• 한국지진공학회논문집
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• 제18권5호
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• pp.221-230
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• 2014

The purpose of this study is to investigate the seismic performance of hollow RC bridge columns with reinforcement details for material quantity reduction. The proposed reinforcement details provide economy, are rational and shorthen the construction periods. The accuracy and objectivity of the assessment process can be enhanced by using a sophisticated nonlinear finite element analysis program. Solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor (HHT) algorithm. The adopted numerical method gives a realistic prediction of seismic performance throughout the input ground motions for several test specimens investigated. As a result, the proposed reinforcement details for material quantity reduction develop equal performance to that required for existing reinforcement details.

• 한국지진공학회논문집
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• 제7권3호
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• pp.79-88
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• 2003

1992년 내진규정 도입이전에 설계시공된 공용중의 철근콘크리트 교각은 대체로 소성힌지구간에 겹침이음 시공되었다. 본연구는 형상비 2.5의 철근콘크리트 교각실험체의 내진 연성도 평가를 위한 실험적 연구이다. 실험에 사용된 6기의 실험체는 횡방향 구속력, 주철근의 겹침이음 그리고 섬유보강을 변수로 가지고 있다. 이 실험체는 한국도로공사가 개발한 인공지진동을 사용하여 유사동적실험을 수행하여 지진이력을 주었으며, 유사동적실험 후에는 일정한 축력, P＝0.1 $f_{ck}$ $A_{g}$을 유지하면서 변위제어방식으로 유사정적실험을 실시하여 잔류내진성능을 평가하였다. 실험 결과 소성힌지구간에 겹침이음 된 RC 교각이 낮은 연성에서 파괴에 도달하였다. 이는 주철근 겹침이음이 주철근의 충분한 연성발달을 저하시킨 결과라 할 수 있다. 또한, 섬유보강된 실험체는 ？강성과 변위연성도의 현저한 개선능력을 보였다..

• Computers and Concrete
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• 제17권3호
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• pp.387-406
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• 2016

Confined transverse reinforcement was arranged in a plastic hinge region to resist the lateral load that increased the lateral confinement effect in the bridge substructure. Columns increased the seismic performance through securing stiffness and ductility. The calculation method of transverse reinforcements at plastic hinges is reported in the AASHTO-LRFD specification. This specification was only proposed for solid reinforced concrete (RC) columns. Therefore, if this specification is applied for another column as composite column besides the solid RC column, the column cannot be properly evaluated. The application of this specification is particularly limited for composite hollow RC columns. The composite hollow RC column consists of transverse, longitudinal reinforcements, cover concrete, core concrete, and an inner tube inserted in the hollow face. It increases the ductility, strength, and stiffness in composite hollow RC columns. This paper proposes a modified equation for economics and rational design through investigation of displacement ductility when applying the existing specifications at the composite hollow RC column. Moreover, a parametric study was performed to evaluate the detailed behavior. Using these results, a calculation method of economic transverse reinforcements is proposed.

• Structural Engineering and Mechanics
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• 제25권1호
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• pp.75-89
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• 2007

Post-earthquake reconnaissance and experimental research indicate that squat reinforced concrete (RC) columns in existing buildings or bridge piers are vulnerable to non-ductile shear failure. Recently, several experimental studies were conducted to investigate upgrading the shear resistance capacity of such columns in order to modify their failure mode to ductile one. Among these upgrading methods is the use of fibre-reinforced polymer (FRP) jackets. One of the preferred analytical tools to simulate the response of frame structures to earthquake loading is the lumped plasticity macromodels due to their computational efficiency and reasonable accuracy. In these models, the columns' nonlinear response is lumped at its ends. The most important input data for such type of models is the element's lateral force-displacement backbone curve. The objective of this study is to verify an analytical method to predict the lateral force-displacement ductility relationship of axially and laterally loaded rectangular RC squat columns retrofitted with FRP composites. The predicted relationship showed good accuracy when compared with tests available in the literature.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.505-511
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• 2003

Experimental investigation was conducted into the flexure/shear-critical behavior of earthquake-damaged reinforced concrete columns with lap splicing of longitudinal reinforcement in the plastic hinge region. Six test specimens in the aspect ratio of 2,5 were made with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes of which magnitude could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P=$0.1f_{ck}A_g. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that RC bridge piers with lap-spliced longitudinal steels in the plastic hinge region appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility, and strain energy ductility.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.194-199
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• 2001

Lap splice in plastic hinge region is inevitable because of due to constructional joint between footing and column. R/C Circular columns with lap-splice in plastic hinge region are widely used in Korean highway bridges. In addition, these columns which constructed before the seismic design code have a number of structural deficiencies. It is, however, believed that there are not many experimental research works for nonlinear behavior of these columns subjected to earthquake motions. The object of this research is to evaluate the seismic performance of existing circular reinforced concrete bridge piers by the Quasi-static test. Existing reinforced concrete bridge piers were moderate seismically designed in accordance with the conventional provisions of Korea Highway Design Specification. This study has been performed to verify the effect of lap spliced longitudinal steel, confinement steel type and confinement steel ratio far the seismic behavior of reinforced concrete bridge piers. Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as displacement ductility, energy absorption, strength degradation etc.

• 콘크리트학회지
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• 제19권5호
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• pp.24-34
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• 2007

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.111-116
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• 2002

The flexural ductility capacity of reinforced concrete columns can be expressed either in terms of curvature ductility or displacement ductility. To evaluate ductility capacity of reinforced concrete columns, analytical models and a non-linear analysis program, NARCC have been developed, which is applicable to the RC columns subjected to seismic loading. The analytical results by using computer program NARCC are in good agreement with the test results. In order to develop relationships between the curvature ductility and the displacement ductility, the analysis for total 21,600 RC circular columns using the computer program NARCC have been carried out for parametric studies. Based on the results from the parametric studies, a correlation equation between the curvature ductility and the displacement ductility was developed.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 춘계 학술발표회 논문집
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• pp.195-202
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• 2002

Lap splices of longitudinal reinforcement steels were practically located in the potential plastic hinge region of most bridge columns that were constructed before the 1992 seismic design provision of Roadway Bridge Design Specification in Korea. The objective of this research is to evaluate the seismic performance of shear-critical reinforced concrete(RC) bridge piers with poor detailing of the starter bars in the plastic hinge region, and to develop the enhancement scheme of their seismic capacity by retrofitting with fiber composites. Seven test specimens in the aspect ratio of 2.5 were made with three confinement ratios and two types of lap splices. Quasi-static test was conducted in a displacement-controlled test mode. A significant reduction of displacement ductility ratios were observed for test columns with lap splices of longitudinal steels.

• 콘크리트학회논문집
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• 제15권5호
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• pp.715-725
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• 2003

본 연구는 철근콘크리트 교각에 대한 새로운 내진설계법을 개발하기 위한 연구의 일환으로서, 지진하중을 받는 철근콘크리트 교각의 연성도와 심부구속철근량의 상관관계를 분석하고 설계식을 제시함을 목적으로 한다. 이를 위하여, 반복하중을 받는 철근콘크리트 기둥의 횡하중-변위 포락곡선 실험결과를 비교적 정확하게 예측하며, 특히 변형능력 및 연성도에 대하여는 실험결과에 비하여 안전측의 결과를 제공하는 비선형해석 프로그램 [NARCE]를 이용하였다. 해석의 대상 교각으로는, 단면지름, 형상비, 콘크리트 강도, 축방향철근 항복강도, 심부구속철근 항복강도, 축방향철근비, 축력비, 심부구속철근비 등을 주요변수로 하여 총 7,200개의 철근콘크리트 나선철근 기둥 모델을 채택하였다. 해석결과 자료를 대상으로 상관관계를 분석하여 소요연성도에 따른 심부구속철근량의 새로운 설계식을 제안하였으며, 이 식은 연성도에 기초한 철근콘크리트 교각의 새로운 내진설계법에 적용될 수 있을 것이다.