Mechanical model for the shear strength of steel fiber reinforced concrete (SFRC) beams without stirrups (original) (raw)
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2021
14 Numerous studies have shown that adding steel fibers to the concrete mixture improves both the shear 15 strength and ductility of reinforced concrete beams. Most current shear design formulations for steel 16 fiber reinforced concrete beams are empirically based and their predictions provide acceptable results 17 when compared with tests results, but only in limited ranges of the parameters involved. On the other 18 hand, many shear theoretical models suggested in the literature are derived by extending previous 19 formulations for conventional reinforced concrete beams, just introducing the stresses transferred across 20 the critical shear crack. Since the effects of steel fibers on the others shear resisting mechanisms are not 21 accounted for, “adjusting” empirical factors must be used to fit the experimental results. There is, 22 therefore, the need for developing mechanical models capable to rationally account for the effects of 23 steel fibers on the global shear strength a...
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 behaviour of steel fibre reinforced concrete beams
Materials and Structures, 2005
The present work sets out to investigate the potential advantages of adding steel fibres to the concrete mix in order to enhance the structural response of concrete structures. In particular, the shear behaviour of steel-fibre-reinforced concrete (SFRC) beams was studied using Nonlinear Finite-Element Analysis (NLFEA). The work aimed at assessing the potential of using steel fibres to reduce the amount of conventional steel reinforcement without compromising ductility and strength requirements set out in design codes. To achieve this, the spacing between shear links was increased while steel fibres were added to see whether or not the loss of shear strength can be compensated for in this way. This can speed construction as laying out shear links can be time consuming. It is also useful in situations where the amount of shear reinforcement required can lead to congestion of shear links.
Simulation of the Influence of Steel Fibers on the Shear Behavior of Reinforced Concrete Beams
2016
An analytical model is presented for predicting complete shear load-deformation response of reinforced concrete sections taking into account the steel fibers reinforced concrete. This model is based on the equilibrium, compatibility equations and stress-strain relationships which are formulated in term of average stresses and average strains. This model is able to analyze sections having unusual forms or reinforcing details, loaded in combined bending, axial load and shear. In the case of the steel fiber reinforced concrete, a stress-strain relation proposed by Kachi and al (2002) is adopted. Predictions of the model are compared with several calculated reinforced beams and are shown to estimate the effect of the steel fibbers on the shear stiffness of the sections in the case of the elastic linear domain, after concrete cracking and after reinforcement yielding.
Shear behaviour of 0.6 % and 0.7 % steel fibre reinforced concrete beams without stirrups
IOP Conference Series: Earth and Environmental Science, 2020
Concrete is a brittle material and respectively weak in tensile strength and tensile strain. Concrete technology is applied at which concrete is reinforced with steel fibre, as known as steel fibre reinforced concrete (SFRC) to produce a versatile structural material to exhibit superior strength properties in terms of ductility, fracture energy, toughness, strength and durability. The introduction of short, discontinuous and randomly oriented steel fibres into conventional concrete mixes possesses a strong bond with the concrete matrix with high elastic modulus. The goal of this study is to create a standard foresight in determining the potentiality of steel fibre as secondary shear reinforcement to partially or fully replace shear stirrups in conventional concrete. For this purpose, the series of SFRC beam specimens without stirrups which have the same concrete mixing ratios were produced with the inclusion of 0.6 % and 0.7 % steel fibre by volume fractions and compared with conven...
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%.
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.
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...
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