• Magazine of the Korea Concrete Institute
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• v.5 no.1
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• pp.103-113
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• 1993

일반적으로 스터럽이 없는 철근콘크리트 보의 전단강도는 콘크리트 압축강도, 주철근비, 전단스팬비 및 보 유효깊이에 좌우된다는 것이 많은 연구를 통하여 밝혀지고 있다. 따라서, 본 연구에서는 고강도 콘크리트를 사용한 철근콘크리트 보의 거동 및 전단강도 특성을 분석하기 위하여 주철근비, 전단스팬비 및 보 유효깊이를 변수로 두고 총 22개의 단철근 보 실험체를 제작하여 실험을 수행하였다. 실험결과는 ACI규준식, Zsutty식 및 Bazant & Kim식의 예측값들과 함께 비교, 분석되었는데, ACI 규준식은 주철근비 및 전단스팬비의 효과를 과소평가할 뿐만 아니라 유효깊이가 915mm인 큰 보의 경우 안전측이 아니어서 이에 대한 고려가 필요할 것으로 판단된다. Zsutty식은 주철근비의 효과를 적절하게 평가하는 것으로 나타났으며, Bazant & Kim 식은 유효깊이 증가에 따른 전단강도 감소 경향을 잘 예측하는 것으로 나타났다. 또한, 다른 연구자들의 실험치와 비교, 분석해본 결과 주철근비 및 전단스팬비의 효과는 콘크리트 압축강도 수준에 따라 큰 변화가 없는 것으로 판단된다.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.187-197
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• 2010

The longitudinal reinforcement ratio for the performance-based design of columns was studied. Unlike the existing design codes using uniform minimum reinforcement ratio and effective stiffness for all columns, the longitudinal reinforcement ratio of columns was defined as the function of various design parameters. To evaluate the minimum reinforcement ratio, two conditions were considered: 1) prevention of passive yielding of compression re-bars due to the creep and shrinkage of concrete under sustained service loads; and 2) ultimate flexural strength greater than the cracking moment capacity to maintain the ductility of columns for earthquake design. In addition, the effective flexural stiffness of columns for structural analysis was determined according to the longitudinal reinforcement ratio. The design method addressing the three criteria was proposed. The proposed method was applied to a design example.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.292-299
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• 1998

In this study, the size effect in flexural and shear behaviors of reinforced concrete beams with stirrup has been studied. The specimens of different size with same longitudinal reinforcement ratio are tested. The major variables of test include the size(relative depth) of the members as well as the longitudinal reinforcement ratios. The nominal resistances in flexure and shear are obtained for various sizes and steel ratios. It is found from the present study that the size effect is also very pronounced for the flexural resistance in reinforced concrete structures. The prediction formulas for the size effect of reinforced concrete beams in flexure and shear are proposed. The proposed equations agree relatively well with experimental data. The present study will provide useful bases for more accurate analysis and design of reinforced concrete structures.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.749-757
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• 2006

Many losses of life and extensive damage of social infrastructures have occurred due to moderate and strong earthquakes all over the world. In this research various design parameters have been evaluated to develop a rational seismic design code of rectangular reinforced concrete(RC) bridge piers. It was confirmed from this study that the axial force ratio and longitudinal steel ratio were most influencing design parameters on the seismic displacement ductility from experimental results of 54 rectangular RC bridge piers, which were tested at domestic and foregin countries. However, these important parameters are not considered in the confinement steel ratio of Korea Highway Bridge Design Specification(KHBDS). The objective of this study is to propose a rational design provision for the transverse reinforcement of rectangular RC bridge piers. New confinement steel ratio is proposed by reflecting the effect of the axial force and longitudinal steel into the current code of KHBDS. furthermore, minimum transverse confinement steel ratio is also proposed to avoid a probable buckling of longitudinal reinforcing steels of RC bridge piers with a relatively low axial force. New practical code can alleviate the rebar congestion in the plastic hinge region of RC bridge pier, which contributes to construct RC bridge piers in a simple and economic way.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.775-784
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• 2005

In this research, major design factors have been evaluated for the establishment of the rational seismic design code of circular RC(reinforced concrete) bridge pier Previous experimental researches have drawn a conclusion that transverse confinement reinforcements have been excessively used for RC bridge piers in Korea. Thus, the objective of this study is to propose a rational design equation for transverse reinforcements of RC bridge piers in Korea which would be classified as a low or moderate seismic region. Newly proposed equation further considers the effect of the axial force ratio and the longitudinal steel ratio. Minimum transverse confinement steel ratio is also proposed to avoid probable buckling of the longitudinal reinforcing steels subjected to relatively low axial force. It is thought that these new codes seem to alleviate the rebar congestion in the plastic hinge region of RC bridge piers which contribute to the enhancement of constructibility and economization for RC bridge construction.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.71-76
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• 1994

Eight singly reinforced high strength concrete beams were tested to investigate their flexural behavior. The variable is tensile steel raio. The test results are presented in terms of load-deformation behavior, ductility indexes, and cracking patterns. The flexural strengths obtained experimentally are compapred to the analytical results, and good agreements are obtained. The flexural design provisions of the ACI Building Code are found to be adequate to predict the strength of reinforced high-strength concrete beams.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.131-136
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• 1992

Eight singly reinforced high strength concrete beams without web reinforcement were tested to investigate their behavior and to determine their ultimate shear capacities. In this study, the main variable was the ration of longitudinal reinforcement. Test results were compared with strength predicted by using ACI code, Zsutty's dquation and Bazant & Kim's equation. As the result, for the beams of low steel ratio, the margin of safety in ACI code may be disappeared. It was shown that Zsutty.s equation well predict the trend of the test data.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.457-458
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• 2009

Totally, 12 precast RC piers were constructed and tested to evaluate the seismic performance. Experimental variables of the specimens were confinement steel amount, longitudinal steel ratio, aspect ratio, segment connecting method. Only deformed bars were used for longitudinal steel to maximize economical efficiency.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.155-168
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• 1998

In this paper, the structural properties of the existing reinforced concrete(RC) piers are surveyed and the major factors influencing the member strength and deformation capacity are identified. Also a seismic evaluation procedure of RC piers is presented. The factors controlling the member strength are the applied axial load, the reinforcement ratio and yield strength of longitudinal rebar for flexural strength, and the transverse reinforcement for shear strength. Member deformation capacity largely depends on transverse reinforcement ratio and anchor detail, and splice location of longitudinal reinforcement. The above structural detail should be investigated for the detail seismic evaluation of RC piers. The most of existing RC piers have inadequate transverse reinforcement anchor details and the splices of longitudinal reinforcement in the pier bottom where plastic hinges are formed after yielding. Therefore the deformation capacity is not enough for the ductile flexural behavior of the RC piers. The presented evaluation procedure can be used for the rational decisions as to seismic retrofitting of the existing RC piers.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.73-82
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• 2000

본연구의 목적은 반복하중을 받는 철근콘크리트 교량 교각의 비선형 이력거동을 해석적으로 예측하는 것이다 이를 위해서 반복적인 횡하중이 작용하는 경우에 실험결과와 일치하는 교각의 하중-변위 이력곡선을 도출하고자 수정된 trilinar 이력거동모델을 이용하였다 철근과 콘크리트의 비선형 거동특성과 각 하중단계에 따른 교각의 중립축을 구하여 소성힌지부의 모멘트와 변형률을 구하고 반복하중하에서의 강성의 변화를 해석적으로 모형화하기 위하여 각기 다른 강성을 갖는 5가지 지선을 갖춘 형태의 이력거동모델식을 제안하였다 본 연구에서는 실험적으로 구한 하중-변위 이력곡선을 이용하여 축하중비 주철근비 및 구속철근비에 따른 강도감소지수와 강성감소지수의 영향을 회귀분석을 이용하여 일반식으로 제안하였다 새로운 이력거동 해석 모델을 프로그램 SARCF III에 적용함으로써 기존 철근콘크리트 교각에 강도 및 강성감소 현상을 정확하게 예측하였다