• 콘크리트학회논문집
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• 제12권4호
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• pp.23-30
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• 2000

The purpose of this paper is to study on the shear strength of high strength concrete beams with steel fibrous. In general, the shear strength of reinforced concrete beams is affected by the compressive strengths of concrete( c), the shear span-depth ratio(a/d), the longitudinal steel ratio($\rho$ $\omega$), and shear reinforcement. An experimental investigation of the shear strength of high strength concrete beams with steel fibrous was conducted. In each series the shear span-depth ratio(a/d) was held constant at 1.5, 2.8, or 3.6, while concrete strengths were varied from 320 to 520, to 800kgf/$\textrm{cm}^2$. To verify the proposed equations the experimental results were compared with those from other researches such as equation of ACI code 318-95 or equation of Zsutty. To deduce equation for shear strength from experimental data carried out MINITAP program. According to the experimental results, the addition of steel fibrous has increased the deflection and strain at failure load, improving the brittleness of the high strength concrete.

• 한국공간구조학회논문집
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• 제6권2호
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• pp.53-60
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• 2006

고강도 재료(고강도 콘크리트, 고강도 철근)가 사용된 철근콘크리트 부재의 전단파괴모드는 보통강도 재료를 사용한 부재의 전단파괴모드와 상이한 결과를 나타낼 수 있다. 고강도 재료가 사용될 경우에 구조설계기준식에서 요구하는 전단보강철근이 먼저 항복한 후에 콘크리트가 압축파괴하는 것과는 다르게, 철근이 항복하기 이전에 콘크리트가 압축파괴할 수 있다. 이 논문에서는 고강도 재료가 사용된 철근콘크리트 부재의 최대철근비를 균형파괴시의 재료의 응력 및 변형률 상태를 이용하여 계산하였다. 제안식에서 최대철근비는 콘크리트의 압축강도와 전단보강철근의 상호관계에 의하여 변화하였다. 제안식은 97개의 철근콘크리트 부재에 대한 실험결과와 비교되었다. 실험결과 및 계산결과는 철근콘크리트 부재의 파괴모드가 전단보강철근의 양과 콘크리트의 압축강도와 밀접한 관계가 있음을 나타내었다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.387-390
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• 2003

Direct tensile tests were carried out for the tensile members of steel-reinforced polymer concrete with different steel diameters and steel ratios to figure out the effect of tensile strength of polymer concrete. In the experiments, polymer concrete with $1000kgf/cm^2$ of compressive strength, steel with $5200kgf/cm^2$ of tensile strength, and the tensile members with 100 cm of constant length were used. Experimental results showed that, regardless of steel diameters and steel content, the strain energy exerted by concrete till the initial crack was 14-15% of the total energy till the point of yield: The energy was much larger than the one of high-strength cement concrete. The behaviors of tensile members of steel-reinforced polymer concrete were in relatively good agreement with the model suggested by Gupta-Maestrini (1990), which was idealized by the effective tensile stress-strain relationship of concrete and the load-strain relationship of members, while those showed a big difference from CEB-FIP model and ACI-224 equation suggested for the load-displacement relationship that was defined as the cross sectional stiffness of effective axis. Modified ACI-224 model code about the load-displacement relationship for the tensile members of steel-reinforced polymer concrete and theoretical equation for the polymer concrete tensile stiffness of polymer concrete suggested through the results of this study are expected to be used in an accurate structural analysis and design for the polymer concrete structural members.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.284-292
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• 1995

This paper is on experimental study on the behavior of reinforced concrete columns subjected to longitudinal steel ratio To investigate the effects of concrete strength and longitedinal steel ratio on the behavior of reinforced concrete columns. a series of tests were carried out for thirty-six tied reinforced concrete columns with a 100mm square cross section and three slendemess ratio of 15, 30 and 50. And To study and illustrate the change of the ultimate loads and that of displacements, two different concrete strength of 180,26kfg/$\textrm{cm}^2$, 819,36kfg/$\textrm{cm}^2$ and five different longitudinal steel ratio of 0.5, 1.0, 4.0, 5.7 and 10.3% were used. The boundary conditions at the ends were both hinged and the end eccentricities (17mm) were equal and of the same sign. While the ultimate load capacity of high-strength concrete column was much increased when the columns were short, that was not when the columns were slender. The effect of longitudinal steel ratio on the increased of ultimate load of column was more evident for slender columns than for short ones and the ultimate of longitudinal steel ratio were more pronounced with increasing concrete strength. The more inserted the longitudinal steel, the more increased the ultimate load, but the superabundance of longitudinal steel ratio over the limitation of maximum steel ratio in ACI code was used, it was showed that the ultimate load was rather decreased.

• Computers and Concrete
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• 제11권2호
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• pp.149-167
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• 2013

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52-80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.183-188
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• 2002

In locations where the cost or concrete is relatively high, or in situations where the weight or concrete members is to be kept to a minimum, it may be economical to use hollow reinforced concrete vertical members. Hollow reinforced concrete columns with low axial load, moderate longitudinal steel percentage, and a reasonably thick wall were found to perform in a ductile manner at the flexural strength, similar to solid columns. However, hollow reinforced concrete columns with high axial load, high longitudinal steel percentage, and a thin wall were found to behave in a brittle manner at the flexural strength, since the neutral axis is forced to occur away from the inside face of the tube towards the section centroid and, as a result, crushing of concrete occurs near the unconfined inside face of the section. If, however, a steel tube is placed near the inside face of a circular hollow column, the column can be expected not to fail in a brittle manner by disintegration of the concrete in the compression zone. Design recommendation and example by moment-curvature analysis program for curvature ductility are presented. Theoretical moment-curvature analysis for reinforced concrete columns, indicating the available flexural strength and ductility, can be conducted providing the stress-strain relation for the concrete and steel are known. In this paper, a unified stress-stain model for confined concrete by Mander is developed for members with circular sections.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.442-445
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• 1997

With increasing use of high strength concrete tied columns in structural engineering, it becomes necessary to examine the applicability of related sections of current design codes. High strength concrete has an advantage of strength capacity and stiffness especially for column elements. This paper presents an experimental study of high strength concrete tied columns subjected to eccentric loading. The main variables included in this test were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 34.9Mpa(356kg/$\textrm{cm}^2$ ) to 93.2Mpa(951kg/$\textrm{cm}^2$ ) and the longitudinal steel ratios were between 1.1% and 5.5%. The eccentricity was selected for the different failure modes, i.e., compression control, balanced point, and tension control. The slenderness ratio varied from 19 to 61. The column specimens with same slenderness ratio but with different concrete compressive strength were constructed and tested. The purpose of this paper is to show failure modes of high strength reinforced concrete columns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.220-225
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• 1993

This paper is an experimental study on shear capacity of the high strength lightweight reinforced concrete beams with shear-depth ratio between 1.5 and 2.5. Thirteen T & rectangular beams were tested to determine their diagonal cracking and ultimate shear capacity. The major variables are shear span-depth ratio (a/d=1.5, 2.0, 2.5), concrete compressive strength(f'c=210, 24., 270㎏/㎠) and tensile steel ratio( =0.6, 1.2%). Based on results obtained from experiment of high strength lightweight reinforced concrete Beam & normal concrete, the following conclusions were drawn. (1) The shear capacity of high-strength lightweight concrete is less 15% than that of normal concrete under same condition. (2) As the results of Comparing this experimental datas with other various formulas. It is regarded that ACI 318-89 shear strength formula related tensile strength is proper to design formula of shear strength of high-strength lightweight reinforced concrete using lightweight concrete.

• KCI Concrete Journal
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• 제14권4호
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• pp.145-150
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• 2002

Reinforced concrete is inherently a durable composite material. When properly designed for the environment to be exposed and carefully constructed, reinforced concrete is capable of giving maintenance-free performance. However, unintentionally using improper materials such as non-washed sea sand having much salt together with poor controlled quality, or the concrete are placed in highly severe environment such as marine atmosphere, the corrosion of reinforcing steel in concrete becomes one of the most significant concerns of concrete. The purpose of this experimental research is to evaluate the performance of corrosion inhibitors for normal strength and high strength concrete, and to propose desirable measures for controlling corrosion of reinforcing steel in concrete. Test specimens in normal strength and high strength concrete were made with and without corrosion inhibitors. The accelerated corrosion test for reinforcing steel in concrete was adopted in accordance with JCI-SC3, which required the periodic 20 cycles for 140 days. One cycle includes 3 days for the wetting condition of $65^{\circ}C$ and $90\%$ RH, and 4 days for the drying condition of $15^{\circ}C\;and\;60\%$ RH. It was observed from the test that corrosion inhibitors in normal strength concrete and high strength concrete showed excellent corrosion resistance for reinforcing steel in concrete, but the silica fume in high strength concrete was found to have a negligible corrosion resistance if not used with corrosion inhibitors, since the chloride corrosion threshold limit in concrete containing silica fume without corrosion inhibitor was found to be considerably smaller than that of the case with corrosion inhibitor.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.308-311
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• 2004

Many researchers have reported that adding steel fiber to concrete improved its tensile and flexural strength significantly, but relatively few studies have been made on the compressive behavior of SFRC(steel fiber reinforced concrete). It is still less in case of high strength SFRC. The main objective of this research is to examine the effect of adding steel fiber on the compressive strength of high strength SFRC using fiber reinforcing index$(RI,\;V_f(l/d))$. It was found from the study that compressive strength was noticeably increased in proportion to RI.