Shear Behavior Of Concrete Beams Research Articles

Experimental and Theoretical Studies on the Shear Performance of Concrete Beams Reinforced with Fiber-Reinforced Polymer Stirrups.

In this paper, the shear behavior of concrete beams reinforced with FRP stirrups is studied. The shear performances of six concrete beams with a size of 150 mm × 300 mm × 3000 mm under four-point loading up to failure were experimentally analyzed. The critical parameters included the shear span to depth ratio (λ) and stirrup spacing (S). The test results revealed that as λ increased from 1 to 2, 3, and 4, the ultimate shear capacity of the beam decreases by 50.5%, 67.7%, and 69.2%, respectively. Meanwhile, as S increased from 100 mm to 150 mm and 200 mm, the ultimate shear capacity decreased by 16.1% and 44.6%, respectively. A new shear capacity calculation model of concrete beam reinforced with FRP stirrups was also proposed, which further considered the shear capacity of the FRP stirrups on the basis of the shear capacity of an RC beam without stirrups using the strut-and-tie model. Finally, the experiment and calculation results of 56 beam specimens reinforced with FRP stirrups extracted from this paper and previous studies were compared using the calculation models proposed in this paper, in order to evaluate the accuracy of these calculation models.

Numerial study on shear behavior of concrete beams strengthened with textile reinforced concrete

This paper presents the numerical simulation study using the finite element method to determine the shear behavior of reinforced concrete (RC) beam strengthened with textile reinforced concrete (TRC). Numerical simulation results, then, are compared with experimental results on three points bending tes. The obtained results show the similarity between numerical simulation model and experimental results in aspects such as displacement - force curve, failure mode. Besides, some parameters affecting to shear behavior of RC beam strengthened with TRC have been also investigated.

Investigation of the Shear Behavior of Concrete Beams Reinforced with FRP Rebars and Stirrups Using ANN Hybridized with Genetic Algorithm.

The shear strength prediction of concrete beams reinforced with FRP rebars and stirrups is one of the most complicated issues in structural engineering applications. Numerous experimental and theoretical studies have been conducted to establish a relationship between the shear capacity and the design variables. However, existing semi-empirical models fail to deliver precise predictions due to the intricate nature of shear mechanisms. To provide a more accurate and reliable model, machine learning (ML) techniques are adopted to study the shear behavior of concrete beams reinforced with FRP rebars and stirrups. A database consisting of 120 tested specimens is compiled from the reported literature. An artificial neural network (ANN) and a combination of ANN with a genetic optimization algorithm (GA-ANN) are implemented for the development of an ML model. Through neural interpretation diagrams (NID), the critical design factors, i.e., beam width and effective depth, shear span-to-depth ratio, compressive strength of concrete, FRP longitudinal reinforcement ratio, FRP shear reinforcement ratio, and elastic modulus of FRP longitudinal reinforcement rebars and FRP stirrups, are identified and determined as input parameters of the models. The accuracy of the proposed models has been verified by comparing the model predictions with the available test results. The application of the GA-ANN model provides better statistical results (mean value Vexp/Vpre equal to 0.99, R2 of 0.91, and RMSE of 22.6 kN) and outperforms CSA S806-12 predictions by improving the R2 value by 18.2% and the RMSE value by 52.5%. Furthermore, special attention is paid to the coupling effects of design parameters on shear capacity, which has not been reasonably considered in the models in the literature and available design guidelines. Finally, an ML-regression equation considering the coupling effects is developed based on the data-driven regression analysis method. The analytical results revealed that the prediction agrees with the test results with reasonable accuracy, and the model can be effectively applied in the prediction of shear capacity of concrete beams reinforced with FRP bars and stirrups.

Shear-transfer mechanisms in reinforced concrete beams with GFRP bars and basalt fibers

An increase in the use of glass fiber reinforced polymer (GFRP) bars and discrete fibers in reinforced concrete structures, associated with the limited understanding of the shear behavior of concrete beams, highlights the need for a comprehensive study of various force transfer mechanisms. This article investigates the experimental behavior of four slender reinforced concrete beams with GFRP bars. The testing program includes beams with and without GFRP stirrups and dispersed basalt fibers in the concrete matrix. The displacement fields throughout the shear span were monitored according to the digital image correlation (DIC) technique and shear-transfer constitutive models from the literature assessed the contribution of each mechanism. The sum of such contributions consistently agreed with the experimental shear strength and the use of fibers in beams with GFRP stirrups modified the relative influence of both shear reinforcements, i.e., one of them can preponderate over the other in function of load stage and failure mode.

Shear behavior of polypropylene fiber-reinforced concrete beams containing recycled aggregate and crumb rubber

The growth of unavoidable waste rubber and the demolition of old concrete structures have become a concern for environmental sustainability. The incorporation of crumb rubber and demolished concrete into the new concrete mix is likely to promote environmentally friendly practices. This paper investigates the shear behavior of concrete beams containing crumb rubber (CR), recycled concrete aggregate (RCA), and polypropylene (PP) fiber. A total of fifteen reinforced concrete (RC) beams were prepared with recycled concrete aggregate (RCA) (0%–50%), CR as fine aggregate (0%–10%), and PP fiber fractions (0%–1%). All RC beams made without any shear reinforcement were tested under a four-point bending test up to failure. The ultimate shear strength, crack pattern, post-diagonal cracking, concrete strain, toughness, and deformation behavior of fresh concrete properties were investigated at different combinations. The surface strain of concrete was closely observed by using Digital Image Correlation (DIC) technique. The experimental result suggested that the introduction of CR in the concrete mix negatively affects the ultimate shear strength, post diagonal cracking resistance, toughness, and deformability of the beam. These effects may be remedied and enhanced by inserting PP fiber in the concrete at RCA replacement levels up to 30%. The beam made of 30% RCA along with 5% CR and 1% PP fiber demonstrated the best performance in terms of shear resistance, deformability, and toughness. Interestingly, the application of 50% RCA with or without CR and PP fiber adversely affected the shear strength parameters of concrete. The beam deformability increased with the addition of a small percentage of rubber (up to 5%). The post-diagonal crack resistance increased with the presence of fibers, whereas the response is the opposite with the addition of rubber.

Shear behavior of fiber reinforced concrete beams with high fly ash content

The shear behavior of Fiber Reinforced Concrete (FRC) beams with high Fly Ash (FA) content is investigated experimentally. Despite greater understanding of FRC shear behavior for the design of structural elements such as beams, the practicality of FRC with a high FA content has yet to be determined. Despite the fact that substantial study has been undertaken to establish the optimal usage of FA as a cement and fine aggregate replacement in concrete while investigating the shear behavior of conventional concrete, only a few studies have focused on the influence of FA in the FRC on concrete's shear behavior. The findings of shear tests performed on the FRC concrete beams of dimension 900 mm long by 80 mm wide by 120 mm high containing a high FA content up to 50 % are presented in this study. This study's principal goal is to investigate the impact of factors such as FA replacement level with fine aggregate and fiber volume on the shear behavior of concrete beams. Concrete mix with different combinations of 50 % FA by weight, as a replacement for fine aggregate, and steel fiber 1 % by volume is investigated. A four-point loading setup was used to test each of the beams. The results on FRC shear resistance capacity at failure load, as well as the effect of fiber volume and high FA content on ultimate load, have been presented and discussed. Mid-span deflection and crack patterns are also investigated during testing. The test results reveal that FRC overperforms in the presence of FA at a level of 50 % fine aggregate replacement with FA. Fibers, as expected, delayed crack formation and significantly reduced their width. As a result, it can be concluded that 50 % fine aggregate replacement with FA can be used effectively in concrete construction with no significant loss in shear strength, both in the presence and absence of steel fibers.

Prediction of shear strength for CFRP reinforced concrete beams without stirrups

Design guidelines in international codes show noticeable differences with regards to shear strength prediction of concrete beams reinforced with Fiber Reinforced Polymers, (FRP). These discrepancies in shear strength predictions are attributed to many factors affecting the shear behavior, such as shear span/depth ratio (a/d), beam size, rectangular and flanged cross-sectional shape (R-section and T-section), and concrete compressive strength. Shear resistance of beams longitudinally reinforced with carbon FRP, (CFRP), bars is not well defined in the literature compared to beams reinforced with steel bars. This is mainly attributed to the low modulus of elasticity of CFRP compared to traditional steel reinforcement resulting in relatively high strains generated in CFRP reinforcement and consequently wider cracks and lower contribution of the aggregate interlocking mechanism as well as dowel action in shear resistance. This paper numerically investigates the behavior of concrete beams reinforced in flexure with CFRP bars without transverse reinforcement to quantify concrete contribution in shear resistance. Specimens with R and T sections having different shear span-to-depth ratio, concrete compressive strength, and longitudinal CFRP reinforcement ratios are studied to determine the concrete contribution to shear resistance. The nonlinear program ATENA is used to simulate the actual behavior of concrete beams failing in shear and is verified against experimental results gathered from the literature to check the validity of the numerical model. The comparison shows good agreement between experimental and numerical results with a difference of 6% and then a parametric study is conducted to provide a better understanding of the effect of each parameter on the shear behavior of concrete beams reinforced with CFRP bars. The results of numerical models are compared to their counterparts predicted using different equations in codes and guidelines. It is found that the shear capacity of T-section is higher than R-section by about 15% to 25% mainly due to a change in cracking pattern due to the presence of the flange. Furthermore, the shear failure load increased by increasing the longitudinal reinforcement ratio as a result of decreasing strain and enhancement of dowel action. The effect of increasing concrete compressive strength was more pronounced on the shear capacity in arch action as opposed to diagonal tension regions. Finally, an equation is proposed to predict the shear capacity of concrete beams reinforced in flexure with CFRP bars. The shear capacity predicted by the proposed equation provided a good agreement with experimental results for 163 beams with a mean value of 1.01 and COV of 0.17.

Effect of hybrid-fiber- reinforcement on the shear behavior of high-strength-concrete beams

The shear behavior of concrete beams is highly affected by the implementation of better performance concrete. Hybrid fibers addition to concrete mixture has proven to improve the performance compared to just using single type of fiber. Thus, in this current study, the shear behavior of hybrid-fiber-reinforced-high-strength-concrete beams was investigated experimentally. In addition, the effect of the span-to-depth ratio and the transverse reinforcement ratio were examined. Results showed that, when .45% of the cement weight is replaced with polypropylene fiber and 7% of the cement weight is replaced with steel fibers, the shear strength of the beam was enhanced by 18% in comparison to the control beam. The Formation and progression of cracks were also better controlled. The behavior of hybrid-polypropylene-steel-fibers-high-strength-concrete beams was observed to be comparable to that of conventional concrete ones as the shear strength increased with the decrease in span to depth ratio or the increase in transverse reinforcing ratio. A non-linear numerical model was developed and validated using the experimental results. The shear capacities of beams were calculated using ACI, which was compared to experimental and numerical results. The ACI’s calculations were conservative when compared with the experimental or numerical results. The coefficient of variance between the ACI and experimental shear capacity results was 4.8%, while it was 9.2% between the ACI and numerical shear capacity results.

Modelagem computacional de vigas de concreto simples e reforçados com fibras de aço sem armadura transversal

Abstract Finite element analysis with nonlinear material behavior modeling can be used to design concrete structures. This study aimed to develop a computational model to represent the shear behavior of concrete beams without transverse reinforcement described in the literature, with or without steel fibers. Two different approaches of finite element analysis were investigated, namely smeared and discrete crack models. The results of the smeared crack model were compared with the results of double-notched push-through tests, and an empirical equation for the shear retention factor of plain concrete was suggested. The computational model using a discrete crack approach with representation of the aggregate interlocking mechanism was compared with the results of push-of test, and an accurate correlation was observed up to the maximum shear stress. It was concluded that the discrete crack approach provided the most accurate representation of the shear behavior of a non-reinforced beam with a shear span-to-depth ratio of 2.17. However, for a non-reinforced beam with a shear span-to-depth ratio of 2.66, the smeared crack approach accurately represents the shear strength and stiffness of the beam. The shear retention factor had little influence on the overall behavior of a steel fiber-reinforced concrete beam. Finally, it was concluded that a variable shear retention factor should be used in the smeared crack approach with fixed crack, as a constant shear retention factor tends to overestimate the shear strength of beams.

Shear behavior of concrete beams reinforced with corrosion-resistant and ductile longitudinal steel-FRP composite bars and FRP stirrups

Inheriting excellent corrosion resistance of FRP bars, steel-FRP composite bar (SFCB) has better elastic modulus and ductility, promising to be longitudinal reinforcement for concrete structures in harsh environments. While previous research primarily focused on the flexural behavior of hybrid longitudinal SFCB and FRP stirrups reinforced concrete (hybrid-RC) beams, the study about shear behavior has rarely been reported and valuable experimental observations are limited. The unique mechanical properties of SFCB causes the inapplicability of existing shear design method and the risk of brittle shear failure. Here, a simplified shear design method is proposed for hybrid-RC beams by analytical investigation and the shear behavior of hybrid-RC beams is investigated experimentally. Results show that SFCB exhibits similar transverse shear behavior to steel bar. Compared with steel bars reinforced concrete beams, hybrid-RC beams based on the proposed design method have better shear performance including same failure modes, similar deflection, narrower shear crack, and higher shear capacity, due to the post-yielding stiffness of SFCB. Furthermore, a modified calculation method of the shear capacity for hybrid-RC beams is proposed, exhibiting great feasibility and accuracy. These results can provide valuable experimental observations of shear behavior and promote the development of shear design tactics for hybrid-RC beams.

Behavior of R.C Beams Reinforced with Onsite Manufactured GFRP shear reinforcement

This paper includes an experimental program to study the shear behaviour of concrete beams reinforced in shear with fiber glass reinforced polymer GFRP and carbon fiber reinforced polymer CFRP stirrups manufactured onsite. A total of six specimens were tested to study several parameters including the type of FRP material used to manufacture the stirrups, the angle of inclination of the stirrups and the thickness to bend radius ratio (r/t) of the stirrups. The experimental results showed that the ultimate strength of beams reinforced with carbon fiber stirrups is significantly higher than that of beams reinforced with fiber glass stirrups for the same area, for the same area increasing the diameter increases the failure load and strains in the stirrups while decreasing the thickness decreases the failure load and strains in stirrups, due to the reduction of the stress concentration at the corners of the stirrups and that increasing the inclination angle of the stirrups with the horizontal increases the strain in the stirrups and ultimate strength.

Combined effect of handmade CFRP strip stirrups and forta-ferro fibers on shear behavior of concrete beams

Combined effect of handmade CFRP strip stirrups and forta-ferro fibers on shear behavior of concrete beams

Comparison of shear behaviour of concrete beams reinforced with GFRP bars and steel bars

This paper presents the results of an experimental program focused on a comparison of the shear behaviour of concrete beams reinforced by longitudinal GFRP bars and beams reinforced by ordinary steel reinforcement. Altogether, 24 tests were conducted on 12 beams reinforced with GFRP bars and 28 tests on 14 beams reinforced with steel reinforcement. The beams were subjected to three-point loading with shear slenderness of 3.0. An effect of axial stiffness of longitudinal reinforcement was examined. Six different reinforcement ratios, ranging from 1.34% to 7.44%, in the case of beams with GFRP bars and six reinforcement ratios ranging from 0.89 % to 2.38% in the case of beams with steel reinforcement were tested until its failure occurred. An effective depth of the beams of 100 mm was kept constant and beams were without any transverse reinforcement. The results show a favourable effect of the axial stiffness of the longitudinal reinforcement on the shear capacity in both cases. However, in the case of beams with GFRP bars, a better shear performance per unit increase of the axial stiffness was observed than in beams with steel bars. The experimental program revealed that the relation between the reinforcement ratio and the shear strength can be approximated by the cubic root of the ratio. A comparison of measured shear strengths with state-of-art design provisions for predicting shear capacity indicates good quality of all the considered models when the CoV of shear strength ratio Vtest/Vmodel ranged from 0.079 to 0.109 in the case of beams with GFRP bars and from 0.062 to 0.110 in the beams with steel bars.

Experimental investigation of the shear behaviour of concrete beams with CFRP strip stirrups under static and fatigue loading

Existing reinforced concrete (RC) structures often decrease in safety and service life owing to reinforcement corrosion or fatigue. Therefore, there are urgent requirements to propose new structures for engineering applications. This study investigates the static and fatigue shear behaviours of concrete beams using carbon fibre reinforced polymer (CFRP) strips instead of steel stirrups. The study mainly conducted the shear tests on nine statically loaded beams and six cyclically loaded beams with varied shear span ratios (a /d = 1.0, 2.5 and 3.5) and configurations of CFRP strip stirrups. The results reveal that concrete beams with CFRP strip stirrups have similar static shear behaviour to RC beams. Nevertheless, the CFRP strip stirrup beams exhibit superior fatigue life compared to that of RC beams, which significantly restrain the development of deflection, concrete cracks, and stirrup strain. Using CFRP strip stirrups instead of steel stirrups can effectively improve the shear resistance of the concrete beams under static and fatigue loading.

Shear behavior of concrete beams reinforced with closed-type winding glass fiber-reinforced polymer stirrups

Conventional pultruded fiber-reinforced polymer (FRP) rod stirrups are susceptible to premature bent corner rupture and bond slip failure of overlapping legs. This research proposed a new type FRP shear reinforcement, closed-type winding GFRP (CW-GFRP) stirrups, featuring a fully closed rectangular cross-section. CW-GFRP stirrups completely avoided slip and significantly improved the strength of bent portion of stirrups. To investigate the feasibility of using CW-GFRP stirrups as shear reinforcement, shear test of 8 concrete beams reinforced with conventional pultruded stirrups and CW-GFRP stirrups was conducted. The beams were 300 mm deep and 150 mm wide, and their shear span ratio were 2.07. The effect of the material of stirrups, the spacing of stirrups, and the width of CW-GFRP stirrups were investigated. The test results showed that pultruded stirrups exhibited bond slip failure, in contrast, CW-GFRP stirrups reinforced beams prevented this failure and showed enhanced stiffness, narrower shear crack width and 1.09–1.12 times higher shear capacity. The splitting failure typical of CW-GFRP stirrups was reported, and a smaller stirrups width is expected to avoid splitting and generate greater strain at ultimate. It can be concluded that the new type of CW-GFRP stirrups is an optimized form of FRP shear reinforcement to supersede conventional pultruded stirrups. Strut-and-tie models based on ACI 318-19 and CSA S806-14 were used to predict the shear strength and produced a safe but relatively accurate prediction.

Contribution of Glass Textile to the Shear Behavior of Concrete Beams Reinforced with GFRP Rebars

Contribution of Glass Textile to the Shear Behavior of Concrete Beams Reinforced with GFRP Rebars

Carbon fiber-reinforced polymer mesh fabric as shear reinforcement in reinforced concrete beams

Steel corrosion is a significant threat to the durability of traditional reinforced concrete (RC) members. An effective method of counteracting steel corrosion is replacing steel reinforcement bars in concrete with fiber-reinforced polymer (FRP) bars. However, the FRP bar resists being bent into a stirrup because of its in-situ manufacturing techniques. Moreover, the tensile strength of the bent portion of an FRP stirrup is significantly lower than that of the longer straight bar because of stress concentration. This paper presents an experimental and analytical study on the shear behavior of concrete beams reinforced with a carbon FRP mesh fabric (CFRP-MF) as shear reinforcement for RC members. A new CFRP-MF, which was woven in vertical and parallel directions, as an alternative to the traditional methods used for shear reinforcement, was investigated. Six concrete beams were cast with CFRP-MF as the shear reinforcements, and three concrete beams were cast as controls to investigate the shear behavior of the novel composite beams. The configuration of CFRP-MF and the overlapping condition of the intersection point were the research variables. The test results indicated that these novel composite beams have similar shear capacities and ductilities to traditional concrete beams with steel stirrups. The predictions of the shear strength of the specimens using shear design provisions in ACI 440.1R-15, CSA S6-19 and CSA S806-12 are examined and compared. The finite element method was used to compare the experimental results with numerical values, and the percentage error in all scenarios was lower than 8%.

Enhancement the Shear behavior of concrete beams reinforced with hybrid-wires bars by using steel fibers.

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Experimental investigation on shear behavior of concrete beams with CFRP grid shear reinforcements

Fiber Reinforced Polymer (FRP) is one of the most ideal substitutes for steel reinforcement because of its low density, high tensile strength and excellent corrosion resistance. Carbon-FRP (CFRP) grid is one type that is commonly used in engineering and has shown promising results in shear strengthening of beams. In this study, eight concrete beams, including one steel reinforced concrete (RC) beam and seven concrete beams with CFRP grids in two configurations (parallel to longitudinal axis as stirrup or perpendicular to longitudinal axis), were tested until failure. The influence of variables on shear span ratio and shear reinforcement ratio were analyzed. All the eight beams experienced shear failure as expected. As the shear span ratio increased, the shear capacity decreased while the deflection of beam increased. CFRP grids parallel to the longitudinal axis could effectively reduce the deflection and increase the cracking load of specimens. When CFRP grids were laid perpendicular to the longitudinal axis, the maximum strength of CFRP grid can reach 84% of the ultimate strength and the contribution of CFRP grid stirrups to shear capacity was higher than that of steel stirrups. Finally, experimental results of shear capacity were compared with the theoretical ones calculated by various specifications.

Influence of using two types of recycled aggregates on shear behavior of concrete beams

This paper investigates experimentally and theoretically the shear behavior of thirteen reinforced concrete (RC) beams made of Recycled Asphalt Pavement (RAP) and Recycled Coarse Aggregate (RCA). The span length of the beams was 2240 mm, and the width and depth of the beams were 200 and 400 mm, respectively. Three groups of beams were used in this study: The first group was five beams made of RAP and natural aggregate (NA), where the NA was substituted by RAP with replacement levels of 20%, 40%, 60%, 80%, and 100% by the total weight of NA. The second group was four beams made entirely of RAP and RCA. The third group was four RC beams made of RCA and NA, where NA was replaced by RCA with replacement levels of 20%, 40%, 60%, and 80%. The beams were tested under four-point loading setup. The maximum shear forces, deflections, and cracking patterns were studied. The experimental results were compared with theoretical results determined from the equations of selected international codes and fracture mechanics approaches available in the literature. The results showed that the experimental shear capacity increased as the RAP and RCA replacement levels decreased for the beams in group one and three, and decreased for group two beams when the RCA replacement levels increased. The theoretical shear strength capacities were more conservative when compared to the experimental results. Therefore, the theoretical shear equations can be applicable to the beams constructed with recycled aggregates. In general, using RAP and RCA in RC beams can be considered as an effective approach.