Steel Fiber Reinforced Concrete Beams Research Articles

Avaliação da substituição da armadura transversal mínima por fibras de aço em vigas de concreto armado

Abstract The shear strength of fiber reinforced elements is usually predicted through analytical models calibrated from experimental tests. Few results obtained from these tests consider the mechanical characterization of the material, allowing to evaluate the different performances of fiber reinforced concrete. This work evaluates the possibility of replacing the minimum shear reinforcement of reinforced concrete beams with steel fibers. For this, comparations were made evaluating the shear strength of 240 experimental tests of steel fiber reinforced concrete (SFRC) beams using formulations from the literature and international standards, to define which equations are in better agreement with the experimental data. Thus, once this expression was identified, SFRC beam design abacuses were developed to determine the amount of steel fibers needed to replace the minimum shear reinforcement, according to NBR 6118 [1]. The results showed that the model by Kwak et al. [2] presented results similar to those obtained in experimental tests of beams. Finally, it is concluded that the developed abacuses will facilitate decision-making in the design of SFRC beams.

Nonlinear finite element analysis of steel fiber reinforced concrete beams subjected to impact loads

Steel fiber reinforced concrete, compared to the conventional concrete; is a composite building material that performs much better in terms of parameters such as ductility, energy absorption capacity, fracture toughness, fatigue resistance, and the use of steel fiber reinforced concrete (SFRC) in structures has become widespread. In this study, a nonlinear finite element model (FEM) has been developed that can represent the behavior of beams produced by using steel fiber concrete subjected to impact load. For this purpose, a finite element model of beam series produced with fiber-reinforced concrete obtained from the literature was created. The ABAQUS package program was used to create models simulating the behavior. Numerical results showed that the model could successfully capture the experimental results of beams selected from the literature. In addition to simulation, a parametric study was also performed to investigate the effect of stirrups, reinforcement ratio, and drop height on the behavior of SFRC beams under impact loads. The results of the parametric study showed that increasing the fiber ratio and reinforcement ratio positively affected the behavior of SFRC beams in terms of displacement recovery.Steel fiber reinforced concrete, compared to the conventional concrete; is a composite building material that performs much better in terms of parameters such as ductility, energy absorption capacity, fracture toughness, fatigue resistance, and the use of steel fiber reinforced concrete (SFRC) in structures has become widespread. In this study, a nonlinear finite element model (FEM) has been developed that can represent the behavior of beams produced by using steel fiber concrete subjected to impact load. For this purpose, a finite element model of beam series produced with fiber-reinforced concrete obtained from the literature was created. The ABAQUS package program was used to create models simulating the behavior. Numerical results showed that the model could successfully capture the experimental results of beams selected from the literature. In addition to simulation, a parametric study was also performed to investigate the effect of stirrups, reinforcement ratio, and drop height on the behavior of SFRC beams under impact loads. The results of the parametric study showed that increasing the fiber ratio and reinforcement ratio positively affected the behavior of SFRC beams in terms of displacement recovery.

Hooking Effect on Flexural Strength and Toughness of Steel Fiber-Reinforced Concrete Beams

Hooking Effect on Flexural Strength and Toughness of Steel Fiber-Reinforced Concrete Beams

MODELING THE BENDING BEHAVIOR OF STEEL FIBER-REINFORCED CONCRETE BEAMS

In this study, modeling of the bending behavior of large-scale steel fiber-reinforced concrete beams (SFRC) was investigated using the Modified Compression Field Theory (MCFT) based non-linear finite element (NLFE) method and an analytical method. The two analysis methods included different modeling approaches for the contribution of steel fibers to the tensile strength of reinforced concrete. In the first approach, the residual tensile strength of fibrous concrete was related to the crack width and adopted into the MCTF-based NLFE method. However, the residual tensile strength was free from the crack width in the second approach, which was employed in the analytical method. The capabilities of the mentioned analysis methods were investigated on an experimental study selected from the literature. The experimental study included the four-point bending tests of five four-meter-long simply supported SFRC beams having various ratios of longitudinal reinforcement and fiber content. Results revealed that the MCTF-based NLFE method performed superior in representing the large-scale member responses (such as load-carrying capacity, crack profiles, and flexural stiffness) for the selected loading and boundary conditions while the simplified analytical tool was found to be always conservative in the determination of strength regardless of conventional reinforcement and fiber ratio. However, the rate of error was apparently proven to be highly dependent on the tensile reinforcement ratio.

Experimental investigation on the flexural behavior of concrete reinforced by various types of steel fibers

The benefit of steel fiber on the mechanical behaviors of concrete has been well accepted. The flexural behavior of steel fiber reinforced concrete (SFRC) is complicated which depends on many factors, such as matrix properties, fiber material properties, fiber geometries, fiber volume contents, and interface properties. Thus, the investigations on the flexural behavior of SFRC are needed to be expanded. In this study, the effects of fiber type with varying shapes and aspect ratios on the flexural performance of SFRC were investigated. Five steel fibers were adopted in this study: milled fiber (M), corrugated fiber (C) and three hooked fibers with aspect radios of 45 (HA), 55 (HB), and 65 (HC). Two volume fractions (0.4% and 1.0%) of steel fiber and two compressive strengths (normal and high strengths) of matrix were considered. The load-deflection curves, energy absorption capacity and equivalent flexural strength were discussed. The results show that the flexural behavior of SFRC beams reinforced by 1.0% fibers is significantly higher than that of the beams reinforced by 0.4% fibers. Hooked fiber reinforced beams performed the best flexural load-deflection response compared to the beams reinforced by milled fiber and corrugated fiber reinforced, and exhibited an increasing trend of flexural performance as the fiber aspect ratio increased. The differences between specimens with different fibers for high strength matrix are more obvious compared to the normal strength matrix.

Effects of pre-cracked width and seawater erosion on the cracking behavior of SFRC beams with BFRP bars subjected to cyclic loading

This study aims to explore the effects of various pre-cracked widths, seawater erosion and BFRP reinforcement ratios on the cracking behavior of steel fiber reinforced concrete (SFRC) beams with Basalt Fiber Reinforced Polymer (BFRP) bars subjected to cyclic loading. Pre-cracked beams were made by applying loads to obtain a predetermined crack width, such as 0.02 mm, 0.2 mm, and 0.4 mm crack widths. Eleven beams were poured and tested by a four-point bending load under cyclic loading. The crack pattern and load-crack width curves of beams were drawn and analyzed. The effects of pre-cracked width, seawater erosion, and BFRP reinforcement ratio on crack behaviors of beams were investigated and discussed. The results showed that the tensile strength of BFRP bars degenerated after seawater corrosion, and its degradation rates increased with the increase of diameter. The failure mode of beams after seawater erosion may transform from concrete crushing failure to BFRP tensile failure; The maximum crack width of all beams under service load was less than 0.5 mm. Increasing the BFRP reinforcement ratio can significantly improve the crack resistance of beams, but pre-cracked width and seawater erosion had adverse effects on the crack behavior. Existing codes overestimated the crack width of SFRC beams reinforced with BFRP bars. Finally, a new calculation model of crack width of SFRC beams with BFRP bars after seawater corrosion was proposed, and its results were closer to the experimental results.

Bending damage and fractal characteristics of steel fiber-reinforced concrete under three-point bending test

Steel fiber-reinforced concrete (SFRC) has outstanding mechanical properties and is widely used in the construction industry. To investigate the damage characteristics of SFRC beams with different steel fiber (SF) contents (0, 15, 30, 45, and 60 kg/m3) accurately, this study analyzed the bending damage (including the load-crack mouth opening displacement curve, flexural–tensile strength, fracture toughness, and microstructure and macrostructure) and fractal characteristics of SFRC beams under three-point bending tests. The crack propagation process in the SFRC beams was monitored by the digital image correlation technique. Information on microcrack evolution and macrocrack development during the loading process was collected using acoustic emission techniques. Furthermore, the correlation dimension reflecting the development state of the cracks was obtained based on the Grassberger–Procaccia algorithm. Test results showed that the performance of concrete beams in terms of deformation and cracking significantly improved by adding SFs. The beam with an SF content of 45 kg/m3 had the highest flexural–tensile strength of 6.979 MPa, which was 1.668 times higher than that of a plain concrete beam. The beam with a 60 kg/m3 SF content had the highest fracture toughness of 1.691 MPam1/2, which was 53.87% higher than that of the plain concrete beam. The fractal analysis results showed that when the correlation dimension increased, numerous small-sized, low-evolution microcracks accumulated in the fracture process zone. When the correlation dimension decreased, the microcracks converged and formed macrocracks. The peak value of the correlation dimension can be used as precursor information for SFRC beam fracture prediction.

Global Resistance Methods for the Design of Fiber-Reinforced Concrete (FRC) Beams with Material Nonlinear Finite Element Analysis

This article explores the application of the global resistance methods (GRMs) on the design of hybrid glass fiber-reinforced polymer (GFRP) and steel fiber-reinforced concrete (SFRC) beams. Addressing challenges posed by GFRP-reinforced beams, this study aims to assess the impact of material uncertainties on the behavior of such hybrid beams. The investigation involves the experimental testing of I-shaped SFRC beams, which are used to develop and validate nonlinear finite element analysis (NLFEA) models. These models incorporate material non-linearities while minimizing uncertainties related to modeling assumptions. Through the application of GRM, the study evaluates the global resistance safety factor, offering insights into the structural performance of hybrid reinforcement SFRC beams. Ultimately, this research seeks to facilitate a transition from traditional localized approaches to more accurate and comprehensive analyses for the design of hybrid reinforcement SFRC beams, contributing to the advancement of structural engineering by promoting safer, more resilient, and sustainable construction systems.

Influence of Fiber Orientation on the Shear Properties of Steel Fiber-Reinforced Reactive Powder Concrete Beams

Steel fiber-reinforced reactive powder concrete (SFRPC) has good mechanical properties and is thus useful for engineering applications. Generally, the fibers in SFRPC are randomly distributed. To study the effects of the amount, length, and orientation of steel fibers on the shear strength of SFRPC beams, nonreinforced aligned steel fiber-reinforced reactive powder concrete (ASFRPC) beams were prepared using a large-scale electromagnetic field orientation device. Shear tests of specimens with a shear span ratio of 1.5 were performed under two fiber contents (1.0% and 2.0%) and three fiber lengths (20, 30, and 40 mm). The full-field strain during the loading process was obtained via the digital image correlation method, and the effects of fiber quantity and orientation on the shear strength of the beams were analyzed. The ASFRPC beams exhibited higher ductility but lower shear capacity than the SFRPC beams under the same conditions. The shear capacity increased with the quantity of steel fibers. According to the test results, the calculation formulas of the shear-bearing capacities of ASFRPC and SFRPC beams were established.

A novel analytical framework for assessing the impact response of SFRC beam

This paper presents a novel model for predicting the impact response of steel fiber reinforced concrete (SFRC) beams. The model utilizes the principles of energy conservation and impulse-momentum theorem to calculate the maximum reaction force and peak impact force. A tensile behavior model for simulating the concrete behavior is proposed considering the effect of volume fraction of steel fibers and the effect of strain rate on the concrete properties. Additionally, the conventional beam theory, along with a cross-section-layered approach, is used to express the total beam's reaction forces vs deflection relationship. Afterwards, the model calculates the maximum midspan deflection of SFRC beams subjected to impact loading by applying the principle of conservation of energy and considering the effect of strain rate. The proposed model is compared with 121 impact tests, and the results show that the model can estimate the maximum reaction force of SFRC beams with acceptable accuracy.

Numerical analysis of the shear behavior for steel fiber reinforced concrete beams with corroded reinforcing bars

Steel fiber reinforced concrete (SFRC), which improves mechanical properties after cracking, became an interesting material for reinforced concrete structures. However, there is limited research on the performance of SFRC beams in corrosive environments. This paper concerns numerical simulations to validate and evaluate the impact of design-oriented parameters contributing to the shear behavior of SFRC beams corroded under chloride attack. The finite element analysis (FEA) results were compared with the experimental data for both non-corroded and corroded SFRC beams. To minimize the differences, the comparison between the proposed models and experiment showed a close agreement on the load–displacement relationship, failure mode, and cracking pattern. After conducting parametric investigations, the numerical results reveal that the shear reinforcement ratio insignificantly affects the shear strength of corroded SFRC beams. In contrast, concrete compressive strength, shear span-to-depth ratio, and corrosion degree of tensile longitudinal reinforcements significantly impact the shear strength of corroded SFRC beams.

A Finite Element Approach to Evaluate and Predict the Shear Capacity of Steel Fiber-Reinforced Concrete Beams

Adding steel fibers to a concrete matrix enhances the shear capacity of reinforced concrete beams. A comprehensive understanding of this phenomenon is essential to evaluate engineering designs accurately. The shear capacity of Steel Fiber Reinforced Concrete (SFRC) beams is affected by many parameters, such as the ratio of the shear span to the effective depth of the SFRC beam, the compressive strength of concrete, the longitudinal reinforcement ratio, volume fraction, aspect ratio, and the type of fibers. Therefore, to cover the influence of these parameters on the shear capacity of SFRC beams, 91 beams from previous studies, divided into 10 groups, were considered in the current study. Two approaches have been used to predict the shear capacity of SFRC beams. The first approach used 7 predicting equations derived from previous studies and the second one used finite element analysis (ANSYS software) to simulate the 91 beams. Despite the many approaches to simulate the structure elements, there is no reliable approach able to simulate satisfactorily 91 SFRC beams as this study does. The log file of ANSYS software was used to simulate and calculate the shear strength capacity of the beams. The results show a reasonable agreement with the experimental tests. The extracted results were much closer and more realistic than those obtained by the predicting equations. Also, the χ factor (squared value of experimental shear capacity to the predicted shear capacity) of the ANSYS software results is 97%, while the closest proposed equation gives 91%.

Serviceability evaluation model of SFRC beams reinforced with FRP bars based on deformation control

This research investigated the flexural behavior of steel fiber-reinforced concrete (SFRC) beams reinforced with fiber-reinforced polymer (FRP) bars to promote its application in engineering. Ten beams with widths of 150 mm, heights of 250 mm and lengths of 1800 mm were tested under four-point bending. The experimental parameters included the reinforcement type, steel fiber volume fraction, concrete strength, and longitudinal reinforcement ratio of the FRP bars. Based on the test results, a prediction model was proposed for the balanced reinforcement ratio (ρfb), considering the influence of steel fibers. Deformation prediction equations in the current design codes in the US, China, and Canada were compared based on the experimental results. The increase in the reinforcement ratio (ρf) can improve both the service moment (Ms) and the ultimate moment (Mu). With an increase in ρf/ρfb, the Ms/Mu value decreased for under-reinforcement beams but increased for over-reinforcement beams. Based on the linear regression theory, a new calculation model for the flexural moment utilization efficiency of SFRC beams reinforced with FRP bars in serviceability limit states is established. The ductility indices of all beams are above the minimum limit of 4, as proposed by CSA S6-14.

The effect of recycled-tire steel fiber and engineered steel fiber on rebar corrosion and shear behavior of corroded RC beam

The implementation of steel-fiber reinforced concrete (SFRC) can improve the durability of reinforced concrete structures exposed to corrosive environments. More recently, the recycled-tire steel fibers (RTSF) impressively boosted mechanical performance and post-cracking strength of plain concrete. Unlike the engineered steel fiber (ESF), RTSF is capable of arresting both micro- and macro-cracks. Micro-crack arresting via RTSF incorporation can reduce chloride penetration in SFRC. In this study, first, the influence of low dosage of RTSF and/or ESF on mechanical properties of concrete is explored. Second, the effect of RTSF, ESF and their hybrid utilization on the corrosion development on embedded steel rebars is surveyed. Artificial corrosion procedure was implemented for inducing corrosion in rebars embedded in reinforced concrete (RC) beam. Finally, the flexural performance of corroded SFRC beam with different corrosion rates (0%, 2%, 5%, 7%, and 10%) were evaluated upon a three-point bending test setup. According to the results, the compressive strength of plain concrete improved 37% by 40 kg/m3 RTSF incorporation. Moreover, the tensile and post-cracking strengths of concrete enhanced significantly by hybrid utilization of RTSF and ESF. The residual strength of SFRC mix at both service and ultimate load was improved by the hybrid utilization of both RTSF and ESF by 25-120%. For uncorroded RC beams containing SFRC mix, the RTSF incorporation improved the shear capacity of the plain RC beam by 25%. Among different types of fibers, RTSF was more effective in decreasing the actual corrosion rate of rebars embedded in RC beams. Additionally, corrosion of embedded rebars up to 8% slightly reduced the rotation capacity of FRC beams.

Numerical Study of the Shear Behavior of Ultra-High-Performance Concrete Beams


 
 
 In the last decades, experimental and numerical studies on steel fiber-reinforced concrete have shown that providing suitable fiber content and distribution in the matrix can improve the post-cracking strength of concrete. Although there is a large database of experimental and numerical shear tests of steel fiber-reinforced concrete beams, there are not profuse test data and numerical models available for steel fiber-reinforced concrete beams with traditional transverse shear reinforcement (stirrups). In this work, the shear behavior of ultra-high-performance fiber-reinforced concrete beams is analyzed using the plastic damaged model developed in Abaqus. For this purpose, a comparative study is previously carried out by means of an experimental test available in the literature to validate the finite element model with conventional rebars. Then, the shear behavior of different ultra-high-performance concretes without fiber reinforcement, with the addition of 13 mm steel straight fibers, with 30 mm steel hooked-end fibers, and a mixture in 50% of 13 and 30 mm steel fibers are analyzed.
 
 

Comparative Evaluation of Flexural Toughness of Steel Fiber-Reinforced Concrete Beams.

Specifications are available to quantify flexural performance of steel-fiber reinforced concrete beams with several parameters. Each specification provides different results. This study comparatively evaluates existing flexural beam test standards that are used to evaluate the flexural toughness of SFRC beam specimens. Two standards, EN-14651 and ASTM C1609, were followed to test SFRC beams under the three-point bending test (3PBT) and the four-point bending test (4PBT), respectively. Both normal tensile strength steel fiber (1200 MPa) and high tensile strength steel fiber (1500 MPa) in high-strength concrete were considered in this study. The reference parameters recommended in the two standards, which include equivalent flexural strength, residual strength, energy absorption capacity, and flexural toughness, were compared based on the tensile strength (normal or high) of the steel fiber in high-strength concrete. The 3PBT and 4PBT results indicate that both standard test methods yield similar results to quantify the flexural performance of SFRC specimens. However, unintended failure modes were observed for both standard test methods. The adopted correlation model shows that the flexural performance of SFRC is similar for 3PBTs and 4PBTs, but the residual strength obtained from the 3PBTs tends to be greater than that obtained from 4PBTs with an increase in the tensile strength of steel fiber.

Performance of hybrid steel fiber-reinforced self-compacting concrete RC beam under flexure

Hybrid steel fiber-reinforced self-compacting concrete (HSFRSCC) has desirable properties for improving the performance of structures. But the literature is sparse on the flexural performance of the reinforced concrete (RC) beam reinforced with hybrid fibers. The impact of the combined action of micro- and hooked-end steel fibers on the flexural performance of the SCC beam to which mineral admixtures and superplasticisers have been added to improve their workability is investigated in this study. In the experiment, beam specimens, reinforced with micro-steel and hooked-end fibers, with a compressive strength of 60 and 80 MPa and of size 150×230×3000 mm were prepared. The results clearly demonstrate that the flexural performance of the SCC beam significantly improved with the addition of hybrid steel fibers. The combination of 0.5% of hooked-end steel fibers and 0.25% of micro-steel fibers offers a better flexural performance than the addition of hybrid fibers in other proportions. Adding hybrid steel fibers in RCSCC beam increases the beam’s load- and moment-carrying capacities by 40.64% and 40%, respectively, compared to the RCSCC beam without hybrid steel fibers. The crack spacing and crack width are also reduced by 16–45% and 25–75%.

Shear Strength Prediction of Steel-Fiber-Reinforced Concrete Beams Using the M5P Model

This article presents a mathematical model developed using the M5P tree to predict the shear strength of steel-fiber-reinforced concrete (SFRC) for slender beams using soft computing techniques. This method is becoming increasingly popular for addressing complex technical problems. Other approaches, such as semi-empirical equations, can show known inaccuracies, and some soft computing methods may not produce predictive equations. The model was trained and tested using 332 samples from an experimental database found in the previous literature, and it takes into account independent variables such as the effective depth d, beam width bw, longitudinal reinforcement ratio ρ, concrete compressive strength fc, shear span to effective depth ratio a/d, and steel fiber factor Fsf. The predictive performance of the proposed M5P-based model was also compared with the one of existing models proposed in the previous literature. The evaluation revealed that the M5P-based model provided a more consistent and accurate prediction of the actual strength compared to the existing models, achieving an R2 value of 0.969 and an RMSE value of 37.307 for the testing dataset. It was found to be a reliable and also straightforward model. The proposed model is likely to be highly helpful in assessing the shear capacity of SFRC beams during the pre-planning and pre-design stages and could also be useful to help for future revisions of design standards.

Flexural behavior of steel fiber-reinforced coal gangue aggregate concrete beams

The flexural behavior of steel fiber-reinforced coal gangue aggregate concrete (SFCGC) and steel fiber-reinforced ordinary concrete (SFOC) beams were investigated in this study. 11 specimens were tested using four-point bending tests to investigate the effect of coal gangue replacement rate (CGRR) (0%, 50%, 100%), steel fiber volume content (SFVC) (0%, 0.5%, 1%, 1.5%), rebar ratio (0.6%, 1.17%, 1.94%), and beam height (200 mm, 300 mm) on the beam flexural performance. The failure modes, flexural capacities, flexural stiffness, ductility, and energy dissipation coefficient of the specimens were analyzed. In addition, the stress-strain curve of SFCGC was obtained by axial compressive tests in this study. A equations for the stress-strain relationship of SFCGC beams were obtained by data fitting. a finite element model (FEM) of SFCGC beams was established in ABAQUS. A self-programmed Python script was used to create the steel fiber model in FEM of an SFCGC beam, in which steel fibers were distributed randomly and discretely to investigate the strengthening effect of steel fibers on SFCGC beams. Finally, a comparative analysis shows good agreement in the load-deflection curves and transverse strain obtained from simulations using the established FE model and tests.

Numerical study on the effect of steel fibers on fracture and size effect in concrete beams

The construction sector uses concrete extensively all around the world. Concrete contains a lot of microcracks even before it is loaded. When a tensile force is applied, these microcracks attempt to open up. While designing, the strength of concrete in its tensile zone is ignored. The strength and ductility of the concrete can be improved due to the addition of steel fibers. Steel fibers use a bridge mechanism to restrict the micro-cracks spread. This study uses ABAQUS to numerically analyze the behaviour of the Steel Fiber Reinforced Concrete (SFRC) beams. Two grades of concrete are studied, M20 and M60, for varying volumetric percentages of steel fibers. It was observed from the study that the ultimate load increases by around 52% and 41% for M25 and M60 grade concrete, respectively, by adding 1% of steel fiber. Fracture properties such as fracture toughness and fracture energy are calculated. The addition of steel fibers enhanced fracture toughness and energy significantly. Adding 1% fiber increases fracture toughness by around 56% and 34% and fracture energy by around 169% and 136% for M25 and M60 concrete, respectively. The size effect on SFRC beams is studied to determine the size-independent fracture parameters.