• Journal of the Korean Society of Industry Convergence
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• v.11 no.1
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• pp.35-40
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• 2008

Various characters of the concrete are greatly improved as the effect of the steel fiber. As the improvement effect of the steel fiber, the increment in flexural strength, shear strength, toughness, and impact strength are remarkable, and tenacious concrete is obtained. This paper presents model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus and tensile strength were performed with self-made cylindrical specimens of variable aspect ratios. This paper presents an analytical study on the behavior of a beam specimen with steel fiber reinforced concrete(SFRC). The effect of the SFRC on the crack pattern, failure mode and the flexural behavior of the structure were investigated. The analysis model based on the nonlinear layered finite element method was successfully able to find the necessary amount of steel fibers, tensile steels and beam section which can best approximate flexural strength and ductility of a given conventionally reinforced concrete beam.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.523-536
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• 2014

Before incorporating the earthquake-resistance design in design standard (1988) in South Korea, most of existing residential buildings were built without having lateral resistance capacity in addition to their structural peculiarity, such as exterior stair ways, exterior elevator room. For these reasons, the demands on retrofitting research for existing buildings arise recently and many retrofitting methods are proposed. These tasks are important to reduce the enormous economic loss and environmental issues. As the main purpose, this study was intended to examine the performance improvement in terms of ductility and strength in the wake of retrofitting and to suggest retrofitting details.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.159-163
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• 2006

The effects of annealing temperature and time on mechanical properties and microstructures were studied in cold drawn pearlitic steel wires containing 0.84wt% Si. Annealing was performed from $200^{\circ}C$ to $450^{\circ}C$ with different time of 30sec, 1min, 15min and 1hr. The increase of tensile strength at low temperature was related with strain ageing. The decrease of tensile strength at high annealing temperature was related with spherodization of cementite and the occurrence of recovery of the lamellar ferrite in the pearlite. The improvement of ductility was connected with spherodization of cementite plate in pearlite and recovery process by reduction of high dislocation density at short time annealing temperature of $400^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.377-380
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• 2006

HPFRCCs(High performance fiber reinforced cementitious composites) is a class of FRCCs(Fiber reinforced cementitious composites) exhibit multiple crack. Multiple crack lead to improvement in ductility, toughness, and deformation capacity under compressive and tensile stress. These properties of HPFRCCs are affected by type of fiber, water cement ratio, type of admixture and rate of substitution. Furthermore these influence dispersion of fiber, mixing performance and fluidity of mixture. In this paper, HPFRCCs made of steel cord and carbon fiber were tested with water cement ratio, type of admixture and rate of substitution to evaluate characteristics of mixing and flexural strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.167-168
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• 2009

The CFT structure is applied to newly developed CFTA girder because of improvement of ductility deformation, stiffness and internal force of structure owing to the interaction between steel tube and core concrete. CFTA girder is the structure which can reduce tensile stress due to external loads by using its arch shape and prestress force. This paper proposed constructional stage procedure and represented analytical technique considering constructional stage to investigate the safety against bridge collapse on construction and on operation.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.339-342
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• 2003

The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to deterioration of the lap-spliced longitudinal reinforcements without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP wrapping showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by quasi-static experiments.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.1
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• pp.1-6
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• 2013

The B2-ordered NiAl has attracted much attention as one of the candidates as a next generation high temperature material, because it has a high melting temperature, a low specific gravity and an excellent high temperature oxidation resistance. However, the application of NiAl to structural materials needs the improvement of its brittleness at room temperature. The study was carried out on the relation between several properties of NiAl and some variation of Ni content within NiAl phase, which means deviations from the stoichiometric composition. The main results were as follows; (i) Good ductility was obtained at the testing temperature more than 1073 K irrespective of Ni content. (ii) Increasing Ni content offered preferable tensile properties. (iii) Every NiAl with varying Ni contents showed the superior oxidation resistance.

• Journal of Korean Association for Spatial Structures
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• v.15 no.4
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• pp.91-98
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• 2015

This paper has proposed a reinforcing method for damaged RC columns with SRF sheets and Aramid rods. In order to verify the effectiveness and performance, two original columns and two reinforced columns with SRF sheets and Aramid rods were developed and tested under lateral cyclic displacement and a constant axial load. The test showed that the improvement of energy dissipation capacity was increased in terms of strength and ductility. In addition, an analytical modeling of the standard specimens was proposed using Response-2000 and ZeusNL program. The results of analytical and experimental studies for two standard columns were compared in terms of loading-displacement curve and energy dissipation capacity based on the nonlinear static analysis.

• Structural Engineering and Mechanics
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• v.43 no.5
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• pp.623-636
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• 2012

The aim of the current work is to describe the flexural behaviour of simply supported concrete beams with tension reinforcement spliced at mid-span. The parameters included in the study were the type of the concrete, the splice length and the configuration of the hooked splice. Fifteen beams were cast using an ordinary concrete mix and two fiber reinforced concrete mixes incorporating steel and polypropylene fibers. Each concrete mix was used to cast five beams with continuous, spliced and hooked spliced tension steel bars. A test beam was reinforced on the tension side with two 12 mm bars and the splice length was 20 and 40 times the bar diameter. The hooked bars were spliced along 20 times the bar diameter and provided with 45-degree and 90-degree hooks. The test results in terms of cracking and ultimate loads, cracking patterns, ductility, and failure modes are reported. The results demonstrated the consequences due to short splices and the improvement in the structural behaviour due to the use of hooks and the confinement provided by the steel and polypropylene fibers.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1041-1042
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• 2006

High heat-resistant Al-Fe-V-Si and Al-Fe-V-Si-X rapidly solidified powder metallurgy (RS P/M) alloys have been developed under well-controlled high purity argon gas atmosphere. The $Al_{90.49}Fe_{6.45}V_{0.68}Si_{2.38}$ (at. %) RS P/M alloy exhibited high elevated-temperature strength exceeding 300 MPa and good ductility with elongation of 6 % at 573 K. Reduction of $H_2O$ partical pressure in P/M processing atmosphere led to improvement in mechanical properties of the powder-consolidated alloys under elevated-temperature service conditions. Ti addition to the Al-Fe-V-Si conduced to enhancement of the strength at room temperature. The tensile yeild strength and ultimate strenght were 545 MPa and 722 MPa, respectively.