Behavior Of Concrete Beams Research Articles

Analysis of whole loading process of concrete beams reinforced with hybrid rebars allowing for confinement effect

Concrete beams reinforced with hybrid longitudinal reinforcements (a combination of steel and FRP rebars) exhibit superior performance in ductility, stiffness and durability compared with conventional concrete beams. However, most available approaches rely on some empirical assumptions and ignore the slip between longitudinal rebars and adjacent concrete and the confinement effect of steel stirrups on concrete. The purpose of this paper is to propose a generic analytical approach to overcome these limitations. The main advantages of the proposed analytical approach are that it requires only the shear-friction and bond-slip material properties of concrete beams and can reasonably predict the whole loading process of concrete beams reinforced with longitudinal steel rebars, FRP rebars or a combination of both. Finally, a parametric study is conducted to investigate the effects of stirrups and longitudinal reinforcement on the behaviour of concrete beams. It is found that stirrups have a significant effect on the strength and ductility of concrete beams and hence cannot be ignored in the design of beams.

Deterioration Behavior of Concrete Beam Reinforced with Carbon Fiber-Reinforced Plastic Rebar Exposed to Carbonation and Chloride Conditions.

The absence of carbon fiber-reinforced rebar performance standards in Korea has limited its reliability. This study investigates the durability performance of carbon fiber-reinforced polymer rebar as an alternative to traditional steel reinforcement in concrete structures. Concrete beams reinforced with carbon fiber-reinforced polymer rebar were exposed to chloride environments for durations of 35 and 70 days and then subjected to bending tests to evaluate their durability. The results demonstrate that the strong bond between the carbon fiber-reinforced polymer and concrete effectively prevented brittle fracture, even under exposure to harsh chloride. A scanning electron microscope analysis of the specimens exposed to chloride showed no deterioration of the carbon fiber-reinforced polymer rebar, highlighting its exceptional resistance to corrosion. Furthermore, durability tests were conducted in a carbonation chamber for 8 and 12 weeks, with no signs of degradation in the carbon fiber-reinforced polymer rebar. These findings suggest that carbon fiber-reinforced polymer rebar offers excellent resistance to both chloride-induced corrosion and carbonation, making it a promising solution to enhance the longevity and durability of reinforced concrete structures exposed to aggressive environmental conditions.

Flexure Behaviour of Corroded Reinforcement Concrete Beams Under Sustained Loads

Abstract The long-term behaviour of concrete beams with corroded reinforcement is a critical aspect that demands thorough comprehension to ensure the serviceability and durability of reinforced concrete structures. This paper aims to investigate the long-term performance of reinforced concrete (RC) beams with corroded reinforcement numerically. Two experimental datasets from existing literature were selected to build a nonlinear finite element model. The selected beams were tested under four-points sustained bending load and three bending point flexural test with deferent level of corrosion. A parametric study was then conducted taking into account concrete compressive strength, reinforcement yield strength, ambient temperature, relative humidity and sustained load level to get a better understanding on the factors that effecting the long-term behaviour of concrete beams with corroded reinforcement. Results demonstrated that, Diana FEA has an excellent ability to predicating the long-term behaviour of RC beams with corroded reinforcement. The analysis of the parametric study revealed that increasing relative humidity from 70% to 90% resulted in a 45% to 53% reduction in developed deflections. Whereas once the temperature rose from 20°C to 40°C the developed deflection increased from 13.9% to 17.2%. This outcome demonstrating the significant impact of environmental factors on the long-term behaviour of corroded reinforced concrete beams. Finaly, once the yiled stregth of the steel reinforcement increased from 380 Mpa to 550 Mpa, the developed deflection rate increased from 46% to 54%.

Experimental investigation on the effect of natural fire exposure on the post‐fire behavior of reinforced concrete beams using electric radiant panel

AbstractIn this study, the effects of natural fire exposure on the post‐fire behavior of concrete beams are investigated. The study is based on laboratory tests where three reinforced concrete beams were subjected to fire exposure using an electric radiant panel. This panel enables a precise application of radiative heat exposure closely mimicking natural fire exposure in a safe manner. During the test, the deflections, deformations and temperature changes are measured for all three concrete beams. Additionally, finite element modeling (FEM) is applied to supplement these tests, demonstrating the performance of existing structural fire engineering calculation tools in evaluating the burnout performance of concrete beams. The results of the tests show that the electric radiant panel provide a novel approach for fire simulation which is effective in replicating natural fire conditions, by applying the heat flux as specified in the Eurocode Parametric Fire Curve in a highly controlled manner. The uniformity of the temperature field measured inside the beams and the consistent deformations observed during the heat exposure across all three tests underscores the accuracy of the fire simulation. Furthermore, post‐fire assessments reveal that while the exposed beams suffered some reduction in load‐bearing capacity, they retained a significant portion of their original strength that was consistent across all three beams. The numerical simulations conducted in this study demonstrate a high level of accuracy in predicting the behavior of the concrete beams during fire exposure. These simulations effectively mirrored the experimental results, validating that they are a valuable tool for assessing concrete structures' performance in fire scenarios.

Behavior of Concrete Beam Encasing Castellated Steel Section with Different Opening Size

This research aims to investigate the behavior of castellated steel sections with varying hole sizes enclosed in a concrete beam. Should two different opening size types (depth 140mm and depth 280mm) be used? When we use two types of shear connectors with full and partial interaction, stud connections integrate the steel and concrete parts. This research demonstrates We examined five simply-supported composite beams under two-point loading conditions. We constructed four examples using castellated steel beams and produced one specimen using standard steel beams as a control. We examine the maximum load support capacity. Examined are the specimens of composite beams' deformations. Among the many characteristics assessed are the castellated beam size of the aperture and the whole and partial composite interactions. According to test results, the sample had a 140mm hexagonal hole. The sample experienced an increase in final load percentages of approximately 11.11%. Compared to the sample featuring a 280mm hexagonal opening size, the mid-deflection and horizontal displacement showed a significant increase. The figures indicate a final load of approximately 18.82% and 16.7%, respectively. Full interaction also revealed a higher ultimate load for the sample with the same aperture. When the sample was fitted with a 140mm hexagonal hole, the percentages increased by approximately 6%. Additionally, the percentage of deflection at midspan and the percentage of horizontal displacement decreased by approximately 16.7% and 26.8%, respectively, compared to the sample with a hexagonal opening size of 280 mm.

The effect of compression reinforcement on the shear behavior of concrete beams with hybrid reinforcement

The effect of compression reinforcement on the shear behavior of concrete beams with hybrid reinforcement

Monitoring evolutionary damage of bended concrete beams subjected to freeze-thaw cycling through piezoelectric-enabled wave propagation method

Tunnels in cold regions are often subjected to freeze-thaw cycling, which poses a great challenge to a large number of tunnels in operation or to be built in these regions. Therefore, structural health monitoring (SHM) for lining concrete in cold regions is essential to ensure the safety and long-term operation of tunnels. In this study, the wave propagation method (WPM) is applied for the first time to monitor the cyclic freeze-thaw damage of lining concrete. First of all, the failure behaviors of concrete beams subjected to the coupling effect of flexural loading and freeze-thaw cycling are investigated. Particularly, the authors propose a refined numerical model to simulate the freeze-thaw cycling damage process of concrete beams considering the ice-water phase transition and concrete elastoplastic damage. Based on the numerical results, the internal damage expansion and flexural strength attenuation of concrete beams are revealed. Furthermore, the dynamic attenuation characteristics of stress waves are analyzed by using the wavelet packet decomposition and continuous wavelet transform to reveal. In addition, the WPM-based energy index is proposed to characterize the freeze-thaw damage degree of the lining concrete. A strong correlation is found between the stress wave signal and freeze-thaw damage, with a favorable correlation coefficient of 0.932, suggesting the excellent performance of the WPM in assessing the freeze-thaw damage of lining concrete. This research sufficiently manifests the applicability of the WPM method to monitoring the freeze-thaw damage within cold regional tunnel linings.

Experimental study on the behavior of polypropylene fiber-reinforced concrete beams

This research aimed to analyze the behavior of concrete beams reinforced with polypropylene fibers. This type of reinforcement has been increasingly used in construction to improve the tensile properties of concrete, mitigate the propagation of microcracks due to shrinkage, enhance impact capacity, and extend the durability of concrete structures. An experimental study was conducted on twelve concrete beams with dimensions of 150 x 150 x 600 mm, reinforced with polypropylene fibers, divided into four groups: 0.35%, 0.45%, and 0.55% fibers/m³ of concrete, along with a reference group without fibers. Four-point flexural tests were performed following the recommendations of the NBR 12142 (ABNT, 2010) to evaluate the influence of the fibers on the contribution to tensile strength in flexure. The results showed that the beams reinforced with 0.35% fibers/m³ exhibited the best performance, with a significant increase in strength compared to the other groups, with and without fiber reinforcement. All fiber-reinforced groups showed a shift from brittle to ductile behavior. Additionally, the beams with 0.55% fiber content demonstrated greater ductility but less contribution to tensile strength.

Shear performance and capacity of FRP reinforced concrete beams: Comprehensive review and design evaluation

To enhance the durability of concrete structures in harsh environments, replacing steel bars with FRP bars is judged a feasible method. The low elastic modulus and transverse strength of FRP bars result in the weak shear capacity of concrete beams reinforced with FRP bars. Reviewing and summarizing existing literature are important for addressing this challenge. The research progress on the shear behaviour of concrete beams reinforced with FRP bars was systematically described from two aspects in this paper. In the aspect of literature review, shear mechanisms and main influencing factors of concrete and FRP stirrups were summarized. In addition, achievements and shortcomings of existing literature were summarized, and potential research directions were pointed out. In the aspect of design method evaluation, a database containing 525 samples was established and calculation models of shear capacity of concrete beams reinforced with FRP bars in seven codes were evaluated. Evaluation parameters mainly included shear span ratio, effective height, and maximum strain of FRP stirrups. Based on the calculation model in Italian code CNR DT203-06, an optimized model was proposed to improve the accuracy in predicting concrete shear contribution. The review and evaluation in this paper had important reference significance for improving the design level of concrete structures reinforced with FRP bars and promoting the engineering application of FRP bars.

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

This research investigated the shear behavior of concrete beams reinforced with Carbon Fiber Reinforced Polymer (CFRP) bars and grids as longitudinal reinforcements and stirrups, in experiment and finite element (FE) methods. Five concrete beams were tested under a monotonical load and experienced shear failure as expected. The test variables including stirrup ratio and grid dimension were considered to investigate the interaction between grid and concrete, and the influence between the horizontal and vertical fibers of the grid. It found that reducing the grid dimension with the constant stirrup ratio could effectively improve the stress distribution of the grid and the shear capacity of the beam. The grid dimension greatly determined the shear capacity of specimens when the stirrup ratio changed in a small range. The horizontal fibers of the grid had anchoring effects on the vertical fibers and directly carried the tensile stress from concrete at the top and bottom of the beam. In FE analysis, the fiber composite layer was adopted to simulate the CFRP grid. The load-midspan deflection of specimens and strain development of the grid in the FE model showed good agreement with the tests. In parameter analysis, the grid configuration with the horizontal fiber arranged in the middle or upper part of the section was recommended.

Structural Behavior of Concrete Beams Strengthened with Near-Surface-Mounted BFRP Reinforcement

Structural Behavior of Concrete Beams Strengthened with Near-Surface-Mounted BFRP Reinforcement

Flexural Behavior of Concrete Beams Reinforced with a CFRP Grid Exposed to Chloride-Containing Environments: An Experimental Study

Flexural Behavior of Concrete Beams Reinforced with a CFRP Grid Exposed to Chloride-Containing Environments: An Experimental Study

Experimental Investigation on Pure Torsion Behavior of Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars

The failure mechanism of torsional concrete beams with fiber-reinforced polymer (FRP) bars is essential for developing the design method. However, limited experimental research has been conducted on the torsion behavior of concrete beams with FRP bars. Therefore, the pure torsion test of four large-scale FRP-RC beams (2800 mm × 400 mm × 200 mm) was conducted to investigate the influence of the stirrup ratio (0, 0.49%, and 0.98%) and longitudinal reinforcement ratio (3.01%, 4.25%) on torsion behavior. The test results indicated that three typical failure patterns, including concrete cracking failure, stirrup rupturing failure, and concrete crushing failure, were observed in specimens without stirrups (stirrup ratio 0), partially over-reinforced specimens (stirrup ratio 0.49%), and over-reinforced specimens (stirrup ratio 0.98%), respectively. The tangent angle of spiral cracks at the midpoint of the long side of the cross-section was approximately 45° initially for all specimens. The torque–twist angle curves exhibited a linear and bilinear behavior for specimens without stirrups and specimens with stirrups, respectively. As the stirrup ratio increased from 0 to 0.98%, torsion capacity increased from 24.9 kN∙m to 27.8 kN∙m, increased by 12%, ultimate twist angle increased from 0.0018 rad/m to 0.0403 rad/m. As the longitudinal reinforcement ratio increased from 3.01% to 4.25%, the torsion capacity increased from 27.8 kN∙m to 28.3 kN∙m, and the ultimate twist angle decreased from 0.0403 rad/m to 0.0244 rad/m. Based on test results, the stirrup strain limit of 5200 με and spiral crack angle of 45° was suggested for torsion capacity calculation. In addition, based on the database of torsion tests, the performance of torsion capacity provisions was assessed.

A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars

A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars

Macro-meso cracking inversion modelling of three-point bending concrete beam with random aggregates using cohesive zone model

An accurate description of concrete crack propagation is essential to practical engineering. In this paper, the cohesive zone model (CZM) is used to investigate the macroscopic mechanical properties and the microscopic crack damage behavior of concrete beams in the three-point bending test. Five key factors controlling the cracking of cohesive elements, namely mode I fracture energy, mode II fracture energy, shear strength, tensile strength, and elastic modulus (stiffness), are subjected to parametric examinations. Based on macro-mechanical properties and micro-cracking, the test results and parametric models of specimens are inversely analyzed. The applicable parameter range of control factors in the three-point bending simulation is obtained. Considering the quantitative aggregate information of specimens with different mix proportions, three computation models with different aggregate areas are established. The quantitative results of crack propagation are derived by applying the parameter range. Finally, the accuracy of the parameter range is validated based on the simulated and experimental mechanical properties and quantitative results of cracks.

An integrated optimization and ANOVA approach for reinforcing concrete beams with glass fiber polymer

Concrete beams are commonly used in construction projects to provide structural support. Reinforcing these beams with steel and Glass Fiber Reinforced Polymer (GFRP) can increase their strength and durability. Steel reinforcement is a traditional method used for decades, while GFRP is a newer material that offers several advantages, including corrosion strength and lighter weight. Combining both materials to reinforce concrete beams can result in a stronger and more resilient structure, making it an ideal choice for many construction projects. In this study, the behavior of reinforced concrete beams with steel and GFRP reinforcement is numerically investigated, and the effect of steel percentage and GFRP percentage on the mechanical strength and energy response of the beam is determined using the Response Surface Methodology (RSM). Using the ABAQUS software, a widely used Finite-Element Analysis (FEA), the numerical modeling is first verified, and then targeted analyses are performed on the beam using the tests specified by the RSM. Then, based on the strength and energy of the beam, a two-variable Analysis of Variance (ANOVA) and two-objective optimization are performed to investigate the effect of changing each parameter of steel percentage and GFRP percentage on beam strength and energy. Several laboratory studies have been conducted on the behavior of concrete beams with steel and GFRP bars, but no research has statistically and numerically examined their behavior. We also simultaneously optimized both strength and energy parameters based on the ratio of steel and GFRP and compared them with numerical values. We show an interaction relationship between steel and GFRP ratio in the strength and energy of concrete beams. In the beam with hybrid reinforcement, with the increase of steel and GFRP ratios, the amount of strength and energy does not increase linearly, and there is a quadratic relationship between them.

Strength enhancement of recycled fine aggregate beam through chemical treatment - A waste to wealth Approach

The present research used detailed experimental data to examine the structural behavior of concrete beams incorporating recycled fine aggregates, both treated and untreated.This paper also reveals that microstructural analysis of both treated and untreated recycled fine aggregates. The hydrochloric acid was used for treatment of recycled fine aggregates. Two groups of beam specimens prepared were controlling specimnes and testing specimens. Totally five beam specimens were prepared out of which one control beam with natural fine aggregates, four testing beams with untreated recycled fine aggregates and three beams with treated recycled fine aggregates. The varying molarity of HCL acted as the parameter for examining the structural behavior of the RCFA beams under flexure. The flexural strength of untreated RCFA beams was marginally impacted by the RCFA content, whereas the crack pattern of treated RCFA beams was comparable to that of NCFA beams. Untreated RCFA beams had greater fracture width. Nonetheless, the RCFA concentration had no discernible effect on the beam's ductility. The flexural strength of the RCFA concrete beams was conservatively projected by the present provisions, according to a comparison of the testing data and the calculations from the IS codes, ACI 318, and EC2 regulations for the flexural.

Flexural and Bond Behavior of Concrete Beams Strengthened with Carbon Fiber-Reinforced Polymer Sheet

Concerns have been expressed regarding the issue of using conventional steel rebar in civil engineering structures. One contributing factor is the corrosion that occurred on the steel rebar. The corrosion process was not promptly detected due to the gradual reaction time exhibited by the steel, concrete, and environmental conditions. Corrosion problems often manifest when corrosion has progressed to a critical point and damaged the concrete structure. Consequently, to address this issue, this research proposed the application of carbon-fiber reinforced polymer sheet (CFRP). The aim is to measure the flexural load of conventional and FRP-reinforced concrete beams, to test the effects of cracking and deflection on concrete beams strengthened with FRP sheet, and to determine the degree to which these loads damaged these beams. A repair method was implemented by applying two distinct diameters of CFRP: 50 mm × 100 mm and 100 mm × 200 mm. The finding shows that the concrete beam's significantly higher flexural strength resistance was observed for CFRP of greater dimensions. This is mostly because the CFRP can disperse the applied stress more effectively. Alternative applications of fibre-reinforced polymer should be explored for further research to facilitate the development of substitutes for CFRP.

A Comparative Study of the Structural Behavior of Concrete Beams Reinforced with Different Configurations of GFRP and Steel Bars

This study examined experimentally and numerically the performance of five concrete beams reinforced with longitudinal and transverse bars made of Glass Fiber Reinforced Polymer (GFRP) or steel. All beams had the same dimensions of 2700 mm in length, 180 mm in width, and 260 mm in depth. The beams were classified into two groups with different variables and compared with a reference beam reinforced with longitudinal and transverse steel bars. The first group consisted of two beams with longitudinal GFRP bars and no stirrups, varying the main reinforcement ratio. The second group comprised two beams with longitudinal GFRP bars and transverse GFRP or steel stirrups, varying the stirrup type. The results indicated that the beams with GFRP bars improved their flexural strength for different ratios but had limited shear resistance when using GFRP stirrups because increased deflection causes the number and width of cracks to grow, reducing the shear strength. All the tested beams exhibited linear elastic behavior until failure, with GFRP being more brittle than steel due to no yield point or plastic behavior in GFRP. The numerical simulation of the five beams using ABAQUS software showed good agreement with the experimental data obtained in the laboratory.

Experimental and Numerical Study on Flexural Behavior of Concrete Beams Using Notches and Repair Materials

In a concrete beam, cracking is generated on the tension side under the effect of flexure, shear, and torsional loadings. Accordingly, these weak concrete members require repair and/or strengthening to increase or restore their internal load capacity. In the current experimental and numerical investigations on concrete beams, the impact of using notches with different width to depth ratios on the ultimate flexural load under a three-point test was considered. Further, the flexural behavior performance of a notched concrete beam repaired using the three repair materials—cement mortar, bacterial mortar, and adhesive—was also examined. Consequently, a comparative study was implemented between the experimental and numerical results. A concrete damage plasticity (CDP) model was used for the finite element numerical analysis of the beams. The differences in numerical and experimental measured results ranged from 0.65 to 22.20% for the ultimate load carrying capacity. As the notch size increased, the ultimate load carrying capacity of the beam reduced. Additionally, a linear regression model was used to predict the ultimate load values at a notch width interval of 5 mm up to a maximum notch width of 100 mm. It was observed that the ultimate load capacity for a repaired beam increased as compared to the notched beam for all three repair materials under consideration. And the maximum ultimate load increased in the case of notched beams repaired using adhesive. Furthermore, in comparison to the cement mortar, the performance of the bacterial mortar in terms of the ultimate load was more. The bacterial mortar was found to be more sustainable and more durable as a repair material for concrete structures.