• 콘크리트학회논문집
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• 제16권1호
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• pp.111-124
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• 2004

축방향철근의 연결상세에 따라 7개 그룹 총 21개의 원형나선철근 기둥 시험체를 제작하여 준정적 실험을 수행하였다. 축방향철근 연결상세(단일철근, 겹침이음 및 기계적연결), 심부구속철근비, 축력비 등을 주요 실험변수로 채택하였으며 실험결과 축방향철근 연결상세에 따라 다른 파괴거동을 나타내었고, 내진성능에서도 차이를 나타내었다. 축방향철근이 겹침이음된 시험체의 실험결과, 모든 축방향철근이 겹침이음된 시험체는 내진성능이 상당히 저하되는 것으로 나타났으나, 축방향철근의 $50\%$가 겹침이음된 시험체의 경우 제한적이지만 한정적인 연성능력을 나타내었다. 또한, 축방향철근을 커플러를 사용하여 기계적으로 연결한 시험체는 축방향철근이 단일철근으로 구성된 시험체와 유사한 파괴거동 및 강도저감거동을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.77-78
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• 2010

이 연구에서는 고강도 나선철근으로 횡구속된 콘크리트 압축강도의 영향을 평가하였다. 주요 실험 변수는 콘크리트의 압축강도, 나선철근의 항복강도 및 단면형상으로 하였다. 실험체는 총 48체로 원형과 각형 단면을 가지며, 단조 집중하중 상태에서 실험을 수행하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.151-156
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• 2003

On the basis of the philosophy that "the compressive axial load capacity after spalling of shell concrete should be maintained as that before spalling" by applying the confinement model of high strength concrete proposed in the previous proceeding paper and equivalent lateral confining pressure considering configurations of transverse reinforcement, the amounts of transverse reinforcement from the compressive capacity design method about high strength reinforced concrete tied columns can be calculated through the formula proposed in this paper. The proposed design equation of transverse steel amounts for high strength reinforced concrete tied columns was quite agreeable with the test results of HSC tied columns conducted by other researchers as well as author.as author.

• Steel and Composite Structures
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• 제48권5호
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• pp.565-582
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• 2023

The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (>5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift >3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.692-695
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• 2004

Seismic performance of reinforced concrete(RC) column bent piers to bidirectional seismic loadings was investigated experimentally. RC column bent piers represent one of the most popular forms of piers used in highway bridges. Further to series of previous experimental researches for the performance of single bridge columns subjected to seismic loadings, four column bent piers were constructed in 400 mm diameter and 2,000 mm height. Each pier has two circular supporting columns. These piers were tested under lateral load reversals with axial load of $0.1f_{ck}A_g$. Bidirectional lateral loadings were applied. The test parameters included: different transverse reinforcement contents and lap-spliced longitudinal reinforcing steels. Test results indicate that lap-splices of longitudinal reinforcing steels have significantly influence on hysteretic response of column bent piers. Column capacity changed with the level of transverse confinement, and bidirectional repeated loadings induced more strength and stiffness degradation than unidirectional repeated loading.

• Structural Engineering and Mechanics
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• 제23권5호
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• pp.469-486
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• 2006

The main objective of this study was to investigate the seismic behavior of damaged reinforced concrete frames rehabilitated by introducing cast in place reinforced concrete infills. Four bare and five infilled frames were constructed and tested. Each specimen consisted of two (twin) 1/3-scale, one-bay and two-story reinforced concrete frames. Test specimens were tested under reversed-cyclic lateral loading until considerable damage occurred. RC infills were then introduced to the damaged specimens. One bare specimen was infilled without being subjected to any damage. All infilled frames were then tested under reversed-cyclic lateral loading until failure. While some of the test frames were detailed properly according to the current Turkish seismic code, others were built with the common deficiencies observed in existing residential buildings. The variables investigated were the effects of the damage level and deficiencies in the bare frame on the seismic behavior of the infilled frame. The deficiencies in the frame were; low concrete strength, inadequate confinement at member ends, 90 degree hooks in column and beam ties and inadequate length of lapped splices in column longitudinal bars made above the floor levels. Test results revealed that both the lateral strength and lateral stiffness increased significantly with the introduction of reinforced concrete infills even when the frame had the deficiencies mentioned above. The deficiency which affected the behavior of infilled frames most adversely was the presence of lap splices in column longitudinal reinforcement.

• 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.

• 콘크리트학회논문집
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• 제15권2호
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• pp.263-272
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• 2003

내진상세가 적용되지 않은 RC중공구형단면 교각의 지진 시 거동특성 및 내진성능을 파악하기 위하여 축소모델 실험을 수행하였다. 축소모델은 교각의 소성힌지영역내에 동일한 위치에서 모든 주철근이 겹침이음된 모델과 연속된 철근을 사용하여 겹침이음을 없앤 모델로 설계하였다. 실험은 축력이 재하된 상태에서 준정적 반복하중을 재하하였다. 실험결과 겸침이음모델은 주철근의 겹침이음부에서의 부착파괴가 발생하였지만 비교적 큰 연성거동을 나타냈으며 연속철근을 사용한 모델은 전형적인 휨파괴 특성과 매우 큰 연성거동을 보였다.

• 한국구조물진단유지관리공학회 논문집
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• 제16권1호
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• pp.131-139
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• 2012

콘크리트 기둥에 사용되는 횡방향 철근은 압축콘크리트 파괴 시 횡방향 벌어짐을 구속하여 폭렬을 줄일 수 있고 콘크리트의 연성을 증가시키는 데에 유효하며 강도손실 보상효과가 있다. 이를 규명하기 위하여, 띠철근의 간격과 나선철근을 변수로 한 실험체를 제작하여 가열실험을 수행하였다. 이 때 전기로 온도를 $300^{\circ}C$, $600^{\circ}C$ 및 $800^{\circ}C$로 설정하여 $13.33^{\circ}C$/분의 속도로 가열하고 2시간동안 그 온도를 유지시켰다. 냉각된 실험체에 대해 응력-변형률 곡선을 구하기 위한 압축실험을 수행하고, 이로부터 탄성계수, 잔존 내력 및 변형률 등의 잔존 역학적 특성을 분석하였다. 실험결과 횡방향 철근비가 높을수록 철근이 콘크리트를 구속하여 다축 응력 상태가 되기 때문에 고온을 받은 콘크리트의 잔존 최대응력이 커지고 더욱 큰 변형을 발휘할 수 있는 있는 것을 확인하였다. 이울러, 콘크리트의 잔존 탄성계수의 감소율은 횡방향 철근의 구속효과로 작아지는 것으로 분석되었다.

• 콘크리트학회논문집
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• 제24권6호
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• pp.705-714
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• 2012

프리캐스트 중공 사각형 철근콘크리트 교각에 대하여 준정적 실험을 수행하여 내진성능을 검증하였다. 기둥 실험체는 프리캐스트 세그먼트를 접합하고 나서, 미리 배치된 쉬스관에 축방향 철근을 연결 없이 연속으로 배치한 후 모르타르로 그라우팅하는 방법으로 제작하였다. 실험의 주요변수는 형상비, 축방향 철근비, 횡방향 철근량, 프리캐스트 세그먼트의 접합위치이다. 기둥 실험체의 형상비는 4.5와 2.5, 축방향 철근비는 1.15%와 3.07%로 각각 두 가지의 값을 가진다. 횡방향 철근량은 도로교설계기준에서 규정하고 있는 완전연성 설계에 요구되는 양의 99%, 55%, 50%, 27%로 배근되었다. 소성힌지 구역에서의 프리캐스트 세그먼트 접합위치는 기둥 하단에서 기둥단면 두께의 0.5배와 1.0배인 위치로 하였다. 실험 결과로서 균열 및 파괴모드, 축력-휨 강도, 하중-변위 포락선, 변위연성도를 분석하였으며, 도로교설계기준의 연성도 내진설계법을 적용하였을 때의 안전율을 분석하였다. 기둥 실험체는 축방향 철근이 모르타르와 쉬스관에 의하여 구속되고, 쉬스관이 횡방향 철근으로 구속되는 구조로 인하여 큰 변위까지 축방향 철근의 좌굴이 지연되어 연성도가 크게 나타났다.