• Structural Engineering and Mechanics
• /
• 제33권2호
• /
• pp.137-158
• /
• 2009

This paper investigates the behavior of reinforced concrete (RC) circular columns under combined loading including torsion. The main variables considered in this study are the ratio of torsional moment to bending moment (T/M) and the level of detailing for moderate and high seismicity (low and high transverse reinforcement/spiral ratio). This paper presents the results of tests on seven columns subjected to cyclic bending and shear, cyclic torsion, and various levels of combined cyclic bending, shear, and torsion. Columns under combined loading were tested at T/M ratios of 0.2 and 0.4. These columns were reinforced with two spiral reinforcement ratios of 0.73% and 1.32%. Similarly, the columns subjected to pure torsion were tested with two spiral reinforcement ratios of 0.73% and 1.32%. This study examined the significance of proper detailing, and spiral reinforcement ratio and its effect on the torsional resistance under combined loading. The test results demonstrate that both the flexural and torsional capacities are decreased due to the effect of combined loading. Furthermore, they show a significant change in the failure mode and deformation characteristics depending on the spiral reinforcement ratio. The increase in spiral reinforcement ratio also led to significant improvement in strength and ductility.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.101-106
• /
• 2001

This paper presents experimental results for the confining characteristics of cylinder with center-hole and spiral reinforcements. The experiments have been conducted for the specimens with primary variables i.e., spiral reinforcement ratio and diameter of center-hole which affect the compressive strength and stress-strain relationship. Through this research, it was found that the compressive strength and ductility were increased with the ratio of spiral reinforcement because the lateral expansion of the concrete inside the spiral was restrained by the spiral, but dependent on the size of center-hole.

• Earthquakes and Structures
• /
• 제22권1호
• /
• pp.39-51
• /
• 2022

The axial compression behavior of nine self-compacting concrete columns confined with CFRP-PVC spirals was studied. Three parameters of spiral reinforcement spacing, spiral reinforcement diameter and height diameter ratio were studied. The test results show that the CFRP strip and PVC tube are destroyed first, and the spiral reinforcement and longitudinal reinforcement yield. The results show that with the increase of spiral reinforcement spacing, the peak bearing capacity decreases, but the ductility increases; with the increase of spiral reinforcement diameter, the peak bearing capacity increases, but has little effect on ductility, and the specimen with the ratio of height to diameter of 7.5 has the best mechanical properties. According to the reasonable constitutive relation of material, the finite element model of axial compression is established. Based on the verified finite element model, the stress mechanism is revealed. Finally, the composite constraint model and bearing capacity calculation method are proposed.

• 한국구조물진단유지관리공학회 논문집
• /
• 제21권6호
• /
• pp.1-9
• /
• 2017

원형 기둥의 나선철근은 축방향 철근의 위치 고정 및 좌굴방지와 코어콘크리트의 충분한 횡구속으로 기둥의 연성거동에 효과적인 역할을 한다. 각국은 기둥에 요구되는 연성을 확보하기 위하여 나선철근의 최소철근비를 제시하고 있다. ACI 318-14와 국내 콘크리트 구조설계 기준에서 제시하는 나선철근 최소철근비는 Richart et al.(1928)의 이론에 기초하여 개발되었으며 현재까지 사용되고 있다. 그러나 Richart et al.(1928)의 이론은 현대의 고강도 콘크리트, 고강도철근 그리고 나선철근의 배근조건 등의 영향을 고려하지 못한다. 이 연구에서는 나선철근으로 구속된 철근콘크리트 원형 기둥의 내력회복 및 연성증진에 요구되는 나선철근에 대한 수정 최소철근비 산정식을 제시한다. 수정 최소철근비 산정식은 콘크리트 압축강도, 나선철근 항복강도, 기둥의 단면적, 나선철근 배근간격, 나선철근 직경의 영향을 고려하고 있다. 이 논문에서는 재료강도 및 나선철근 최적비를 변수로 한 실험체의 일축 압축실험을 통하여 ACI 318-14에 제시하는 나선철근 최소철근비 산정식의 타당성을 검토하고, 그 결과를 토대로 나선철근 최소철근비 산정식의 수정방안을 고찰하였다.

• Steel and Composite Structures
• /
• 제24권1호
• /
• pp.1-13
• /
• 2017

In order to improve the deformation capacity of the high-strength concrete shear wall, five high-strength concrete shear wall specimens confined with high-strength rectangular spiral reinforcement (HRSR) possessing different parameters, were designed in this paper. One specimen was only adopted high-strength rectangular spiral hoops in embedded columns, the rest of the four specimens were used high-strength rectangular spiral hoops in embedded columns, and high-strength spiral horizontal distribution reinforcement were used in the wall body. Pseudo-static test were carried out on high-strength concrete shear wall specimens confined with HRSR, to study the influence of the factors of longitudinal reinforcement ratio, hoop reinforcement form and the spiral stirrups outer the wall on the failure modes, failure mechanism, ductility, hysteresis characteristics, stiffness degradation and energy dissipation capacity of the shear wall. Results showed that using HRSR as hoops and transverse reinforcements could restrain concrete, slow load carrying capacity degeneration, improve the load carrying capacity and ductility of shear walls; under the vertical force, seismic performance of the RC shear wall with high axial compression ratio can be significantly improved through plastic hinge area or the whole body of the shear wall equipped with outer HRSR.

• 한국공간구조학회논문집
• /
• 제17권1호
• /
• pp.59-67
• /
• 2017

In this study, load transfer tests based on KCI-PS101 were conducted to verify the performance of spiral anchorage zone reinforcement for banded post-tensioning (PT) monostrands. With results, the compressive strength of spiral reinforcement was increased by about 20% than that of specimens with two horizontal steel bars and 8% than that of U-shaped bars. Advanced spiral reinforcement for corner increases compressive strength and can resist the spalling forces or fall-out effect at the corner by shear. The ratio of maximum load to amount of steel of the spiral reinforcement is about twice than that of U-shaped reinforcement. With increase of compressive strength capacity and improvement of constructability, the spiral reinforcement is considered to have advantages of promoting the performance of PT anchorage zone compared to conventional methods.

• 한국구조물진단유지관리공학회 논문집
• /
• 제15권1호
• /
• pp.103-111
• /
• 2011

이 연구에서는 나선철근으로 횡구속된 순환골재 콘크리트의 구조적 거동을 평가하였다. 주요 실험변수는 골재의 종류와 나선철근의 철근비로 계획하였다. 총 18체의 실험체를 제작하였으며, 실험체의 직경과 높이는 각각 150mm와 300mm이었다. 실험체는 사용된 굵은 골재의 종류에 따라 2가지로 구분할 수 있으며, 나선철근의 철근비는 0%에서 1.75%까지 변화하도록 계획하였다. 실험체의 축방향 및 횡방향 변형을 측정하기 위하여, 6개의 LVDT를 실험체에 부착하였다. 또한 나선철근의 변형률을 측정하기 위하여 스트레인 게이지를 120도 간격으로 나선철근에 부착하였다. 실험결과로부터, 나선철근으로 횡구속된 순환 골재 콘크리트의 구조 성능은 나선철근의 철근비와 관계없이 천연골재 콘크리트와 서로 유사함을 확인하였다.

• Earthquakes and Structures
• /
• 제17권5호
• /
• pp.435-445
• /
• 2019

The collapses of curved bridges are mainly caused by the damaged columns, subjected to the combined loadings of axial load, shear force, flexural moment and torsional moment, under earthquakes. However, these combined loadings have not been fully investigated. This paper firstly investigated the mechanical characteristics of the bending-torsion coupling effects, based on the seismic response spectrum analysis of 24 curved bridge models. And then 9 reinforced concrete (RC) and circular column specimens were tested, by changing the bending-tortion ratio (M/T), axial compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratio, respectively. The results show that the bending-torsion coupling effects of piers are more significant, along with the decrease of girder curvature and the increase of pier height. The M/T ratio ranges from 6 to 15 for common cases, and influences the crack distribution, plastic zone and hysteretic curve of piers. And these seismic characteristics are also influenced by the compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratios of piers.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
• /
• pp.306-311
• /
• 1994

Experimental research was carried out to investigate the confinement effect of concrete specimens confined by interlocking spirals subjected to the concentric axial compressive load. Main variables are the compressive strength of concrete with 2 levels(normal and high strength), the spacing of the spiral reinforcement, the yield strength of the spiral reinforcement with 2 levels and 4 different interlocking lengths. For the same volumetric ratio, the use of interlocking spirals is not as effective as the single spirals, provided that the spirals have the same diameter.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2001년도 춘계학술대회 논문집
• /
• pp.241-248
• /
• 2001

The ductility of circular hollow reinforced concrete columns with one layer of longitudinal and spiral reinforcement placed near the outside face of the section and the steel tube placed on the inside face of the section is investigated. Such hollow sections are confined through the wall thickness since the steel tube is placed. The results of analytical moment-curvature analyses for such hollow sections are compared with those for the circular section with the sane diameter. In this study, moment-curvature analyses are conducted with Mandel's confined concrete stress-strain relationship in which the effect of confinement is to increase the compression strength and ultimate strain of concrete. The moment-curvature analyses confirmed that the ductility is primarily influenced on the ultimate strain. The variables influenced on the ultimate strain is the ratio and yield strength of confining reinforcement and the compression strength for confined concrete. From this ultimate strain - the transverse reinforcement ratio relationship, the transverse reinforcement ratio for circular hollow reinforced columns with confinement is proposed. The proposed transverse reinforcement ratio is confirmed by experimental results.