• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.35-46
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• 1999

The steel fiber reinforced concrete may affect substantially to the tension stiffening at post cracking behavior. Even if several tension stiffening models exist, they are for plain and normal strength concrete. Thus, the development of tension stiffening models for steel fibrous high strength RC members are necessary at this time when steel fiber reinforced and high strength concretes are common in use. This paper presents tension stiffening effects from experimental results on direct tension members with the main variables such as concrete strength, concrete cover depth, steel fiber quantity and aspect ratio. The comparison of existing models against experimental results indicated that linear reduced model closely estimated the test results at normal strength level but overestimated at high strength level. Discontinuity stress reduced model underestimated at both strength levels. These existing models were not valid enough in applying at steel fibrous high strength concrete because they couldn't consider the concrete strength nor section area. Thus, new tension stiffening models for high strength and steel fiber reinforced concrete were proposed from the analysis of experimental results, considering concrete strength, rebar diameter, concrete cover depth, and steel fiber reinforcement.

• Advances in concrete construction
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• v.17 no.4
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• pp.233-243
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• 2024

The behavior of confined steel fiber-reinforced concrete (including confinement models) with compressive strengths ranging from normal to high strength is still rarely studied. This paper presents the results of an investigation of fifteen confined concrete cylinders containing steel fiber. The design parameters evaluated in the experiment included concrete compressive strength (covers normal to high strength), volume fraction of steel fiber and hoop spacing. The main objective of this study was to evaluate the behavior of confined steel fiber concrete by reviewing several design parameters, such as concrete strength (normal to high strength). It is then developed to be an analytical stress-strain expression for confined steel fiber concrete. The experimental program was carried out by making cylindrical specimens with a diameter of 100 mm and a height of 200 mm. The cylindrical test object is compressed in a monotonic uniaxial loading. Experimental results have shown steel fiber in concrete has an important role in increasing the compressive strength and strain of cylindrical concrete without steel fiber. In addition, the value of strength enhancement of confined concrete (K) along with increasing fiber fraction volume; which applies to normal to high-strength concrete. The value of K also increases if the compressive strength of the concrete tends to decrease and the spacing of the hoops is closer. The comparison of stress-strain behavior between the confined steel fiber concrete proposed by other researchers and the experimental results in general significantly different in post-peak response. The statistical analysis indicates that the value of Coefficient of Variation for the confinement model by Campione is the closest compared to other existing confinement models in predicting the values of K and Toughness Index. Furthermore, the analytic stress-strain expression of confined steel fiber concrete was developed by adopting and modifying several equations from the present models. The proposed analytical expression is then verified with the experimental results. The results of the verification show that the stress-strain behavior of confined steel fiber concrete is relatively close.

• Journal of the Korea Institute of Building Construction
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• v.8 no.3
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• pp.75-83
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• 2008

In this paper, concrete material tests were carried out to investigate influence of steel fiber volumn ratios on variations of workability and strength characteristics of steel fiber reinforced high-strength concrete, $50MPa{\sim}90MPa$ of compressive strength, according to increase of fiber volume. Test specimens were arranged with six levels of concrete compressive strength and fiber volumn ratios, 0.0%, 0.5%, 1.0%, 1.5%, 2.0%. The test results showed that steel fiber reinforced high-strength concrete($70MPa{\sim}90MPa$, 1.5% fiber volumn ratio) with good workability of slump 20cm could be used practically and effects of steel fiber reinforcement in improvement of concrete strength and toughness characteristics such as splitting tensile strength, flexural strength, and diagonal tensioned shear strength, were more distinguished in high-strength concrete than general strength concrete. And the test results indicated that splitting tensile strength of fiber reinforced concrete was proportioned to the product of steel fiber volumn ratios, $V_f(%)$ and sqare root of compressive strength, $\sqrt{f_{ck}}$, and the increasing rate was in contrast with that of flexural strength, and increase of diagonal tensioned shear strength was remarkable at steel fiber volumn ratio, 0.5%.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.5-8
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• 2005

The purpose of this study is to investigate the mechanical characteristics of plain and steel fiber high strength concrete under uniaxial and biaxial loading condition. A number of plain and steel fiber high strength concrete cubes having 28 days compressive strength of 82.7Mpa (12,000psi) were made and tested. Four principal compression stress ratios, and four fiber concentrations were selected as major test variables. From test results, it is shown that confinement stress in minor stress direction has pronounced effect on the strength and deformational behavior. Both of the stiffness and ultimate strength of the plain and fiber high strength concrete increased. The maximum increase of ultimate strength occurred at biaxial stress ratio of 0.5 in the plain high strength concrete and the value were recorded 30 percent over than the strength under uniaxial condition. The failure modes of plain high strength concrete under uniaxial compression were shown as splitting type of failure but steel fiber concrete specimens under biaxial condition showed shear type failure.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.631-637
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• 2007

This study was to evaluate bond properties between high-strength steel fiber reinforced concrete and high strength steel rebar. An direct bond test were performed to evaluate the bond performance of high strength steel rebar in two types of high-strength concrete with steel fiber volume fraction (0, 20, $40kg/m^3$). Also, relative bond strength was defined to determine the effect of steel fiber volume fraction on bond strength. The bond test results showed that the bond performance of high strength steel rebar and high strength concrete tended to increase with higher compressive strength and steel fiber volume fraction. Relative bond strength which performed to analyze effect of steel fiber volume fraction showed increased relative bond strength with increased steel fiber volume fraction.

• Journal of the Korea Concrete Institute
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• v.12 no.2
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• pp.13-20
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• 2000

In this study, the compression test of steel fiber reinforced high-strength concrete have been performed with varying strengths and volume factions of steel fiber. Three types of matrices including low strength concrete( c'=30 MPa), medium strength concrete( c'=50 MPa), and high strength concrete( c'=70 MPa) were selected. Five types of fiber fractions were studied including 0.0%, 0.5%, 0.75%, 1.0%, and 1.5% by volume. From the results of the compressive strength test, the post-peak characteristics of the stress-strain relationship were investigated, and the existing equations to predict the elastic modulus were experimentally evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.241-242
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• 2009

This study showsUltra high performance concrete with steel fiber to obtain the high ductillity. the results of high strength concrete specimences with existing steel fiber and liquid metal fiber were compared with them of plain high strength mortal through bending test. The result that the ductility of high strength concrete with liquid metal fiber was superior to that with bundrex steel fiber was found through toughness test mathod like ASTM C 1018, JSCE-SF4.

• Journal of Korean Association for Spatial Structures
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• v.23 no.2
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• pp.69-78
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• 2023

This paper investigates the effects of aspect ratio and volume fraction of hooked-end normal-strength steel fibers on the compressive and flexural properties of high-strength concrete with specified compressive strength of 60 MPa. Three types of hooked-end steel fibers with aspect ratios of 64, 67 and 80 were considered and three volume fractions of 0.25%, 0.50% and 0.75% for each steel fiber were respectively added into each high-strength concrete mixture. The test results indicated that the addition of normal-strength steel fibers is effective to improve compressive and flexural properties of high-strength concrete but fiber aspect ratio had little effect on the modulus of elasticity and compressive strength. As steel fiber content and aspect ratio increased, flexural beahvior of notched high-strength concrete beams was effectively improved.

• Steel and Composite Structures
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• v.23 no.5
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• pp.611-621
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• 2017

This paper presents an investigation on the fire resistance of high strength fiber reinforced concrete filled box columns (CFBCs) under combined temperature and loading. Two groups of full-size specimens were fabricated. The control group was a steel box filled with high-strength concrete (HSC), while the experimental group consisted of a steel box filled with high strength fiber concrete (HFC) and two steel boxes filled with fiber reinforced concrete. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The test results show that filling fiber concrete can improve the fire resistance of CFBC. Moreover, the configuration of longitudinal reinforcements and transverse stirrups can significantly improve the fire resistance of CFBCs.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.137-145
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• 1999

The use of steel fiber reinforced to improve the strength and flexural toughness of concrete is well known, but reinforcement of polymer concrete with steel fibers has been hardly reported till now. Polymer concrete has high strength, durability and freeze-thaw resistance than that of cement concrete, but it has disadvantage such as low flexural toughness. In this paper, the strength characteristics and flexural toughness of steel fiber reinforced polymer concrete are investigated experimentally with various steel fiber aspect ratios($\ell$/d), and contents(vol.%). As the result, the flexural and splitting tensile strengths and flexural toughness were increased aspect ratio, and reach the maximums at a aspect ratio of 50. The relationship between the compressive, flexural and splitting tensile strength were high. And the relationship between flexural strength and strain energy was approximately linear.