• 콘크리트학회논문집
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• 제16권5호
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• pp.719-724
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• 2004

The ribs of deformed bars can split the cover concrete by wedging action or shear off the concrete in front of the ribs. As slip of deformed bars increases, the rib face angle is flattened by the crushed concrete wedge, which reduces the rib face angle to a smaller bearing angle. The roles of bearing angle are explored to simulate this observation. Analytical expressions to determine bond strength for splitting and pullout failure are derived, where the bearing angle is a key variable. As the bearing angle is reduced, splitting strength decreases and shearing strength increases. When splitting strength becomes larger than shearing strength, the concrete key is supposed to be sheared off and the bearing angle is reduced with decreasing the splitting strength. As bars slip, bearing angle decreases continually so that splitting bond strength is maintained to be less than shearing bond strength. The bearing angle is found to play a key role in controlling the bond failure and determination of bond strength of ribbed reinforcing steel in concrete structures.

• Earthquakes and Structures
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• 제9권6호
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• pp.1233-1250
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• 2015

The behavior of reinforced concrete (RC) columns made from high strength materials was investigated experimentally. Six high-strength concrete specimen columns (1:4 scale), which included three with high-strength transverse reinforcing bars and three with normal-strength transverse reinforcement, were tested under double curvature bending load. The effects of yielding strength and ratio of transverse reinforcement on the cracking patterns, hysteretic response, shear strength, ductility, strength reduction, energy dissipation and strain of reinforcement were studied. The test results indicated that all specimens failed in splitting failure, and specimens with high-strength transverse reinforcement exhibited better seismic performance than those with normal-strength transverse reinforcement. It also demonstrated that the strength of high-strength lateral reinforcing bars was fully utilized at the ultimate displacements. Shear strength formula of short concrete columns, which experienced a splitting failure, was proposed based on the Chinese concrete code. To enhance the applicability of the model, it was corroborated with 47 short concrete columns selected from the literature available. The results indicated that, the proposed method can give better predictions of shear strength for short columns that experienced a splitting failure than other shear strength models of ACI 318 and Chinese concrete codes.

• 한국도로학회논문집
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• 제9권4호
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• pp.205-213
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• 2007

본 연구에서는 포장용 콘크리트의 강도실험을 통해 강도간의 상관관계식을 도출하는 것을 목적으로 하였다. 강도로서 재령별 압축강도, 휨강도, 할렬인장강도와 탄성계수를 측정하였다. 배합변수는 조골재(화강암, 석회암, 사암), 세골재(자연사, 세척사, 부순모래) 및 단위시멘트량(315-375kg)을 변수로 하였다. 전체적으로 골재나 단위시멘트량보다는 재령에 의해 전형적인 강도곡선을 따라 뚜렷하게 변화함을 보여준다. 이러한 강도결과를 바탕으로 휨강도와 압축강도, 할렬인장강도와 압축강도, 탄성계수와 압축강도, 할렬인장강도와 휨강도의 상관관계를 분석한 결과 휨강도와 압축강도, 탄성계수와 압축강도는 기존의 관례대로 제곱근(n=0.5)의 상관관계식이 잘 맞음을 알 수 있었다. 할렬인장강도와 휨강도는 선형의 상관관계식으로 표현하였고, 할렬인장강도와 압축강도는 n=0.87의 지수승을 사용한 경우가 가장 적합한 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.173-178
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• 1993

In order to quantify the effect of transverse reinforcement on the bond splitting behavior of reinforcement monotonic loading tests of 8 slmply beams were carried out. The reinforcing details and material properties were so determined that the bond splitting failure proceded the shear and flexural failure. A bond splitting strength derived from the experimental data and it accounts for following parameters: 1) Concrete Strength 2) Transverse reinforcement ratio and shape 3) Thickness of concrete cover 4)Deformation of reinforcement

• Advances in concrete construction
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• 제10권1호
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• pp.81-92
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• 2020

Flexural and splitting strength behavior of conventional concrete can significantly be improved by incorporating the fibers in it. A significant number of research studies have been conducted on various types of fibers and their influence on the tensile capacity of concrete. However, as an important property, tensile capacity of fiber reinforced concrete (FRC) is not modelled properly. Therefore, this paper intends to formulate a model based on experiments that show the relationship between the fiber properties such as the aspect ratio (length/diameter), fiber content, compressive strength, flexural strength and splitting strength of FRC. For the purpose of modeling, various FRC mixes only with steel fiber are adopted from the existing research papers. Automated neural network search (ANS) is then developed and used to investigate the effect of input parameters such as fiber content, aspect ratio and compressive strength to the output parameters of flexural and splitting strength of FRC. It is found that the ANS model can be used to predict the flexural and splitting strength of FRC in a sensible precision.

• Advances in concrete construction
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• 제2권4호
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• pp.301-308
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• 2014

The present research work is on the effect of sawdust ash (SDA) on the mechanical strengths of self compacting concrete (SCC) using naphthalene sulfonate (NS) as a plasticizer. Experiments on compressive, flexural and splitting tensile strengths are conducted and the data analyzed using the Minitab 15 software. The results showed that SDA can defer the reaction of cement hydration and prolong the setting times of cement paste. This was very much pronounced on the flexural and splitting tensile strengths at 90 days of curing which are 36 % and 33 % higher than the control strengths, respectively. The study has proposed strength relations of mortar compressive strength with the flexural and splitting tensile strengths and these are, 5 and 7 times respectively. The flexural strength is 1.5 times that of the splitting tensile. Finally, linear models were developed on these relationships.

• 한국방재학회 논문집
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• 제11권2호
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• pp.23-29
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• 2011

본 연구는 거친 표면을 갖는 GFRP 보강근의 쪼갬에 의한 부착파괴 거동과 파괴강도를 인발실험을 통해 규명하였다. 실험변수로서, 보강근의 직경, 콘크리트 피복 및 콘크리트 압축강도에 대하여 실험을 수행하였으며, 동일한 변수에 대하여 5개의 실험 결과를 평균하여 실험에 대한 오차를 최소화 하였다. 또한 쪼갬에 의한 부착파괴거동을 인발력과 변위결과로부터 고찰하였다. 쪼갬부착파괴강도 결과는 여러 연구자가 제안한 이형철근 및 FRP 보강근의 쪼갬부착파괴강도 평가모델식과 비교하였다. 분석결과, 거친표면을 갖는 GFRP 보강근의 쪼갬부착파괴강도는 Harajli 등(1995)이 제안한 모델을 이용하여 가장 근사하게 평가할 수 있는 것으로 나타났다.

• Computers and Concrete
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• 제3권6호
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• pp.389-400
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• 2006

This paper presents the investigations towards developing a better understanding on the contribution of steel fibers on the tensile strength of high-performance fiber reinforced concrete (HPFRC). An extensive experimentation was carried out with w/cm ratios ranging from 0.25 to 0.40 and fiber content ranging from zero to 1.5 percent with an aspect ratio of 80. For 32 concrete mixes, flexural and splitting tensile strengths were determined at 28 days. The influence of fiber content in terms of fiber reinforcing index on the flexural and splitting tensile strengths of HPFRC is presented. Based on the test results, mathematical models were developed using statistical methods to predict 28-day flexural and splitting tensile strengths of HPFRC for a wide range of w/cm ratios. The expressions, being developed with strength ratios and not with absolute values of strengths and are applicable to wide range of w/cm ratio and different sizes/shapes of specimens. Relationship between flexural and splitting tensile strengths has been developed using regression analysis and absolute variation of strength values obtained was within 3.85 percent. To examine the validity of the proposed model, the experimental results of previous researchers were compared with the values predicted by the model.

• 한국농공학회논문집
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• 제47권4호
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• pp.25-32
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• 2005

This study was performed to evaluate the strength properties of polymer concrete using recycled aggre-gate. The compressive strength, splitting tensile strength, flexural strength and pulse velocity of polymer concrete were decreased with increasing the content of recycled aggregate. At the curing age of 7days, the compressive strength was $80.5\~88.3$ MPa, the splitting tensile strength was $9.1\~10.6$ MPa, the flexural strength was $19.2\~21.5$ MPa and the pulse velocity was $3,931\~4,041$ m/s, respectively. Also, the compressive strength, splitting tensile strength, flexural strength and pulse velocity of concrete using recycled fine aggregate were higher than that of the silica sand. Therefore, these recycled aggregate polymer concretes were estimated for high strength concrete without major problem.

• 한국구조물진단유지관리공학회 논문집
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• 제21권6호
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• pp.206-215
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• 2017

이 연구에서는 고강도 콘크리트의 역학적 특성을 파악하기 위한 실험연구를 수행하였다. 80~120 MPa 범위의 압축강도를 갖는 고강도 콘크리트를 대상으로 실험연구를 수행하였다. 물-결합재비의 압축강도에 대한 영향, 시간에 따른 압축강도의 발현 및 양생조건의 압축강도에 대한 영향을 분석하였다. 또한, 양생조건에 따른 콘크리트의 탄성계수, 쪼갬인장강도 및 파괴계수 특성을 파악하였다. 탄성계수, 쪼갬인장강도 및 파괴계수의 실험결과와 기존설계코드에 의한 예측결과를 비교하였다. 콘크리트구조기준의 탄성계수 제안식은 실험값을 합리적으로 예측한다. 반면에, 콘크리트구조기준은 파괴계수 실험값을 과소평가하고 있다. ACI 363R의 쪼갬인장강도와 파괴계수 예측값과 실험값은 잘 일치하고 있다. 따라서, ACI 363R의 쪼갬인장강도와 파괴계수 예측식은 120 MPa까지의 고강도 콘크리트에 효과적으로 활용될 수 있다.