Shear Strength Of Concrete Beams Research Articles

Shear strength model of FRP-reinforced concrete beams without shear reinforcement

The current design codes for evaluating the shear strength of concrete beams reinforced with fiber-reinforced polymer (FRP) bars predominantly rely on a semi-empirical approach through test data calibration without a robust theoretical background. This approach may lead to either overestimation or underestimation, resulting in significant scattering in strength predictions. This study proposed a modified approach to enhance the existing unified shear-strength model developed for steel-reinforced concrete (RC) beams based on the compression zone failure mechanism, for predicting the shear strength of FRP-RC beams without shear reinforcement. The proposed model integrates strain and stress approaches, accounting for the distinctive characteristics associated with FRP reinforcement. Additionally, the overall shear resistance capacity of the FRP-RC beam is considered as the sum of contributions from the intact concrete of the compression zone and the aggregate interlock mechanism. The reliability of the proposed model is verified by comparing its predictions with a comprehensive database comprising 264 FRP-RC beam specimens without shear reinforcement reported by 41 research groups. Furthermore, the accuracy of the proposed model was assessed through a comparative analysis with existing evaluation methods, encompassing machine learning-based models, empirical models, theoretical models, and design codes. The results indicate that the proposed model satisfactorily predicts the shear strength of FRP-RC beams within a wide range of design parameters. In comparison with machine learning-based models, the proposed theoretical model exhibits a similar level of accuracy in terms of the mean shear strength ratio and coefficient of determination (R2) values but with less scattering, indicated by lower coefficient of variation (COV) and root mean square error (RMSE) values. In addition, the proposed model outperforms existing empirical and theoretical models, as well as current design codes, by significantly enhancing prediction accuracy, demonstrated by lower COV, RMSE, and higher R2 values. Finally, a parametric study was conducted to investigate the effects of the key parameters on the shear strength of FRP-RC beams using both the proposed model and representative existing evaluation methods.

Shear Contribution of GFRP Reinforced Concrete Beams Mixed with Seawater, Freshwater, and Chopped Glass Fiber

The behavior and shear strength of concrete beams reinforced with longitudinal GFRP bars mixed with seawater are the subject matter of experimental research discussed in this paper. Seven beams were tested in bending to determine how much concrete contributes to shear resistance. The beams were longitudinally reinforced with glass fiber-reinforced polymer bars and were similar in size and concrete strength; however, they were not even shear-reinforced. The 3,100 mm long, 400 mm deep, and 200 mm wide beams underwent thorough testing until the failure. The test parameters included chopped fiber content (0, 0.5, 2, and 3 kg/m3), longitudinal reinforcement ratios (1.0, 1.4, and 2.0%), and mixing water type (freshwater and seawater). The test findings showed that Increasing the reinforcement ratio raised the neutral-axis depth, enabled the formation of more closely spaced cracks, and minimized the loss of flexural stiffness after cracking, according to the test results. The contribution of aggregate interlock as well as the contribution of uncracked concrete are both enhanced through increasing the area of concrete in compression. Additionally, increasing the reinforcement ratio enhances the dowel action, which reduces the tensile stresses produced in the surrounding concrete. Keywords: Seawater; Chopped Fiber; Fiber-Reinforced Polymer (FRP); Shear Strength.

Analytical truss model for concrete beams reinforced with FRP bars

A truss model supplementing the concrete contribution is introduced in this paper to predict the shear strength of concrete beams reinforced with various types of FRP bars. The contributions from truss and direct strut mechanisms are considered in the analytical model. The truss model which has struts at various angles considering concrete contribution is derived in this paper. The concept of equivalent transverse FRP reinforcement is applied to integrate the concrete contribution into the proposed truss model. The shear strengths of concrete and FRP transverse reinforcements in the proposed model are calculated based on El-sayed et al. and CSA S806, respectively. The validity and applicability of the proposed model are evaluated by comparison with available experimental database, which consists of concrete beams reinforced with glass, carbon, aramid and basalt FRP bars. The comparison has shown a good correlation between the experimental data and analytical results. The proposed model is also compared with ACI 440.1R and CSA S806’s shear strength models and the better correlation is found. The results from this research shows that the properly-treated truss analogy can be used to assess the shear strength of concrete beams reinforced with various types of FRP bars.

Shear Strength Prediction of Concrete Beams Reinforced with FRP Bars and Stirrups Using Gene Expression Programming

Existing reinforced concrete (RC) structures in humid regions suffer from deterioration due to the corrosion of ordinary reinforcement bars damaging the whole system. The deterioration of the transverse reinforcement leads to shear failure, which is one of the most dangerous failure modes. Therefore, researchers suggested using fiber-reinforced polymer (FRP) bars as a replacement for reinforcement bars in humid regions to integrate sustainability and improve their serviceability and durability. A simple model that can accurately estimate the shear strength of concrete beams designed with FRP longitudinal bars and stirrups is lacking. This research proposed a simplified Gene expression programming (GEP) based model to estimate the shear strength of FRP concrete beams. Seven parameters that principally dominate the shear behavior of FRP beams were utilized to create the GEP model. The parameters are the beam width, beam depth, concrete compressive strength, FRP tensile longitudinal reinforcement ratio, area of stirrups, spacing between the stirrups, and the ultimate FRP strength of stirrups. A comparison was made between the GEP and ACI-440 models; the R2 values of the total database were 92% and 54% for the GEP and ACI models, respectively. The R2 of the GEP model is considerably higher than that measured for the ACI model, and the errors of the GEP model are low, which affirms that the GEP is superior to the ACI model in estimating the shear strength of FRP beams. The trends of the GEP and ACI-440 models and the empirical results are similar, confirming the GEP model’s consistency. Using the GEP model to estimate the shear strength of concrete beams designed with FRP longitudinal bars and stirrups is recommended.

Shear Performance of GFRP Reinforced Concrete Beams with Seawater and Chopped Fiber

This paper reports an experimental study on the behavior and shear strength of concrete beams reinforced with longitudinal GFRP bars mixed with sea water. In order to evaluate how much concrete contributes to shear resistance, seven beams were tested in bending. Similar in size and concrete strength, the beams were longitudinally reinforced with glass fiber-reinforced polymer bars; however, they did not even have shear reinforcement. The beams, which measured 3,100 mm in length, 400 mm in depth, and 200 mm in width, were conducted and tested up to failure. The test variables were longitudinal reinforcement ratios (1.0, 1.4, and 2.0%), chopped fiber content (0, 0.5, 2, and 3 kg/m3), and mixing water type (freshwater and seawater). The test findings showed that increasing the reinforcement ratio increased the neutral-axis depth and allowed the formation of more closely spaced fractures while decreasing the loss of flexural stiffness after cracking. By increasing the area of concrete in compression, this in turn enhances the contribution of aggregate interlock as well as the contribution of uncracked concrete. Furthermore, increasing the reinforcement ratio improves the dowel action, which reduces the tensile stresses that are created in the concrete around it. Doi: 10.28991/CEJ-2023-09-04-05 Full Text: PDF

Shear Strength of Concrete Beams without Stirrups Made with Recycled Coarse Aggregate

Eco-friendly concrete that considers waste material and requires less energy for production is in demand because it produces less carbon dioxide, reduces the consumption of raw material, and can be a cheaper option to conventional concrete. The objectives of this study are to investigate the shear behavior of reinforced concrete beams made with locally produced recycled coarse aggregate from construction demolition waste, study the important parameters that affect the shear strength and ductility, and check the applicability of the available theoretical shear strength predictive equations to recycled concrete. An experimental program that involved the testing of fifteen half-scale beams in shear without stirrups was carried out with a theoretical component. Results of the study showed that recycled concrete beams employing 50% recycled coarse aggregate had on average 27% lower shear strength than corresponding beams made with natural aggregate when tested at a shear span-to-depth ratio equal to 1.15, and almost the same strength as the natural aggregate beams when subjected to a shear span-to-depth ratio equal to 2.5. On the other hand, the average shear strength of beams utilizing 100% recycled aggregate was lower by 5% than the strength of their natural aggregate counterparts, irrespective of the shear span-to-depth ratio. The longitudinal steel reinforcement ratio had less effect on the shear strength provided by recycled concrete beams than on those made with natural aggregate, possibly due to the reduced ability of such concrete to develop strong dowel action. Although the use of higher strength concrete improved the shear strength of recycled aggregate beams, there was no clear correlation between the square-root of the concrete compressive strength and the shear strength provided by the concrete. The theoretical part of the study showed that the ACI 318 code and the strut-and-tie method can be reliably used to predict the shear strength of concrete made with recycled coarse aggregate employed in shallow and deep beams, respectively.

The Effect of Adding Waste Plastic Fibers on The Concrete Properties And Shear Strength of Rc Beams: A Review

Plastic waste has been significantly increasing globally. Manufacturing procedures, service sectors, and municipal solid waste all produce a lot of waste plastic items. Concern over the environment and how to dispose of the generated waste has increased due to the rise in plastic waste. Additionally, the use of PET in concrete manufacturing should minimize concerns with plastic waste management and carbon dioxide emissions re-cycling plastic waste, thus replacing the need to dispose of it in a landfill, which has a limited capacity. One alternative is to develop "green concrete" by using plastic waste as a recycled ingredient in concrete buildings. However, before any structure is constructed out of concrete that contains plastic, it is important to know how the use of PET in concrete affects the concrete properties and structural behavior. Especially the shear strength of concrete beams, which is one of the fundamental problems in civil engineering. Therefore, this study serves as an overview of experiments that substituted polyethylene terephthalate (PET) for concrete as a volume ratio additive. It provides information on the mix design and behavior of concrete when PET is utilized

Mechanical properties and shear strength of rubberized fibrous reinforced concrete beams without stirrups

• Presenting the experimental shear strength results of sixteen rubberized RC beams with/without fibers. • Investigating the impact of crumb rubber on mechanical properties and shear strength of concrete beams. • Investigating the effect of fiber types and ratios on the shear strength of rubberized reinforced concrete beams. • Investigating the effect of shear span to depth ratio on the shear strength of rubberized RC beams with/without fibers. This study investigates the mechanical properties and shear strength of rubberized reinforced concrete (RC) beams with/without fibers with no web reinforcement. A total of 16 RC beams were cast and tested under four points bending to fail in shear. The study parameters are; replacement ratio by volume of fine aggregate by crumb rubber (CR) (0, 15, 30, and 40%), types of fibers (hooked long steel fiber, smooth short steel fiber, and polypropylene fiber), fiber volume fraction (0, 0.4, and 0.8%) and shear span to depth ratio a/d (2.5, 3.5, and 4.5). The results show that the mechanical properties of rubberized concrete and its weight are reduced with increasing the CR content due to the low strength, stiffness, and elastic modulus of CR, while the addition of different types of fibers, particularly hooked large steel fiber, significantly improves the mechanical properties of rubberized concrete. Using lightweight CR contributes to increasing the deformability of the tested beams and reducing their self-weight. However, increasing the CR content decreased their ultimate shear force, post-diagonal crack shear resistance, and energy absorption capacity. The inclusion of CR and fibers in concrete production can be considered as a potential technique to develop new types of eco-friendly concrete with decreased self-weight and exhibits higher shear strength than that of the control beam. Moreover, the comparison of experimental results with the predicted results of five codes and six equations from the literature showed that most of them overestimate the shear capacity of rubberized RC beams; therefore, a new predicted equation is required to predict the combined effect of rubberized fibrous RC beams.

Shear strength of concrete beams using stay-in-place flexible formworks with integrated transverse textile reinforcement

This study investigates the fabrication and the structural performance of concrete beams using weft-knitted tubular fabrics as stay-in-place formworks with integrated textile reinforcement. The use of non-corrosive high-strength textile materials for flexible formworks offers great potential for efficient construction processes and a bespoke design of material-efficient concrete structures. To this end, an experimental campaign consisting of ten three-point bending tests on beams with rectangular cross-sections made with flexible stay-in-place formworks was conducted, where aramid rovings were integrated within the textile as transverse reinforcement to withstand the shear forces while the longitudinal reinforcement consisted of conventional deformed steel bars. The use of digital image correlation measurements and distributed fibre optical sensing allowed the refined analysis of the deformations, including the strains in the textile reinforcement and the estimation of the crack kinematics, which were used to assess various contributions from the reinforcement and the concrete to the shear strength in the governing crack. The amount of textile reinforcement proved to be a decisive parameter in increasing the shear strength, although the full tensile capacity of the rovings could not be exploited due to the lack of ductility in the material behaviour. The thorough consideration of the shear transfer mechanisms revealed a strong dependence of the concrete contribution, specifically aggregate interlock and the formation of a direct strut, on the crack patterns. The combination of the brittle aramid rovings as shear reinforcement and conventional steel reinforcing bars in the tension chord provided a large deformation capacity if the shear reinforcement was able to sustain the load until a bending failure was reached.

A Proposed Formula for Predicting Size Effect on Shear Strength of Concrete Beams Without Coarse Aggregate

In this research, the size effect on shear strength of concrete beams without coarse aggregate has been studied by evaluating the ACI 318-14, ACI 318-19, and Eurocode 2 formulas. The beam specimens had the width, length, a/d, and maximum aggregate size of 6 cm, 110 cm, 2.744, and 0.6 mm, respectively. The beam's depths had been set to have a range from 6 to 18 cm. The compressive strengths of the beam were in between 58.51 and 99.80 MPa. The beams had been tested under two concentrated loads. The longitudinal reinforcement consisted of two diameter 16 mm. The beams were designed without any stirrups. Based on the analysis, the ACI 318-19 approach provides the best prediction with the mean strength ratio and coefficient of variation of 1.5086 and 0.26, respectively. The ACI 318-19 also indicates insignificant downward trend on the strength ratio vs. effective depth. The test results show that the size effect is in good agreement with the Bažant’s size effect law. In this paper, modifications to the existing formula are given to provide more accurate prediction.

Shear Capacity Prediction of FRP Reinforced Concrete Beams Using Hybrid GMDH–GA

In recent years, the use of composite rebars in reinforced concrete structures has received much attention due to its high corrosion resistance, significant tensile strength, and appropriate non-magnetization characteristics. Due to the lower modulus of elasticity of composite rebars than steel rebars, concrete beams reinforced with composite rebars have relatively lower shear strength compared to beams reinforced with steel rebars. On the other hand, shear failure in concrete beams reinforced with composite rebars is generally brittle and requires accurate prediction of the behavior of these members. Therefore, in this study, the shear strength of concrete beams reinforced with composite rebars is predicted using a combination of GMDH type neural networks and genetic algorithms based on a wide range of experimental results. The key effective parameters that consider in this study are the width of the web, effective depth of the beam, shear span to depth ratio, concrete compressive strength, modulus of elasticity of FRP longitudinal bars, and longitudinal reinforcement ratio. The accuracy of the proposed method has been verified by comparing the model predictions with the collected experimental results and existing shear design equations. The results show that the proposed model has more accurate results in calculating the shear strength of concrete beams than other existing relationships. A sensitivity analysis is also performed to assess the effect of the input parameters on the shear strength of FRP-reinforced concrete beams.

Shear Behavior in Beams Reinforced with Glass-Fiber Reinforced Polymer Bars (GFRPB) without stirrups

The behavior and shear strength of concrete beams reinforced with glass fiber-reinforced polymer (GFRP) bars was investigated. Total of six reinforced concrete beams without stirrups were constructed and tested up to failure. The beams measured 1400 mm long, 150 mm wide and 300 mm deep and were tested in two-points bending with constant shear span 350 mm in all tested beams, and shear span to depth ratio a/d 1.37. The test variable was the reinforcement ratio. The test beams included three beams designed as tension control (T.C) with GFRP bars, three beams designed as compression control (C.C) with GFRP bars. The test results were compared with predictions provided by ACI 440.1R-15 design guideline and proposed equations in the literature. The test results indicated that the relatively low modulus of elasticity of FRP bars resulted in reducing shear strength. In addition, shear strength provided by ACI 440.1R-15 guideline underestimate shear strength capacity in which proposed equations in the literature had given better prediction than ACI 440.1R-15. The failure mode in T.C beams is diagonal tension by bond failure not by rupture of FRP and C.C beams is shear compression by crushing of the web in extreme fiber.

Behaviour of Rubberized Concrete Beams in Shear

The shear strength of concrete beams manufactured from a mix including fine pieces of waste tire rubber (rubberised concrete) have been studied in several experimental programmes, with results showing a reduction in shear strength when using rubberised concrete instead of conventional concrete. In much of the recent research in this area. The main goal of the current investigation was thus to determine the extent of such reduction and to find ways to compensate for this reduction by the addition of steel fibre. A total of eight rubberised concrete beams of (140 mm width, 240 mm height, and 1240 mm length) were tested experimentally with replacement ratios by volume fraction of coarse and fine aggregate volume with fine tire waste of 0%, 25%, and 50% investigated. Additions of, 0%, 0.5% and 1.5% steel fibre content were also made to the rubberised concretes, in an attempt to test improvements in the resulting shear strength. A four-points load testing configuration was used for testing the specimens. The compressive strength of the rubberised concrete, volume fraction of steel fibres, longitudinal reinforcement ratio, replacement ratio of conventional aggregate by fine waste rubber, and shear span to depth ratio were the variables considered in this investigation, with the load-deformation behaviour and ultimate load investigated through experimental work. The test results showed that an increase in replacement ratio from 25% to 50% reduced the shear strength by 3.4%, while adding 0.5% steel fibre to the rubberised concrete increased the shear strength by 7.4% as compared with that of conventional strength concrete specimens without steel fibre. Overall, the shear modes of failure in rubberised concrete were similar to those of conventional concrete.

Forecasting of Shear Strength of Concrete Beam Reinforced with FRP Bar

This study develops a new approach for forecasting shear Strength of concrete beam without stirrups based on the artificial neural networks (ANN). Proposed ANN considers geometric and mechanical properties of cross section and FRP bars, and shear span-depth ratio. The ANN model is constructed from a set of experimental database available in the past literature. Efficiency of the ANN model was compared with existing approaches in the literature using comprehensive database. ANN is powerful tools in solving complex problems of civil engineering. The Levenberg–Marquardt (LM) method was applied for training algorithm. These existing approach include the American Concrete Institute design guide (ACI 440.1R-06), ISIS Canadian design manual (ISIS-M03-07), the British Institution of Structural Engineers guidelines (BISE), JSCE Design Recommendation, CNR-DT 203-06 Task Group, and Kara. The results demonstrate that ANN method has good agreement in calculating the shear strength of concrete beam reinforced with FRP bar among existing equations in recent decades.

Effect of Corrosion in the Transverse Reinforcements in Concrete Beams: Sustainable Method to Generate and Measure Deterioration

A consistent method to generate and measure deterioration by corrosion in transverse reinforcements for concrete beams is presented and discussed in this work. This approach could be applied in other circumstances, such as bending, compression or combinations of stresses, with comparable results and therefore can be used to ensure sustainability. In marine environments, macro-cells are produced primarily from a transverse reinforcement, which works as an anode and therefore becomes a critical part of the structural analysis. To evaluate the adaptation efficiency of our proposed method, the corrosion potential, mass losses and cross-section reductions of the steel were measured. The shear stress behavior of the beams was investigated, including beam responses to load deformations, failure modes and cracking. The method ensured that all the beams exhibited a shear failure from diagonal stress with almost 50% less deflection when mechanically tested. The critical cross-sectional area, calculated according to the experimental diameter with the greatest cross-sectional loss due to the corrosion of the deteriorated stirrup, proved to be a reliable value for predicting the ultimate shear strength of concrete beams deteriorated by severe corrosion. A reduction of up to 30% in the shear strength of deteriorated versus non-deteriorated beams was found. Additional results showed that there is a correlation between the experimental and theoretical results and that the method is reproducible.

Shear capacity estimation of FRP-reinforced concrete beams using computational intelligence

Fibre Reinforced Polymer (FRP) bars have great potential for the strengthening of the existing buildings. They also can be used as a suitable replacement for steel bars. Therefore, the structural behavior and predicting the strength of the constructed elements by this type of material is an important issue. However, the existing equations to determine the shear capacity of concrete elements reinforced with FRP are conservative and usually derived from developing the available relationships for steel-reinforced members, especially for beams. In this study, an Artificial Neural Network (ANN) model was trained to extract a new equation to predict the shear strength of concrete beams reinforced with FRP bars. To this end, a large number of experimental data was applied to the proposed ANN to predict the shear strength. Also, to investigate the effective percentage of each independent parameter on the considered output, sensitivity analyses were performed and discussed in detail. Finally, the accuracy of the proposed equation was investigated in comparison with the existing models. It could be approved that the provided equation with high accuracy presented better results than the other relationships.

Experimental investigation on M50 grade concrete beams with influence of aggregate interlocking and dowel action under flexural loading

The shear strength of the concrete beam without shear reinforcement is usually determined by shear strength of concrete compression zone, shear force due to dowel action and shear force due to aggregate interlock. The existing theories, predict shear strength of concrete beams based on geometric theories related to beam action and arch action, neglecting the influence of aggregate interlock and dowel action, as not much research information is available. The current research mainly focuses on an extensive experimental investigation on eight reinforced concrete beams with M50 grade concrete were cast and tested under flexural loading. Out of eight test specimens, four beams were provided with predetermined shear cracks having width of 5 mm, 170 mm height and inclination of 45° on either side of test specimen, whereas remaining four test specimens were not provided with predetermined shear cracks as parametric study. In eight test specimens, two beams were cast without provision of shear and flexural reinforcement and the remaining six beams were cast with increase in percentage of flexural reinforcement at 30%, 60% and 90%. Clear span of the beam was 2200 mm and cross section of the beam was 150 mm × 300 mm. The behavior of aggregate interlocking has been investigated in terms of applied load vs displacement response, stress- strain behavior, normalization curve, stiffness degradation and energy dissipation. From the test results on M50 grade reinforced concrete beam, ultimate load carrying capacity is increased with increase in percentage of flexural reinforcement for beams with predetermined shear cracks than without predetermined shear cracks. The beams with predetermined shear cracks and with additional increase in flexural reinforcement showed significant strength and stiffness.

Experimental Study on the Shear Strength of Dune Sand Concrete Beams

An experimental study was performed to investigate the shear strength of concrete beams made with dune sand (DS) from the Gurbantunggut Desert in the Chinese province of Xinjiang. The test consisted of 3 series of beams which explored the shear properties of dune sand concrete (DSC) beams. The failure mode, crack pattern, load deflection, and stirrup strain were investigated. Meanwhile, the effect of shear span‐to‐depth ratio (a/d), stirrup ratio, and dune sand replacement ratio on the shear strength of DSC beams was discussed. The results showed that the dune sand replacement ratio had insignificant influence on the failure mode of beams, so it was feasible to use DS to fabricate beams in regions of Xinjiang in China. Furthermore, the measured shear strengths of the DSC beams were compared with the calculated values of current design codes, and the results indicated that the shear strength of DSC beams was not precisely predicted by current design codes. Therefore, a modified formula was proposed to calculate the shear strength of DSC beams.

Modified imperialist competitive algorithm-based neural network to determine shear strength of concrete beams reinforced with FRP

Fiber reinforced polymers (FRPs), unlike steel, are corrosion-resistant and therefore are of interest; however, their use is hindered because their brittle shear is formulated in most specifications using limited data available at the time. We aimed to predict the shear strength of concrete beams reinforced with FRP bars and without stirrups by compiling a relatively large database of 198 previously published test results (available in appendix). To model shear strength, an artificial neural network was trained by an ensemble of Levenberg-Marquardt and imperialist competitive algorithms. The results suggested superior accuracy of model compared to equations available in specifications and literature.

Shear capacity of fiber-reinforced concrete beams without transverse reinforcement

This study studied the effect of using fiber on the shear strength of concrete beams without transverse reinforcement. The concrete mixture does not use coarse aggregate and uses stainless steel fiber with a diameter of 0.2 mm and a length of 36 mm. This study explains the effect of concrete quality on shear strength that can be carried by concrete beams with a ratio of 45 / 10.5, 25 / 10.5 and 20 / 10.5. The making of test specimens in this study was a beam of varying lengths of 110 cm, 70 cm and 60 cm while a width of 7 cm, and a height of 12.5 cm. From the test results, the shear stress value is calculated using the formula v / (b x d x √ (fc)) > 2 in international units, in which the shear capacity value is bigger than the code states. Diagonal tension failure occurs on 110cm beam and shear tension failure on 70 cm and 60 cm beams.