• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.96-98
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• 2003

The evolution of texture and microstructure during continuous confined strip shearing (CCSS) in aluminum 3003 alloy sheets was investigated. The tools of CCSS based on the equal channel angular pressing (ECAP) were designed to provide a constant shear deformation of the order of 0.5 per pass while preserving the original sheet shape. FEM results indicated that the shear formation is not homogeneous throughout the sample thickness, in particular at the surface layers. A randomization of textures took place during the CCSS deformation. Observations by TEM and EBSD revealed the formation of sub-micrometer sized grains after CCSS.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.923-928
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• 2002

Experimental and analytical study were conducted to develop the confined model of reinforced high strength concrete tied columns subjected to monotonically increasing concentric axial compression. Twenty-one large-scale columns(260$\times$260$\times$1200mm) used high strength concrete of 50 and 85MPa were fabricated to simulate an actual structural members size. Test results indicated that gains of strength and ductility of high strength concrete columns could be increased, if efficient arrangements and volumetric ratios of transverse reinforcements were provided. The proposed model satisfactorily predicted the experimental stress-strain curves for high strength concrete up to 100MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.557-562
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• 2002

This paper describes the results of spalling by fire prevention of high performance concrete confining with metal-lath and containing PP fiber. According to test results, all the specimens without PP fiber shows entire failure after exposed to fire, while the other specimens confined with metal-lath has somewhat better spatting prevention performance than plain concrete specimens, which only show surface scale spatting combination of PP fiber with confinement of metal-lath leads to favorable spatting resistance. As PP fiber contents and thickness of metal-lath which is confined at concrete specimens increase, residual strength after exposed to fire shows to be increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.835-840
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• 2002

The purpose of this study is to analyze the reinforcement effect of the RC compressive member confined with carbon fiber sheets and to suggest better transverse confinement coefficient(k$_1$) than one's in the existing analysis equations. Showing amounts of CPS in terms of ratio of transverse reinforcement to cross-section, it comes to be possible to calculate the objective and quantitative reinforcement amounts and to estimate the overlapping length of CFS that can influence on all its confinement effect. The previous parameters were compared using the existing experimental test data, then analyzed for the merits and demerits of existing parameters through the coefficient of correlation(R). The proposed parameters were derived in such a way that established parameters and their combination were obtained from the analytical study and then determined by regression analysis using the previous test data.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.556-563
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• 2005

Recently, it is used to join an building to an underground shopping-area in urban. When we construct Seo-Cho Complex building which is in Seoul, we also construct an underground passage to the Gangnam underground shopping-area. But it is difficult to excavate in the downtown area, because excavations induce traffic jam and public discontent. Considering safety, a confined area, settlements, we decided to use DSM(Divided Shield Method) which is based on messer shield. This paper will produce our experience and the results provide a useful guide in a connection tunnel

• Computers and Concrete
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• v.14 no.2
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• pp.163-174
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• 2014

Damping as a material property plays an important role in decreasing dynamic response of structures. However, very little is known about the evaluation and application of the actual damping of Fiber Reinforced Polymer Confined Reinforced Concrete (FRP-C RC) material which is widely adopted in civil engineering at present. This paper first proposes a stress-dependent damping model for FRP-C RC material using a validated Finite Element Model (FEM), then based on this damping-stress relation, an iterative scheme is developed for the computations of the non-linear damping and dynamic response of FRP-C RC columns at any given harmonic exciting frequency. Numerical results show that at resonance, a considerable increase of the loss factor of the FRP-C RC columns effectively reduces the dynamic response of the columns, and the columns with lower concrete strength, FRP volume ratio and axial compression ratio or higher longitudinal reinforcement ratio have stronger damping values, and can relatively reduce the resonant response.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.111-135
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• 2013

An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.113-122
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• 2002

The purpose of this study is to verify that the modified Lagrangian model can predict temperature, flow and scalar fields in the high temperature recirculation region of swirling confined diffusion flame. In the meantime numerical results from EBU and Equilibrium PDF models as well as experimental results are compared with those from the modified Lagrangian model. Adaption of three different turbulent models were accompanied with this procedure. Look-up table of the ignition characteristic time scale which is one of important factors of the Lagrangian model was referred to the 11-step reduced mechanism. Eventually, results with the Lagrangian model show a good accordance with experimental results, which shows the validity of this model. Results from Chen's model differ from those of the others. Numerical results of ${\widetilde{k}$ show significant deviation from experimental results for three models.

• Structural Engineering and Mechanics
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• v.16 no.1
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• pp.63-81
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• 2003

This paper describes experimental and theoretical investigations on the behaviour of thin walled composite (TWC) filled columns under eccentric loading conditions. Details of the experimental investigation including description of the test columns, testing arrangements, failure modes, strain characteristics, load-deformation responses and effects of various geometric and material parameters are presented. The current paper also introduces the use and effect of lightweight Volcanic Pumice Concrete (VPC) in TWC columns. Analytical models for the design of columns under eccentric loading conditions have been developed taking into consideration the effect of confined concrete. The performance of design equations is validated through experimental results. The proposed design models are found to produce better results compared with available design procedures and Code based formulations. A computer program is developed to generate the interaction diagrams based on the proposed design equations that can be used for design purposes.

• Journal of the Korean Society of Combustion
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• v.1 no.1
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• pp.41-49
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• 1996

Effects of ambient geometry on the liftoff characteristics are experimentally studied for nonpremixed turbulent jet flames. To clarify the inconsistency of the nozzle diameter effect on the liftoff height, the ambiences of finite and infinite domains are studied. For nonpremixed turbulent jet issuing from a straight nozzle to infinite domain, flame liftoff height increases linearly with nozzle exit mean velocity and is independent of nozzle diameter. With the circular plate installed on the upstream of nozzle exit, flame liftoff height is lower with plate at jet exit than without, but flame liftoff characteristics are similar to the case of infinite domain. For the confined jet having axisymmetric wall boundary, the ratio of the liftoff height and nozzle diameter is proportional to the nozzle exit mean velocity demonstrating the effect of the nozzle diameter on the liftoff height. The liftoff height increases with decreasing outer axisymmetric wall diameter. At blowout conditions, the blowout velocity decreases with decreasing outer axisymmetric wall diameter and liftoff heights at blowout are approximately 50 times of nozzle diameter.