• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.225-232
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• 2003

The behaviour of ground induced by tunneling of 2arch tunnels may differ from the one caused by usual type tunnels. This paper describe the behaviour created by the size of pilot tunnel and the condition on the construction method of center piller Also, loads acting on the supports of the first tunnel and the center pillar during the excavation of second tunnel is investigated by numerical analyses. The results of numerical analyses are compared to the data records of measurement results, i.e. force on the support system and ground displacement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2212-2218
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• 2015

In order to find out the load bearing behavior of sand and clay which sustain three types of shallow footing, finite element analyses were performed. Failure zone of sand which sustain strip footing was affected by relative density of sand whereas, failure zone of clay was not affected by soil strength and it was similar to the failure zone which is considered in theory. Considering the shape of load-settlement curves obtained by numerical analyses, punching shear failure can be seen in loose sand and ultimate bearing load can not be seen in dense sand whereas, yielding point can be seen in clay. Ultimate bearing loads for sand predicted by theory were greater than those obtained by numerical analyses and ultimate bearing loads for clay predicted by theory were similar to those of numerical analyses. Ultimate bearing loads determined by 1 inch settlement criteria were slightly less than those of numerical analyses.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.59-66
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• 2014

This paper presents the pullout behavior of suction pile using finite difference method; and the commercial software, FLAC3D, was employed for the numerical analyses. The ultimate pullout capacity of suction pile was predicted using conventional equations, and the results were compared with the results from numerical analyses with varying pile diameter, pile length, and the undrained shear strength of clays. Based on the results from 24 analyses, it was found that the failure pattern depends not only on the drainage condition of suction pile, but also on the pile dimensions and the material properties of surrounding soils. The developed side shear (DSS) along the internal surface of the suction pile was collected from numerical analyses, which was used to classify the failure type between sliding failure and tensile failure. Regardless of the external DSS, the high internal DSS tends to result in sliding failure in the numerical analyses, which conforms well to the estimation from conventional equations.

• Tunnel and Underground Space
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• v.2 no.1
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• pp.152-163
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• 1992

The study of rock mass behaviour through a numerical analysis is important for the design, construction and maintenance of large rock caverns. The objectives of the numerical analysis are to design reasonably and construct safely the underground structures, to maintain them soundly after construction and to extend them securely for a desired period of time. Methods of numerical analyses included in this case study are the finite element method, the boundary element method, and the distinct element method. The numerical models are purely elastic, elastoplastic, visco-elastic, visco-plastic, easto-visco-plastic and jointed-discontinuous materials. The results of this case study indicate that the rock mass behaviour could be predicted exactly through continuous comparisons of the numerical results with the in-situ measurements.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.183-190
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• 2000

Effective range of Hydraulic Hammer Compaction was studied by numerical analysis instead of empirical method. Numerical analyses were carried out with commercial FEM code, ABAQUS, and verified by comparing the numerical results with field tests of Hydraulic Hammer Compaction. Most of material properties were evaluated by data from laboratory and in-situ tests. Vertical effective range was estimated by distribution curve of plastic strain energy dissipated through soil layers under dynamic load and these results were in good agreement with field tests. Based on verification, the effects of governing properties of Hydraulic Hammer Compaction such as number of hit can be determined by numerical analyses. In addition, vertical effective range can also be determined by Menard's empirical equation using the external work at converging time of plastic strain energy in numerical analysis. This implies that the minimum energy of Hydraulic Hammer Compaction for improvement can be determined by Menard's equation.

• Journal of the Korean Geotechnical Society
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• v.34 no.8
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• pp.15-26
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• 2018

Recently, as the seismic performance based design methods have been introduced, dynamic numerical analyses need to be performed to evaluate the actual performance of structures under earthquakes. The verification of the numerical modeling is the most important for the performance based design. Therefore, 2-dimensional numerical analyses were performed to simulate the seismic behavior of a pile-supported structure, to provide the proper numerical modeling and to determine of input parameters. A dynamic centrifuge test of a pile group in dry loose sand was simulated to verify the applicability of the numerical model. The numerical modeling was carefully made to reflect the actual condition of the centrifuge test including dynamic soil properties, soil-pile interaction, boundary condition, the modeling of the group pile and structure and so on. The predicted behavior of the numerical analyses successfully simulated the acceleration variation in ground, the moment and displacement of the pile, and the displacement and acceleration of the structure. Therefore, the adopted numerical modeling and the input parameters can be used to evaluate the seismic performance of pile groups.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.49-56
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• 2006

In this thesis, centrifuge model experiments and numerical analyses were carried out to investigate the behavior of an excavated slope in soft clay ground. Centrifuge model tests were performed with various slopes for the excavated ground, such as 1:1.5 and 1:2. Pore pressuresthe model ground were measured to find their effects on the stability of the excavated slope. These experiments showed that the model with 1:2.5 maintained its stability within a short period of time and failed gradually. Therefore, anexcavated slope of soft soil with this slope might maintain stable conditions within a certain time. The mode1 with a 1:3 slope was observed to maintain a very stable condition, showing insignificant deformation in the ground after being excavated. Numerical analyses with PLAXIS, a commerciallyavailable software implemented with the finite element numerical technique, were performed to find the pore pressure distribution within the ground mass and the deformation of the soil. From the results of numerical analysis, a negative pore pressure was developed after the excavation and thus the stability of the slope was maintained. The safety factor for slope failure was found to decrease with time because of the dissipation of negative pore pressure with time.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.77-82
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• 1999

Resistance spot welding process is completed in very short time and there are many factors affecting on the generation of heat. It is difficult to control these experimental factors and monitor distribution of the temperature and stresses in the experimental analysis case. and too much time and expense are required for the experimental trials to fine proper welding condition. So numerical analyses have been attempted steadily, but most numerical analyses on the resistance spot welding are mainly focused on thermal behavior. Therefore, in this paper, the numerical analysis of mechanical behavior as well as heat conduction is carried out for the spot welding process. For this numerical analysis, axial symmetric computer program for the spot welding analysis by F.E.M. has been developed considering heat conduction and thermal elastic-plastic theory. Material properties depending on temperature such as density, heat conductivity, heat expansion coefficient, specific heat, yield stress, elastic modulus, and specific resistance are considered. Using the results of temperature distribution obtained from heat conduction analysis, the thermal elastic-plastic analysis is carried out to clarify mechanical behavior of spot welded specimen. In order to evaluate the effect of residual stresses, numerical analyses are carried out under tension-shear load in two cases respectively; one with residual stress, the other without residual stresses.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.511-529
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• 2023

This paper aims to better understand the bonding behavior in Reinforced Concrete beams strengthened with an Ultra-High Performance Fiber Reinforced Concrete (RCUHPFRC) layer on the compression side using experimental tests and numerical analyses. The UHPFRC mix design was obtained through an optimization procedure, and the characterization of the materials included compression and slant shear tests. Flexural tests were carried out in RC beams and RC-UHPFRC beams. The tests demonstrated a debonding of the UHPFRC layer. In addition, 3D finite element analyses were carried out in the Abaqus CAE program, in which the interface is modeled considering a zero-thickness cohesive-contact approach. The cohesive parameters are investigated, aiming to calibrate the numerical models, and a sensitivity analysis is performed to check the reliability of the assumed cohesive parameters and the mesh size. Finally, the experimental and numerical values are compared, showing a good approximation for both the RC beams and the RC strengthened beams.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1566-1571
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• 2003

The cold plate used for a CEU(Control Electronics Unit) of an EV(Electric Vehicle) is extremely important since the dissipation of the heat generated from power devices like IGBT(Insulated Gate Bipolar Transistor) and diode has a significant effect on the performance as well as the durability of the CED. The cold plate consists of seven power devices, and coolant flows through the passage bonded to a groove of the cold plate. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for the cold plate with enhanced coolant passages were conducted. Based on results of the numerical analyses, an improved model of the cold plate has been proposed. The experiments under the various conditions have been conducted to compare the performance of the proposed cold plate to the present one. As a result of the numerical analyses together with the experiments, the ideal design of the cold plate could be offered.