• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.785-793
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• 2007

An electrochemical transient response technique was used to study the corrosion of reinforcing steel bar in the concrete. Analysis of the transient electrochemical potential response in a corrosion interface to an applied current has enabled the separate components that make up the measured transient response to be isolated. These components display a range of resistances and capacitances, dependent on the corrosion conditions of the reinforcing steel, which may be attributed to the corrosion process, to effects within the concrete cover or to film effects on the surface of the concrete. In this technique, the corrosion rate was evaluated by summing all of the resistances in the separate components to obtain an aggregated corrosion resistance. However, it is possible that not all resistances identified are associated with the corrosion process. The results obtained show that the corrosion rates are significant dependent on the assignment of the separate components to either corrosion or to other processes. The assignment of resistive components associated with the corrosion rate can be clearly identified by taking a series of the transient measurement at different lateral distances from the corroding reinforcing steel. An inappropriate selection of measurement time however may result in an additional resistance, which is not associated with corrosion, being included or part of the resistance associated with corrosion being left out.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.283-292
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• 2005

This paper predicts premature failure load of reinforced concrete beams by epoxy-boned partially steel plates. A parametric study is conducted to estimate premature failure load of beams such as with or without stirrups, unplated length ratio, steel and reinforcement ratio, shear span to depth ratio of reinforcement beam. By results of finite element analysis, it turned out that the unplated length played a dominant role in partially plated beams but reinforcement ratio and shear span to depth ratio effected the premature failure load. The approximate expression with regard to combined design variables is compared with experimental results. It shows closely agreement.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.685-693
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• 2012

The yield strength of shear reinforcement is restricted in the present design codes. In this study, the possibility of the yield strength increase in shear reinforcement is evaluated according to ACI318-08, EC2-02 and CSA-04 by comparing the experimental and calculated results. Three cases were used to analyze the shear strength of the beam. One had no limitation in the yield strength of shear reinforcement, another had restriction on the yield strength of shear reinforcement, and the other had a restriction on the yield strength of shear reinforcement and the shear reinforcement ratio. The study results showed that the case with unlimited shear reinforcement yield strength predicted the test result better than other two cases. Even though the rebar yield strength higher than the strength required in present code was applied to existing shear design equation, the result was reasonable. Therefore, the design equation seemed to be appropriate even if the high-strength shear reinforcement is used in practice based on the existing shear design method.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.719-727
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• 2009

The requirements of the maximum shear reinforcement in the EC2-02 and CSA-04, which are developed based on the truss model, are quite different to those in the ACI-08 code and AIJ-99 code, which are empirical equations. The ACI 318-08, CSA-04, and EC2-02 codes provide an expression for the maximum amount of shear reinforcement ratio as a function of the concrete compressive strength, but Japanese code does not take the influence of the concrete compressive strength into account. For high strength concrete, the maximum amount of shear reinforcement calculated by the EC2-02 and CSA-04 is much greater than that calculated by the ACI 318-08. Ten RC beams having various shear reinforcement ratios were tested and their corresponding shear stress-shear strain curves and failure modes were compared to the predicted ones obtained by the current design codes.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.165-165
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• 2011

내진 설계규정이 적용되기 이전에 시공되어 사용 중인 교량의 경우 지진 발생시 교각의 파괴 또는 구조적 피해는 교량 전체 시스템의 붕괴를 초래하므로 지진하중에 대하여 피해를 최소화해야 한다. 이를 위해 내진설계규정이 적용되기 이전의 교량 또는 지진취약지역으로 분류된 곳의 교량, 사회적 중요도가 높은 교량에 대해 교각의 내진성능보강을 실시하고 있다. 2007년 말 국토해양부가 관리하고 있는 11,940개 교량 중 지진 발생시 피해가 우려되는 1,342개(일반국도 682개, 고속국도 600개) 교량에 대해 2006년부터 내진보강이 착수되었고 2009년에는 확대 추진하여 일반국도 80개교, 고속국도 100개교에 대한 보강을 실시하였다. 이와 같이 확대 추진되고 있는 정책에 반해, 내진보강 기술 및 제품이 부족하고 새로운 내진보강재 개발이 불가피해지고 있는 것이 현실이다. 소성영역에서의 횡방향 철근은 지진 시 종방향 철근의 좌굴과 콘크리트의 압축강도저하를 방지하며, 전단보강철근으로도 중요한 역할을 하여 교각의 전단강도를 증가시킨다. 그러나 이러한 횡방향 철근은 초기 설계에 의한 시공이 종료된 후 기존의 성능을 증가시키기 위하여 철근량을 증가하거나 단면의 변화를 주기에는 매우 어려운 일이다. 따라서 내진성능을 위한 단면력 증가를 위하여 다양한 재료의 보강재와 형식이 사용되고 있다. 본 연구에서는 원형교각 모델의 구조해석을 이용해 내진성능평가를 선행한 후 실험체를 제작, Helical Bar를 보강하여 준정적 실험을 통해 내진보강성능을 평가하였다. 압축설계강도 $f_{ck}=240kgf/cm^2$를 기준으로 교량등급 2등교인 일반적인 도로교의 1/4축소모형을 설계, 기초부는 $1,200{\times}600{\times}600$ (mm)으로 철근과 콘크리트로 구성하였으며, 기둥부는 직경 400mm, 높이 1,250mm 크기의 철근콘크리트 원형 교각 실험체를 제작하였다. 제작된 실험체는 총 3개로, 분류는 무보강 일반 실험체, Helical Bar 직경에 따른 분류, 보강간격에 따른 분류로 나누어진다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.289-292
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• 2008

In this study, we interpreted 20 story building by applying the modified modulus of elasticity considering the reinforcing steel proposed in previous literature, and analyzed the movement of the structure according to axial reinforcing steel ratio and lateral reinforcing steel volume ratio. Additionally, we tried to get the result similar to the actual movement considering the order of the construction by performing the analysis by construction stage. Finally, we tried to reduce the section of the column through the analysis considering the reinforcing steel of the column. When interpreting the 20 story building considering the reinforcing steel in the columns, we can reduce the column members up to 4.94% comparing to the general analysis. If we do the same for each construction stage, it is analyzed that we can reduce up to 19%.

• Land and Housing Review
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• v.12 no.4
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• pp.119-125
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• 2021

The study presents the ductility reinforcement effect of the RC bending member using the CFRP Grid as an experimental result. Experimental variables include a non-reinforced RC bending member (ORI), a bottom reinforced RC bending member (REB), and an RC bending member reinforced at the bottom and side (REBS). The experiment was carried out with four points bending test. As a result of the experiment, it was confirmed that the maximum bending strength increased by 17-20% through reinforcement. In addition, the ductility index calculation results confirmed that the ductility index of REB and REBS increased by 2 and 3 times, respectively, compared to the ORI.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.3-4
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• 2009

This study predicts the structural behavior of RC beams using high strength shear reinforcement and evaluates current design codes restricting the strength of shear reinforcement steel. Under the present design codes, the yield strength of shear reinforcement steel is restricted to 400MPa. In case that use high yield strength reinforcement steel, could incure heavily crack and deflection at the members of structure, and have not verified ductility capacity, fatigue resisting capacity, shear and torsion resisting capacity, anchoring capacity and seismic capacity. To this end, we evaluate structural behavior of reinforced concrete beams using high strength shear reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.18-26
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• 2012

Recently, research about Near-Surface-Mounted Rertofit (NSMR) method has been being widely performed as a method for retrofit of RC structure using FRP. This method requires additional work to make grooves during retrofit but makes it possible to improve retrofit effect and reduce the attack by environment. In this paper, the retrofit effect of NSMR method, especially the method using FRP plate instead of bar is investigated through experiment. Six RC beams were made and retrofitted using by FRP plate following the planned methods; Surface-Bonding Retrofit (SBR), NSMR without debonding region and NSMR with debonding region. Flexural capacity of all specimens was evaluated by beam test with simple support condition. As a result, NSMR method with FRP plate had more improved structural capacity than SBR method. The calculation process of ACI 440-2R can be used to predict the member retrofitted by NSMR with FRP plate with consideration on the three anchorage failure mechanism.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.649-656
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• 2013

Coupled shear walls can provide an efficient structural system to resist lateral force. However, the reinforcement detail for diagonally reinforced coupling beams required by ACI-318 often causes the difficulties in construction due to the reinforcement congestion and interference among reinforcement. This paper is to evaluate cyclic behavior of High-Performance Fiber-Reinforced Cement Composite (HPFRCC) coupling beams having reduced transverse reinforcement around the beam perimeter. Experimental test was conducted using three specimens having a beam aspect ratio 2.0. Test results showed that HPFRCC coupling beams with half of transverse reinforcement required by ACI-318 provided similar energy dissipation capacities compared with the coupling beams having reinforcement satisfy the requirement of ACI-318.