Concrete Beam Specimens Research Articles

Destructive and Non-Destructive Evaluation of Fibre-Reinforced Concrete: A Comprehensive Study of Mechanical Properties.

Ultrasonic pulse velocity (UPV) and rebound hammer tests are accepted as alternatives to destructive testing to determine the compressive strength, dynamic modulus of elasticity, and Poisson’s ratio, which are needed for structural design. Although much work has been conducted for plain concrete, the research data for fibre-reinforced concrete (FRC) is insufficient. In this regard, this study explains the correlations between compressive strength, rebound hammer, and UPV tests for plain concrete and FRC contains 0.25%, 0.50%, and 1.00% of 30 mm and 50 mm long steel fibres. A total of 78 concrete cube and beam specimens were tested by direct, semi-direct, and indirect UPV and rebound hammer test methods. The study found that the rebound hammer test is more suitable for measuring the compressive strength of matured FRC than young concrete. The UPV test revealed that the volume fraction does not, but the length of steel fibres does affect the UPV results by the direct test method. The UPV direct method has the highest velocity, approximately two times the indirect velocity in FRC. UPV measurements can be effectively used to determine the dynamic modulus of elasticity and Poisson’s ratio of FRC. The dynamic elastic modulus increases while the Poisson’s ratio decreases for the same steel fibre length when at increasing FRC fibre content. The results of this study will be significant for non-destructive evaluations of FRC, while additional recommendations for future studies are presented at the end of the paper.

Three-Dimensional Impact Localization on Concrete Structures Using Novel Enhanced Cross-Correlation Algorithm and Designed Concrete Implantable Module

Concrete structures are often subjected to undesirable impact loads. Impact localization in near real time is greatly essential for providing early warnings and evaluating impact load effects. In this article, a novel enhanced cross-correlation (ECC) algorithm enabled by a designed concrete implantable module (CIM) is proposed for precise prediction of the impact location on concrete structures. The stability of the ECC algorithm under the noise condition was numerically studied. The numerical results demonstrate that the proposed ECC algorithm has high adaptability in the low signal-to-noise ratio (SNR) condition compared with the traditional algorithm, which provides the possibility for employing this approach in real projects. In the experimental study, a series of impact tests on a concrete beam specimen were conducted to verify the accuracy of the proposed method for impact localization. The results indicate that the maximum and minimum distance errors between the real and predicted impact positions are 54.1 and 12.5 mm, respectively. Both the numerical and experimental studies demonstrate the feasibility of the proposed method for the prediction of impact locations.

Structural Behavior of Reinforced Concrete Beams Containing Pet Waste Particles as Sand Replacement

Abstract This paper examined the polyethylene terephthalate (PET) polymer waste effect that using as a partial replacement for fine aggregate on the R.C beams structural behavior. Six replacement percentages by weight were used in this study: 5 %, 7.5 %, 10 %, 12.5 %, 15 %, and 20 %. Seven concrete beam specimens with dimensions of 150 × 300 × 2300 mm were tested, in which one specimen for each PET replacement percentage was added to the reference specimen. four-point load setting were used to test all specimens via failure load, maximum deflection, energy absorption, stiffness, ductility index, flexural strain, first crack load, and crack pattern. Results showed that raising of PET percentage in the concrete beams leads to an increase in failure load, maximum deflection, ductility index, strain, and energy absorption compared with the reference beam in the ranges 0 – 4 %, 23.2 – 93.7 %, 12.13 – 93 %, 432 – 1139 %, and 51.8 – 275.4 %, whereas its causes a decrease in initial stiffness and secant stiffness in the ranges 5.8 – 38.44 % and 19.2 – 46.4 %. Moreover, crack investigations revealed that the load at which the first crack forms raise when the PET waste content increases.

Shear capacity and behavior of high-strength concrete beams with openings

Transverse openings alter the structural behavior and undermine the integrity of concrete beams, resulting in stiffness degradation, shear strength reduction, stress concentration, premature cracking, and force-flow disturbances. Consequently, they require special attention during the design and construction of concrete beams with openings. Owing to the abrupt change in the beam's cross-sectional area, the strain distribution in the region around an opening is disturbed and nonlinear, making conventional bending and shear theories irrelevant. Few studies have investigated the impact of openings on concrete beams, especially that of openings on high-strength concrete (HSC) beams. Therefore, in this study, we perform tests on 12 reinforced concrete beam specimens to investigate the influence of depth, length, and location of openings on the ultimate shear strength of HSC beams with openings. The results revealed that the opening depth and length of HSC beams are negatively and almost linearly correlated to the ultimate shear strength; furthermore, based on their size and location, the shear capacity reduces by 2–53%. Similarly, the opening location along the shear span had a substantial impact on the capacity and behavior of the beam. Subsequently, finite element models of the tested beams were developed in ABAQUS software package and validated in compliance with the experimental results. The simulations exhibited good performance in predicting the ultimate strength, load–deflection relationship, and crack propagation in the beams. Accordingly, the developed models can be utilized to conduct further parametric studies and develop strut-and-tie models.

Experimental Study on the Shear Strength of Reinforced Concrete Beams with Various Integrated Shear Reinforcements

The purpose of this study was to evaluate the shear performance of concrete beams with integrated shear reinforcements made of steel plates and rebar bent in an N shape (N-type rebar), and to evaluate the applicability of the current relevant design standards. For this purpose, four concrete beam specimens were manufactured. Four-point loading tests were performed with all the specimens. The experiments confirmed that both types of shear reinforcements had a shear-reinforcing effect (an about 60% increase in shear strength), but the N-type rebar did not exceed the nominal shear strength, probably because the rebar did not yield sufficiently. A sufficient number of steel-plate-type shear reinforcements yielded in the shear crack. When evaluating the shear performance of a new shear reinforcement, it is necessary to calculate the design strength by actually reflecting whether the shear reinforcements’ yields are due to the angle of the diagonal crack. Calculating the shear contribution based on the strain of the shear reinforcements and comparing this shear strength with those five design standards, the shear strength of the shear reinforcements were evaluated conservatively. It is considered that there will be no problem in structural safety even if the shear design is carried out according to the current design standards.

Research on Damage Localization of Steel Truss–Concrete Composite Beam Based on Digital Orthoimage

Most structural health monitoring is carried out for a limited number of key measurement points of a bridge, and incomplete measurement data lead to incomplete mechanical equation inversion results, which is a key problem faced in bridge damage identification. The ability of digital images to holographically describe structural morphology can effectively alleviate the problem of damage identification due to incomplete test data. Based on digital image processing technology, a matrix similarity damage identification method based on a structural digital orthoimage was proposed. Firstly, a steel truss–concrete composite beam specimen with a complex support bar system was designed and fabricated in the laboratory, and the digital orthoimage of the test beam was obtained by the perspective transformation of the original image of the test beam. The body contour of the structure was extracted from the digital orthoimage of the test beam, and wavelet threshold denoising was performed on the lower edge profile to obtain the deflection curves of the structure under different working conditions. The verification results show that the maximum error of the deflection curve is 3.42%, which proves that the digital orthoimage can accurately and completely reflect the deformation of the structure. Finally, based on the digital orthophoto of the test beam, a matrix similarity test before and after the damage was carried out, and the results show that the singularities of the similarity distribution are consistent with the location of the damage; furthermore, the accurate positioning of the damage in different working conditions is achieved.

Experimental Investigation on Flexural Capacity of Reinforced Concrete Beams Strengthened with 3D-Fiberglass, CFRP and GFRP

The main objective of this study is to investigate the structural performance of reinforced concrete (RC) beam specimens strengthened with 3D-fiberglass as compared with fiber-reinforced polymers (FRP) sheets. For this purpose, six RC beams were fabricated, strengthened, and tested under a four-point bending machine. One of the beams served as the control beam (REF), while the others were strengthened with carbon FRP (RCFRP), glass FRP (RGFRP), 3D-fiberglass and epoxy resin (R3DTR), 3D-fiberglass and epoxy resin extended to the sides (R3DTRB), and 3D-fiberglass and concrete repair (R3DTG). Failure mode, crack development, flexural capacity, ductility, the effectiveness of wrapping configurations, and the performance of epoxy resin in comparison with concrete repairer were studied between various beams. The results attest to the better performance and effectiveness of 3D-fiberglass over FRP in terms of flexural capacity, crack pattern, and ductility. The R3DTR and RGFRP specimens, compared to the control specimen, had the highest and lowest flexural capacity growth, with 19% and 8.4%, respectively. In addition, the failure modes observed in this study were in good agreement with the failure modes present in ACI.440.2R-17. Moreover, finite element (FE) models were proposed to predict the residual capacity of the specimens strengthened with FRP, using Abaqus software.

Effect of steel fiber on flexural performance of bilayer concrete beams with steel and GFRP rebars: Experiments and predictions

Replacing steel rebars with glass fiber reinforced polymer (GFRP) rebars in concrete beams can lead to the production of lightweight and durable structural members. Meanwhile, layering concrete beams and using different volume fractions of steel fibers in the layers can be a proper method for improving structural performance and reducing construction costs of fiber reinforced-concrete beams. Therefore, this research aims to evaluate how bilayer steel fibrous concrete beam specimens with GFRP rebars behave under flexure. For this, 14 beam specimens reinforced with GFRP and steel fibers were manufactured in seven experimental groups without using any shear reinforcement. The effect of key variables such as reinforcement ratio, the volumetric content of steel fiber, and compressive strength of concrete on the performance of bilayer beams was examined. The main experiment of the current study involved three-point flexural tests, which were conducted on flexural specimens. The effective parameters on flexural behavior of beams such as flexural resistance, flexural stiffness, toughness, fracture energy, and load–displacement curve were extracted from the results. The results showed that the flexural properties of concrete beams increased by adding 0.75% steel fibers. Nevertheless, per the same fiber ratio, bilayer fibrous beam specimens had weaker flexural performance relative to one-layer fibrous concrete beam specimens. Additionally, when the GFRP bar was replaced with steel bar in the bilayer concrete flexural specimen, flexural resistance, toughness, fracture energy, and stiffness decreased while deflection in peak load increased significantly. Moreover, using high-strength concrete (HSC) in comparison to normal strength concrete (NSC) in bilayer GFRP reinforced beams improved flexural properties by almost 28%. After comparing the formulation to capture the flexural capacity of beam specimens in different specifications with results observed in this research, it is concluded that ACI 440.1R-06 and CAN/CSA S806-12 predict the deformation in service mode to great accuracy for beams reinforced with FRP as well as ACI 318, CAN/CSA A23.3, and ACI 440.1R-15 for steel-reinforced beams.

Flexural strengthening of fire-damaged GFRP-reinforced concrete beams using CFRP sheet: Experimental and analytical study

Since the strengthening of fiber-reinforced polymer (FRP) bar-reinforced structures after a fire incident has rarely been considered in research works, in this work, the flexural response of plain and fiber-reinforced concrete beam specimens with embedded glass FRP (GFRP) bars strengthened with carbon FRP (CFRP) sheets was examined after a fire. Variables understudy in 10 GFRP bar-reinforced concrete beams included the exposure temperature (20, 400, and 600 °C), percentage of steel fiber in volume (0 and 1%), ratio of rebars (0.00314 and 0.00872), and CFRP sheet layers (0, 1, and 2), together with the presence or absence of the U-shaped anchorage. After conducting the four-point quasi-static bending experiment on the non-heated and heated beams, several parameters including the ductility, cracking pattern, and failure mode of the beams, together with their load–deflection diagrams, were assessed. The results showed that the flexural strengthening using CFRP sheets improved the flexural capacity of the specimens and this performance improvement became more notable with an increase in the exposure temperature. In the end, the sectional analysis method was utilized to propose an analytical model capable of estimating the load–deflection response of beams strengthened with CFRP sheets; this model properly estimated the test results.

Shear strength of steel fibrous concrete beams strengthened by CFRP using various techniques

In recent years, carbon fiber-reinforced polymers (CFRP) have been widely used as the strengtheners in reinforced concrete members. This paper is an experimental study on steel fiber-reinforced concrete (SFRC) beam specimens strengthened by CFRP against shear than using externally bound reinforcement (EBR) and externally bound reinforcement on grooves (EBROG). Sixteen concrete beams with dimensions of 110 mm width, 150 mm depth, and 1300 mm length were tested to assess the effect of steel fibers and to evaluate the effects of grooving techniques in terms of improving the shear capacities of SFRC beams strengthened by CFRP. The beams were designed to fail via a shear failure mode. Five volume fractions of steel fibers were used: 0.0%, 0.8%, 1.5%, 1.5%* and 2%. The beams are tested under four-point loading with two values of shear span-to-depth (a/d) ratios, which were 2.2 and 2.85. The results show that the shear strength and the ductility increase with increasing fiber volume fraction, and that the load-carrying capacity of SFRC beams increased by 33% to 68% compared to the load-carrying capacity of the control beam (without steel fibers). Also, the test results show that strengthening beams using CFRP sheets enhanced the strength and stiffness of the tested beam specimens. The increase in the load-carrying capacity of SFRC beam strengthened by CFRP sheet using the EBR method was 79%, while the increase in the load-carrying capacity of SFRC beams strengthened by CFRP sheet using the EBROG method ranged from 89% to 110% compared to the control beam. Furthermore, the results show that the shape of the grooves influenced the capacity and the failure mode of the tested beams. Finally, it may be noted that the grooving method has a significant effect on the load-carrying capacity and failure mode in comparison with the EBR method.

Numerical investigation of RC deep beams containing recycled aggregates

In this study, the behavior of reinforced concrete deep beams containing natural coarse aggregates (NCA), recycled concrete aggregates (RCA), and recycled asphalt pavement aggregates (RAP) was numerically investigated. The required parameters for use in the nonlinear finite element analysis were discussed in detail. To examine the accuracy of the nonlinear analysis, the numerical analysis results for deep beams containing NCA, RCA, and RAP were validated with experimental results. The most important parameters that could affect the behavior of concrete deep beams were proposed. The numerical analysis results for 63 concrete deep beam specimens indicated that the deep beams containing NCA and RCA exhibited nearly similar behavior for any a/h and L/h ratios, whereas RAP deep beams behaved differently from the two corresponding specimens. The deep beams made with RCA and NCA had brittle behavior for any value of the a/h and L/h ratios, while those containing RAP showed more ductility. The energy absorption was far greater for RAP deep beams compared with the NCA and RCA specimens. The absorbed energy in NCA and RCA deep beams was nearly the same. The size effect phenomenon was almost similar in the deep beams made with NCA and RCA, whereas in the RAP deep beams, the intensity of this effect was less severe.

Prediction on Crack Propagation of Concrete due to Time-Dependent Creep under High Sustained Loading

AbstractTo investigate the effects of sustained loading on crack propagation of concrete, three-point bending tests were conducted on prenotched concrete beam specimens under 90% and 95% of the ult...

Study on the bond behavior of steel bars embedded in concrete under the long-term coupling of repeated loads and chloride ion erosion

Twenty-seven reinforced concrete beam specimens were cast to study the bond properties between steel bars and concrete under the coupling of chloride ion erosion and repeated load (0, 0.25, 0.45, and 0.65 of ultimate load) for 210 days. The bond strength and slip of steel bars embedded in concrete were measured by the flexural bond test. Based on the test results, the higher the level of repeated load alone, the lower the bond strength. The bond strength of beam specimens under the coupling of repeated load and chloride ion erosion is lower than that under repeated load alone or chloride ion erosion alone. The bond strength decreases gradually when the corrosion ratio exceeds 1.5%. The slip between steel bars and concrete decreases with the increase of repeated load level under the coupling of chloride ion erosion and repeated load when splitting failure occurs. Based on the test results, the bond strength-slip constitutive relationship was proposed.

Effect of using Waste Rubber as Partial Replacement of Coarse Aggregate on Torsional Strength of Square Reinforced Concrete Beam

The aim of this study is to test the rubberized concrete beams subjected to pure torsional moments. The study focused on the effect of the partial replacement of coarse aggregates with waste rubber chips of different proportions 10%, 20%, and 30% in volume on the beams ultimate torque, and rotation, as well as the ductility index, stiffness, cracking torque, and failure modes. Six specimens of concrete beams as the same size (225×225mm) have been tested. The same steel reinforcement has been applied to four specimens and two without reinforcement. According to experimental findings for reinforced specimens, the ultimate torque for the control beam (without replacement) is higher than beams with replacement rubber but the angle of twist of beams with replacement rubber rose more than the control beam. the ultimate torque decreases compared with the control beam by 4.49%, 10.08%, 13.98%, while the twist angle increases at ultimate torque by 11.16%, 26.79%, 39.69% when the percentage replacement of rubber is 10%, 20%, 30% respectively. When coarse aggregate was replaced with 30% rubber, the ductility index of specimens increased by 39.83%, and ultimate cracking stiffness was lowered by 38.42% as compared with the control beam.

Structural Performance of a Precast Concrete Modular Beam Using Bolted Connecting Plates

In modular structures, prefabricated modular units are joined at the construction site. Modular structures must ensure splicing performance by connecting modular units sufficiently. The bolted connection using steel plates may suffer from alignment issues and corrosion problems. In a precast concrete (PC) modular system, there is difficulty grouting the sleeves when splicing reinforcing bars. This study proposed a PC modular beam using a bolted connecting plate to deal with issues in typical steel modules and PC modules. The structural performance was evaluated by flexural and shear tests on two monolithic beams and two proposed PC specimens. The test results showed that the structural performance of the PC modular specimen was 88% of that of the monolithic reinforced concrete (RC) beam specimen and 102% of the strength calculated by ACI 318-19. Therefore, the proposed PC modular system using bolted connecting plates can solve the problems observed in typical steel and PC modules and improve the structural performance.

Assessment of fatigue damage of prefabricated concrete composite beams with piezomagnetic signal

For prefabricated concrete structures constructed by the wet joining process, appropriate damage indicators need to be adopted to characterize fatigue damage development considering the effects of interface damage. In this study, through the cyclic load testing of 12 prefabricated concrete composite beam specimens with three different cross-section types, comparisons among the traditional damage indicators, such as deflection, stiffness, energy consumption, interface deformation and steel strain, and a new indicator – the piezomagnetic signal – are conducted. All damage indicators, including the piezomagnetic indicator, could characterize fatigue damage development. Furthermore, the piezomagnetic signal indicator could also reflect the impact of interface damage, similar to local indicators such as interface deformation and steel reinforcement strain. However, compared with local indicators, the piezomagnetic signal technique has the advantages of providing long-term monitoring provability and being a non-destructive method.

THE STUDY OF BENDING BEAMS MECHANICALS PROPERTIES WITH MICRO REINFORCEMENT

research on fiber concrete is currently growing very rapidly. The alternative fibers used in the concrete mix-ture is to use natural fibers. In this study, researchers used bamboo fiber as a substitute for artificial fiber, where Bamboo has a good tensile strength. The aim of this study to increase beam strength in sustaining ex-ternal loads by added bamboo fibers. The content of fiber additional to the concrete mixture was 1.5% of the cement weight. The mix design of concrete using ratio of cement water 0.25. The plasticizer and filler added in the mixture with the content of 2% and 15% cement weight, respectively. Two reinforced concrete beam specimens and 24 concrete cylinder specimens used in the study. Tests carried out of 28 days, and 56 days for cylindrical concrete, while bending test conducted of CBR1 and CBR2 at 28 test life only. In study show that addition 1.5% bamboo fiber to reinforced concrete beams increased the flexural capacity and ductility of the beams

Fatigue damage analysis of prefabricated concrete composite beams based on metal magnetic memory technique

Current studies have shown that using magnetic field change around the ferromagnetic material to characterize the fatigue damage is very effective, but researches on using metal magnetic memory (MMM) technique to detect fatigue damage are mostly limited to the material level. There are few studies on the mechanism of the magnetic signal change or numerical simulations at the member level. In this paper, cyclic loading tests were carried out on 8 prefabricated concrete composite beam specimens using wet connection technology. The relationship between the variation in the magnetic field of the steel reinforcement and the interface peeling damage of the specimens were investigated. Based on the magnetic flux density, the interface deformation, and the longitudinal bar strain, the mechanism of the magnetic signal change in different stages as well as interface peeling’s effect on the magnetic flux density were revealed. The feasibility of using the MMM field to characterize the fatigue damage of the composite spcimens was thus verified. Meanwhile, based on the modified J-A-S model, the model for magnetization change of prefabricated reinforced concrete components was established. By comparing the experimental and the simulation results, it is verified that the proposed model could effectively describe the magnetization change trend of the composite spcimens during the fatigue process.

Experimental method for determining the fracture toughness of concrete based on the modified two‐parameter model and DIC technique

AbstractAn experimental method, based on the modified two‐parameter model and digital image correlation technique, was proposed for determining the mixed mode fracture toughness (KI+II) of concrete. Three‐point bending tests on notched concrete beam specimens of different sizes, maximum aggregate sizes, and aggregate volume contents were conducted, and the values of KI+II were evaluated considering the crack deflection. The values of KI+II and KI under mode I loading were compared. The results show that KI+II increases with the specimen size and gradually stabilizes. In addition, KI+II decreases with the maximum aggregate size, but the aggregate volume content has little effect on KI+II. Higher values of KI+II are presented after considering the effect of crack deflection. Only a monotonic loading process is required for the proposed method to determine KI+II.

Influence of Additives on the Fatigue Life and Stiffness of Asphalt Concrete

Implementation of additives to the asphalt binder can enhance the overall physical properties of the modified asphalt concrete. In the present assessment, an attempt has been made to use 2 % of silica fumes and 4 % of fly ash class F for modification of asphalt binder in wet process. Asphalt concrete wearing course mixtures have been prepared and compacted by roller in the laboratory. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The specimens were subjected to the four-point repeated flexural bending beam test. The flexural stiffness was calculated under three constant micro strain levels of (250, 400, and 750). The fatigue life was monitored in terms the number of load repetitions to reach the required reduction in stiffness. It was concluded that the flexural stiffness increases by (11, and 15) %, (17.7, and 63.6) %, (57.2, and 65) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. However, the fatigue life of asphalt concrete beam specimens increases by (40, and 72.8) %, (115, and 220.6) %, (46, and 94.6) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. It is recommended to use modified binder with fly ash and silica fumes in asphalt concrete to enhance the fatigue life and stiffness.