• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.315-320
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• 2003

Two different strength types of plain concrete plate specimens (200$\times$200$\times$60mm) were tested under different biaxial load combinations. The specimens were subjected to biaxial combinations covering the three regions of compression-compression, compression-tension, and tension-tension. The loading platens with Teflon pads were used to reduce a confining effect in boundary surface between the concrete specimen and the solid platen. The principal deformations in the specimens were recorded, and the failure modes along with each stress ratio were examined. Based on the strength data, the failure envelops were developed for each type of plain concrete. The biaxial stress-strain responses of concrete plate specimens for three biaxial loading regions were also plotted. The test data indicated that the strength of concrete under biaxial compression ($f_2 / f_1$$_1$=-1/-1) is about 17 percent larger than under uniaxial compression.

• 대한토목학회논문집
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• 제30권2A호
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• pp.185-191
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• 2010

콘크리트 구조물의 사용성과 내구성 저하의 원인이 되는 균열은 응력의 크기, 응력구배 및 기타 구조적 재료적 원인 등에 의하여 발생하기 때문에 콘크리트의 균열강도를 정확히 예측하기는 매우 어렵다. 특히 판구조의 경우 기존의 일축휨강도에 의한 균열평가가 실제 구조물의 균열강도와 상이할 수 있다. 본 연구에서는 이축휨인장강도 평가에 적합한 시험체 제원을 적용하여 일축과 이축휨강도 특성을 비교, 평가하였다. 실험결과 골재의 크기 및 실험체 크기의 증가에 따라 일축 및 이축휨강도 모두 강도가 저하되는 것으로 나타났다. 일축휨강도에 비하여 이축휨강도가 일축휨강도의 39.5~99.2%로서 전반적으로 낮은 강도를 갖는 것으로 평가되었으며, 특히 20 mm 골재를 사용한 경우에는 76%정도로 고찰되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제7권2호
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• pp.239-246
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• 2003

In the PCA Load Contour Method, the biaxial bending design coefficient of columns(${\beta}$) is based on the equivalent rectangular stress block (RSB). And coefficient of ${\beta}$ estimates the reinforcement index to be a influencing parameter on biaxial moment strength of RC columns without considering the arbitrary condition of bar arrangement. The experimental results of high strength concrete (HSC) columns subjected to combined axial load and biaxial bending moment were compared to the analysis results of RSB method. As result, the accuracy of RSB method is still acceptable for HSC columns and, as the reinforcement is placed densely in each corner of column section, the ${\beta}$ is decreased.

• 콘크리트학회논문집
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• 제20권2호
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• pp.139-146
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• 2008

본 연구에서는 콘크리트의 이축 휨인장 특성을 일축 휨인장 특성과 실험적으로 비교, 분석하였다. 이를 위하여 일축 휨인장강도는 현재 많이 사용되고 있는 콘크리트 휨강도 실헙 방법을 사용하여 측정하였으며, 이축 휨강도의 경우는 지광습 외, Zi and Oh에 의해 제안된 새로운 이축 휨강도 실험 방법을 사용하였다. 골재의 크기에 따른 휨파괴강도 변화를 분석하기 위하여 세 가지 크기의 실험체를 제작하였다. 또한 통계적 특성 분석을 위하여 각 변수별로 32개의 실험체를 제작하여 실험을 수행하였다. 실험 결과 평균 이축 휨파괴강도가 일축의 경우보다 20% 정도 큰 것으로 나타났으나, COV의 경우에는 이축의 경우가 18% 큰 것으로 해석되었다. 이는 이축 휨균열 확률이 일축 보다 클 수도 있음을 의미한다.

• Computers and Concrete
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• 제16권2호
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• pp.209-222
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• 2015

This paper presents results of biaxial compressive tests and strength criterion on two replacement percentages of recycled coarse aggregate (RPRCA) by mass for plain structural recycled aggregate concrete (RAC) at all kinds of stress ratios. The failure mode characteristic of specimens and the direction of the cracks were observed and described. The two principally static strengths in the corresponding stress state were measured. The influence of the stress ratios on the biaxial strengths of RAC was also analyzed. The experimental results showed that the ratios of the biaxial compressive strength ${\sigma}_{3f}$ to the corresponding uniaxial compressive strength $f_c$ for the two RAC are higher than that of the conventional concrete (CC), and dependent on the replacement percentages of recycled coarse aggregate, stress states and stress ratios; however, the differences of tensile-compressive ratios for the two RAC and CC are smaller. On this basis, a new failure criterion with the stress ratios is proposed for plain RAC under biaxial compressive stress states. It provides the experimental and theoretical foundations for strength analysis of RAC structures subject to complex loads.

• 대한치과기공학회지
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• 제30권1호
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• pp.41-47
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• 2008

This study was to evaluate the biaxial flexural strength of zirconia ceramics after glass-infiltration on zirconia core. The zirconia specimens were made with diameter-15mm, thickness-0.6mm using zirconia block which divided into 1) sintered group, 2) heat - treated group, 3) Glass - infiltrated group and experimented fracture strength by each 10 specimens in experimental group. The biaxial flexural test was performed at crosshead speed of 0.1${\beta}\;{\AE}$ min. The experiment result average fracture strength was shown 541.0${\beta}\acute{A}$ in sintered group and glass-infiltrated group as 662.2${\beta}\acute{A}$ river of 22.4% rise appear. Weibull coefficient sintered group is 3.462 and glass-infiltrated group improved believability about fracture strength from melting permeation processing of glass by 4.716.

• 한국세라믹학회지
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• 제37권7호
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• pp.713-720
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• 2000

The biaxial fracture behavior of alumina ceramics was studied using ball-on-3-ball test. The polished surfaces of alumina specimens were indented at 0mm, 1mm, 2mm, 3mm apart from the center of the specimen along path A, passing between the two supporting balls from the center of the specimen, and along path B, passing above the three supporting balls from the center of the specimen. The fracture strength of the indented specimens was measured using the ball-on-3-ball test, a kind of biaxial strength test. The fracture strength increased with increasing the distance from the center to indented position. The fracture strength of the specimen indented along path B was higher than that of the specimens indented along path A. It was presented that the fracture caused by tangential stress rather than radial stress when the indented positions are 1mm and 2mm from the center of the specimen. This phenomenon was in good agreement with FEM analysis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.35-40
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• 2001

The exact solution of strength of reinforced concrete RC columns subjected to axial compression combined with biaxial bending needs trial and adjustment procedure to find the depth and inclination of the neutral axis. Thus, approximate methods of analysis and design for biaxial bending are used in practice. Load contour interprets the relation of biaxial bending and equivalent uniaxial bending by u factor which is related to material properties and column shapes. The purpose of this study is to investigate the behavior of high strength RC columns subjected to the combined axial compression and biaxial bending. Fifteen test specimens with dimensions of 200mm$\times$200mm and 4-Dl3 longitudinal steel were examined. The variable of the test is compressive strength of concrete (350, 585, 650kgf/$cm^{2}$), compression load ratio (0.2$P_{o}}$, 0.35$P_{o}}$, 0.5$P_{o}}$), and inclination of loading ($\theta$=0, 22.5, $45^{\circ}$). Test results of coefficient $\alpha$ depending on the compressive strength of concrete are compared with ACI code.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.41-46
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• 2001

The main objective of this study is to provide data on high strength concrete columns subjected to axial load and biaxial bending. For the design of biaxial bending, the approximate method (Bresler load contour method, PCA load contour method) is presented in ACI code. The present study investigate whether the methods are valid in high strength concrete and compare analysis results(by FEM method) with experimental results. Also, this study examines whether statics method and failure surface equation(by Hsu) are adequate.

• Structural Engineering and Mechanics
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• 제39권3호
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• pp.303-316
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• 2011

Experimental tests have shown that glass exhibits very different strengths when tested under biaxial and uniaxial conditions. This paper presents a study on the effects of biaxial stresses on the notional ultimate strength of glass. The study involved applying the theory of elasticity and finite element analysis of the Griffith flaw in the micro scale. The strain intensity at the tip of the critical flaw is used as the main criterion for defining the limit state of fracture in glass. A simple and robust relationship between the maximum principal stress and the uniaxial stress to cause failure of the same glass specimen has been developed. The relationship has been used for evaluating the strength values of both new and old annealed glass panels. The characteristic strength values determined in accordance with the test results based on 5% of exceedance are compared with provisions in the ASTM standard.