How do steel fibers improve the shear capacity of reinforced concrete beams without stirrups?

Lantsoght, Eva O. L.

doi:10.1016/j.compositesb.2019.107079

Cited by 95 publications

(76 citation statements)

References 84 publications

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“…Comparing experimental results on the shear capacity of SFRC beams without stirrups to the capacity predicted using the expressions from Table 1 shows that predicting the shear capacity of SFRC beams without mild steel shear reinforcement is still difficult [20]. The reason for this difficulty is the complex mechanics of the problem, since, as previously mentioned, the steel fibers affect each of the shear-carrying mechanisms [2].…”

Section: Authors Ref Expressionmentioning

confidence: 91%

“…One failure mode where crack shape and width is essential, is shear failure. When steel fibers are included in the concrete mix, and the reinforced concrete element built with this concrete mix is tested in shear, then the addition of the steel fibers influences all mechanisms that contribute to the shear-carrying capacity of the member [2]. Since the mechanics of the problem are still not fully understood, it is interesting to study the behavior of steel fiber-reinforced concrete (SFRC) with longitudinal steel reinforcement and without shear reinforcement.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Authors Ref Expressionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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

Abambres

Lantsoght

2019

Fibers

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“…It is also well known that the initial shear cracking capacity of a RC member is governed by the tensile strength of concrete and, for this reason, any enhancement of the deficient concrete behavior under tension would improve the shear performance of the member. Thus, the effectiveness of non-traditional shear reinforcement such as steel fibers and spirals instead of common steel stirrups has been indicated as a potential alternative technique which provides noticeable improvement of the shear response [1][2][3][4][5]. specimens were bw/h/bf/hf = 150/200/300/50 mm, as shown in Figure 1, whereas the effective depth was equal to d = 175 mm.…”

Section: Introductionmentioning

confidence: 99%

U-Jacketing Applications of Fiber-Reinforced Polymers in Reinforced Concrete T-Beams against Shear—Tests and Design

Chalioris

Zapris

Karayannis

2020

Fibers

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The application of externally bonded fiber-reinforced polymer (EB-FRP) as shear transverse reinforcement applied in vulnerable reinforced concrete (RC) beams has been proved to be a promising strengthening technique. However, past studies revealed that the effectiveness of this method depends on how well the reinforcement is bonded to the concrete surface. Thus, although the application of EB-FRP wrapping around the perimeter of rectangular cross-sections leads to outstanding results, U-jacketing in shear-critical T-beams seems to undergo premature debonding failures resulting in significant reductions of the predictable strength. In this work, five shear-critical RC beams with T-shaped cross-section were constructed, strengthened and tested in four-point bending. Epoxy bonded carbon FRP (C-FRP) sheets were applied on the three sides and along the entire length of the shear-strengthened T-beams as external transverse reinforcement. Furthermore, the potential enhancement of the C-FRP sheets anchorage using bolted steel laminates has been examined. Test results indicated that although the C-FRP strengthened beams exhibited increased shear capacity, the brittle failure mode was not prevented due to the debonding of the FRP from the concrete surface. Nevertheless, the applied mechanical anchor of the C-FRP sheets delayed the debonding. Moreover, the design provisions of three different code standards (Greek Code of Interventions, Eurocode 8 and ACI Committee 440) concerning the shear capacity of T-shaped RC beams retrofitted with EB-FRP jackets or strips in U-jacketing configuration are investigated. The ability of these code standards to predict safe design estimations is checked against 165 test data from the current experimental project and data available in the literature.Strengthening of existing low-capacity RC structures using externally bonded fiber-reinforced polymers (EB-FRP) has become very popular because of the advantages of these materials such as their superior strength-to-weight ratio, their easy-to-apply character, their durability and their chemical and corrosion resistance [6][7][8]. For shear-critical RC elements with rectangular cross-sections in particular, full jacketing application of EB-FRP sheets wrapping around the cross-section and along their entire length provides increased strength and enhanced structural performance since it alters the shear brittle response to a ductile one [9][10][11][12]. However, common constructional limitations, such as the existence of a slab, usually prevent the wrapping of EB-FRP sheets around the cross-section. Thus, most RC beams with a T-shaped cross-section are shear strengthened using EB-FRP sheets (jackets or strips) on the three sides of the web of the beam (U-shaped retrofitting). A significant deficiency of this technique is the premature failure of the strengthened member due to the debonding of the EB-FRP at the adhesive composite and concrete interface [13][14][15][16][17][18][19][20].Several experimental studies have demonstrated the effectiveness...

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“…However, one of the significant disadvantages of concrete is the weakness of tensile strength and shear resistance. Many studies have been performed to overcome this weakness by focusing on additional components to reinforce concrete [4]. Over the decades, fibers have gained tremendous attention from the research community as a potential improvement to the mechanical properties of concrete [5].…”

Section: Introductionmentioning

confidence: 99%

“…The sensitivity analysis results showed that web width, effective depth, and a clear depth ratio were the most important parameters in modeling the shear capacity of steel fiber-reinforced concrete beams.Sustainability 2020, 12, 2709 2 of 34 flexural toughness and tensile strength, the capacity in absorbing energy, ductile behavior, cracking reduction, and improvement of the shear behavior when reinforced [8][9][10]. For this reason, the use of steel fiber-reinforced concrete (SFRC) has become extensively popular in different civil engineering applications such as tunnel shells, concrete sewer pipes, higher upper layers, and slabs of large industrial buildings [4]. Despite many advantages, designing SFRC structures still faces challenges, as it is difficult to determine critical shear capacity by conventional methods [11][12][13].In the literature, various experimental and numerical studies have been performed on SFRC in order to investigate shear strength capacity [10].…”

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confidence: 99%

Computational Hybrid Machine Learning Based Prediction of Shear Capacity for Steel Fiber Reinforced Concrete Beams

et al. 2020

Sustainability

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Understanding shear behavior is crucial for the design of reinforced concrete beams and sustainability in construction and civil engineering. Although numerous studies have been proposed, predicting such behavior still needs further improvement. This study proposes a soft-computing tool to predict the ultimate shear capacities (USCs) of concrete beams reinforced with steel fiber, one of the most important factors in structural design. Two hybrid machine learning (ML) algorithms were created that combine neural networks (NNs) with two distinct optimization techniques (i.e., the Real-Coded Genetic Algorithm (RCGA) and the Firefly Algorithm (FFA)): the NN-RCGA and the NN-FFA. A database of 463 experimental data was gathered from reliable literature for the development of the models. After the construction, validation, and selection of the best model based on common statistical criteria, a comparison with the empirical equations available in the literature was carried out. Further, a sensitivity analysis was conducted to evaluate the importance of 16 inputs and reveal the dependency of structural parameters on the USC. The results showed that the NN-RCGA (R = 0.9771) was better than the NN-FFA and other analytical models (R = 0.5274–0.9075). The sensitivity analysis results showed that web width, effective depth, and a clear depth ratio were the most important parameters in modeling the shear capacity of steel fiber-reinforced concrete beams.

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How do steel fibers improve the shear capacity of reinforced concrete beams without stirrups?

Cited by 95 publications

References 84 publications

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

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

U-Jacketing Applications of Fiber-Reinforced Polymers in Reinforced Concrete T-Beams against Shear—Tests and Design

Computational Hybrid Machine Learning Based Prediction of Shear Capacity for Steel Fiber Reinforced Concrete Beams

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