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

• 한국구조물진단유지관리공학회 논문집
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• 제16권4호
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• pp.89-98
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• 2012

이 연구에서는 콘크리트 압축강도에 따른 고강도 나선철근의 횡구속 성능을 평가하고자 하였다. 총 24체의 실린더형 콘크리트 실험체($150{\times}300mm$)를 제작하고 단조 압축하중 실험을 수행하였다. 주요 실험변수는 나선철근의 항복강도와 콘크리트 압축강도로 계획하였다. 나선철근의 항복강도에 따른 횡구속 효과를 효과적으로 평가하기 위하여 나선철근의 외경을 실험체 직경과 동일하게 계획하였다. 실험결과, 나선철근의 횡구속 성능은 나선철근의 항복강도가 증가할수록 그리고 콘크리트 압축강도가 낮아질수록 증가하였다. 또한 기존 해석모델을 이용하여 실험체의 응력-축변형률 관계를 예측한 결과, 해석결과는 나선철근의 항복강도와 콘크리트 압축강도가 증가할수록 정확성이 떨어지는 것으로 확인되었다.

• Steel and Composite Structures
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• 제31권6호
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• pp.559-573
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• 2019

Spiral spacing effect on axial compressive behavior of reinforced concrete filled steel tube (RCFST) stub column is experimentally investigated in this paper. A total of twenty specimens including sixteen square RCFST columns and four benchmarked conventional square concrete filled steel tube (CFST) columns are fabricated and tested. Test variables include spiral spacing (spiral ratio) and concrete strength. The failure modes, load versus displacement curves, compressive rigidity, axial compressive strength, and ductility of the specimens are obtained and analyzed. Especially, the effect of spiral spacing on axial compressive strength and ductility is investigated and discussed in detail. Test results show that heavily arranged spirals considerably increase the ultimate compressive strength but lightly arranged spirals have no obvious effect on the ultimate strength. In practical design, the effect of spirals on RCFST column strength should be considered only when spirals are heavily arranged. Spiral spacing has a considerable effect on increasing the post-peak ductility of RCFST columns. Decreasing of the spiral spacing considerably increases the post-peak ductility of the RCFSTs. When the concrete strength increases, ultimate strength increases but the ductility decreases, due to the brittleness of the higher strength concrete. Arranging spirals, even with a rather small amount of spirals, is an economical and easy solution for improving the ductility of RCFST columns with high-strength concrete. Ultimate compressive strengths of the columns are calculated according to the codes EC4 (2004), GB 50936 (2014), AIJ (2008), and ACI 318 (2014). The ultimate strength of RCFST stub columns can be most precisely evaluated using standard GB 50936 (2014) considering the effect of spiral confinement on core concrete.

• 콘크리트학회논문집
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• 제17권5호
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• pp.835-842
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• 2005

This paper presents an experimental investigation of bond-strengthening hooks as a new method to increase bond strength along flexural reinforcing bars in reinforced concrete (RC) beams and columns. The RC members, which consisted of 1,300 MPa-class spirals as shear reinforcement, often suffered from bond splitting failure. The proposed method attempts to increase confining stiffness around the flexural bars by placing U-shaped hooks and to prevent premature bond splitting failure. Twelve specimens with varied amounts and sizes of the hooks were prepared to verify the strengthening effectiveness under monotonic and cyclic loading conditions. The test result indicated that the hooks increased the bond strength along the flexural bars although the strengthening effectiveness was limited by effective reinforcement ratio $P_{be}$. This limit is determined by size of stress-transmitting zones of concrete around anchors of the hooks. Anchors of the hooks are recommended to be longer than twelve times the hook diameter and inserted deeper than a quarter of the member depth (D/4). Proposed design equations provide modest estimates of the shear strengths.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.280-285
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• 1995

In order to predict the behavior of column confined with spirals, the accurate estimation of confining stress by spiral is very important, Thus a number of models have been proposed for calculating the confining stress by spiral. However, in these equations, it was not considered the effects of the difference of mechanical characteristics related to the application of high strength concrete and spiral in structures. In this study, a model equation for calculation of the confining stress by spiral was proposed based on the test results investigated here. The proposed equation included the effects of concrete strength, spacing and yield strength of spirals

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.1-8
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• 2012

이 연구는 횡보강근의 배근형상에 따른 횡구속된 콘크리트의 성능을 평가하였다. 주요 변수는 횡보강근의 항복강도와 횡보강근의 배근형상으로 하였다. 총 27개의 직사각형 형태의 실험체를 제작하였으며, 단조 집중하중상태에서 실험을 수행하였다. 이 연구에서는 배근형상을 사각형인 R-type, 원형인 C-type 및 이 연구에서 제안한 사각과 팔각이 혼합된 O-type으로 계획하였다. 실험결과, 이 연구에서 제안한 배근형상이 사각형 나선철근과 비교하여 뛰어난 연성능력을 가짐을 확인할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.15-16
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• 2009

본 연구에서는 콘크리트 실린더에 대한 고강도 횡보강근의 구속 효과를 검토하였다. 이 실험에서는 콘크리트의 강도, 횡보강근의 항복강도 및 간격을 변수로 하여 고강도 횡보강근이 콘크리트 거동에 미치는 영향을 평가하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.577-578
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• 2009

For cases where the column concrete strength exceeds 1.4 times the slab concrete strength, the KCI Code requires that either: puddled high-strength concrete(HSC) be used in the slab, or the use of vertical dowels and spirals through the joint, or the use of an effective concrete strength in the joint. This paper studies on the third strategy. A prediction model of the effective concrete strength for interior columns was proposed using an analogy of brick and mortar in brick masonry. The proposed prediction model is verified by comparison with experimental results and various design equations.

• 천문학회보
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• 제36권1호
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• pp.55.1-55.1
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• 2011

We investigate dynamical evolution of gas in barred galaxies using a high-resolution, grid-based hydrodynamic simulations on two-dimensional cylindrical geometry. Non-axisymmetric gravitational potential of the bar is represented by the Ferrers ellipsoids independent of time. Previous studies on this subject used either particle approaches or treated the bar potential in an incorrect way. The gaseous medium is assumed to be infinitesimally-thin, isothermal, unmagnetized, and initially uniform. To study the effects of various environments on the gas evolution, we vary the gas sound speed as well as the mass of a SMBH located at the center of a galaxy. An introduction of the bar potential produces bar substructure including a pair of dust lane shocks, a nuclear ring, and nuclear spirals. The sound speed affects the position and strength of the bar substructure significantly. As the sound speed increases, the dust lane shocks tend to move closer to the bar major axis, resulting in a smaller-size nuclear ring at the galactocentric radius of about 1 kpc. Nuclear spirals that develop inside a nuclear ring can persist only when either sound speed is low or in the presence of a SMBH; they would otherwise be destroyed by the ring material with eccentric orbits. The mass inflow rates of gas toward the galactic center is also found to be proportional to the sound speed. We find that the sound speed should be 15 km/s or larger if the mass inflow rate is to explain nuclear activities in Seyfert galaxies.