Shear Capacity Of Concrete Beams Research Articles

SHEAR CAPACITY OF REINFORCED CONCRETE BEAMS WITHOUT SHEAR REINFORCEMENT: A REVIEW

Shear failure in reinforced concrete beams has gained excessive study, particularly beams without stirrups. Because shear failure is considered the most serious due to it occurring suddenly without warning. Because of the seriousness of the matter concerning shear failure, many researchers are looking to use additive materials that differ from traditional concrete constituents in order to improve the shear resistance of the beams, such as the use of silica fume, steel fiber, metakaolin, and many others. The current studies focused on understanding the resistance provided by the interlocking forces between the aggregate and that provided by the non-cracked compression zone, with the use of some materials that are intended to improve the properties of concrete. This paper presents a review of the previous literature that included studying the mechanism and behavior of shear failure of concrete beams without web reinforcement and also includes a presentation of the most important equations used to predict the shear capacity of concrete beams, especially those without stirrups, to understand the mechanism of failure and to know the most important factors affecting the failure of shear.

Shear behaviour of SWSS-SCC beams reinforced with GFRP bars and Stirrups: Experimental and analytical investigations

This paper presents a study of shear behaviour of sea-water and sea sand self-compacting concrete (SWSS-SCC) beams reinforced with glass fibre reinforced polymer (GFRP) bars and stirrups. Nine full-scale beams were conducted and tested under four-point loading up to failure. The investigated experimental variables were the shear-span ratio, configuration of GFRP stirrups, type of the concrete, longitudinal reinforcement ratio and beam depth. The crack pattern, failure mode, load–deflection response, load–strain response and shear capacity of concrete beams were discussed. It is evident in the test results that the ultimate shear capacity of test specimens is enhanced by reducing the shear-span ratio, using the GFRP stirrups, improving the longitudinal FRP reinforcement ratio and increasing the beam depth. The shear behaviours of SWSS-SCC beam reinforced by GFRP bars and stirrups were found to be similar to that of fresh-water and river sand self-compacting concrete (FWRS-SCC) beam. The ultimate shear capacity of the test beams was predicted by the theoretical models reported in the literature. In addition, the effect of the experimental parameters on shear capacity was discussed and the theoretical models of shear strength were evaluated based on the summarized database. It is found that the nominal shear strength is barely affected by the axial compressive strength and is optimal when the longitudinal reinforcement ratio is about 2%. The CSA-S806 2012 specification has more accurate prediction results for the shear capacity of concrete beams reinforced with FRP bars and stirrups.

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.

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.

Strengthening Shear Resistance of Beams without Web Reinforcements Using Vertical Prestressed Steel Bars

Ensuring the shear capacity of concrete structures is crucial. The vertical prestressed steel bar (VPSB) strengthening method is effective for improving the shear behaviour of concrete structures. Four concrete beams are investigated to reveal the effect of VPSBs on the shear capacity of concrete beams without web reinforcement. Test results indicate that the shear capacity of the test beam strengthened by VPSBs in the beam is significantly increased by more than 95%, and the failure mode of the test beam changes from diagonal tension failure to shear compression failure. Additionally, the results provide insights into the strengthening mechanism of VPSBs, i.e., the shear contribution of the VPSBs can be categorised into two stages. The vertical compressive stress provides shear contribution in the first stage and provides control in terms of crack development; meanwhile, in the second stage, the stirrup action by VPSBs contributes to shear.

Study on the Shear Capacity of Concrete Beam Reinforced with Glass Fiber Reinforced Polymers Grid Reinforcement

Abstract: Fiber Reinforced Polymer (FRP) composites have been widely used as a high-performance material in concrete structures as replacement of commonly using materials Corrosion of the internal reinforcing steel is the main cause of deterioration in reinforced concrete structures. This steel in reinforced concrete structures has cost a significant amount of resources globally over the past, also expensive as compared to FRP. Glass fiber reinforced polymer (GFRP) bars have been introduced as a light-weight, corrosion resistant FRP material which can be used as replacement for traditional steel reinforcing bars and stirrups in concrete structures. Glass fiber reinforcement polymer (GFRP) bars are also feasible and cost effective FRP products commercially available with significant cost advantage over stainless steel. The aim of this paper is to let engineers gain a better knowledge of the overall behaviour of GFRP as internal reinforcement so that they have more confidence using it as a sustainable material. In this study GFRP is used as longitudinal reinforcement and GFRP grid is used as stirrups A Finite Element (FEM) model has been developed using ANSYS 21 to analyses beams. For these six concrete beams, including one steel reinforced concrete (RC) beam and five beams with GFRP grids laid parallel to longitudinal axis was tested until failure. Parametric study on shear span ratio is conducted in four specimens. Load deflection curve are noted in each specimen analytically by using ANSYS software.

Shear behavior analysis and capacity prediction for the steel fiber reinforced concrete beam with recycled fine aggregate and recycled coarse aggregate

This paper mainly studies the shear behavior of steel fiber reinforced concrete beams with recycled fine aggregate and recycled coarse aggregate. A total of thirteen beams with 150 mm width, 300 mm height, and 3000 mm length were tested under four-point bending. The shear span-to-depth ratio was kept the constant of 2. The spacing of stirrups was 150 mm, 200 mm, and 250 mm, respectively. The recycled fine aggregate and recycled coarse aggregate obtained from building demolition waste were introduced in the concrete mixes with the replacement ratio of 0%, 50%, and 100%, the steel fiber volume fractions in the beams were 0%, 0.5%, 1.0%, and 1.5%, respectively. The shear capacity, the mid-span deflection, and the stirrups strain were measured in this test. The results indicated that the shear capacity of the concrete beam with recycled aggregate and steel fibers decreased with the increase in the replacement ratio of recycled coarse aggregate, and gradually improved as the increase in steel fiber volume fractions, respectively. The steel fiber volume fraction of 1.0% in concrete was almost sufficient to offset the shear capacity degradation induced by 100% recycled fine aggregate replacement ratio and 100% recycled coarse aggregate replacement ratio. Finally, the effects of recycled fine aggregate, recycled coarse aggregate, and steel fibers on the shear behavior of the concrete beams were severally quantified by the linear equations, and a model for predicting the shear capacity of concrete beams with recycled fine aggregate, recycled coarse aggregate, and steel fibers was proposed and verified.

Development of enhanced fiber beam element with multi-axial material constitutive models for reinforced/prestressed concrete beams

In order to consider the interactive behavior of flexure and shear, an enhanced displacement-based fiber beam element is developed by utilizing multi-axial material constitutive models for fibers, in particular, with the Modified Compression Field Theory (MCFT) for fibers representing concrete with smeared stirrups in RC/PC beams/girders. The potential shear-locking problem is avoided by adopting a mixed interpolation form with a bubble term for the displacement field, and the validity of the approach is verified by a classic example. The proposed element is first validated through a classic test series of shear-critical RC beams from the literature and then applied to a PC girder recently tested under both shear-critical and flexure-dominated scenarios. It is shown that the proposed element can be used to predict the structural behavior of RC beams and PC girders satisfactorily, after enhancing the conventional fiber beam element by considering the coupling of flexure and shear. In addition, the proposed element provides a tool to predict both flexure and shear capacities of concrete beams with adequate accuracy.

INFLUENCE OF LONGITUDINAL REINFORCEMENT RATIO ON SHEAR CAPACITY OF NO COARSE-AGGREGATE CONCRETE

The study investigated the effect of longitudinal reinforcement ratio on the shear capacity of concrete beams without transverse steel. The concrete mixture did not include coarse aggregate. The Joint ACI–ASCE Committee 426 (1973) has shown that the shear is transferred across the surface where there is slip and it is called the aggregate interlock. To study the effect of longitudinal reinforcement ratio on the shear capacity of concrete without coarse aggregate, six beam specimens with the size of 110 × 7 × 12.5 cm and a/d ratio of 45/10.5 were investigated. The longitudinal reinforcement ratios were set from the minimum to the maximum, i.e. 0.0073, 0.0132, 0.0213, 0.0302, 0.0547, and 0.0782. The ratios of the ultimate shear to the shear capacity of concrete (Vu/Vc) were found between 1.0705 and 2.8748. When the longitudinal reinforcement ratio increases particularly from the minimum ratio, the value of Vu/Vc also significantly increases. The values of Vu/Vc were found less than 2, thus Vs is required. When the longitudinal reinforcement ratio approaches maximum, Vu/Vc becomes relatively constant and was found more than 2. This concludes that the ratio of Vu/Vc of the concrete without coarse aggregate is lower than normal concrete. The existing ACI’s formula for computing the shear capacity contributed by concrete, which has not been changed for decades, is only applicable for normal concrete (with coarse aggregate). This research proposes a theory to develop a new shear capacity formula specifically for concrete without coarse aggregate.

Shear behaviour of lightweight aggregate concrete beamsusing palm-oil by-products as coarse aggregate

One of the main concerns of engineers to design a structural member using structural lightweight concrete is the shear performance of this concrete due to its lower tensile strength. This research presents an experimental investigation on the shear behaviour of reinforced palm-oil by-product lightweight concrete beams without shear links. The used by-products are wastes from oil palm industry i.e., oil palm shell (OPS) and oil-palm-boiler clinker (OPBC). They used as coarse aggregate in the concrete mixture while normal sand was used as fine aggregate. Nine reinforced OPS and OPS-OPBC lightweight concrete beams were prepared and their structural performance in terms of shear behaviour have been investigated. Three sets of the lightweight aggregate concretes with the maximum oven dry density less than 2000 kg/m3 were designed and each set contained three concrete mixes of grades 25, 35, and 45. The results of this study show that the OPS concrete beams have lower ultimate capacity in comparison with blended coarse aggregates (OPS-OPBC) concrete beams. The contribution of OPBC aggregate in the OPS concrete improved the structural performance and the failure nature of the beams, significantly. It was found that from the existing prediction models for estimating shear capacity of concrete beams, the shear capacity can be predicted about 10% underestimate and up to 60% overestimate.

Stepwise Regression for Shear Capacity Assessment of Steel Fiber Reinforced Concrete Beams

Inclusion of steel fibers to concrete progresses the flexural and tensile capacities of concrete. Consequently the shear capacity of concrete flexural members improve. Predicting the shear capacity of concrete beams containing steel fiber is an important issue not only in structural design but also to retrofitting of existing structures. Since there are several variables to assess the shear capacity of steel fiber reinforced concrete (SFRC) beams, presenting a suitable equation is a complicated task. The aim of the present paper is to evaluate an empirical formulae based stepwise regression (SR) method for shear capacity of SFRC beams. A series of reliable experimental data has been provided from literatures for model development. The obtained results based SR model were compared with experimental data in training and testing state. A practical formulae based SR method has been developed for shear capacity assessment of SFRC beams. Besides, several equations based models also presented to compare with the equation based SR model. The comparison showed the SR formulae gives the most exact accuracy than others in terms of shear capacity assessment of SFRC beams.

Shear behavior of concrete beams pre-stressed with carbon fiber reinforced polymer tendons

This article presents experimental and numerical studies on the shear behavior of reinforced concrete beams pre-stressed with carbon fiber reinforced polymer tendons. A total of 23 beams were tested to analyze the failure mode and shear performance of pre-stressed concrete beams. Experimental results revealed that there were two typical shear failure modes, that is, shear compression failure and inclined compression failure. Next, the experimental and numerical results were used to explore factors influencing the failure mode and the shear behavior of the concrete beams, including the type of pre-stressing tendons, stirrup ratio, shear span–depth ratio, number of pre-stressing tendons, and their initial pretension levels. It is demonstrated that shear span–depth ratio and stirrup ratio are the two main determinants of the failure mode and shear capacity of the concrete beams pre-stressed with carbon fiber reinforced polymer tendons. However, the bonding conditions of the pre-stressing carbon fiber reinforced polymer tendons have no significant effect on the shear capacity of the pre-stressed concrete beam.

Soft computing-based techniques for concrete beams shear strength

Despite the abundance of research works, both experimental and theoretical, conducted since the middle of the previous century up to today, the determination of the shear stress value is still remains an open issue of great interest in structural engineering. The need for further research is indicated by the fact that the majority of available proposals, whether proposed by regulatory agencies or various individuals researchers, lead to the estimation of different shear stress values; moreover, the comparison of estimated values with experimental values demonstrates that the available proposals lead to an overestimation or to an underestimation of the “true” shear stress. In this research study, the artificial neural networks approach is used to estimate the ultimate shear capacity of reinforced concrete beams with transverse reinforcement. More specifically, artificial neural network models have been examined for predicting the shear capacity of concrete beams, based on experimental test results available in the pertinent literature. The comparison of the consequent results with the corresponding experimental ones as well as with available formulas from previous research studies or code provisions makes obvious the ability of artificial neural networks to evaluate the shear capacity of reinforced concrete beams in a trustworthy and effective manner. Furthermore, the preliminary results presented in this work reveal the crucial parameters that affect the value of the shear strength of reinforced concrete beams with or without transverse reinforcement.

Shear behavior of high‐performance basalt fiber concrete—Part I: Laboratory shear tests on beams with macro fibers and bars

This paper presents findings from an experimental study on shear properties of high‐performance concrete beams reinforced with basalt fiber reinforced polymer bars and macrobasalt fibers. The test specimens comprised seven beams for shear testing and five beams for measuring the residual tensile strength of fiber concrete. No stirrups were used in the test beams. As part of the experiments, the compressive strength and bulk electrical resistivity were measured. To assess the influence of fiber dosage on shear capacity of concrete beams, five‐volume fractions of 43 mm macrobasalt fibers were investigated. The experimental results verified the hypothesis that shear capacity of concrete beams is associated with the fiber dosage. Furthermore, the results show a good correspondence with the predictions of Swedish standard (SS 812310:2014) and the fib Model Code 2010 predictions of shear strength of fiber reinforced concrete beams without shear stirrups.

Influence of Longitudinal GFRP Reinforcement Ratio on Shear Capacity of Concrete Beams without Stirrups

Fiber reinforced polymer (FRP) bars due to their excellent corrosion resistance, high tensile strength, good non-magnetic properties have been proposed for reinforcing concrete structures instead of traditional steel. Many research use glass fiber reinforcement as it is much cheaper than carbon one. The aim of this paper is to analyze the influence of longitudinal GFRP reinforcement on shear capacity of concrete beams without stirrups and to investigate a dowel effect of this reinforcement on the shear strength. The paper presents experimental test results of T- shaped, single span, simply supported beams without stirrups reinforced with longitudinal GFRP bars. The following parameters were investigated in the research: flexural reinforcement ratio, number of reinforcement layers, number and diameter of bars in one layer. Test results indicated no significant influence of the longitudinal reinforcement ratio on the shear strength in the beams with one reinforcement layer. However, in the beams with two layers of longitudinal reinforcement the significant increase in the shear strength was observed with increase in the reinforcement ratio (in a range from 1,02% to 1.85%). The beams reinforced with two layers of GFRP reinforcement showed more extensive crack pattern than the beams with one reinforcement layer. It confirms that application of two reinforcement layers more effectively enhance the shear strength mainly due to higher tension stiffening effect provided by the flexural reinforcement in the beams with two reinforcement layers.

Shear Capacity Research on Transversely Reinforced Concrete Beams

Inner transverse prestressed bars were used to enhance the shear capacity of concrete beams in this paper, which can be used in transformer beams to reduce the sectional size. Two transversely prestressed one ordinary concrete beams were tested and calculated by finite element method, and the following conclusions can be drawn: (a)The shear capacity of transversely prestressed concrete beam increase rapidly with the increase of the prestressing force level, which means that prestressing force level has a great influence on the shear capacity of transversely prestressed concrete beam. (b) The transverse prestressing bars can efficiently enhance the anti-crack performance of the reinforced concrete beams.

Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement

This paper presents the shear capacities of concrete beams reinforced with glass fiber reinforced polymer (GFRP) plates as shear reinforcement. To examine the shear performance, we manufactured and tested a total of eight specimens. Test variables included the GFRP strip-width-to-spacing ratio and type of opening array. The specimen with a GFRP plate with a3×2opening array showed the highest shear strength. From the test results, the shear strength increased as the strip-width-to-strip-spacing ratio increased. Also, we used the experimental results to evaluate whether the shear strength equations of ACI 318-14 and ACI 440.1R can be applied to the design of GFRP shear reinforcement. In the results, the ACI 440 equation underestimated the experimental results more than that of ACI 318.

Study on Shear Behaviour of Concrete Beams Prestressed with External CFRP Tendons

Based on independent research and development of a CFRP tendons wedge-type anchorage, the shear tests of six CFRP external prestressing concrete beams were done. Among them, CFRP external tendons of three pieces were installed in straight line while other pieces were installed in curved line. The results of experimental research show that shear behaviour of concrete beams prestressed with CFRP external tendons are the similar process to the traditional prestressed reinforced concrete beams. They go through the elastic stage, the stage of crack extension, the yield stage of internal hoop reinforcements at the intersection of inclined cracks and the failure stage. When external CFRP tendons are arranged in the same situation, the cracking load and the shear capacity of concrete beams prestressed with CFRP external tendons reduce gradually along with the increase of shear-span ratio,.When shear-span ratio is equal, the cracking load and the shear capacity of concrete beams prestressed with curved arrangement of CFRP external tendons are larger than those of concrete beams prestressed with straight arrangement of CFRP external tendons. Compared with traditional concrete beams prestressed with external steel bars, due to elasticity modulus and shear modulus of CFRP tendons are both smaller than those of steel bars, the mid-span deflection of concrete beams prestressed with CFRP external tendons at the time of shear failure is bigger than that of traditional concrete beams prestressed with external steel bars under the same circumstance.

Shear Capacity of Concrete Beams Reinforced with Continuous FRP Rectangular Spirals

The failure modes and the shear capacity of concrete beams reinforced with FRP reinforcement were discussed through an experimental investigation, in which continuous FRP rectangular spirals were used for shear reinforcement, while ordinary deformed steel bars are used for longitudinal reinforcement. Six concrete beams reinforced with FRP spirals were tested, the main variables considered were the shear reinforcement ratios, the shear span to depth ratios and the longitudinal reinforcement ratios. Two concrete beams of equal shear capacity which reinforced with continuous steel rectangular spirals were also tested to compare the behavior of concrete beams reinforced with different materials of spirals. All beams were tested as simply supported members subjected to a three-point load, the span of the beams varied in terms of different shear span to depth ratios. The test results show that the shear capacity and shear failure modes are greatly influenced by the shear reinforcement ratios and the shear span to depth ratios, the shear resistance provided by steel spirals is higher than that provided by FRP spirals in the case of equal shear capacity of beams, which is attributed to the differences in material properties and may result in different shear failure types. Based on the experimental program, four mechanical models are derived to give more accurate predictions of the shear capacity of test beams, the calculation results of these models are compared with that of the existing shear formulas or equations for concrete beams reinforced with FRP stirrups or spirals. The rotating-angle softened truss model, the strut-and-tie model, the shear formulas derived from the truss-arch model and Zsutty equations are suggested through comparison.

Finite Element Analysis of Reinforced Concrete Beams with Transversely Prestressed Bars

This paper presents a method that using inner transverse prestressing bars to enhance the shear capacity of concrete beams, which can be used in new transformer beams to decrease the sectional dimensions. Four transversely prestressed concrete beams and one ordinary reinforced concrete beam were tested. The nonlinear finite element method was applied to analyze them, and the following conclusions can be drawn: (a) The transverse prestressing bars can efficiently increase the shear capacity and failure load of the reinforced concrete beam, the improvement effect is more obvious when exerting the prestressing force on them properly. (b) On the whole, the simulated load-deflection relationships and failure loads of the five specimens agree well with the corresponding tested load-deflection relationships and failure loads. It indicated that the FE models used in this paper predict the structural behavior of the transversely prestressed concrete beams satisfactorily. (c) From the contour of first principal stress, it can be seen that the transverse prestressing bars can efficiently enhance the shear crack resistance of the reinforced concrete beams, if the area of transversely prestressing bars is almost same, the transverse bars with smaller diameter and smaller spacing will be better. It agrees well with the test results.