Experimental analysis of the efficiency of steel fibers on shear strength of beams (original) (raw)
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Influence of Steel Fiber on the Shear Strength of a Concrete Beam
Civil Engineering Journal, 2018
The shear failure in a concrete beam is a brittle type of failure. The addition of steel fibers in a plain concrete mix helps to bridge and restrict the cracks formed in the brittle concrete under applied loads, and enhances the ductility of the concrete. In this research an attempt was made to investigate the behavior and the ultimate shear strength of hooked end steel fiber reinforced concrete beams without traditional shear reinforcement. Four simply-supported reinforced concrete beams with a shear span-to-depth ratio of about 3.0 were tested under two-point loading up to failure. Steel fibers volumetric fractions that used were 0.0, 0.5, 0.75 and 1.0%. Test results indicated that using 1.0% volume fraction of hooked steel fiber led to exclude shear failure and enhanced the use of steel fibers as shear reinforcement in concrete beams. The results also showed that a concrete beam with hooked steel fiber provided higher post-flexural-cracking stiffness, an increase in the shear capacity and energy absorption and an increase in the maximum concrete and steel reinforcement strains.
Influence of Fiber Content on Shear Capacity of Steel Fiber Reinforced Concrete Beams
2019
For shear-critical structural elements where the use of stirrups is not desirable, such as slabs or beams with reinforcement congestion, steel fibers can be used as shear reinforcement. The contribution of the steel fibers to the shear capacity lies in the action of the steel fibers bridging the shear crack, which increases the shear capacity and prevents a brittle failure mode. This study evaluates the effect of the amount of fibers in a concrete mix on the shear capacity of steel fiber reinforced concrete beams with mild steel tension reinforcement and without stirrups. For this purpose, twelve beams were tested. Five different fiber volume fractions were studied: 0.0%, 0.3%, 0.6%, 0.9%, and 1.2%. For each different steel fiber concrete mix, the concrete compressive strength was determined on cylinders and the tensile strength was determined in a flexural test on beam specimens. Additionally, the influence of fibers on the shear capacity is analyzed based on results reported in th...
Experimental analysis of steel fiber reinforced concrete beams in shear
Revista IBRACON de Estruturas e Materiais
Some normative recommendations are conservative in relation to the shear strength of reinforced concrete beams, not directly considering the longitudinal reinforcement rate. An experimental program containing 8 beams of (100 x 250) mm2 and a length of 1,200 mm was carried out. The concrete compression strength was 20 MPa with and without 1.00% of steel fiber addition, without stirrups and varying the longitudinal reinforcement ratio. Comparisons between experimental failure loads and main design codes estimates were assessed. The results showed that the increase of the longitudinal reinforcement ratio from 0.87% to 2.14% in beams without steel fiber led to an improvement of 59% in shear strength caused by the dowel effect, while the corresponding improvement was of only 22% in fibered concrete beams. A maximum gain of 109% in shear strength was observed with the addition of 1% of steel fibers comparing beams with the same longitudinal reinforcement ratio (1.2%). A significant amount...
An Experimental Study On Shear Behavior Of Steel Fiber Reinforced Concrete Beam
2015
The present study investigate the influence of Steel Fiber Reinforcement on the mechanical behavior of reinforced concrete beams in shear.The major test variables are the aspect ratio of steel fiber, shear reinforcement, shear span(a) to depth ratio(d).The test result show that the first crack shear strength increases as fiber is added and also ultimate shear strength increases and change the mode of failure. It is concluded that fiber reinforcement can reduce the amount of shear stirrups required and that the combination of fibers and stirrups meet the strength and ductility requirements.
2016
Recently, several studies have been conducted to investigate the shear behaviour of steel fiber reinforced concrete (SFRC). Over the last few decades, steel fibers have been shown to be applicable and effective in improving the shear reinforcement. This paper presents a summary of the main findings from the primary research contributors. Besides discussion on the research efforts, recommendations for the future research in using steel fibers to improve shear reinforcement are provided. This paper conclude that using steel fibers in reinforced concrete slab can possibly reduce the thickness of slab and fibers has substantial effect to serve as part of shear reinforcement in reinforced concrete slab
Shear Behavior of Fiber-Reinforced Concrete Beams: An Experimental Study
International Journal of GEOMATE, 2021
Eight steel fiber-reinforced normal strength concrete beams (200 mm wide, 250 mm deep and 1500 mm long) were tested in bending under two concentrated loads, without and with stirrups. The concrete beams were designed to have marked shear behavior. Three types of steel fibers (SFs), straight, hooked and corrugated, were investigated as a possible replacement for standard transverse reinforcement. The fiber volume content, the aspect ratio of fibers, and the existence of stirrups were the major testing parameters in this regard. Four fiber volume proportions (R f of 0%, 0.5%, 1.0% and 1.5%) and three aspect ratios (l/d of 50, 55 and 60) were utilized. According to the experimental data, the shear behavior of steel fiber-reinforced normal strength concrete beams (SFRCBs) without stirrups was similar, if not superior, to that of normal strength concrete beams (RCBs) with stirrup reinforcement. The SFRCBs displayed extremely thin diagonal cracks and higher shear strengths, especially for fiber fractions of 1% and 1.5%. The experimental results were compared to major universal codes and existing models from the literature. The major codes undervalue the concrete contribution to shear strength while exaggerating the contribution of the stirrups. Furthermore, some of the existing models overestimate the fibers' contribution to the shear strength, while others underestimate it when compared to the present experimental findings.
Shear Behavior of Steel Fiber Reinforced Concrete Beams
ACI Structural Journal, 1993
Twelve simply-supported steel fiber reinforced concrete (SFRC) wide beams without conventional stirrups were tested to investigate their shear behavior. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The variables were fiber volumetric ratio, concrete compressive strength, longitudinal reinforcement ratio and shear span-to-depth ratio. Eight tested beams were steel fiber reinforced concrete wide beams and four beams were reinforced concrete wide beams without steel fiber for comparison purposes. End-hooked steel fibers of volumetric ratio ranging from 0% to 1.25% were used in the specimens. All beams were tested under four-point loading to investigate their behavior in shear, cracking pattern, ultimate capacity and ductility. Test results showed that the shear cracking, the ultimate shear strength and ductility increased with increasing fiber volumetric ratio, decreasing shear span to depth ratio, increasing concrete compressive strength and increasing longitudinal reinforcement ratio. The using of a dose of 0.75% fiber content in the wide beams without shear stirrups was adequate to achieve the ultimate resistance that is the same as the conventional RC wide beam with conventional stirrups. Evaluation of the ultimate shear strength of the SFRC wide beams based on previous models is presented.
IOP Conference Series: Earth and Environmental Science
This paper presents the experimental results and theoretical study on the shear strength of reinforced steel fibre concrete beams. Failure of reinforced concrete beams in form of diagonal tension failure has been very complex to predict accurately. The inclusion of steel fibre substantially increased the ductility of the concrete and improves the shear behaviour of the beams. Due to bridging effects provided by the steel fibre, it reduces the brittle shear failure of plain concrete. Previous test data were categorized by the influence of steel fibre in reinforced concrete beams. All test results showed that steel fibre has a significant influence on the ultimate shear strength of reinforced concrete beam and control the development of crack propagation. A discussion on the contribution of steel fibre on the shear strength is also presented, with reference to the past researcher formula and RILEM provisions. The shear strength prediction for steel fibre reinforced concrete beams were compared with those obtained by the experimental test. The comparison shows that the mean value of the ratio of the experimental ultimate shear strength to predicted ultimate shear strength for the beams tested was about 0.59 to 1.96.
The Effect Of Steel Fiber As Additional Reinforcement In The Reinforced Concrete Beam
Steel fiber reinforced concrete has been increasingly used in structural applications during the last four decades. It is generally accepted that addition of steel fibers significantly increases tensile toughness and ductility, also slightly enhances the flexural strength. Effects of steel fibers as addition reinforcement in reinforced concrete (RC) beams are the main objectives of this study. The hooked-end steel fibers with the dimensions of 0.75 mm in diameter, 33 mm in length and with the aspect ratio of 44 were used in this study. Initially the optimum percentage addition of steel fibers in concrete was determined. In order to accomplish this task, eighteen concrete beams with the same mix proportioning of concrete and different volume fractions of steel fiber (0.5 % and 0.75%) were prepared. Then, by determining the flexural strength and deflection of samples, it was concluded that the optimum volume fraction was 0.50 % (0.44 kg). In the next step,the flexural behavior and deflection of RC beams with the addition of steel fibers in concrete was considered. The study was conducted on two types of beam which is beam with 5 links and no steel fibers as a contol beam and the other one was beam with 4 links and 0.50% and 0.75% volume of steel fibers. The overall dimensions of the beams were 150 mm in height, 150 mm in width, and 500 mm in length. The beams were tested under four-point loading test. The results showed that addition of steel fibers increases the cracking load, load, stiffness and ductility of the concrete beams.
2011
This research investigates the mechanical shear behavior of twelve reinforced concrete beams. The type of loading (normal or reverse), the presence or absence of steel fibers (30 kgf/m 3), and the concrete compressive strength (40MPa, 60 MPa, or 80 MPa) were the mains test variables studied. The beams had nominally identical cross-sections, effective depths, and longitudinal and transverse reinforcements. The loads were increased at 10 kN intervals until shear failure occurred, defined by the yielding of the first stirrup. The ultimate shear loads observed in these tests were compared to three empirical and semi-empirical formulas proposed in the literature. Based on the test results it could be concluded that concrete compressive strength has no significant influence on the reduction of ultimate shear load caused by reverse loading. Reverse-loaded beams with fibers had approximately the same ultimate shear strength as concrete beams without fibers subjected to normal loading, regardless of the compressive strength of the concrete.