Equivalent Flexural Strength Ratio Research Articles

Compressive and flexural toughness indices of lightweight aggregate concrete reinforced with micro-steel fibers

There remains a lack of comprehensive investigations examining ductility of the fiber-reinforced lightweight aggregate concrete (LWAC) elements, necessitating a deeper exploration. The purpose of this study is to assess the effect of micro-steel fibers on the compressive and flexural toughness capacities of LWAC. A total of twenty-one LWAC mixtures were prepared, varying the test parameters of the compressive strength of concrete and fiber volume fraction. The toughness capacities of fiber-reinforced LWAC were calculated using the stress–strain curves in compression and flexural load–deflection curves measured for each specimen, in accordance with ASTM C1018. These were compared with those of the previous normal-weight concrete and LWAC specimens reinforced by single macro-steel fibers or a combination of macro-steel fibers and micro synthetic fibers. The effect of numerous fiber parameters on the toughness of concrete was considered as a function of the fiber reinforcing index. Simple closed-form equations from the literature were modified to reliably determine the compressive and flexural toughness indices of micro-steel fiber-reinforced LWAC. Additionally, the relationship between equivalent flexural strength ratio and flexural toughness indices was formulated from a regression analysis using test datasets. Test results showed that the addition of only 0.25% micro-steel fibers significantly enhanced strength and toughness in compression and flexure. Moreover, better dispersion of steel microfibers enabled greater LWAC strength and toughness increases through a denser restriction of crack propagation.

Comparison of compressive, flexural, and temperature-induced ductility behaviours of steel-PVA hybrid fibre reinforced OPC and geopolymer concretes after high temperatures exposure

This paper presents a comparison of the performances of geopolymer concrete (GPC) and ordinary Portland cement concrete (OPCC) with and without fibres after exposure to 200, 500, and 800 ˚C. The influences of elevated temperatures on the concretes were investigated by the cracking patterns, residual compressive strength, flexural toughness, failure modes, ductility, and thermogravimetric analysis. The results indicate that steel-PVA hybrid fibre is effective to improve the initial flexural strength, flexural toughness, and equivalent flexural strength ratio of GPC and OPCC. Exposure to temperatures at 500 ˚C and above caused distinct deterioration in mechanical properties of the concrete specimens. Additionally, temperature-induced ductility behaviour, which is quantitatively characterised by equivalent flexural strength ratio and normalized absorbed energy (NAE), is observed in concrete specimens after exposure to 500 and 800˚C. The temperature-induced ductility behaviour having an obvious characteristic of ultimate flexural strength reduction and ductility increase, which is influenced by decomposition of the components at elevated temperatures. The decomposition of calcium compound is the primary factor for the higher mass loss values for OPC than the geopolymer specimens.

The impact of specimen size and alteration of fiber configuration on the flexural performance of high-performance concrete

This study examines the impact of fiber configuration and specimen size on the flexural performance and thus the energy absorption capacity of moderate and high-performance fiber reinforced concrete (FRC). A total of 180 specimens were produced using hooked-end steel fibers in lengths of 30-mm and 60-mm, and 54-mm long macro synthetic fibers. The specimens, in the form of small beams (75 × 75 × 320 mm3), large beams (150 × 150 × 750 mm3), and square panel specimens (600 × 600 × 100 mm3), were tested in accordance with EN14488-5 and ASTM C1609 standards. The results showed that as the amount of fibers increased, the flexural performance of FRC improved significantly, provided that precautions were taken to avoid mixing and placement issues when using higher amounts of fibers. 60-mm hooked-end steel fibers had the best performance among all the fibers tested with higher ultimate and post-cracking flexural strengths. 54-mm synthetic fibers seemed to be a cost-effective alternative with comparable energy absorption performance when compared to 30-mm hooked-end steel fibers. Small beams had a slightly higher ultimate (∼15% more) and post-cracking (∼35% more) flexural strengths than large beams, but the equivalent flexural strength ratio was not significantly affected by the specimen size. No clear relationship between fiber dosage and ultimate flexural strength was observed, but a relationship was observed between the fiber dosage and the equivalent flexural strength ratio, with R2 values ranging from 65% to 93% depending on the concrete matrix and the fiber type. The study also showed strong correlations (R2>91%) between the energy absorption capacity of plate specimens and beam specimens, suggesting that plate specimens can be used to reduce the time and effort required in testing during trial batches and product development. Finally, the use of high-performance concrete does not seem to be necessary, when the target is to improve the energy absorption capacity of FRC, particularly at low fiber volumes.

The influences of metakaolin, w/b ratio and fibers on the properties of green-HFLWC

A new approach to control depletion of natural resources and CO2 emission during concrete production, lightweight aggregate, low-C3A cement and supplementary cementitious materials were utilized to develop a green-high strength flowable lightweight concrete (green-HFLWC). The green-HFLWC was developed incorporating low-C3A cement, metakaolin (MK), fly ash (FA) stalite and silica sand. Effects of metakaolin, w/b ratio and different types of fibers on concrete properties were investigated. The results showed that the green-HFLWC incorporating MK with 0.26 w/b ratio could reach high strength (28-day compressive strength of 89 MPa), high flowability (slump flow of 652 mm) and lightweight (oven-dry density of 1883 kg/m3). In addition, it was found that long polypropylene (LPP) fibers increased the splitting tensile strength of HFLWC by 71 % and reached 136 % of equivalent flexural strength ratio of HFLWC compared to the control mix. Moreover, flexural strength of HFLWC with 2 % volumetric ratio of LPP fiber was better than that of the short polypropylene (SPP). At the same time, the steel-LPP hybrid fibers decreased compressive strength by 56 % compared to the control mix. Also, the water absorption ratio for most of mixes was less than 2 %. Furthermore, the CO2 emission and cost of each mix were calculated and a new carbon emission intensity index (Csi) is proposed. Considering the excellent mechanical (high specific strength >40, high ductility with fibers) and durability performance (low water absorption ratio <2 %, high carbonation resistance) of green-HFLWC (Csi <12), it is recommended for the future high-rise buildings located in harsh environment.

Toughness, Reinforcing Mechanism, and Durability of Hybrid Steel Fiber Reinforced Sulfoaluminate Cement Composites

As a low-carbon ecological cement-based material, SAC (sulfoaluminate cement) has become a research hotspot. This study developed a SAC-based high-performance concrete material with good durability and high toughness. The mechanical properties of different scales of MSF (macro steel fiber) and mSF (micro steel fiber) reinforced sulfoaluminate cement-based composites were mainly studied, including their compressive strength, flexural strength, toughness index, and toughness ratio, and their resistance to sulfate erosion was characterized. The results show that adding MSF and HSF (hybrid steel fibers) can significantly improve concrete’s compressive and flexural strength compared with the Plain group. The compressive strength of SSF1 (1% MSF) and SSF2 (1.5% MSF) increased by 10.9%, 19.6%, and the compressive strength of HSF1 (0.1% mSF, 1.4% MSF), HSF2 (0.2% mSF, 1.3%MSF), HSF3 (0.3% mSF, 1.2% MSF), and HSF4 (0.5% mSF, 1.0% MSF) increased by 23.9%, 33.7%, 37.0%, 29.3%, respectively, while the flexural strength of HSF1, HSF2, HSF3, and HSF4 groups increased by 51.4%, 84.9%, 88.1%, and 64.2%. Compared with the single steel fiber (SSF) group, the HSF group has higher initial crack strength, equivalent flexural strength, toughness index, and toughness ratio. Hybrid fibers have a higher synergistic effect when mSF content is 0.2–0.3% and MSF content is 1.2–1.3%. The mechanism of multi-scale reinforcement of hybrid-steel-fiber-enhanced sulfoaluminate cement-based composites was researched. MSF bridges macro-cracks, mSF bridges micro-cracks, and these two different scales of steel fibers, through filling, bridging, anchoring, pulling off, and pulling out, improve the toughness of composite materials. The mechanism of sulfate corrosion resistance of sulfoaluminate cement-based composites was obtained. SO42− entered the matrix and reacted and formed AFt, filling the matrix’s pores. The whole process is similar to the self-healing process of concrete.

Mechanical Optimization of Concrete with Recycled PET Fibres Based on a Statistical-Experimental Study.

Discarded polyethylene terephthalate (PET) bottles have damaged our ecosystem. Problems of marine fauna conservation and land fertility have been related to the disposal of these materials. Recycled fibre is an opportunity to reduce the levels of waste in the world and increase the mechanical performance of the concrete. PET as concrete reinforcement has demonstrated ductility and post-cracking strength. However, its performance could be optimized. This study considers a statistical-experimental analysis to evaluate recycled PET fibre reinforced concrete with various fibre dose and aspect ratio. 120 samples were experimented under workability, compressive, flexural, and splitting tensile tests. The results pointed out that the fibre dose has more influence on the responses than its fibre aspect ratio, with statistical relation on the tensional toughness, equivalent flexural strength ratio, volumetric weight, and the number of fibres. Moreover, the fibre aspect ratio has a statistical impact on the tensional toughness. In general, the data indicates that the optimal recycled PET fibre reinforced concrete generates a superior performance than control samples, with an improvement similar to those reinforced with virgin fibres.

Comparative Flexural Toughness Evaluation of Steel Fibre-Reinforced Concrete

A comparative appraisal of the protocols recommended in the ASTM and Japanese standards for evaluation of flexural toughness of three concrete grades reinforced with steel hooked-end fibres is presented. Target 28-day cube compressive strengths of the three concrete grades were 25 MPa, 35 MPa and 45 MPa and the fibres having an aspect ratio of 80 were used at volume fractions of 0%, 0.13%, 0.19%, 0.25%, 0.31% and 0.38%. Testing for toughness was carried out in the form of displacement-controlled four-point bend tests on prismatic specimens of size 150 mm × 150 mm × 700 mm and stable load–deflection behaviour was obtained only when fibre dosage was at least 0.25%. For fibre volume fractions of 0.25% and more, the toughness parameters obtained from the ASTM and the Japanese standard were comparable. From the results of the comparative study, it is recommended that for an Indian standard, if the toughness characterisation is to be done, then equivalent flexural strength should be considered as the parameter over residual strength. In addition, ‘equivalent flexural strength ratio is also to be considered, since it represents the load retaining capacity of the specimen after the peak load. Nevertheless, equivalent flexural strength is the average flexural strength up to the specified deflection limit which does not specify any post-peak behaviour, hence need not be a characterising parameter for understanding fibre performance in concrete.

Flexural strength and toughness of steel fiber reinforced concrete beams

This study has proposed to evaluate the flexural response of reinforced concrete (RC) beam elements of size 150 mm × 200 mm × 1000 mm (with conventional steel rebars of reinforcement ratio of 0.6%) with and without steel fibers of varying reinforcement index (RI) (product of fiber aspect ratio, AR and volume fraction, Vf%). The mechanical strength (compressive, split tensile and prismatic flexural strength) of concrete are ascertained with hooked steel fibers (HSF) and crimped steel fibers (CSF) in RI of 0.25–1.50 in comparison to controlled concrete (CC) with no fibers. RC beams (with and without HSF and CSF of RI = 0.5–1.0) have been tested under flexure and the loads and deflection at first cracking, yielding, peak and ultimate failure points show that the performance of fibrous beams are higher than non-fibrous beams, and CSF is effective than HSF in RC beams. The RC beams with CSF has higher residual strength and toughness (at deflection point, L/150, L being the span), and total absorbed energy than the specimens with HSF. The residual strength and toughness (at L/150) and the total absorbed energy (TAE) of RC beams with HSF and CSF are higher than the control beams (without fibers). The experimental reserve flexural capacity (ERFC) of RC beams ≥ 1.30. The stiffness of the fibrous RC beams at initial pre-cracking, post-cracking and pre-peak stages are higher than the non-fibrous beams. The deflection ductility indices (yield and peak) have shown an increase when RI is increased from 0.5 to 1.0. The flexural test results have shown that addition of HSF and CSF has improved the first cracking, yielding and peak loads of RC beams (at RI = 0.5, 0.6 and 1.0). The crack spacing and width of flexural cracks in the RC beams have reduced due to the addition of steel fibers, and CSF has shown better cracking behavior than HSF in the beams. The equivalent flexural strength (toughness factor) and strength ratio of RC beams (with conventional reinforcement) with CSF are higher than the beams with HSF, and, therefore, crimped fibers are recommended for effective use in construction.

Flexural Behavior of Compacted-Cement Sand Reinforced with Geogrid

An improvement of flexural strength of cement stabilized soils using geogrid designated as compacted cement-geogrid-sand (CCGS) is investigated in this research. The studied material performance of the CCGS includes postpeak behavior, toughness, and equivalent flexural strength ratio. The geogrid inclusion significantly improves the postpeak flexural behavior, which is a requirement for bound pavement materials. The first peak flexural strength f1 and stiffness of both compacted-cement-sand (CCS) and CCGS are essentially the same for the same cement content. The tested soils were obtained from Ayutthaya province, Thailand, and is commonly used as a construction material for backfill and pavement applications. The backfill soils were used sand. In this study, Type I Portland cement was used as a cementing agent and geogrid two type were used as a reinforcement material. Properties of the cement and the geogrid, which were obtained from the manufacturers. The specimens were subjected to a flexural performance test according to ASTM C1609/C1609M-10 (2010). The results showed that in the flexural performance of the CCGS includeing postpeak behavior, toughness, and equivalent flexural strength ratio depends on the type and shape of apertures of the geogrid. It was found that the triaxial geogrid with shape of triangular apertures was more effective in reinforcing and provided the high equivalent flexural strength over uniaxial geogrid.

Using post-cracking strength to determine flexural capacity of ultra-thin whitetopping (UTW) pavements

Utilizing fibrillated polypropylene fibers (FPP) in Ultra-thin whitetopping (UTW) has become increasingly popular to improve the flexural capacity of concrete slabs. The calculated flexural strength (i.e., modulus of rupture (MOR)) depends on the elastic formula of ASTM C78 does not illustrate the fiber’s benefits. Therefore, the concept of effective modulus of rupture (MOReff.) that is determined from the equivalent flexural strength ratio has been used to quantify the added flexural capacity of fibers on unreinforced concrete. The purpose of this study is to investigate the benefits of testing the FRC/asphalt composite beam on the flexural capacity of UTW. Three main parameters have been taken into consideration: FPP content, pavement thickness, and failure mode. Furthermore, comparison was made to verify the effectiveness of composite beams for flexural capacity. Six different cases of concrete beams and ten cases of FRC/asphalt composite beams were performed. The results of the composite beam showed that the flexural capacity was higher than the capacity of the concrete layer. In addition, using FPP in the composite beams improved the MOReff.. The results also revealed that testing UTW under noncommon failure modes did not reflect the real flexural capacity of UTW. The required UTW thickness depends on the proposed flexural capacity of the composite beam being less than the required thickness that is calculated depends on the concrete beam.

Compressive and flexural properties of ultra-high performance fiber-reinforced cementitious composite: The effect of coarse aggregate

The inclusion of coarse aggregate in the cementitious composite can improve the mechanical property and simultaneously curb the cement demand thus lowering the production cost in concrete built infrastructure. This study investigates the effects of different coarse aggregate types and contents on the compressive and flexural properties of ultra-high performance fiber-reinforced cementitious composite (UHPFRC). Four types of coarse aggregates (granite, basalt, limestone and steel slag) and four contents denoted by the volume of mortar replacement (0%, 15%, 30% and 40%) are the main variables. The test results have shown a significant increase in compressive strength and elastic modulus of UHPFRC after moderate addition of coarse aggregate with only an expense of a slight reduction in the flexural strength and post-peak ductility. The aggregate types having different stiffness can be effective in either increasing the compressive strength or enhancing the post-peak ductility, which is also true for the increase in aggregate content. With respect to the flexural behavior, it is found that coarse aggregate type significantly affects the flexural strength and equivalent flexural strength ratio, whilst no considerable variations in the first crack strength is observed. Furthermore, an analytical model is proposed to generate the complete compressive stress-strain curves of UHPFRC.

Effect of Polypropylene Fiber on the Flexural Strength Properties of Lightweight Foam Mixed Soil

This study examines the effect of polypropylene fiber on the flexural strength properties of lightweight foam mixed soil (LFS). The flexural properties of LFS comprising different proportions of polypropylene fiber (58 mm) at different volume fractions (0.5%, 0.75%, and 1%), three different cement contents of 100, 150, and 200 kg/m3, and densities of 0.8, 1.0, and 1.2 g/cm3 were thoroughly investigated. The flexural performance of LFS according to ASTM C1609 was achieved after 28 days of aging. The results show that the flexural characteristics of LFS could be enhanced by fiber additives, as indicated by the increase in the flexural/residual strength and equivalent flexural strength ratio. The flexural performance is also related to the mixing components, including the density and cement content. For the toughness behavior, the equivalent flexural strength ratio reached up to 100%, which could be achieved with the strain-hardening specimens. The fiber inclusion is more efficient with an increase in the density and cement content of specimens as shown by the overall rating of the flexural performance.

Flexural capacity and crack-closing performance of NiTi and NiTiNb shape-memory alloy fibers randomly distributed in mortar beams

This study assesses the flexural capacity of cement mortar beams that are randomly reinforced with discrete NiTi and NiTiNb shape-memory alloy (SMA) fibers. To achieve this goal, material tests were first performed to analyze the element components and the thermal and mechanical properties of the SMA fibers. The phase change temperature to the austenite was designed to be around 100 °C without damaging the mortar matrix during the heating process. Using fiber volume fractions of 0.50, 0.75, and 1.00%, four-point bending tests were performed with beam specimens that have 40 ✕ 40 mm2 square cross-section with a length of 160 mm. The cracking and post-cracking strengths and the energy absorption capacity were mainly dependent on the mechanical properties and content of SMA fibers. Based on the flexural strength and energy absorption capacity, an equivalent flexural strength ratio that is used in the flexural design of fiber-reinforced cement composites can be proposed to account for the improvement of the ductility in the SMA fiber-reinforced beams. Additionally, this study evaluates the crack-closing performance induced by the activation of the shape memory effect of SMA fibers. The amount of the closed flexural cracks increased with increasing fiber content and depended on the recovery performance of the fiber. The linear trend analysis shows that the crack-closing stress can be generated by approximately 0.36 and 0.06 MPa per 1.00% increase in NiTi and NiTiNb fibers in cement composite beams, respectively.

Shear capacity of cast-in headed anchors in steel fiber-reinforced concrete

This paper investigates the concrete breakout shear capacity of a single cast-in headed anchor embedded in steel fiber-reinforced concrete (SFRC). Experiments were carried out for anchors with a diameter of 30 mm, embedment depth of 240 mm, and edge distance of 150 mm. Fiber volume fractions of 0.33, 0.67, and 1.00% were examined. In addition to shear tests, four-point bending tests were carried out to evaluate the relationship between the material properties of SFRC and the shear capacity of anchors. The experimental results show that the current design formulas are valid for anchors in conventional plain concrete but not appropriate for the shear capacity of anchors in SFRC. Using the equivalent flexural strength ratio, a revised design equation is proposed to incorporate the effect of the steel fiber content on the concrete breakout shear capacity and provide reasonably similar safety for anchors in both un-reinforced and SFRC.

Comparative flexural performance of compacted cement-fiber-sand

This research investigates the influence of seven different fiber types on the flexural performance of compacted cement-fiber-sand (CCFS) with four fiber fractions (0.5, 1, 1.5 and 2% by volume). The seven types of fibers are 12 mm polypropylene, 19 mm polypropylene, 40 mm polypropylene, 55 mm polypropylene, 33 mm steel, 50 mm steel and 58 mm polyolefin fibers. The overall CCFS performance was divided into seven sub design performance indicators: (1) peak strength; (2) peak strength ratio; (3) residual strength ratio; (4) ductility index; (5) toughness; (6) equivalent flexural strength ratio; and (7) maximum crack width. The interaction mechanism of the fiber/cement-sand interface was investigated by scanning electron microscopy. Finally, the effectiveness of each fiber type was compared and rated in terms of the overall performance. The results show that the 50 mm steel fiber provided the best overall sub performance, resulting in an excellent overall flexural performance; in comparison, the 12 mm polypropylene fiber exhibited very poor performance. However, the 19 mm polypropylene and 33 mm steel fiber specimens provided very good and good overall performances, respectively. The nature of the fiber surface and the fiber length affects the overall performance of CCFS. The surface of the steel fibers, compared to the other synthetic fiber types, is more hydrophilic and is more compacted in a cemented-sand matrix without separation of the interfacial zone, providing the best overall flexural performance.

Combined effects of steel fiber and coarse aggregate size on the compressive and flexural toughness of high-strength concrete

This paper investigates the effects of steel fiber content and coarse aggregate size on the mechanical properties of high-strength concrete with a specified compressive strength value of 60 MPa. The paper also explores the correlation between the compressive and flexural toughness of high-strength steel fiber-reinforced concrete (SFRC). For this purpose, twelve high-strength SFRC mixtures with four fiber volume fraction of steel fiber (Vf = 0.5%, 1.0%, 1.5%, and 2.0%) and different aggregate sizes were designed and fabricated. Compressive and flexural tests for each concrete mixture were conducted, and the test results were used to investigate the effects of steel fiber volume fraction and aggregate size on the compressive and flexural toughness of high-strength SFRC prims. The results indicate that the mechanical properties of SFRC are related more closely to volume fraction than to aggregate size. The compressive and flexural toughness ratios of the SFRC significantly improved with an increase in fiber content. Also, equations that are suggested to determine the compressive toughness ratio based on the equivalent flexural strength ratio were used to predict the mechanical properties of the SFRC in this study.

Benefits of using amorphous metallic fibers in concrete pavement for long-term performance

This study aims to examine the implications of amorphous metallic fibers on the mechanical and long-term properties of concrete pavement. Two different amounts of amorphous metallic fibers were incorporated into concrete, and plain concrete without fibers was also adopted as comparison. Test results indicated that the overall mechanical properties of concrete were improved by including the fibers, and the improvement increased when a higher amount of fibers was used. In particular, the equivalent flexural strength and flexural strength ratio were substantially improved by incorporating the amorphous metallic fibers. This may enable the thickness of airfield concrete pavement to decrease. The resistance to surface cracking of concrete pavement by repeated wheel loading was also improved with the addition of amorphous metallic fibers. In addition, by adding 5kg/m3 and 10kg/m3 amorphous metallic fibers in concrete pavement, roughly 1.2 times and 3.2 times longer service life was expected, respectively, as compared to their counterpart (plain concrete). Based on a life cycle cost analysis, the use of amorphous metallic fibers in concrete pavement was effective at decreasing the life cycle cost compared to plain concrete pavement, especially for severe traffic conditions.

Flexural capacity of fiber reinforced concrete with a consideration of concrete strength and fiber content

An experimental study was performed to examine the effects of concrete strength and fiber content ratio on the flexural capacity of steel fiber-reinforced concrete. Three fiber volume fractions, 0.25, 0.375, and 0.5%, and three concrete compressive strengths, 25, 35, and 45MPa, were designed for the experiments. The stress and deflection relationship, first peak and post-cracking strength, and energy absorption capacity were evaluated with respect to the variance in the fiber volume fraction and concrete strength. The results showed that the equivalent flexural strength ratio, which is determined from the first peak strength and energy absorption capacity, increased with the increase in the fiber volume fraction but decreased with the increase in the concrete strength. Furthermore, the effects of the concrete strength and fiber content ratio are discussed in a steel fiber-reinforced concrete floor slab. The ultimate flexural capacity also required a consideration of the influence of the content ratio of steel fiber as well as the strength of cement composite matrix.

Influence of concrete strength combined with fiber content in the residual flexural strengths of fiber reinforced concrete

Recently, the design and construction of fiber reinforced concrete structures, such as floor slabs and precast tunnel linings, require using the actual values of the residual flexural strength instead of the average concept of the equivalent residual flexural strength ratio. An experimental study was performed to examine the direct residual flexural strengths of steel fiber reinforced concrete beams with various concrete strengths, 25, 35, and 45MPa, and fiber volume factions, 0.25, 0.375, and 0.50%. The influence of the concrete strength and fiber content in the limit of proportionality, residual flexural strength, and energy absorption capacity were evaluated. The fiber reinforced concrete beams with a strength of 45MPa showed a higher increase in the residual flexural strength immediately after concrete cracking, particularly for a fiber volume fraction of 0.5%. On the other hand, as concrete cracking propagated, the residual flexural strength and energy absorption capacity values rapidly decreased in the beams with a concrete strength of 45MPa.

강섬유 보강 콘크리트 인장성능 평가방법에 따른 지반 바닥슬래브의 설계

Flexural strength of concrete ground slab reinforced with steel fiber is evaluated using the equivalent flexural strength ratio of steel fiber reinforced concrete based on the yield line theory. Recently, the European standard specifies that the tensile performance of the steel fiber reinforced concrete be evaluated directly from the residual flexural strength after the cracking of concrete. Thus, in the study, an experiment was carried out to evaluate the conventional equivalent flexural strength ratio and the residual flexural strength of the steel fiber reinforced concrete. Then the design flexural strength was investigated according to the location of a point load, based on the ratio of the radius of contact area of the load to the radius of relative stiffness. Design flexural capacity obtained from ACI 360R-10 was smaller than that from TR 34 (2003 & 2013). In addition, TR 34 (2013), which evaluates the design flexural capacity based on the residual flexural strength, showed slightly smaller value than TR 34 (2003).