Effect of Steel Fibers on Minimum Shear Reinforcement of High-Strength Concrete Beams

Kim, Chul-Goo; Lee, Hyerin; Park, Hong-Gun; Hong, Geon-Ho; Kang, Su-Min

doi:10.14359/51689782

Cited by 16 publications

(9 citation statements)

References 8 publications

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“…Referring the conducted test results, the addition of 1.5 vol% short straight fibers to the UHPC mixture was enough to change the failure mode without requiring any shear reinforcement. This observation was well-supported with those presented in Kim et al [22], Zagon et al [30], Lim and Hong [31], and Hegger and Bertram [33]. It can be deduced that the steel fiber use provided a preferable structural performance for both fiber volume fractions against the reference beam exhibiting flexural behavior.…”

Section: Cracking Behavior and Failure Modessupporting

confidence: 87%

“…Even though no shear reinforcement is provided in the UHP-FRC beams, in contrast with the requirements in design codes, the inclusion of steel fiber use of 1.5% by volume is sufficient to guarantee the flexural behavior. This observation consisted with those deduced from the researches by others [22,30,31,33].…”

Section: Discussionsupporting

confidence: 71%

“…It is important to point out that the steel fibers to be added to the mixture at an optimum proportion may be able to replace or reduce the shear reinforcement and/or shear link, which may be a reason to reinforce congestion for small cross-sections, since the UHP-FRC beams have very high compressive and tensile strengths [17]. However, the addition of steel fibers restricts the formation and propagation of cracks [17][18][19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

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Steel Fiber Use as Shear Reinforcement on I-Shaped UHP-FRC Beams

et al. 2019

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In the presented paper, the effectiveness of steel fiber use on the shear and flexure behaviors of ultra-high performance concrete (UHPC) beams and the feasibility of steel fibers in place of shear reinforcement were investigated experimentally. In this framework, a total of four I-shaped UHPC beams were produced for a high tensile reinforcement ratio of 2.2%. While two of them were non-fiber UHPC beams with and without the shear reinforcement to show the contribution of steel fibers, the remaining beams were made from the ultra-high performance steel fiber-reinforced concrete (UHP-FRC) having the short straight fibers with 1.5% and 2.5% by volume. The shear and flexural parameters, such as the load–deflection response, cracking pattern, failure mode, deflection, and curvature ductilities were discussed based on the four-point loading test results. While the reference beam without fiber and shear reinforcement failed by the shear with a sudden load drop before the yielding of reinforcement and produced no deflection capability, the inclusion of steel fibers to the UHPC matrix transformed the failure mode from shear to flexure through the fibers’ crack-bridging ability. It might be deduced that the moderate level of steel fiber use in the UHP-FRC beams may take the place of shear reinforcement in practical applications.

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Section: Cracking Behavior and Failure Modessupporting

confidence: 87%

Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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Steel Fiber Use as Shear Reinforcement on I-Shaped UHP-FRC Beams

et al. 2019

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“…The fiber factor F [125][126][127][128] takes into account the geometry of the fibers (length and diameter) [53,129], the amount of fibers (fiber volume fraction) [69,70,130], and the bond properties of the fibers, which depends on the fiber type [4,[131][132][133]. A challenge here was to ascribe bond properties to the less common fiber types that were encountered in the literature.…”

Section: Discussionmentioning

confidence: 99%

ANN-Based Shear Capacity of Steel Fiber-Reinforced Concrete Beams without Stirrups

Abambres

Lantsoght

2019

Fibers

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Comparing experimental results of the shear capacity of steel fiber-reinforced concrete (SFRC) beams without stirrups to the capacity predicted using current design equations and other available formulations shows that predicting the shear capacity of SFRC beams without mild steel shear reinforcement is still difficult. The reason for this difficulty is the complex mechanics of the problem, where the steel fibers affect the different shear-carrying mechanisms. Since this problem is still not fully understood, we propose the use of artificial intelligence (AI) to derive an expression based on the available experimental data. We used a database of 430 datapoints obtained from the literature. The outcome is an artificial neural network-based expression to predict the shear capacity of SFRC beams without shear reinforcement. For this purpose, many thousands of artificial neural network (ANN) models were generated, based on 475 distinct combinations of 15 typical ANN features. The proposed “optimal” model results in maximum and mean relative errors of 0.0% for the 430 datapoints. The proposed model results in a better prediction (mean Vtest/VANN = 1.00 with a coefficient of variation 1 × 10−15) as compared to the existing code expressions and other available empirical expressions, with the model by Kwak et al. giving a mean value of Vtest/Vpred = 1.01 and a coefficient of variation of 27%. Until mechanics-based models are available for predicting the shear capacity of SFRC beams without shear reinforcement, the proposed model thus offers an attractive solution for estimating the shear capacity of SFRC beams without shear reinforcement. With this approach, designers who may be reluctant to use SFRC because of the large uncertainties and poor predictions of experiments, may feel more confident using the material for structural design.

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“…As can be seen in the database, many experiments do not fulfil this requirement. [51,73,81,90,108,114,118,119], a standard laboratory mix with da = 10 mm is assumed. References [51,85,113,114,123,127] do not report the yield strength of the steel.…”

Section: Overview Of Shear Prediction Equationsmentioning

confidence: 99%

Database of Shear Experiments on Steel Fiber Reinforced Concrete Beams without Stirrups

Lantsoght¹

2019

Preprint

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Adding steel fibers to concrete improves the capacity in tension-driven failure modes. An example is the shear capacity in steel fiber reinforced concrete (SFRC) beams with longitudinal reinforcement and without shear reinforcement. Since no mechanical models exist that can fully describe the behavior of SFRC beams without shear reinforcement failing in shear, a number of empirical equations have been suggested in the past. This paper compiles the existing empirical equations and code provisions for the prediction of the shear capacity of SFRC beams failing in shear as well as a database of 487 experiments reported in the literature. The experimental shear capacities from the database are then compared to the prediction equations. This comparison shows a large scatter on the ratio of experimental to predicted values. The practice of defining the tensile strength of SFRC based on different experiments internationally makes the comparison difficult. For design purposes, the code prediction methods based on the Eurocode shear expression provide reasonable results (with coefficients of variation on the ratio of tested to predicted results of 27% - 29%). None of the currently available methods properly describe the behavior of SFRC beams failing in shear. As such, this work shows the need for studies that address the different shear-carrying mechanisms in SFRC and its crack kinematics.

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Effect of Steel Fibers on Minimum Shear Reinforcement of High-Strength Concrete Beams

Cited by 16 publications

References 8 publications

Steel Fiber Use as Shear Reinforcement on I-Shaped UHP-FRC Beams

Steel Fiber Use as Shear Reinforcement on I-Shaped UHP-FRC Beams

ANN-Based Shear Capacity of Steel Fiber-Reinforced Concrete Beams without Stirrups

Database of Shear Experiments on Steel Fiber Reinforced Concrete Beams without Stirrups

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