• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.931-936
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. Lap splicing is also permitted if hoops or spiral reinforcement are provided over the lap length in the current seismic design provision. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is the analytical prediction of nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is considered.

• Advances in concrete construction
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• 제9권1호
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• pp.83-92
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• 2020

The use of spliced reinforcing bars in sustainable concrete members to manage inadequate bars length is a common practical issue which is may be due to some limitations. The lap splicing means two bars overlapped in parallel with specified length called the splice length in order to provide the required bond between the two bars. The bond between sustainable concrete and spliced steel bars is another important issue. The normal strength sustainable concrete specimens of sizes 1700×150×150 mm with tension reinforcement lap spliced were selected according to testing device length limitations. These members were designed to fail in flexure in order to investigate the lap spliced tension bars effect. The selected lap spliced tension bars were of 10 mm size with smooth and deformed surfaces in order to investigate the surface nature accompanied with the splice nature. The sustainable concrete mechanical properties and mix workability were also studied. This study reveals that the effect of number of spliced bars on the response of beams reinforced with smooth bars is found to be more obvious than deformed one. Finite element modeling in three dimensions was carried out for the tested beams using ABAQUS software. A parametric study is carried out using finite elements on considering the following parameters, concrete compressive strength, load type and opening in cross section (hollow section) for weight reduction purposes.The laboratory and numerical results show good agreements in terms of ultimate load and deflection with an average difference of 10% and 15% in ultimate load and deflection respectively.

• 한국지진공학회논문집
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• 제7권5호
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• pp.25-35
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• 2003

소성힌지영역에 50%의 주철근 겹침이음을 갖는 교각의 거동특성을 파악하기 위하여 축소교각모형실험을 수행하였다. 모델의 단면형상은 사각단면으로 중공 및 중실단면으로 각각 1기씩 제작하였다. 주철근은 연속철근과 주철근지름(d$_{b}$)의 39배의 겹침이음을 갖는 철근을 교대로 배치하였다. 겹침이음에 의한 거동특성을 파악하기 위하여 횡철근에 의한 구속효과와 축력에 의한 영향은 배제하였다. 두 시험체 모두 전형적인 휨파괴 형태를 보였으며 비교적 연성적인 거동을 나타내었다. 이로부터 50%의 주철근 겹침이음이 성능기초 내진설계를 위한 주철근상세의 하나의 대안으로서 유효성이 있음을 확인하였다.

• Composites Research
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• 제26권2호
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• pp.135-140
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• 2013

이 연구에서는 이음부가 초고성능콘크리트 교량 바닥판의 정적 거동에 미치는 영향을 실험적으로 규명하고, 이음부 철근의 최소겹침이음길이를 제안하였다. 총 6개의 실험부재를 제작하였으며 4점 휨 실험에 의하여 성능을 평가하였다. 이음부는 UHPC의 높은 부착특성으로 인하여 단순하면서도 매우 효율적인 구조가 될 것으로 기대되는 철근겹침이음을 대상으로 하였다. 실험결과로부터 이음부의 설치에 의한 UHPC의 인장기여도 감소에 따라 약 30% 수준의 휨강도 감소가 발생되는 것으로 측정되었고, 150 mm 이상의 철근겹침이음길이를 확보하면 연속된 철근을 사용한 경우와 거의 유사한 강도와 연성을 확보할 수 있는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제15권6호
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• pp.92-99
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• 2011

초고성능콘크리트(Ultra High Performance Concrete, UHPC)는 높은 강도와 내구성을 가지는 우수한 구조재료이다. 이러한 새로운 재료의 활용 기술은 경량의 슬림한 구조로서 우수한 성능을 가지는 구조물의 건설을 실현할 수 있는 효과적인 방안으로 주목받고 있다. 이 연구는 하이브리드 사장교 적용을 위한 UHPC프리캐스트 바닥판 시스템 개발의 일부로서 정모멘트 구간에서 철근겹침이음 방식에 의하여 연결되는 이음부의 거동 특성을 실험적으로 규명하는데 주된 목적이 있다. 주요 실험변수는 철근겹침이음길이이며 실험변수의 영향을 검증하기 위하여 총 12개의 휨실험체를 제작하였고, 이에 대한 4점 휨재하실험을 수행하였다. 현행 도로교설계기준에서 철근겹침이음에 대한 최소길이 규정은 UHPC를 적용한 프리캐스트 바닥판 시스템에서는 매우 보수적인 규정임을 실험결과로부터 확인할 수 있었다.

• 한국지진공학회논문집
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• 제5권4호
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• pp.83-95
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• 2001

내진상세가 적용되지 않은 철근콘크리트 교각의 거동특성 및 내진성능을 살펴보기 위해서 축소교각모형실험을 수행하였다. 횡방향 철근이 심부를 구속할 만큼 충분히 배근되어 있지 않은 중심 원형 단면의 실교각을 대상으로 기초 상단의 소성 힌지 부위에서 겹침이음이 된 주철근을 사용했을 때와 연속철근을 사용했을 경우로 구분되도록 철근상세를 결정하였다. 이에 따라 3기의 축소교각시험체를 제작하여 수직방향 축하중을 가한 상태에서 준정적 반복하중을 재하하는 실험을 수행하였다. 실험결과를 통해서 겹침이음이 있는 교각시험체는 연성거동을 하지 않지만, 겹침이음이 없이 연속철근을 사용한 교각시험체는 어느 정도의 한정연성거동을 하는 것으로 분석되었다.

• Earthquakes and Structures
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• 제16권3호
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• pp.279-293
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• 2019

The overall seismic performance of existing pre 1960-70s reinforced concrete (RC) structures is significantly affected by the inadequate length of columns' lap-spliced reinforcement. Due to this crucial structural deficiency, the cyclic response is dominated by premature bond - slip failure, strength and stiffness degradation, poor energy dissipation capacity and low ductility. Recent earthquakes worldwide highlighted the importance of improving the load transfer mechanism between lap-spliced bars, while it was clearly demonstrated that the failure of lap splices may result in a devastating effect on structural integrity. Extensive experimental and analytical research was carried out herein, to evaluate the effectiveness and reliability of strengthening techniques applied to RC columns with lap-spliced reinforcement and also accurately predict the columns' response during an earthquake. Ten large scale cantilever column subassemblages, representative of columns found in existing pre 1970s RC structures, were constructed and strengthened by steel or RC jacketing. The enhanced specimens were imposed to earthquake-type loading and their lateral response was evaluated with respect to the hysteresis of two original and two control subassemblages. The main variables examined were the lap splice length, the steel jacket width and the amount of additional confinement offered by the jackets. Moreover, an analytical formulation proposed by Tsonos (2007a, 2019) was modified appropriately and applied to the lap splice region, to calculate shear stress developed in the concrete and predict if yielding of reinforcement is achieved. The accuracy of the analytical method was checked against experimental results from both the literature and the experimental work included herein.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.453-456
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• 2003

This research is to evaluate the seismic performance of reinforced concrete bridge piers with lap-spliced longitudinal reinforcement steels in the plastic hinge region, and to develop the enhancement scheme of their seismic capacity. Six circular columns of 0.6m diameter and 1.5m height were made with two confinement steel ratios. They were damaged under series of artificial earthquakes that could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under an axial load, P=$0.1f_{ck}A_{g}$, and residual seismic performance of damaged columns was evaluated. Test results show that RC bridge piers with lap-spliced longitudinal steels behaved with minor damage even under artificial earthquakes with 0.22g PGA, but failed at low ductility subjected to the subsequent quasi-static load test. This failure was due to the debonding of the lap splice. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region showed significant improvement both in flexural strength and displacement ductility.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.121-126
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• 2003

The objective of this research is to evaluate of seismic performance for reinforced concrete bridge piers with lap splices of longitudinal reinforcement steels using predicting of nonlinear hysteric behavior. For the purpose, enhanced analytical trilinear hystretic model has been proposed to simulate the force-displacement hysteretic curve of RC bridge piers under repeated reversal loads. The moment capacity and corresponding curvature in the plastic hinge have been determined, and the enhanced hysteretic behavior model by five different kinds of branches has been proposed for modeling the stiffness variation of RC section under cyclic loading. The strength and stiffness degradation index are introduced to compute the hysteretic curve for various confinement steel ratios, In addition, the modified curvature factor has been introduced to forecast of seismic performance of longitudinal steel lap spliced and retrofitted specimens. The results of this research will be useful to predict of seismic performance for longitudinal steel with lap spliced and its retrofitted specimens.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.255-262
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• 2003

In present Korea Highway Bridge Standards the lap splice of longitudinal bars in a potential plastic hinge region is allowed so that large amount of transverse rebar specified in high seismicity regions Is required to prevent brittle bond failure If the brittle failure effects can be completely removed from the conventional designed piers, the amount of transverse rebar will be reduced drastically. In this study scaled models with solid and hollow rectangular sections were tested to investigate the seismic behavior of RC piers with 50％ of lap-spliced longitudinal bars in plastic hinge regions. In the tests the typical flexural failure conducting a ductile behavior were observed in both models. It is shown that the 50％ of lap-spliced bars can be considered as a good alternative of seismic detailing for longitudinal bars.