• Journal of the Korea Concrete Institute
• /
• v.12 no.2
• /
• pp.13-20
• /
• 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
• /
• 2001.11a
• /
• pp.579-584
• /
• 2001

The reinforced concrete(RC) beam is developed cracks because the compression strength of concrete is strong but the tensile strength is weak. The structural strength and stiffness is decreased by reduction of tension resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structure and decrease the tensile flexural cracks and deflection. Therefore, The reinforced concrete used the fiber reinforced concrete at tensile part ensure the safety and serviceability of the concrete structures. In this study, analytical model of a dual concrete beam that is composed of the normal strength concrete at compression part and the high tensile strength concrete at tensile part is developed by using the equilibrium condition of forces and compatibility condition of strains and is parted into elastic analytical model and ultimate analytical model. Three group of test beam that is formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio is tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the reinforced concrete beams have an increase in approximately 30%. In addition, the initial flexural rigidity, as used here, refer to the slope of load-deflection curves in elastic state is increased and the deflection is decreased.

• Steel and Composite Structures
• /
• v.11 no.6
• /
• pp.455-468
• /
• 2011

Although retrofitting and strengthening reinforced concrete (RC) columns by wrapping fiber reinforced polymer (FRP) composites have become a popular technique in civil engineering, the study on reinforced high-strength concrete (HSC) columns is still not sufficient. The objective of these companion papers is to investigate the mechanical properties of reinforced HSC square columns confined by aramid FRP (AFRP) jackets under concentric compressive loading. In the part I of these companion papers, an experiment was conducted on 54 confined RC specimens and nine unconfined plain specimens, the considered parameters were the concrete strength, the thickness of AFRP jackets, and the form of AFRP wrapping. The experimental process and results are presented in detail. Subsequently, some discussions on the confinement effect, failure modes, strength, and ductility of the columns are carried out.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.490-493
• /
• 2006

The purpose of this study is to investigate the inelastic behavior of reinforced high-strength concrete bridge columns. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. The increase of concrete strength due to the lateral confining reinforcement has been also taken into account to model the confined high-strength concrete. The proposed numerical method for the inelastic behavior of reinforced high-strength concrete bridge columns is verified by comparison with reliable experimental results.

• Magazine of the Korea Concrete Institute
• /
• v.2 no.4
• /
• pp.53-60
• /
• 1990

Investigations on the behavior of steel fiber reinforced high strength concrete beams with shear confinement are accomplished to determine their ultimate shear strength including diagonal tension strength. The parameters varied were the shear confinement ratio(Ps), and fiber volume fraction(Vs). Ultimate shear strength increased significantly in steel fiber reinforced concrete beam without shear confinement. In steel- fiber reinforced high strength concrete beams with shear confinement, there is no increase of ultimate shear strength but shows much beneficial effects of Ductility Capacity.

• International Journal of Concrete Structures and Materials
• /
• v.2 no.2
• /
• pp.115-122
• /
• 2008

Ductility is important in the design of reinforced concrete structures. In seismic design of reinforced concrete members, it is necessary to allow for relatively large ductility so that the seismic energy is absorbed to avoid shear failure or significant degradation of strength even after yielding of reinforcing steels in the concrete member occurs. Therefore, prediction of the ductility should be as accurate as possible. The principal aim of this paper is to present the basic data for the ductility evaluation of reinforced high-strength concrete beams. Accordingly, 23 flexural tests were conducted on full-scale structural concrete beam specimens having concrete compressive strength of 40, 60, and 70MPa. The test results were then reviewed in terms of flexural capacity and ductility. The effect of concrete compressive strength, web reinforcement ratio, tension steel ratio, and shear span to beam depth ratio on ductility were investigated experimentally.

• Journal of the Korea Concrete Institute
• /
• v.12 no.2
• /
• pp.89-98
• /
• 2000

The mechanical properties of specialty cellulose fiber reinforced concrete and the contribution of specialty cellulose fiber to drying shrinkage crack reduction potential of concrete and theirs evaluation are presented in this paper. The effects of differing fiber volume fraction(0.03%, 0.06%, 0.08%, 0.1%, 0.15%, 0.2%) were studied. The results of tests of the specialty cellulose fiber reinforced concrete were compared with plain and polypropylene fiber reinforced concrete. Flexural performance(flexural strength and flexural toughness) test results indicated that specialty cellulose fiber reinforcement showed an ability to increase the flexural performance of normal- and high- strength concrete(as compared to plain and polypropylene fiber reinforced concrete). Optimum specialty cellulose fiber reinforced concrete were obtianed using 0.08% fiber volume fraction. Drying shrinkage cracking test results confirmed specialty cellulose fibers are effective in reducing the drying shrinkage cracking of normal and high-strength concrete(as compared to popylene fiber reinforced concrete).

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.613-616
• /
• 1999

The bond between reinforcing bar and concrete is a significant factor to confirm that they behave uniformly in the reinforced concrete. Thus, the studies on this field have been conducted by many researchers. But for the high strength lightweight concrete few studies have been done. In this study, the steel fiber reinforced high strength lightweight concrete developed to complement the brittleness of the high strength lightweight concrete was studied experimentally to find the local bond stress. Total 20 specimens were tested and the measured test values were compared with those calculated according to ACI 318-95 code and CEB-FIP code, respectively. The results indicate that the maximum bond stress has been influenced by increment of volume fracture of steel fiber, compressive strength and cover, Especially steel fiber caused not only increment of bond strength but also ductile behaviro.

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

• Computers and Concrete
• /
• v.5 no.1
• /
• pp.21-36
• /
• 2008

Steel fiber reinforced concrete is increasingly used day by day in various structural applications. An extensive experimentation was carried out with w/cm ratio ranging from 0.25 to 0.40, and fiber content ranging from zero to1.5 percent by volume with an aspect ratio of 80 and silica fume replacement at 5%, 10% and 15%. The influence of steel fiber content in terms of fiber reinforcing index on the compressive strength of high-performance fiber reinforced concrete (HPFRC) with strength ranging from 45 85 MPa is presented. Based on the test results, equations are proposed using statistical methods to predict 28-day strength of HPFRC effecting the fiber addition in terms of fiber reinforcing index. A strength model proposed by modifying the mix design procedure, can utilize the optimum water content and efficiency factor of pozzolan. To examine the validity of the proposed strength model, the experimental results were compared with the values predicted by the model and the absolute variation obtained was within 5 percent.