993

An engineering method is suggested to calculate the applied load versus crack extension in the elastic-plastic fracture. The condition for an increment of crack extension is set by a critical increment of crack-up opening displacement(CTOD). The ratio of the CTOD increment to the incremental crack extention is a critical crack-tip opening angle(CTOA), assumed to be constant for a material of a given thickness. The Dugdale model of crack-tip deformation in an infinite plate is applied to the method, and a complete solution for crack extension and crack instability is obtained. For finite-size specimens of arbitrary geometry in general yielding, an approximate generalization of the Dugdale model is suggested so that the approximation approaches the small-scale yielding solution in a low applied load and the finite-element solution in a large applied load. Maximum load is calculated so that an applied load attains either a limit load on an unbroken ligament or a peak load during crack extension. The proposed method was applied to three-point bend specimens of a carbon steel SM45C in various sizes. Reasonable agreements are found between calculated maximum loads and experimental failure loads. Therefore, the method can be a viable alternative to the J-R curve approach in the elastic-plastic fracture analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.59-65
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• 2004

The stress intensity factors have been widely used in numerical studies of crack growth direction. However in many cases, omissive terms of the series expansion are quantitatively significant, so we consider the computation of such terms. For this purpose, we used the finite element method with isoparametric quadratic quarter-point elements. For examples, infinite square plate with a slant crack subjected to a uniaxial load is analyzed. The numerical analysis were performed for the wide range of crack tip element lengths and inclined angles. The numerical results obtained are compared with the theoretical solutions. Also they were accurate and efficient.

• The Korean Journal of Food And Nutrition
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• v.13 no.5
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• pp.477-482
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• 2000

For the purpose of explaining the dewatering phenomena of potato slice soaked in concentrated solution three models were proposed. Earlier model cannot explain the dewatering phenomena of potato slice in concentrated solution because of limiting its condition which is necessary to build a model. Therefore other three models were suggested and a model based on Fick\`s second law of mass transport at infinite plate conditions and numerical analysis was test model for explaining dewatering phenomena of potato soaked in concentrated solution. Apparent diffusion coefficient of water could be readily estimated from model III, and it could explain adequately the difference of the dewatering phenomena of various soaking conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.101-108
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• 2007

This paper presents an efficient meshless method for analyzing cracked piezoelectric structures subjected to mechanical and electrical loading. The method employs an element free Galerkin (EFG) formulation and an enriched basic function as well as special shape functions that contain discontinuous derivatives. Based on the moving least squares (MLS) interpolation approach, The EFG method is one of the promising methods for dealing with problems involving progressive crack growth. Since the method is meshless and no element connectivity data are needed, the burdensome remeshing procedure required in the conventional finite element method (FEM) is avoided. The numerical results show that the proposed method yields an accurate near-tip stress field in an infinite piezoelectric plate containing an interior hole. Another example is to study a ceramic multilayer actuator. The proposed model was found to be accurate in the simulation of stress and electric field concentrations due to the abrupt end of an internal electrode.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.8-15
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• 2002

In order to investigate the vibration characteristics of fluid-structure interaction problem, we modeled two identical rectangular plates coupled with fluid. A commercial computer code, ANSYS was used to perform finite element analysis and FEM solutions were compared with the experimental results to verify the finite element model. As a result, comparison of FEM and experiment showed good agreement, and the transverse vibration modes, in-phase and out-of-Phase, were observed alternately in the fluid-coupled system. The effect of fluid gap size on the fluid-coupled natural frequency were investigated. It was shown that the mode numbers increased, the normalized natural frequencies monotonically increased. And it was also found that an increase of the fluid gap reduced the coupled natural frequencies for the in-phase modes but increased the coupled natural frequencies for the out-of phase modes, and eventually converged to the results of an infinite fluid gap.

• Wind and Structures
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• v.26 no.5
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• pp.317-329
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• 2018

Wake characteristics of the flow over a finite square prism at different incidence angles were experimentally investigated using an open-loop wind tunnel. A finite square prism with a width D = 15 mm and a height H = 7D was vertically mounted on a horizontal flat plate. The Reynolds number was varied from $6.5{\times}10^3$ to $28.5{\times}10^3$ and the incidence angle ${\alpha}$ was changed from $0^{\circ}$ to $45^{\circ}$. The ratio of boundary layer thickness to the prism height was about ${\delta}/H=7%$. The time-averaged velocity, turbulence intensity and the vortex shedding frequency were obtained through a single-component hotwire probe. Power spectrum of the streamwise velocity fluctuations revealed that the tip and base vortices shed at the same frequency as that ofspanwise vortices. Furthermore, the results showed that the critical incidence angle corresponding to the maximum Strouhal number and minimum wake width occurs at ${\alpha}_{cr}=15^{\circ}$ which is equal to that reported for an infinite prism. There is a reduction in the size of the wake region along the height of the prism when moving away from the ground plane towards the free end.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.1
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• pp.35-41
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• 1986

A hybrid modelling technique of a soil-structure system on viscoelastic soil medium is studied in this paper. The hybrid model consists of a near-field and a far-field with their common interface passing through the soil region at some distance from the base of the structure. It makes use of frequency-dependent impedances so as to represent the semi-infinite far-field. The far-field impedances are formulate including the radiation damping characteristics as well as the viscoelastic properties of the soil medium. The verification of the method has been carried out using a rigid circular plate on a viscoelastic half-space. The impedances obtained by the method are compared with the theoretical values. Example analyses have been performed for a tall chimney and the results have been compared with those obtained by other methods which are frequently used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1598-1608
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• 1997

Based on the application of te theory of conjugate approximations and the Loubignac's iterative method in a local region, a method to improve the stress filed in a displacement-formulated finite element solution has been proposed. The validity of the proposed method has been tested through two examples : a thick cylinder under internal pressure loading and an infinite plate with a central circular hole subjected to uniaxial tension. As a result of analysis of the examples, it was found that the stress field obtained for the local region model by the proposed method approximates well for the whole domain model. In addition, it was found that because of a significant decrease in the computing time to obtain the improved stress field, the proposed method is efficient and useful for the detailed stress analysis in local regions.