• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.270-274
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• 1997

The numerical model that can describe the ignition of the pseudospark discharge using hybrid fluid-particle method has been developed. The evolution process of the discharge has been divided into four phases along the potential distribution. After the plasma enters in the hollow cathode, the confining effect which is one of hollow cathode properties occurs and the electron current on anode rises rapidly. As the plasma expands successively, the sheath contracts and as the electric field in the sheath increases, the field-enhanced thermionic emission(Schottky emission) occurs. From numerical results, the physical mechanism that causes the rapid current rise in the ignition of the pseudospark discharge could be identified.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.291-294
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• 2008

A ICH-CFT colunn(internally confined hollow-concrete filled tube column) has many advantages compare with R.C column and CFT column. For example using a hollow section, it is possible to save material and to reduce self weight of column. Also two steel tubes on both sid of concrete, inner and outter tube, can improve ductility of ICH-CFT column. But study about ICH-CFT section has done only theoretically. Thus although ICH-CFT column has many advantages, ICH-CFT column dosen't use in construction. In this thesis, through out 3-D full modeling using ABAQUS analyze the nonlinear behavaior of ICH-CFT column. And using the analysis result, review the theoretical knowledge.

• Structural Engineering and Mechanics
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• v.10 no.6
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• pp.577-587
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• 2000

A 3D nonlinear finite element computation model is presented in order to analyze the concrete filled rectangular tubular (CFRT) composite structures. The concrete material model is based on a hypo-elastic orthotropic approach while the elasto-plastic hardening model is employed for steel element. The comparisons between experimental and analytical results show that the proposed model is a relatively simple and effective one. The analytical results show that the capacity of inner concrete of CFRT column mainly depends on the two diagonal zones, and the confining effect of CFRT section is mainly concentrated on the corner zones. At the ultimate state, the side concrete along the section cracks seriously, and the corner concrete softens with the increase of compressive strains until failure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.165-172
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• 1993

A non-linear mathematical model has been developed for the dynamic analysis of the reactor internals. The model includes a lumped mass and stiffness with non-linear members such as gap-spring. As hydrodynamic couplings have also been considered in the model, the effect of fluid/structure interaction between internals components due to their immersion in a confining fluid can be studied for the dynamic response analysis. The reactor internals responses for seismic and pipe break excitations have been calculated for the case of with-and without-hydrodynamic couplings.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.388-396
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• 2009

Rock bolt is one of the most important supports for tunnelling to prevent excessive ground relaxation at the primary tunnel excavation stage. It forms a ground arch band by confining the ground around a tunnel. Rock bolt has various effects, such as support or hanging effect, internal pressure effect, arching effect, ground improvement effect etc. Most studies on rock bolt focused on the concept of support, but only a few researches on the ground reinforcing effect by pre-tensioning a rock bolts. In this study, large scale model tests are performed to investigate the ground reinforcing effect of rock bolts for regularly jointed rocks. Simple beam model was built to find out the reinforcing effect of jointed rocks, which was reinforced by pre-tensioned rock bolts. Settlement of model beam was analyzed through measuring its sagging for various installation intervals.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.61-71
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• 2009

This paper presents the results of an experiment comparing the current circular CFT columns and circular CFT columns that were additionally confined by carbon fiber sheets (CFS) under axial loading. The main experimental parameters are the numbers of CFS layers and the diameter-to-thickness ratio. 10 specimens were prepared according to the experimental parameter plans, and axial compression tests were conducted. From the tests, the failure procedure, load-axial deformation curve, maximum axial strength, and deformation capacity of the CFT columns and confined CFT columns were compared. The test results showed that the maximum axial strengths of CFT columns additionally confined by CFS are increased higher than those of the current CFT columns, and that local buckling can be delayed due to the confinement effect of CFS.

• Geomechanics and Engineering
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• v.22 no.6
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• pp.519-528
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• 2020

A mathematical wetting model is usually used to predict the deformation of core wall rockfill dams induced by the wetting effect. In this paper, a series of wetting triaxial tests on a rockfill was conducted using a large-sized triaxial apparatus, and the wetting deformation behavior of the rockfill was studied. The wetting strains were found to be related to the confining pressure and shear stress levels, and two empirical equations, which are regarded as the proposed mathematical wetting model, were proposed to express these properties. The stress and deformation of a core wall rockfill dam was studied by using finite element analysis and the proposed wetting model. On the one hand, the simulations of the wetting model can estimate well the observed wetting strains of the upstream rockfill of the dam, which demonstrated that the proposed wetting model is applicable to express the wetting deformation behavior of the rockfill specimen. On the other hand, the simulated additional deformation of the dam induced by the wetting effect is thought to be reasonable according to practical engineering experience, which indicates the potential of the model in dam engineering.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.1-15
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• 2015

This paper presents a series of conventional undrained triaxial compression tests conducted to determine the effect of both tire crumbs and cement addition on Narli sand specimens. The tire crumb contents and cement contents were 3%, 7%, 15%; and 1%, 3%, 5% by dry weight of the sand specimens respectively. Specimens were prepared at about 35% relative density, cured during overnight (about 17 hours) for artificially bonding under a 100 kPa effective stress (confining pressure of 500 kPa with a back pressure of 400 kPa), and then sheared. Deviatoric stress-axial strain, pore water pressure-axial strain behavior, and Young's modulus of the specimens at various mixture ratios of tire crumb/cement/sand were measured. Test results indicated that the addition of tire crumb to sand decreases Young's modulus, deviatoric stress and brittleness, and increase pore water pressure generation. The addition of cement to sand with tire crumbs increases deviatoric stress, Young's modulus, and changes its ductile behavior to a more brittle one. The results suggest that specimen formation in the way used here could reduce the tire disposal problem in not only economically, and environmentally, but also more effectively beneficial way for some geotechnical applications.

• Journal of Korean Association for Spatial Structures
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• v.6 no.2 s.20
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• pp.93-105
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• 2006

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of twelve one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The specimens adopted are two-dimensional (2D) hollow concrete block masonry walls with different parameters such as shear span ratio, inflection point and percent of reinforcement in confining columns and walls. Test results obtained for each specimen include cracking patterns, load-deflection curve, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Computers and Concrete
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• v.19 no.5
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• pp.477-488
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• 2017

In this paper, an innovative technique for finite element (FE) modeling of steel tube-confined concrete (STCC) columns with active confinement under axial compressive loading is presented. In this method, a new constitutive model for the stress-strain relationship of actively-confined concrete is proposed. In total, 14 series of experimental STCC stub columns having active confinement were modeled using the ABAQUS software. The results obtained from the 3D model including the compressive strength at the initial peak point and failure point, as well as the axial and lateral stress-strain curves were compared with the experimental results to verify the accuracy of the 3D model. It was found that there existed a good agreement between them. A parametric study was conducted to investigate the effect of the concrete compressive strength, steel tube wall thickness, and pre-stressing level on the behavior of STCC columns with active confinement. The results indicated that increasing the concrete core's compressive strength leads to an increase in the compressive strength of the active composite column as well as its earlier failure. Furthermore, a reduction in the tube external diameter-to-wall thickness ratio affects the axial stress-strain curve and the confining pressure, while increasing the pre-stressing level has a negligible effect on the two.