Shear Failure 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.

Análise das tendências nos mecanismos complementares de resistência ao cisalhamento de vigas de concreto armado

abstract: The study of shear failure in concrete beams is one of the subjects growing in importance due to both the recent reformulations, and increasingly higher cross-section depths used. For instance, the recent updates in the ACI 318 (2019) shows the need to incorporate the size effect in the design of reinforced concrete elements. In this study, the same database adopted by the ACI-ASCE Committee DAfStb 445-D has been used to calculate shear strength, with and without the consideration of size effect, i.e., the design prescribed by ACI 318 (2014), ACI 318 (2019), Frosch et al. (2017), and the ABNT NBR 6118 (2014). Later these predictions are compared with test results. A dispersion analysis has outlined the trends regarding compressive strength, span to depth ratio, longitudinal reinforcement ratio and beam depth. Every variable was discussed per interval, delineating the causes related to the observable trends. Regarding the most prominent influences (effective depth and longitudinal reinforcement ratio), the approaches considering them directly through factors had provided results with no appreciable trends, with lower coefficients of variation (COV) and substantially more conservative for higher cross-section depths. As the Brazilian code does not consider both, a correction factors, determined by a two-step regression analysis on these parameters to adjust this design, are briefly introduced.

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.

Mesoscale simulations of the impact resistance performance of rein-forced concrete beams exposed to high temperature

Considering the degradation of the mechanical properties of steel and concrete under high temperature and the strain rate effect of the materials, a mesoscopic numerical analysis model of reinforced concrete beam are proposed based on the meso-structure of concrete. The influences of fire duration time and impact energy on the impact resistance behavior of concrete beams in fire are discussed. In this paper, the failure process of reinforced concrete beam subjected to impact load, the impact force time history, the reaction time of support and the displacement response in the middle span are analyzed. The results show that the mesoscopic numerical model can well simulate the heat transfer process of each components of concrete. With the increase of heating time, the concrete beam under the impact load is more serious, meanwhile the duration of the impact force and the maximum displacement of the span increase, but the impact force peak decreases; with the increase of impact energy, the shear failure of concrete beam is more serious, and the impact force peak increases. The maximum displacement increases linearly with the impact energy.

Comparison of main models for size effect on shear strength of reinforced and prestressed concrete beams

AbstractThis paper presents a critical comparison of the existing code provisions for the shear strength of concrete beams. The comparison is based on the computerized filtering‐out of the inevitable statistical bias from the available multivariate database on shear strength, on an examination of the predicted size effects on shear strength and their underlying hypotheses and on the results of recent high‐fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure in concrete beams, which is necessary for future revisions to the design code provisions.

Numerical Investigation on Shear Failure of Concrete Beam Strengthened by Bonded Steel Plate

Based on micromechanics, an elastic-plastic-brittle damage model of concrete beam reinforced with stick steel is proposed by considering the aggregate gradation curve algorithms and the heterogeneity. In the model, the concrete beam reinforced with stick steel is taken as a five-phase composite material that consists of the mortar matrix, coarse aggregate, bonds between mortar and aggregate, steel plate, and the adhesive layer between steel plate and concrete beam. Through the numerical investigation on shear failure of concrete beam reinforced with stick steel under external force, the results show that the model can clearly simulate microscopic plastic yield, and the initiation and extension of crack. The strength of the steel plate is relatively stronger, so it cant enhance the shear capability of the each side of the beam and the concrete beam bears the larger shear stress, which results that a large number of elements, from the supports to the load points, begin to yield. When the strain of the elements exceeds the yield strength, the elements will produce failure until the failure of the whole specimen. The final failure mode of concrete beam reinforced with stick steel is the shear failure.

Shear Strength of Reinforced Concrete Beam Strengthened by Transverse External Post-tension

Problem statement: Shear failure of concrete beam is brittle manner without warning so inadequate design for shear of beam and/or material deterioration lead to the possibility of sudden failure of beam. The change of functional use and future increased load of structure lead to the need for strengthening of concrete structure. Approach: This research focuses on behaviors under static loading of reinforced concrete beam, with shear strengthening by transverse external prestressing force. Post-tension high strength steel is vertically applied in shear span. Total eight beam specimens are divided into two groups each having shear span to depth ratios 2 and 1.5. Each beam, possessing the same reinforcing steels, is intentionally designed to be failing in shear. One of the beams from each group is used as reference, without shear strengthening. The other three specimens from each group are applied different amounts of external prestressing force. Results: The experimental result shows that ultimate load carrying capacity of all shear strengthened specimens significantly improves over the reference specimen. The higher the amount of applied strengthening force, the greater the ability to carry ultimate loading. Failure mode shifts from brittle shear failure closer to ductile flexural failure, with higher ductility and stiffness. External prestressing force in transverse direction of shear span of beam enhances ultimate shear capacity by improving aggregate interlocking, preventing splitting cracks caused by debonding of longitudinal reinforcing steels due to dowel action. Furthermore, load at first diagonal tension cracks are increased as a result of pre-compressed prestressing force leading to the higher ultimate load carrying capacity. Moreover, concrete in compression zone remains uncrushed at ultimate state. Strut-and-tie model can be used to predict ultimate loading capacity of beam specimen and failure mechanism of both specimens with or without strengthening. Conclusion: Shear strength of reinforced concrete beams strengthened by transverse external post tension at shear span is effectively improved over reference beam specimen. Strut and tie model can be conservatively predicted the ultimate shear capacity of both reference and strengthened beam specimen.

Shear Behavior of Externally Prestressed Beams with Carbon Fiber-Reinforced Polymer Tendons

Shear failure in concrete beams is sudden and catastrophic. Unfortunately, research on the effects of external unbonded prestressing on the shear behavior of concrete beams is scarce, especially for beams prestressed with carbon fiber-reinforced polymer (CFRP) rods. This study attempts to improve the understanding of the shear behavior of externally prestressed concrete beams by testing a total of 15 specimens, including three span-depth ratios (a/d), two shear reinforcement setups, and three external prestressing levels to contrast the shear behavior of concrete beams with the shear behavior cf concrete beams prestressed externally with CFRP rods. The test results demonstrated that the development of arch and beam action in prestressed beams does not conform to the traditional a/d of 2.5. Instead, the prestressing force reduced the effective a/d and significantly strengthened the concrete beams in shear. This significant shear enhancement cannot be predicted with the current shear design equations in ACI 318-08. As a result, a better prediction method for the shear capacity of concrete beams externally prestressed with unbonded CFRP rods is needed before this shear strengthening technique can be widely used.

Shear strength of slender reinforced concrete beams without web reinforcement: A model using fuzzy set theory

A reliable shear strength model for slender reinforced concrete beams without web reinforcement is described based on fuzzy set theory. The fuzzy-based model was developed to consider the interaction between the shear modeling parameters and the random and non-random uncertainties in these parameters. The parameters were identified essential for modeling shear strength in slender reinforced concrete beams without web reinforcement being: the compressive strength, the effective depth and the tension reinforcement ratio. A total of 385 experimental datasets obtained from shear tests of simply supported reinforced concrete beams from the literature, are used in learning/developing and verification of the proposed model (164 for learning and 221 for verification). The shear strength predicted by the fuzzy-based model was compared to those predicted by current shear strength models suggested by design codes such as the Eurocode 2 (EC2), the American code ACI (318-05), and Canadian code (CSA A23.3-04). The fuzzy-based model yields a significant enhancement in the prediction of the shear strength while still respecting principles of mechanics governing shear failure in concrete beams.

An upper-bound rigid-plastic solution for the shear failure of concrete beams without shear reinforcement

An upper-bound rigid-plastic solution for the shear failure of concrete beams without shear reinforcement

An upper-bound rigid–plastic solution for the shear failure of concrete beams without shear reinforcement

Synopsis In recent years research workers at the Technical University of Denmark and elsewhere have shown that simple rigid–plastic methods of analysis can be used to predict closely the experimental shear failure loads of reinforced and prestressed concrete beams. The method has proved sufficiently attractive in Europe to be considered as a basis for new code of practice formulations for shear failure, but has so far been rather neglected in the United Kingdom. In this paper, rigid–plastic analysis is applied to the shear failure of reinforced or prestressed concrete beams without shear reinforcement. A new upper-bound solution for this problem is derived and compared with the previous ‘exact’ solution derived by Nielsen and Braestrup. The new upper-bound solution is shown to produce lower failure values of shear stress for certain ratios of compression to tension steel.