Steel Fiber Dosage Research Articles

Flexural behavior of preflex sfrc-encased steel joist composite beams

This research investigates the behavior of encased steel composite beams within steel fiber reinforced concrete (SFRC) in straight and preflex beams, using nonlinear analysis. ABAQUS FEA software has been adopted. Composite steel beams encased in fiber reinforced concrete are analyzed and a comparison is made with available experimental results. Good agreement with the experimental results is observed. Upwards camber of the steel section is introduced on the steel joist. It’s found that the preflex section can increase the ultimate load capacity by 10% and decrease midspan displacement by 13% of the same beams without the preflex steel section. Steel fiber dosages, compressive strength, modulus of rupture are examined. The effect of cambering and mesh refinement is also investigated. The physical properties of SFRC are calculated through testing at the UTA Civil Engineering Laboratory Building. In total, nine (4″ x 8″) cylindrical specimens, nine (6″ x 12″) cylindrical specimens, and nine (6″ x 6″ x 20″) beam specimens were produced and tested for their compressive strength, tensile strength, and modulus of rupture after 28 days of curing. The addition of steel fiber will lead to a significant increase in tensile strength and modulus of rupture of concrete. Adding 1% steel fibers by volume can increase the load capacity by 33% and decrease the midspan displacement by 70% in comparison to the same beam using plain concrete. The increase in steel fibers and cambering shows an improvement to the flexural capacity and cracking point of the beam, which can provide mo re strength to structures such as long-span bridges.

Numerical investigation on ballistic performance of coarse-aggregated layered UHPFRC

The impact resistance of coarse-aggregated layered Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is investigated numerically with LS-DYNA. The Holmquist Johnson Concrete (HJC) model is employed to describe the dynamic behavior of the UHPFRC, and the effect of the coarse aggregates is reflected in the pressure-compaction relation. Mechanical tests are conducted to obtain the material-related inputs for the numerical model, and ballistic experiments are applied to calibrate the model parameter as well as to validate the simulation results. After valuation, the ballistic histories of the projectile and the penetration processes in the UHPFRC targets are analyzed. Furthermore, the study discusses the effects of the target thickness on the depth of penetration, showing the possibility to replace a thicker single-layered target by a thinner triple-layered one to achieve the same level of protection. Finally, perforation limits of the single- and tripled-layered UHPFRC at different impact velocities are estimated, based on which the ACE formulae are modified to accurately predict the perforation limit of the coarse-aggregated layered UHPFRC. The numerical simulations in this study reveal that the triple-layered target requires fewer dosages of cement and steel fibers in comparison to its single-layered counterpart with the same level of ballistic protection.

Influence of Hybrid Fibres on Bond Strength of Concrete

Bond strength between embedded bar and concrete plays vital role in the design of various reinforced concrete structural elements. Use of metallic and synthetic fibres has been shown to be an effective method to enhance tensile strength, reduce shrinkage and improve durability properties of concrete. However, making of synthetic fibres will not only deplete the natural hydrocarbon resources, but also add greenhouse pollutants to the environment. Hence, sisal fibre was considered as a potential alternative to polypropylene fibre. An experimental study was conducted to evaluate the influence of sisal fibres as mono-fibre and in combination with steel as hybrid fibre on bond strength of concrete. The performance of steel polypropylene fibre reinforced concrete (SPFRC) is compared with that of steel sisal fibre reinforced concrete (SSiFRC). Bond strength was conducted onM30 grade concrete for curing periods of 7, 28 and 90 days. Fibre dosages of 0.50%, 1.00%, 1.25% and 1.50% by volume of concrete were used. Results indicated that increase in steel fibre dosage improved the bond strength slightly. However, increase in fibre dosage of either PP fibres or sisal fibres resulted decrease in bond strength. Furthermore, sisal fibre reinforced concrete (SiFRC) showed inferior performance in bond strength as compared to polypropylene fibre reinforced concrete (PFRC). A detailed statistical analysis revealed that although no strong correlation between the compressive strength and the bond strength was evident from the experimental study, means of bond strength of both the hybrid groups did not differ significantly. In addition, empirical equations were proposed to predict the bond strength of fibre reinforced concrete (FRC) based on compressive strength.

Experimental investigation of steel fiber RC hollow columns under eccentric loading

an investigation was conducted to identify the behavior of steel fiber reinforced concrete columns with an opening under eccentricity loading, focusing on square hollow columns section having different square hole sizes and various steel fiber dosages were cast and tested. The holes pass longitudinally at the center of the cross-section of the columns. The research includes a test of nine columns of dimensions (200 × 200 × 1600 mm). Test parameters were the steel fiber contents (0.5%, 1.0% and 1.5% volume fraction) and opening ratio (10% and 20% hollow ratio) with load eccentricity (eccentricity/column depth ratio is 0.75). The compressive strength cylinder tests are conducted for various steel fiber dosages in terms of volume fraction. First cracking load, lateral displacement and ultimate load for each column are calculated and compared with similar columns made of ordinary reinforced concrete with and without a hole. The experimental results show that for concrete columns with hollow ratios 10% and 20% (C2-I, C-II) and without steel fibers, the first cracking load reduction was 28.88% and 49.70% respectively compared with the solid column (C1-I, C1-II). The addition of steel fibers significantly improves the mechanical response of the tested specimens especially the cracking load. The cracking load for specimen C5-I (10% opening ratio with 1.5% steel fibers volume fraction) increased 2.346 times the cracking load for specimen C2-I (10% opening ratio without steel fibers) and for a specimen with a 20% opening ratio and 1.5% steel fibers volume fraction (C5-II), the cracking load increased 2.181 times the same specimen without adding steel fibers. The ultimate load-carrying capacity for specimen C5-I (10% opening ratio with 1.5% steel fibers volume fraction) increased 1.094 times the cracking load for specimen C2-I (10% opening ratio without steel fibers) and for a specimen with a 20% opening ratio and 1.5% steel fibers volume fraction (C5-II), the ultimate load-carrying capacity increased 1.23 times the same specimen without adding steel fibers. The test results indicate the addition of steel fiber enhanced the strength capacity, ductility and allowing these columns to absorb more energy compared with a similar column with ordinary reinforced concrete.

Mechanical properties, durability and environmental evaluation of rubberized concrete incorporating steel fiber and metakaolin at elevated temperatures

In this study, the effects of metakaolin (MK), as a replacement for the Portland cement, in the ratios of 0%, 10% and 20% by cement weight and steel fiber (SF) dosages of 0%, 0.25%, 0.5%, and 1% by concrete volume were investigated on the microstructure, mechanical properties, durability and global warming potential (GWP) of concrete containing 25% volume percentage of crumb rubber replaced with natural fine aggregates at elevated temperatures. Several specimens were exposed to the high temperatures of 150, 300, 450 and 600 °C for an hour, and were then compared in terms of mass loss, compressive strength, ultrasonic pulse velocity (UPV), splitting tensile strength (STS), and impact resistance at the ambient temperature. The role of MK and SF on the concrete microstructure at high temperatures was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The results show that not only does the combination of MK and SF improve the mechanical properties and durability of rubberized concrete at high temperatures, but it can also introduce more environmentally friendly mixes by reducing CO2 emissions, compared to a plain concrete mix.

Experimental Investigation of Utilizing Steel Fiber as Concrete Reinforcement in Bridge Decks

The study aims to investigate and test the behavior of steel fiber reinforcement concrete material at different dosage of fibers in concrete bridge decks. Concrete is a brittle material therefore the tensile resistance of concrete is low. Steel fiber reinforcement concrete material is a developed material that has been proposed to improve the tensile behavior of the concrete. Steel Fiber Reinforcement is popular material that is being studied to improve the structural behavior of reinforced concrete under different load conditions. Steel fiber-reinforced concrete (SFRC) provides improved tensile performance of concrete. This improved performance can be used in slabs to reduce the volume of conventional steel reinforcement, create longer spans, or reduce slab thickness. The project consisted of twelve concrete slabs has dimensions of (45 inches x 20 inches x 3.5 inches), twelve cylinders has dimensions of (6 inches diameter x 12 inches height) for split tensile test, twelve cylinders has dimensions of (4 inches diameter x 8 inches height) for compression test and twelve beams has dimensions of (6 inches x 6 inches x 20 inches) for modulus of rupture test. each three concrete slabs and specimens has same dosage of steel fiber reinforcement starting with 0.0%, 0.5%, 1.0% and 1.5% in order to investigate and exam the concrete behavior. The experiment revealed that the increase in the dosage of steel fiber fraction increases the compressive strength of the concrete in addition to that the breakout strength of concrete in tension increased. It is also found that the steel fiber improves the ductility of concrete and that is clear in the “Load- Deflection response figures” the area under the curves increases compare with normal concrete while the crack width became thinner with the increasing of the steel fiber dosage and preventing the sudden collapse as in normal concrete. Taking those results into consideration this can make a reduction in structural weight and improve the safety and speed up the construction and cost saving in the short term and the long term.

Mechanical Properties of Fibre Reinforced Self Compacting Concrete using Rice Husk Ash

Self-compacting concrete (SCC) is relatively a recent development in the construction world. SCC can flow through dense reinforcement under its own weight without any segregation, bleeding, and vibration. The use of steel fibers is being encouraged to increase mechanical characteristics of SSC. However, adding fibers to fresh concrete results in loss of workability. Steel fibers operate as crack arrestors in concrete and extend the span of structures. In the present study, the mechanical properties of SCC with cement is partially replaced by rice husk ash (RHA) & P500 (ultra-fine fly ash). A total of 5 mixes with 0.3 W/C ratio were cast for 7, 28 and 56 days water curing. The replacement of fibres is considered as 0%, 0.5%, 1%, 1.5%, and 2% by weight of cement. Workability, Compressive, Split Tensile and Flexural strength is studied in this investigation. Superior strength was observed at optimum dosage of steel fibers at 1.5% by weight of cement.

Fuzzy logic model for investigating the effect of steel fibers on mechanical properties of concrete

This study aimed to use fuzzy logic model to predict various mechanical properties such as compressive strength, flexural strength and post-peak deformation of steel-fiber reinforced concrete. For this purpose, five different dosages of steel fibers (10 kg/m3, 12.5 kg/m3, 15 kg/m3, 17.5 kg/m3 and 20 kg/m3) were used in the mix design. A total of 3 specimens (cylinders and beams) were casted for each fiber dosage and experimentally tested. The experimental results were compared with the simulated results obtained from fuzzy model using fuzzy logic toolbox provided in MATLAB®. It was found that the addition of steel fibers improved the flexural strength and post-peak deformation capability of test specimens by almost 12% and 20% respectively. The compressive strength of specimens also increased by 9.15%, when the amount of steel fibers was increased from 10 to 20 kg/m3. Overall, the compressive strength reduced with the addition of fibers as compared to specimens with no fibers. Similarly, it was also observed that fuzzy model can predict the study parameters within acceptable accuracy and the percentage difference between the simulated and experimental values was below 7.5%.

Mechanical behavior of SFRC beams subjected to both impact and fire loadings

To explore the mechanical behavior of SFRC beams subjected to both impact and fire loadings, 4 beams were tested with high-performance drop-weight test system, four point bending test machine and assembled electric furnace. The beams were firstly subjected to impact loadings and then exposed to fire with a constant load. During the test process, the crack patterns of beams were observed while the time histories of mid-span deflections and rebar strain were recorded. Then, the fire resistance of these beams was discussed. Based on the experiment, three-dimensional macroscopic finite element numerical model considering the effects of strain rate and high temperature was established. The impact loading process was simulated firstly; and then taking simulation results as the initial state, SFRC beams subjected to both fire and constant loading were simulated with a sequentially coupled thermal-stress analysis method. Moreover, considering the heterogeneity of concrete’s internal structure, a meso-scale simulation was also conducted with the procedures similar to that in macroscopic simulation. Good agreement between both the macro-/meso-scale simulation results and the test results illustrates the rationality and effectiveness of the present numerical analysis methods. The advantages of mesoscopic model were indicated through the comparison of macro-/meso-scopic results. It has been found that when the impact energy is low, the local concrete is cracked but a small overall deformation is remained. Nevertheless, this degrades the fire resistance of SFRC beams to some ex-tent. When the steel fiber dosage increases, resulting in an increasing shear strength of concrete matrix, the coexistence phenomenon of bending and shear cracks of beams under the impact load is changed to bending cracks as a dominant. Moreover, when subjected to elevated temperatures with a constant load, the distribution of cracks on the impact-damaged SFRC beams is relatively concentrated and a brittle failure occurs.

Flexural strength at high temperatures of a high strength steel and polypropylene fibre concrete

Concrete is a widely used material in building construction. In case of fire concrete is subjected to high temperatures exhibiting thermal instability for certain temperatures. The phenomenon leads sometimes to degradation of the concrete compromising the safety of the structures. This paper reports the results of an experimental investigation for assessing the fracture energy at ambient and high temperatures of a high strength polypropylene and steel fibre concrete. The experimental program was designed to evaluate the influence of various parameters that may influence the fracture energy of the fibre concretes in study. Five concrete compositions were tested with different steel fibre dosages and types: one without steel fibres (reference composition), two with Dramix 3D steel fibres and two with Dramix 5D steel fibres (45 and 75 kg/m3). All compositions had 2 kg/m3 of polypropylene fibres that were used to avoid spalling on the specimens. The results indicated that the addition of steel fibres improving the fracture energy of the concrete increasing its ultimate flexural strength and ductility at ambient temperature. However, at high temperatures a deterioration in the fracture energy and ultimate flexural strength with the increasing of temperature was observed. Concrete compositions with Dramix 5D steel fibres lead to higher fracture energy and flexural strength comparing to compositions with Dramix 3D steel fibres. The same happens when using higher dosages of steel fibres in the concrete composition.

Experimental analysis of static capacity of fibrous concrete cambered slabs after impact loading effect

Fibrous concrete is an enhanced material by adding fibers to the ingredients of normal concrete. This addition improved some properties of the regular concrete, which are growing concrete ductility, decreasing concrete shrinkage, and raising concrete resistance to the dynamic attacks. The aim of this paper is more investigating the properties of fibrous concrete by finding out the effect of impact loading induced by a free fall ball on flexural capacity of fibrous concrete from one side, and finding out the importance of camber construction in reducing the influence of impact loading on the flexural capacity of concrete slabs from another side. For that purpose, three concrete slabs of (80X80X4) cm dimensions were dynamically and then statically loaded. The three specimens had the same steel fiber dosage of 0.5%, but they had different slab camber at the mid span where one specimen had no camber, the second specimen had 10 mm camber, and the third specimen had 20 mm camber. In addition to the difference in the slabs‘ camber, the three slabs were subjected to a different number of impacts and from various heights to get a better explanation. Tests results showed that presence of fibers and increasing slab camber caused an improvement in the specimen resistance to both of impact and flexural loads, decreased the specimen crack width and number, and provided a safer residence for tenants.

Uniaxial tensile behavior of aligned steel fibre reinforced cementitious composites

By applying an external uniform magnetic field to a fresh cement mixture during casting, an aligned steel fibre reinforced cementitious composites (ASFRC) was prepared. This investigation compares the performance of ASFRC with its counterpart—ordinary steel fibre reinforced cementitious composite (SFRC) containing randomly distributed steel fibres. First, the orientation of the steel fibres in ASFRC and SFRC specimens was examined using X-ray computed tomography analysis; this confirmed that the steel fibres were effectively aligned in the ASFRC. Then, uniaxial tensile tests were performed to allow a comparison of the uniaxial tensile stress–strain curves of the ASFRC and SFRC; and to determine the advantages, if any of ASFRC over SFRC in terms of uniaxial tensile strength (fUtu), ultimate strain (εUtu) and energy dissipation (Gf-A). The uniaxial tensile test results were also used to show that, if the tensile strength of ASFRC is equal to that of SFRC (actually slightly exceeding) using the aligned steel fibre technology, the dosage of steel fibres can be reduced at least 40%. It was also found that the alignment of the steel fibres affects the strain-hardening and multiple cracking behavior of the composites during uniaxial tension testing. Finally, the multiple cracking behavior of the composites was analyzed using a digital image correlation method. These results show that ASFRC exhibits a multiple cracking pattern at a much lower fibre content compared to SFRC.

Experimental and Finite Element Analysis of Continuous RC Slab Panels with Steel Fiber Reinforced Concrete (SFRC) as an Alternative to Negative Reinforcement

This paper presents experimental and finite element analysis of RC slab panels with steel fiber reinforced concrete (SFRC). For this purpose, four SFRC slab panels with (2000×250×50mm) dimensions are poured using a concrete class of ( f' c =22MPa) with (15kg/m 3 ) dosage of steel fibers and steel class ( f y =410MPa) without shear stirrups. Two of the slab panels were modeled by using nonlinear material properties adopted from experimental study and analyzed till the ultimate failure by ANSYS (Version-15) software. The tested slab panels are subjected to bending by two-point loading, exactly after having been moist-cured for (28 days). The slab panels were tested up to the failure with control of loads. The applied loads and mid-span deflections are carefully recorded at every (5kN) load increment from the beginning till the ultimate failure. The results obtained from the finite element and experimental analyses are compared to each other. It is seen from the results that the finite element failure behavior indicates a good agreement with the experimental failure behavior. The paper concludes that the traditional negative steel reinforcement (steel bars) can be replaced (partially or totally) by using the adopted technique and the contribution of SFRC in manufacturing of thin slabs panels was enhanced. Keywords: Finite Element, Steel fiber, Continuous Slab, Concrete, NSC, Ansys. DOI : 10.7176/CER/11-3-01 Publication date : April 30 th 2019

Mechanical properties and constitutive stress–strain behaviour of steel fiber reinforced concrete under uni-axial stresses

This paper presents the mechanical properties and stress–strain behaviour of low and high strength concrete (30 and 70 MPa) reinforced with hooked-end steel fibers. In this investigation various strength properties of SFRC are studied such as compressive strength, direct tensile strength, flexural strength and stress–strain behaviour of concrete under uni-axial stresses. Hooked-end steel fibers of 25 mm length and aspect ratio of 62.5 used at different fiber volume fractions varied from 0.0, 0.5, 0.75, 1 and 1.25%. The optimum dosage of steel fiber achieved at 1% fiber volume fraction. Experimental results shows that there is no significant improvement in compressive strength with addition of steel fibers. Unlike the concrete in compression percentage strength improvement in direct tensile strength and flexural strength is more. Addition of hooked-end fibers significantly influenced the stress–strain behaviour of concrete under uni-axial stresses. Non-linear regression analysis of test data for various strength properties are also conducted and obtained results are in good agreement with the test results. The enhancement in strength with the addition of fibers is mainly due to fibers in concrete delay the formation of cracks.

Compressive and flexural behaviors of ultra-high strength concrete encased steel members

One way to achieve sustainable construction is to reduce concrete consumption by use of more sustainable and higher strength concrete. Modern building codes do not cover the use of ultra-high strength concrete (UHSC) in the design of composite structures. Against such background, this paper investigates experimentally the mechanical properties of steel fibre-reinforced UHSC and then the structural behaviors of UHSC encased steel (CES) members under both concentric and eccentric compressions as well as pure bending. The effects of steel-fibre dosage and spacing of stirrups were studied, and the applicability of Eurocode 4 design approach was checked. The test results revealed that the strength of steel stirrups could not be fully utilized to provide confinement to the UHSC. The bond strength between UHSC and steel section was improved by adding the steel fibres into the UHSC. Reducing the spacing of stirrups or increasing the dosage of steel fibres was beneficial to prevent premature spalling of the concrete cover thus mobilize the steel section strength to achieve higher compressive capacity. Closer spacing of stirrups and adding 0.5% steel fibres in UHSC enhanced the post-peak ductility of CES columns. It is concluded that the code-specified reduction factors applied to the concrete strength and moment resistance can account for the loss of load capacity due to the premature spalling of concrete cover and partial yielding of the encased steel section.

Mechanical properties of steel fiber-reinforced UHPC mixtures exposed to elevated temperature: Effects of exposure duration and fiber content

In the present study, ultra-high performance concrete (UHPC) mixtures reinforced with varying dosage of steel fibers were considered for studying the effects of exposure duration and fiber content on mechanical properties of the mixtures subjected to a sustained pre-spalling elevated temperature of 300 °C for different durations. Test results showed an increase in compressive strength and modulus of toughness even after exposing to elevated temperature for 5 h. However, modulus of elasticity and flexural strength decreased significantly with increase in exposure duration. The experimental data were statistically analyzed using analysis of variance (ANOVA) method to examine the effects of fiber content and exposure duration on the mechanical properties. Empirical equations were obtained with excellent degrees of fit correlating the mechanical properties of UHPC mixtures with fiber content and exposure duration.

Flexural performance of steel fibre reinforced concrete beams designed for moment redistribution

This paper presents an experimental study to investigate the flexural and moment redistribution performance of six full-scale two-span continuous reinforced concrete beams with and without steel fibres. The beams were reinforced with conventional bar reinforcement with longitudinal steel reinforcement ratios of between 0.0069 and 0.0138; four of the six beams also contained either 30 kg/m3 or 60 kg/m3 of steel fibres. The specimens were tested under monotonically increasing displacement-controlled loading. The primary variables within different test specimens were the arrangement of longitudinal steel bar and the dosage of steel fibres. The beams were designed for 30% of positive and negative moment redistribution with respect to the linear-elastic condition, the maximum allowed by different codes and standards. Test results showed that the inclusion of steel fibres increases the load carrying capacity of the reinforced concrete beams. Furthermore, the addition of steel fibres increased the number of cracks and decreased the crack spacing. For the steel reinforcement ratios tested, the RC-SFRC beams were found to have good ductility. It was shown that the RC-SFRC beams achieved full moment redistribution demand to form the collapse mechanism, and maintained their load carrying capacity for large plastic-hinge rotations. The guidelines of AS 5100.5-2017 were found to give a good prediction of the load carrying capacity of the tested RC-SFRC beams.

Improvement effect of steel fiber orientation control on mechanical performance of UHPC

In order to improve mechanical properties of ultra-high performance concrete (UHPC), one L-shape device with a narrow horizontal channel was developed to control the flow of fresh mixture and then the orientation of steel fibers was significantly improved. Mixtures with water-to-binder ratios of 0.20, 0.22 and 0.24 were prepared by introducing steel fibers with 1%, 2%, and 2.5% of the total volume respectively. Three fiber orientation parameters (fiber orientation angle, fiber orientation number and fiber orientation coefficient) were quantitatively evaluated by the image analysis method. Based on experimental results, mechanical properties (compressive strength, flexural strength, toughness, deflection at modulus of rupture and maximum deflection) were notably increased with the higher dosage of steel fibers. Compared with specimens prepared by a direct cast, this flow control method improved fiber orientation number and fiber orientation coefficient from 0.6 to 0.7 and 0.4–0.6 to 0.7–0.9 and 0.6–0.8 respectively. The best improvement on flexural strength, toughness, deflection at modulus of rupture and maximum deflection reached 64.3%, 65.1%, 77.1% and 14.9% respectively. Based on experimental results, linear relationships were regressed for fiber orientation parameters and mechanical properties of UHPC. Therefore, a potential method was developed to improve the reinforcement effect of steel fibers in UHPC.

Impact Resistance and Strength Reliability of Novel Two-Stage Fibre-Reinforced Concrete

Two-stage fibre-reinforced concrete (TSFRC) is a novel fibrous concrete that differs from the conventional fibre-reinforced concrete (FRC) in several aspects including its placement technique, implementation, fabrication methodology, and high coarse aggregate content. Consequently, the available data from the open literature on the behaviour of the conventional FRC exposed to falling weight collision may not be applicable to TSFRC. For instance, the impact strength performance of the conventional FRC is well documented; however, for TSFRC this has not been duly examined. For the first time, this study pioneers the concept of impact strength of TSFRC under falling weight collision. For this purpose, short crimped fibres and long hooked end steel fibres at 1.5, 3.0, and 5.0% dosage were used in two-stage concrete (TSC). To this end, seven different mixes were prepared and tested under falling weight collision as per ACI committee 544. In addition, a statistical analysis has been performed to analyse the scattered test results by Weibull distribution. For determining Weibull parameters, 20 probability estimators have been used, and the best estimators are taken for the reliability analysis. Based on the obtained Weibull parameters, the impact strength of TSFRC has been reported in terms of reliability. The results revealed that the ability of using higher fibre dosages allows achieving greater impact resistance properties for novel manufacturing TSFRC. Indeed, the TSC with steel fibre dosages exceeding 5%, can be produced easily thus making this innovative, yet simple to produce concrete, a strong contender in many construction applications. The two-parameter Weibull theory has been found to be adequately suitable for analysing the variations in the number of impacts that induces first crack and failure of all group of TSFRC specimens.

Efficiency of steel and macro-synthetic structural fibers on the flexure-shear behaviour of prestressed concrete beams

The efficiency of steel and structural synthetic fibers on the performance improvement of prestressed concrete (PSC) beams under combined flexure-shear is studied. Results of eleven PSC beams tested at a shear span (a) to depth (d) ratio of five are presented. Discrete steel and macro synthetic structural polyolefin fibers of varying dosages of 0.35%, 0.7% and 1.0% by volume of concrete were used. The effect of fiber addition on overall load – displacement, load- strain, and strain energy absorption capacity of PSC beams is analysed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, prestressing reinforcement ratio were kept constant. The test results portray that the addition of steel fibers stiffens the post cracking response, increases the strain energy absorption capacity more efficiently when compared to macro synthetic fibers (Polyolefin). The failure mode changed from less ductile flexure-shear to more ductile flexure dominant mode at 0.35% and 0.70% volumetric dosage of steel and synthetic fibers, respectively. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers.