• 대한치과보철학회지
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• 제39권6호
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• pp.589-598
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• 2001

The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured PMMA resin using glass fibers, have been suggested over the years. The aim of the present study was to investigate the effect of short glass fibers treated with silane coupling agent on the transverse strength of heat-polymerized PMMA denture base resin. To avoid fiber bunching and achieve even fiber distribution, glass fiber bundles were mixed with PMMA powder in conventional mixer whose blade was modified to be blunt. Composite of glass fiber($11{\mu}m$ diameter, 3mm & 6mm length, silane treated) and PMMA resin was made. Transverse strength and Young's modulus were estimated. Glass fibers were incorporated with 1%, 3%, 6% and 9% by weight. Plasticity and workability of dough was evaluated. Fracture surface of specimens was investigated by SEM. The results of this study were as follows 1. 6% and 9% incorporation of 3mm glass fibers in the PMMA resin enhanced the transverse strength of the test specimens(p<0.05). 2. 6% incorporation of 6mm glass fibers in the PMMA resin increased transverse strength, but 9% incorporation of it decreased transverse strength(p<0.05). 3. When more than 3% of 3mm glass fibers and more than 6% of 6mm glass fibers were incorporated, Young's modulus increased significantly(p<0.05). 4. Workability decreased gradually as the percentage of the fibers increased. 5. Workability decreased gradually as the length of the fibers increased. 6. In SEM and LM, there was no bunching of fibers and no shortening of fibers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.87-88
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• 2010

철근콘크리트 기둥은 횡보강철근으로 구속함으로써 부재의 강도 및 연성능력의 증진효과를 얻을 수 있다. 이에 횡보강철근으로 구속된 콘크리트의 응력-변형률 모델이 다양하게 제시되어왔다. 본 연구에서는 고강도 횡보강철근으로 구속한 원형실린더의 최대 횡구속 응력에 영향을 주는 요소를 파악하고 실험결과로부터 콘크리트와 횡보강철근 사이의 변형률을 분석하여 포아송비식을 제안하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.271-276
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• 2002

Existing design equations generally overestimate the shear strength of the circular transverse reinforcement. This is due to the simplification of the discrete distribution of the reinforcement to the continuous one and the inappropriate application of the classical truss model to the circular section, which is different in shear-resisting component from the rectangular section. The present study introduces a new model considering the starting point of the diagonal crack, the number of transverse reinforcing bars crossing the crack and the effective strength component of the transverse resistance. This model leads to a simple design equation which is derived using the linear regression method and is in agreement with the lower bound of exact strength curve.

• 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.

• 콘크리트학회논문집
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• 제14권3호
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• pp.365-372
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• 2002

본 연구는 700kgf/$\textrm{cm}^2$ 고강도 콘크리트에서 횡보강근 형태, 체적비 그리고 횡보강근 항복강도에 따른 고강도 콘크리트기둥의 거동을 규명하기 위한 실험연구이다. 기둥은 중심축내력의 30%에 해당하는 일정축력과 수평방향의 반복 휨모멘트를 받는다. 본 연구에서 사용된 변수는 횡보강근 체적비(Ps=1.58, 2.25%), 횡보강근 형태(hoop-type, cross-type, diagonal-type) 그리고 횡보강근 항복강도(fy=5,600, 7,950 kgf/$\textrm{cm}^2$)이다. 실험결과로 모든 기둥의 휨강도는 현행규준의 등가응력블럭에 근거하여 산정된 휨강도보다 낮게 나타났다. 횡보강근을 ACI 규준 요구량보다 42%증가시킨 기둥 시험체는 연성적인 거동을 보였다. 그리고, 본 연구에서 적용한 축력비 0.3 P/PO하에서 고강도급 횡보강근을 사용한 시험체의 연성이 저강도급 횡보강근을 사용한 시험체의 경우보다 같거나 다소 큰 경향을 보이고 있었다.

• 콘크리트학회논문집
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• 제28권4호
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• pp.419-426
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• 2016

이 연구에서는 다양한 콘크리트를 갖는 전단계면에서의 전단마찰거동에 대한 횡보강근 및 압축응력의 영향을 평가하였다. 12개 직접전단실험체로부터 균열진전, 전단하중-상대 미끄러짐 관계, 균열발생시 전단응력, 최대전단내력 및 횡보강근의 전단저항력 등이 측정되었다. 실험결과 동일 전단하중에서 상대 미끄러짐 제어에 대한 횡보강근 배근형상 및 콘크리트 압축강도의 영향은 미미하였다. 작용 압축응력의 증가와 함께 콘크리트의 전단전달력을 증가하는 반면, 횡보강근의 전단전달력은 감소하였는데, 횡보강근의 전단저항은 배근형태에 의해 영향을 받지 않았다. AASHTO-LRFD, Mattock 및 Hwang and Yang의 모델은 콘크리트의 전단마찰내력을 과소평가하였다. 반면, Hwang and Yang의 모델은 실험결과와의 비교에 대한 평균과 표준편차 값이 각각 1.02과 0.23으로서 기존 모델에 비해 다양한 변수의 영향을 적절히 고려하면서 콘크리트의 전단마찰내력을 잘 예측하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.505-508
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• 1999

To evaluate the strength of square reinforced concrete shot columns, thirty specimens were manufactured and tested under monotonically increasing concentric compression. The test parameters included the volumetric ratio of transverse reinforcement($\rho$h = 0.49~2.65), and concrete compressive strength (234, 437, 704 kgf/$\textrm{cm}^2$). Test results are shown that : (1) Behavior of high -strength concrete column is improved by providing increased volumetric ratio; and (2) ACI, Eq. is not proper to evaluate HSC short column strength.

• 한국지진공학회논문집
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• 제20권6호
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• pp.361-368
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• 2016

Coupling beams serve as primary source of energy dissipation in coupled shear wall systems during large earthquakes. However, the overestimation of the shear strength of diagonally reinforced coupling beams may be adverse effect on the seismic performance of coupled shear wall systems. In order to force coupling beams to properly work during earthquakes, coupling beams should be designed with accurate shear strength equations. The objective of this study is to propose the accurate shear strength equation for slender diagonally reinforced coupling beams. For this purpose, experimental tests were conducted using three diagonally reinforced coupling specimens with different amount of transverse reinforcement under reversed cyclic loads to evaluate the hysteretic behavior of the specimens. The test results show that transverse reinforcement of slender diagonally reinforced coupling beam affects the maximum strength and drift ratio.

• Earthquakes and Structures
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• 제7권5호
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• pp.779-796
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• 2014

This experimental investigation was conducted to examine the behavior and response of high-strength material (HSM) reinforced concrete (RC) columns under combined high-axial and cyclic-increasing lateral loads. All the columns use high-strength concrete ($f_c{^{\prime}}$=100MPa) and high-yield strength steel ($f_y$=685MPa and $f_y$=785MPa) for both longitudinal and transverse reinforcements. A total of four full-scale HSM columns with amount of transverse reinforcement equal to 100% more than that required by earthquake resistant design provisions of ACI-318 were tested. The key differences among those four columns are the spacing and configuration of transverse reinforcements. Two different constant axial loads, i.e. 60% and 30% of column axial load capacity, were combined with cyclically-increasing lateral loads to impose reversed curvatures in the columns. Test results show that columns under 30% of axial load capacity behaved much more ductile and had higher lateral deformational capacity compared to columns under the 60% of axial load capacity. The columns using closer transverse reinforcement spacing have slightly higher ductility than columns with larger spacing.

• Earthquakes and Structures
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• 제12권2호
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• pp.201-211
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• 2017

This paper experimentally investigates the effect of yield strength of reinforcing bars and stirrups on the seismic performance of reinforced concrete (RC) circular piers. Reversed cyclic loading tests of nine-large scale specimens with longitudinal and transverse reinforcement of different yield strengths (varying between HRB335, HRB500E and HRB600 rebars) were conducted. The test parameters include the yield strength and amount of longitudinal and transverse reinforcement. The results indicate that the adoption of high-strength steel (HSS) reinforcement HRB500E and HRB600 (to replace HRB335) as longitudinal bars without reducing the steel area (i.e., equal volume replacement) is found to increase the moment resistance (as expected) and the total deformation capacity while reducing the residual displacement, ductility and energy dissipation capacity to some extent. Higher strength stirrups enhance the ductility and energy dissipation capacity of RC bridge piers. While the product of steel yield strength and reinforcement ratio ($f_y{\rho}_s$) is kept constant (i.e., equal strength replacement), the piers with higher yield strength longitudinal bars are found to achieve as good seismic performance as when lower strength bars are used. When higher yield strength transverse reinforcement is to be used to maintain equal strength, reducing bar diameter is found to be a better approach than increasing the tie spacing.