• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.96-105
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• 1998

Soil properties, drain conditions and numerical analysis technique have great influence upon consolidation behavior. In relevant to the above described fact, this paper aims to examining the applicability of prediction model of consolidation as well as deformation characteristics for soft clayey foundation improved by sand drain. A case study for actual foundation of Kwangyang steel works was performed. Single drain consolidation model proposed by Hansbo and Biot's consolidation theory coupled with modified Cam-clay model developed during the research were employed for the FEM numerical analysis of the foundation. Both smear effect and drain capacity were taken into account for the analysis. Finally the applicability of the newly developed technique to the behavior of foundation composed of soft clay proved satisfactory.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.255-262
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• 2021

In this study, a jointless bridge that integrates the superstructure and abutment without installing an expansion joint was analyzed. An example of a jointless bridge that has been introduced in Korea since 2009. Owing to the short period of use and lack of experience in design, construction, and maintenance, there is insufficient information regarding the long-term behavior of jointless bridges. When analyzing numerous bridges, the numerical analysis model must maintain the numerical values used and ensure the convenience of model construction. In this study, sensitivity analysis was performed to select a numerical model for various types of jointless bridges using commercial finite element programs, MIDAS Civil and ABAQUS 2018. According to a solid element-based model, we analyzed the mean and maximum relative errors between structural models. Consequently, it was found that the beam element-based model exhibits a significantly small relative error in comparison to the shell element, where a relatively large error was recorded. Therefore, the optimal numerical analysis model, a practical model that maintains the similarity and precision of the displacement shape cause by relative error, was judged to be the most suitable for jointless bridges based on the shell element.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.495-501
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• 2009

In this paper, a numerical anchor bond-slip model is proposed to improve the numerical simulation of concrete-steel structures connected with steel anchor bolts and subjected to extreme cyclic loading. The suggested bond-slip model is composed of a group of nonlinear uniaxial connector elements and its parameters can be determined by calibrating the model with pull-out test data. Numerical analysis results from simulating a concrete foundation-steel column structure using the proposed bond-slip anchor model, which is implemented based on Abaqus elements, and the perfect-bond anchor model are compared with the experimental results. It is concluded that a reasonable anchor bond-slip model is required to realistically simulate concrete-steel structures subjected to extreme cyclic loading, and the proposed anchor bond-slip model shows acceptable performance in the present numerical analysis.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1644-1651
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• 1989

In this paper, a two-dimensional numerical analysis of HEMT's with gate length of 0.6um is performed. In this case, Control Volume Formulation method which has been used in the analysis of heat transfer and fluid flow is used as a numerical method. As a mobility model, empirical formula including the velocithy overshoot phenomena is used instead of two-piece mobility model. The results obtained from this numerical analysis(i.e., the region in which cahnnel is formed, the strength of electric field in the channel, the distribution of potential, and the distribution of electron concentration etc.)are in good agreement with the previous analytic results. And our results also show the parasitic MESFET's operation in the range of the high gate voltage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.253-261
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• 2005

In decades, a substantial body of work on a unified viscoplastic model which considers the mechanism of plastic deformation and creep deformation has developed. The systematic scheme for numerical analysis of unified model is necessary because the dominant failure mechanism is the defect growth and coalescence in materials. In the present study, the unified viscoplastic model for materials with defects suggested by Suquet and Michel was employed for numerical analysis. The constitutive equations are integrated based on the generalized mid-point rule and implemented into a finite element program (ABAQUS) by means of user-defined subroutine (UMAT). To evaluate the validity of the developed UMAT code and the assessment of the adopted viscoplastic model, the results obtained from the UMAT code was compared with the numerical reference solution and experimental data. The unit cell analysis also has been investigated to study the effect of strain rate, temperature, stress triaxiality and initial defect volume fraction on the growth and coalescence of the defect.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.59-65
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• 2005

In this paper a constitutive model for large cracks in concrete and other brittle materials subject to dynamic and cyclic leading is presented. The suggested model is based on the plastic-damage model for cyclic leading. A numerical formulation based on the three-step return-mapping algorithm for the proposed large crack model is also present. The numerical examples show that the present algorithm works appropriately under dynamic leading and should be used in large crack problems to prevent excessive tensive plastic strain development causing unrealistic results.

• Journal of Drive and Control
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• v.19 no.1
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• pp.62-68
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• 2022

Considering the characteristics of industrial machines that lack vehicle-induced wind, forced convection by a cooling fan is mostly required. Therefore, numerical analysis of an engine room is usually performed to examine the cooling performance in the room. However, most engine rooms consist of a number of parts and components at specific positions, leading to high costs for numerical modeling and simulation. In this paper, a new methodology for three-dimensional computer-assisted design simplification was proposed, especially for the pile of components and parts at the engine room outlet. A porous media model and regression analysis were used to derive a meta-model for imitating the flow rate reduction at the outlet by the pile. The results showed that the fitted model was reasonable considering the coefficient of determination. The final numerical model of the engine room was then used to simulate the velocity distribution by changing the mass flow rate at the outlet. The results showed that both velocity distributions were significantly changed in each case and the meta-model was valid in imitating the flow rate reduction by some piles of components and parts.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3367-3382
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• 2023

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian computational fluid dynamics method that has been widely used in the analysis of physical phenomena characterized by large deformation or multi-phase flow analysis, including free surface. Despite the recent implementation of eddy-viscosity models in SPH methodology, sophisticated turbulent analysis using Lagrangian methodology has been limited due to the lack of computational performance and numerical consistency. In this study, we implement the standard and dynamic Smagorinsky model and dynamic Vreman model as sub-particle scale models based on a weakly compressible SPH solver. The large eddy simulation method is numerically identical to the spatial discretization method of smoothed particle dynamics, enabling the intuitive implementation of the turbulence model. Furthermore, there is no additional filtering process required for physical variables since the sub-grid scale filtering is inherently processed in the kernel interpolation. We simulate lid-driven flow under transition and turbulent conditions as a benchmark. The simulation results show that the dynamic Vreman model produces consistent results with experimental and numerical research regarding Reynolds averaged physical quantities and flow structure. Spectral analysis also confirms that it is possible to analyze turbulent eddies with a smaller length scale using the dynamic Vreman model with the same particle size.

• Journal of the Korean Wood Science and Technology
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• v.35 no.3
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• pp.1-9
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• 2007

To analyze the behavior of multiple bolted connection with analytical method, there was a major problem in terms of the number of bolt as two. Multiple bolted connection is wrong in other way, that is impossible to analyze the behavior of connection with various types. So the numerical analysis model was developed to analyze the behavior of connection with various types, and to overcome the limitation of number of bolt. The optimum values for analysis the behavior of multiple bolted connection with numerical methods were obtained as, r=0.35, Kx=137.5, and Ky=257.4. The numerical analysis method was developed in this study showed high efficiency for the existing methods in the behavior analysis of connection.

• Steel and Composite Structures
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• v.38 no.6
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• pp.637-656
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• 2021

The component-based method is widely used to analyze the initial stiffness of joint in steel structures. In this study, an analytical component model for determining the column face stiffness of square or rectangular hollow section (SHS/RHS) subjected to tension was established, focusing on endplate connections. Equations for calculating the stiffness of the SHS/RHS column face in bending were derived through regression analysis using numerical results obtained from a finite element model database. Because the presence of bolt holes decreased the bending stiffness of the column face, this effect was calculated using a novel plate-spring-based model through numerical analysis. The developed component model was first applied to predict the bending stiffness of the SHS column face determined through tests. Furthermore, this model was incorporated into the component-based method with other effective components, e.g., bolts under tension, to determine the tensile stiffness of the T-stub connections, which connects the SHS column, and the initial rotational stiffness of the joints. A comparison between the model predictions, test data, and numerical results confirms that the proposed model shows satisfactory accuracy in evaluating the bending stiffness of SHS column faces.