• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1702-1711
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• 1997

A numerical study for the number of terms of a power series stress function and the effect of hybrid element size on stress analysis around a hole in loaded orthotropic composites is presented. The hybrid method coupling experimental and/or theoretical inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width glass epoxy tensile plate. The tests are done by rarying the number of terms, element size and nodal locations on the external boundary of the hybrid region. The numerical results indicate that the hybrid method is accurate and powerful in both experimental and numerical stress analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1249-1253
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• 2001

Numerical analysis is sometimes used to solve the problems in the engineering and natural science fields. On this reason, the faster, more practical system in computing the numerical solution is required. This paper deals with the numerical evaluation of various numerical integration methods which is frequently used in the engineering fields. This paper choices four integration methods such as Euler method, Heun's method, Runge-Kutta method and Gill's method for evaluating the each integration method. In numerical examples, the free vibration problem on an elastic foundation is chosen. As the numerical results, the natural frequencies and the running time are obtained, and these results are compared to examine the practicality of integration methods.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.2
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• pp.21-27
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• 2008

An inverse method is introduced to construct the problem for the error analysis of the numerical solution of initial value problem. These problems constructed through this method have a known exact solution, even though analytical solutions are generally not obtainable. The process leading to the exact solution makes use of an initially available approximate numerical solution. A smooth interpolation of the approximate solution is forced to exactly satisfy the differential equation by analytically deriving a small forcing function to absorb all of the errors in the interpolated approximate solution. Using this special case exact solution, it is possible to investigate the relationship between global errors of a candidate numerical solution process and the associated tuning parameters for a given problem. Under the assumption that the original differential equation is well-posed with respect to the small perturbations, we thereby obtain valuable information about the optimal choice of the tuning parameters and the achievable accuracy of the numerical solution.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.105-112
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• 2001

The purpose of this study is to assess the stability of tunnel for a high speed railway crossing the fault zone. The area where the tunnel crossed the fault zone can be unstable during construction and operation. Geotechnical investigations have been conducted to determine an optimum excavation method by obtaining the material properties around the fault zone and to check the stability of the tunnel. For the numerical analysis, the FLAC, numerical analysis code based on finite difference method, was utilized to analyze the behavior of the fault at three points having typical ground conditions. Based on the results of numerical analysis, the combinations of compaction grouting and LW grouting were determined as suitable methods for pre-excavation Improvement of the ground surrounding the tunnel opening. In conclusion, the stability of the tunnel construction for the high speed railway within the fault zone may be obtained by adopting the optimum excavation method and the reinforcement method. The numerical analysis based on FLAC program contains errors caused by assumptions used in numerical analysis, therefore constant monitoring with respect to the change of ground condition and groundwater is highly recommended to minimize the numerical error and the possibility of damage to tunnel.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.220-222
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• 1999

This paper presents a numerical analysis of the eddy current testing with cracked pipe using finite element method (FEM). ${\vec{A}},\;{\phi}-{\vec{A}}$ method is adopted for the formulation of 3-dimensional(3-D) FEM with the brick element. The cracks investigated here are the inner and outer surface of axial symmetry, 90 degree circular one. The algorithm of 3-D numerical analysis is employed for the axisymmetric pipe with the cracks. In order to verify the validity of 3-D numerical analysis, the results are compared with those of 2-D analysis with the same type of the model. The differential impedance is obtained by using energy method and its locus are various 8-shaped curves for each cracks. The ICCG method is used for the calculation of a matrix.

• Journal of Industrial Technology
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• v.10
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• pp.69-72
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• 1990

In this paper the numerical method for the study of wave reflection from and transmission through submerged permeable breakwaters using the boundary element method is developed. The numerical analysis technique is based on the wave pressure function instead of velocity potential because it is difficult to define the velocity potential in the each region arising the energy dissipation. Also, the non-linear energy dissipation within the submerged porous structure is simulated by introducing the linear dissipation coefficient and the tag mass coefficient equivalent to the non-linear energy dissipation. For the validity of this analysis technique, the numerical results obtained by the present boundary element method are compared with those obtained by the other computation method. Good agreements are obtained and so the validity of the present numerical analysis technique is proved.

• Structural Engineering and Mechanics
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• v.86 no.1
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• pp.49-68
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• 2023

This study investigates the static and dynamic structural analysis of symmetrical and asymmetrical coupled shear walls using the continuous and modified transfer matrix methods by idealizing the coupled shear wall as a three-field CTB-type replacement beam. The coupled shear wall is modeled as a continuous structure consisting of the parallel coupling of a Timoshenko beam in tension (with axial extensibility in the shear walls) and a shear beam (replacing the beam coupling effect between the shear walls). The variational method using the Hamilton principle is used to obtain the coupled differential equations and the boundary conditions associated with the model. Using the continuous method, closed-form analytical solutions to the differential equation for the coupled shear wall with uniform properties along the height are derived and a numerical solution using the modified transfer matrix is proposed to overcome the difficulty of coupled shear walls with non-uniform properties along height. The computational advantage of the modified transfer matrix method compared to the classical method is shown. The results of the numerical examples and the parametric analysis show that the proposed analytical and numerical model and method is accurate, reliable and involves reduced processing time for generalized static and dynamic structural analysis of coupled shear walls at a preliminary stage and can used as a verification method in the final stage of the project.

• Geomechanics and Engineering
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• v.2 no.1
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• pp.45-56
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• 2010

The current study presents a mathematical model and numerical method for free vibration of tapered piles embedded in two-parameter elastic foundations. The method of Discrete Singular Convolution (DSC) is used for numerical simulation. Bernoulli-Euler beam theory is considered. Various numerical applications demonstrate the validity and applicability of the proposed method for free vibration analysis. The results prove that the proposed method is quite easy to implement, accurate and highly efficient for free vibration analysis of tapered beam-columns embedded in Winkler- Pasternak elastic foundations.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.185-191
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• 2008

This study tried the 1st, 2nd dimensional numerical analysis according to the pier's shape, size and installing method in order to compare the depth of scour calculation method using the variables calculated by using the 2nd dimensional numerical analysis with the calculated depth of scour value by using the calculated variables by using the 1st dimensional numerical analysis. And then verified the problems occurring when the depth of scour is calculated by using the calculated values by using the 1st dimensional numerical analysis, as calculating the deviation depending on it.

• Geomechanics and Engineering
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• v.15 no.6
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• pp.1207-1217
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• 2018

Geomechanics parameters are critical to numerical simulation, stability analysis, design and construction of geotechnical engineering. Due to the limitations of laboratory and in situ experiments, back analysis is widely used in geomechancis and geotechnical engineering. In this study, a hybrid back analysis method, that coupling numerical simulation, response surface (RS) and relevance vector machine (RVM), was proposed and applied to identify geomechanics parameters from hydraulic fracturing. RVM was adapted to approximate complex functional relationships between geomechanics parameters and borehole pressure through coupling with response surface method and numerical method. Artificial bee colony (ABC) algorithm was used to search the geomechanics parameters as optimal method in back analysis. The proposed method was verified by a numerical example. Based on the geomechanics parameters identified by hybrid back analysis, the computed borehole pressure agreed closely with the monitored borehole pressure. It showed that RVM presented well the relationship between geomechanics parameters and borehole pressure, and the proposed method can characterized the geomechanics parameters reasonably. Further, the parameters of hybrid back analysis were analyzed and discussed. It showed that the hybrid back analysis is feasible, effective, robust and has a good global searching performance. The proposed method provides a significant way to identify geomechanics parameters from hydraulic fracturing.