• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.245-253
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• 2002

This study was focused on the effect of concrete strength and lateral ties of concrete columns using high-strength concrete. Thirty-six concrete columns with 20cm square cross-section were tested. Experimental parameters included the concrete strength, the distribution of longitudinal bars and the volumetric ratio, yield strength, spacing of lateral ties. From the experiments, we found that: 1) the increasing rate of the strength and ductility of concrete columns caused by confinement of lateral ties was decreasing, as the concrete strength increased. 2) The high volumetric ratio and the reduction of tie spacing had a tendency to enhance the strength and improve the ductility. 3) The high-strength concrete columns required high volumetric ratio of lateral ties to maintain the proper strength and ductility. It was observed that the current AIK design code to specify the maximum tie spacing of high-strength concrete columns led to the poor strength and ductility for seismic design.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.271-274
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• 2005

In this research, 13 RC slabs connected by hinged joints were tested. the new slab was connected to the existing slab by hinge joint injecting dowel bars between two slabs. Main parameters of the slabs were the spacing of the dowel bars (150mm, 300mm, and 450mm) and the locations of the longitudinal reinforcement of the old slab. The test results indicated that the joint strength of the RC test slabs having various types of dowel bars was about twice that calculated by the ACI 318-02 code. The locations of the longitudinal reinforcement of the old slab slightly increased the strength of the slabs connected by hinged joints.

• Computational Structural Engineering
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• v.4 no.1
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• pp.133-142
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• 1991

A mathematical hysteretic model has been developed to analytically reproduce the experimental hysteretic behavior of reinforced concrete members. This mode[2, 3] can simulate the nonlinear response of reinforced concrete members with sufficient accuacy, which are characterized by following important hysteretic behaviors: stiffness degradation, strength deterioration and shear effect. In order to illustrate the capabilities of the proposed mathematical model, numerical examples are presented with the reproduction of experimental hysteretic behavior of RC members and frames.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.243-254
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• 1997

최근들어 구조물의 노후화와 차량하중 등의 증가로 구조물의 손상이 커지고 있으며 보강의 필요성이 절실히 대두되고 있다. 강판보강공법은 강성의 확실한 증가와 내구성 등으로 인하여 그 동안 폭넓게 사용되어 오고 있으나 효율적 보강을 위한 공법과 이론이 아직까지도 정립되지 않은 상태이다. 따라서 본 연구의 목적은 그 동안의 실험결과를 중심으로 보강도니 철근콘크리트보의 파괴기구와 박리거동을 분석하고 이로부터 합리적인 박리하중 산정이론을 제한하는데 그 목적을 두고 있다. 보강된 강판의 길이와 두께 등의 영향을 고찰하고,기존의 이론을 분석하여 기존이론의 불합리한 점을 밝혔으며, 이들을 보완한 수정이론을 제시하엿다. Roberts의 이론은 강판의 두께가 증가함에 따라 오히려 박리하중이 약간 증가하고 있어 실제적인 실험거동과 차이가 나고 있다. 본 연구의 제안식은 실제 거동을 합리적으로 표현하고 있으며, 앞으로 보강설계에 유용한 자료가 될 것으로 기대되고 있다.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1416-1417
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• 2006

The increase of carbon contents in fly ashes accelerate the corrosion of steel embedded in ordinary portland cement mortar. Cement losses its identity of colour, when the % of carbon is increased. More than 60[%] area was rusted, when carbon content is increased beyond 8[%] for the exposure period of one year. Comparable corrosion rate with OPC was obtained up to 6[%] carbon level only. The tolerable limit of replacement for various admixed carbon system under aggressive alternate wetting and drying condition with 3[%] NaCl was found to be 6 to 8[%].

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.167-174
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• 2000

Ground penetrating radar(GPR) was applied for measuring depths, sizes and intervals of rebars embedded in concrete. A concrete wall was constructed for this study and a sand pool and a concrete block were used for simulation. Result of this study shows that GPR can be used for measuring rebar depths and intervals, even though it is limitary, but that measuring sizes is almost impossible. Simulation with the sand pool was helpful for research on the versatile rebar arrays though signal was not clear as real concrete wall. A concrete block with many cylindrical holes for inserting different sized rebars could not be used for simulator due to many unknown reflective waves. Antenna orientation must be perpendicular to rebars for large reflection signal.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.221-222
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• 2021

Bacterial self-healing concrete is known to improve the durability of concrete by preventing the propagation of microcracks. In the literature, bacteria prevent the corrosion of rebar by inhibiting water transfer through crack, but also can promote the corrosion by acting as an ion acceptor in the rust generation mechanism. Therefore in this study, the electrochemical analysis of bio-filmed rebar was conducted to explore the effects of the self-healing bacteria on the bare rebar without cement composite. As a result of the experiment contradicting trends for Ecorr and Icorr occurred and additional experiment will be conducted in various environments to collect data on the mechanism of corrosion of rebar by bacteria.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.187-188
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• 2023

In this study, the analysis of concrete cracks was conducted with a total of three variables: coating thickness, oxygen diffusion rate, and reinforced diameter of reinforced concrete structures. Cracks occurred after about 3, 4, and 6 years at the coating thickness of 30, 40, and 50mm when the coating thickness was used as a variable, and cracks occurred after about 4, 5, and 10 years at oxygen diffusivity of 2e-9, 2e-11, and 2e-12 (m²/s) when the oxygen diffusion rate was used as a variable. In the case of reinforcing bar diameters, cracks occurred after about 4, 3, and 2 years on the reinforcing bar diameters of D10, D19, and D25.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.143-150
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• 1994

Most widened bridges have been constructed by the joining-construction method that makes new and existmg bridges structurally a single structure. Since the joining-constructiori method has several problems in design and construction viewpoint, this study is conducted in order to investigate the flexural fatigue behavior of RC slabs, which are widened and influenced by traffic-induced vibration of existmg bridge during placing and curing of new concrete, with the prototype fatigue test. It was found that stress concentration at the jclmts anti slips between steel bar and concrete are occured. Hut, the general tx:havinrs are similar to the original state and joining-construction method using expansive concrete nut~gated the influence of the trafflc-induced vibration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.491-498
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• 2011

In this paper, extensive structural behavior and effects of design parameters of steel column-base plate connections under axial and lateral loads were investigated to improve structural details of CFT(Concrete Filled Steel Tube) pier foundation using commercial FE analysis program, ABAQUS. For this study, design criteria of pier foundation was analyzed and numerical study based on the experiment of previous study was conducted to verify analysis methods. The failure behavior and stress distribution of pier foundation were analyzed using the verified analysis method. Various design parameters(base plate, deformed bar, stiffness and sizes of column) were investigated to analyze effects of each design parameters in entire structure.