The shear strength of steel fiber-reinforced concrete beams Resistência ao cisalhamento de vigas de concreto reforçado com fibras de aço (original) (raw)
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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 Strength of Steel Fiber-Reinforced Concrete
ACI Materials Journal, 2002
Twelve tests were conducted on reinforced concrete beams with three steel fiber-volume fractions (0, 0.5, and 0.75%), three shear span-depth ratios (2, 3, and 4), and two concrete compressive strengths (31 and 65 MPa). The results demonstrated that the nominal stress at shear cracking and the ultimate shear strength increased with increasing fiber volume, decreasing shear spandepth ratio, and increasing concrete compressive strength. As the fiber content increased, the failure mode changed from shear to flexure. The results of 139 tests of fiber-reinforced concrete beams without stirrups were used to evaluate existing and proposed empirical equations for estimating shear strength. The test population included beams with a wide range of beam properties, but most of the beams were small. The evaluation indicated that the equations developed by Narayanan and Darwish and the equations proposed herein provided the most accurate estimates of shear strength and the onset of shear cracking. For the proposed procedure, the ratio of the measured strength to the calculated strength had a mean of 1.00 and a coefficient of variation of 15%.
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...
Shear behaviour of fiber reinforced concrete beams
Cement and Concrete Composites, 1997
This paper presents the results of shearl'exure tests on steel and polypropylene fiber reinforced concrete beams. In addition to analyzing the influence of fibers on the structural peeormance in situations of di.erent ratios of shear reinforcement, some aspects of the properties of fresh and hardened concrete are introduced. Fourteen square-section beams were tested. The beams were prepared from seven different mix proportions, varying the type and the volume of fiber added. There were two beams for each composite mix: one model with and the other without stirrups. The main alterations resulting from the use of fibers were increased shear strength, stifj%ess (particularly after first cracking stage) and ductility. Other parameters used in analyzing performance were the properties of the hardened concrete (compressive strength, tensile strength, and modulus of elasticity), and stresses in the stirrups, in the longitudinal reinforcement and in the concrete (at the web and compression zone).
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.
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.
2019
The shear strength of concrete is an ability to resist forces that cause sliding of one part relative to the other at an internal plane. The shear strength depends on the grade of concrete, percentage of fibres and percentage of tension steel in beams. One of the objectives of the present experimental work is to determine the variation of shear strength of M30 and M60 grade concretes with no fibre and with various volume percentages of steel fibres using push-off specimens. The present studies indicate that an increase in volume percentage of steel fibres causes an increase in the shear strength for both the grades of concrete. The workability is observed to reduce as the percentage of fibres increases. The compressive strength of concrete is observed to initially increase with an increase in the percentage of steel fibres and then reduce beyond about one percent of steel fibres.
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...
Shear Capacity of Steel Fiber Reinforced Concrete Beams
Thesis (MSc), 1996
Concrete containing steel fibres were used at the beginning of this century. It is only in the last 20 years that a great approach for predicting the behaviour of steel fibre concrete has started. Some examples of structural and non-structural uses of steel fibre concrete may be mentioned as, hydraulic structures, airport and highway paving and overlays, industrial floors, bridge decks, in shotcrete linings, shotcrete coverings and concrete beams. The aim of this final M.Sc. thesis work was to study and analyze the ultimate shear behaviour of normal strength concrete beams reinforced with hooked steel fibres. This report presents a wide literature survey of previous research programs as well as a testing procedure concerning shear behaviour in normal concrete beams with and without steel fibres. The test program consisted of 8 full-scale concrete beams reinforced in three categories. First, normal concrete beams B1-B2 were reinforced with longitudinal reinforcement only. Secondly, beams B3-B4 reinforced with both longitudinal bars and stirrups. The third category contained beams B5-B8 which were reinforced with steel fibres and longitudinal bars. The mechanical and structural properties of normal concrete beams with and without steel fibres were investigated and are presented in the test program. All beams were subjected to two-point load at various shear span ratios (a/d = 1.2, 1.5, 2.0). The improvements in the shear strength capacity of normal concrete beams due to the addition of steel fibres were investigated. The test results indicate that the ultimate shear capacity of normal concrete beams B1-B2 increased by 55% when 1.0%t steel fibres were added to the concrete beams. Three equations to predicate the ultimate shear strength suggested by ACI 1995 [5], the Swedish Concrete Association 1995 [13] and Narayanan and et.al. 1987 [2] have been studied and compared with the test results. The results of the theoretical calculations showed that the equations suggested by the Swedish Concrete Association and Narayanan and et. al. predicted the best value of ultimate shear strength. Citation Roshani, D.M.R, 1996. Shear Capacity of Steel Fiber Reinforced Concrete Beams. Chalmers Technical University, Department of Structural Engineering, Division of Concrete Structures, ISSN 0280-2864; M.Sc. Thesis 96:5
Shear capacity of fiber-reinforced concrete beams without transverse reinforcement
IOP Conference Series: Materials Science and Engineering
This study studied the effect of using fiber on the shear strength of concrete beams without transverse reinforcement. The concrete mixture does not use coarse aggregate and uses stainless steel fiber with a diameter of 0.2 mm and a length of 36 mm. This study explains the effect of concrete quality on shear strength that can be carried by concrete beams with a ratio of 45 / 10.5, 25 / 10.5 and 20 / 10.5. The making of test specimens in this study was a beam of varying lengths of 110 cm, 70 cm and 60 cm while a width of 7 cm, and a height of 12.5 cm. From the test results, the shear stress value is calculated using the formula v / (b x d x ¥ (f'c)) > 2 in international units, in which the shear capacity value is bigger than the code states. Diagonal tension failure occurs on 110cm beam and shear tension failure on 70 cm and 60 cm beams.