Flexural Behavior Of Beams Research Articles

Flexural Behavior of Steel Fiber Reinforced Concrete Beams: Probabilistic Numerical Modeling and Sensitivity Analysis

One of the principle issues concerning the practical application of steel fiber reinforced concrete (SFRC) is the uncertainty related to its structural behavior, primarily caused by the partially random distribution and orientation of steel fibers in SFRC structural elements. This paper aims to provide a better understanding of how the variance of material properties of the SFRC affects the flexural behavior of SFRC beams. First, a distributed plasticity fiber finite element model of beam flexural behavior is proposed and validated. Then, probability distributions of selected material properties are defined based on existing probabilistic models and experimental results from the literature. Finally, a variance-based sensitivity analysis is performed using Sobol’ indices to identify uncertainties in material properties that contribute most to the uncertainties related to three characteristic points of a beam’s flexural behavior: first crack, yield, and collapse point. Sensitivity analysis is performed by surrogating the numerical model using polynomial chaos expansion. The variance in residual tensile strength is identified as the main contributor to the variance in the flexural behavior of an SFRC beam used in the case study.

Flexural behaviour of ECC and ECC–concrete composite beams reinforced with hybrid FRP and steel bars

Owing to the good ductility of steel and high strength and excellent corrosion resistance of fibre-reinforced polymer (FRP), concrete beams reinforced with hybrid steel and FRP bars exhibit better ductility than FRP-reinforced concrete beams as well as higher load-carrying capacities and better corrosion resistance than steel-reinforced concrete beams. However, the inherent brittleness of concrete in tension results in steel corrosion because of wide cracks and accelerated fracture of FRP reinforcement because of crack-induced stress concentration. This study investigated the effects of ultra-high ductile engineered cementitious composites (ECCs) on the flexural behaviour of hybrid steel and FRP-reinforced beams. Six hybrid-reinforced beams with various reinforcement ratios, matrix types and ECC pouring positions were tested in four-point bending. The flexural behaviours of the beams in terms of failure modes, crack patterns and developments, load versus deformation relationships and ductility are discussed herein in detail. We observed that substituting ECC with concrete results in a higher load-carrying capacity and better ductility of the hybrid reinforced beams owing to the excellent characteristics of ECC materials. When a layer of ECC is poured in the tension zone, the average crack width and crack spacing along the beam decrease; therefore, the longitudinal reinforcements can be adequately protected.

THE FLEXURAL BEHAVIOR OF CORRODED OFFSHORE RC BEAMS REPAIRED BY DIFFERENT TECHNIQUES

RC beams in a marine environment suffer deteriorations caused by the corrosion of reinforcement. Many researches have investigated this problem, yet few repairs techniques have been developed until now. The purpose of this research is to determine the effect of these deteriorations on the flexural behavior of RC beams. Also investigate rehabilitation of corrosion-damaged RC beams with different repair techniques. The flexural performances of the beams were studied. In this study, flexural test have been carried out to study the influence of reinforcing bar corrosion and cracking on ultimate strength of reinforced concrete beams, bearing capacity and ductility. There were totally 5 RC beams (300 mm × 150 mm × 2200 mm) constructed in this research, 4 of which were corroded by marine environment. The flexural behavior of these beams are studied at one level of corrosion of reinforcement bar. However, with progressive increase in corrosion, the ultimate strength, stiffness and toughness decrease rapidly for RC Beams subjected to flexural loading. The results show that the repair methods could provide better load carrying capacity for the beams with different techniques.

Application of nanosilica in reinforced concrete beams

The partial replacement of cement with nanomaterials such as nanosilica (NS) particles in concrete improves its strength and other properties. In this study, the effect of NS as a partial replacement of cement for concrete mixes and concrete beams was examined. The studied response characteristics of reinforced concrete beams included the compressive strength, failure mechanisms, load-carrying capacity and load–deflection behaviour. The results showed that compressive strength increased with an increase in NS content up to 2.0% replacement of cement weight. The rate of increase in compressive strength was no longer significant beyond 2.0% replacement, indeed there was a slight decrease in compressive strength for NS content of 3.0%. The effect of increased NS content on the flexural behaviour of beams was also studied. Increased NS content led to increases in the first-cracking and ultimate loads and reductions in the deflection at cracking and ultimate load levels. No major differences in the structural response parameters were observed for test beams with zoning of NS in the bottom tension or top compression zones. An increase in NS content led to a slight increase in the ultimate strain associated with the ultimate load. Good agreement was found between experimental and theoretical ultimate moments.

Mehanička svojstva pri savijanju betona armiranog vlaknima od nehrđajućeg čelika

An experimental study is performed to evaluate the effect of melt-extract stainless steel fibres on mechanical and flexural properties of concrete. A total of seventy-two specimens are used to determine an optimum fibre dosage and mechanical properties of plain and steel fibre reinforced concrete. Twelve full-scale beam specimens are then exposed to four-point bending tests. The effect of melt-extract stainless steel fibres on flexural behaviour of beams is quantified in this testing. A beam specimen is exposed to four-point bending, after being subjected to 15000 cycles of fatigue load. Pre- and post-fatigue flexural properties of beams with melt-extract steel fibres are compared and discussed.

Flexural Behavior of Reinforced Concrete Beams Reinforced with Glass Fiber Reinforced Polymer Rectangular Tubes

Glass fiber reinforced polymer (GFRP) pultruded rectangular tubes were used externally to confine Reinforced Concrete (RC) beams in this experimental study, aiming to improve the corrosion resistance of the RC beams in the harsh environment (e.g. Hydraulic structures and Marine structures). The flexural behaviour of the composite beams reinforced with GFRP tubes was investigated by using four-point bending test. The experimental program involved the testing of six beam specimens reinforced with or without the GFRP tubes, and the main parameters investigated included the reinforcement ratio of the tensile steel bars and the stirrup spacing. The experimental results show that the flexural strength and stiffness of the RC beam members were significantly improved by using the GFRP tubes. The brittle failure of the beam specimens was caused by the local failure at one loading pints on the top flange of the GFRP tubes. The higher reinforcement ratio of the tensile steel bars contributed to the improvement of the flexural strength and bending stiffness. The stirrup spacing had little effect on the flexural behaviour of the beam specimens in the proposed composite beams.

Flexural behavior of GFRP bar-reinforced calcium aluminate cement concrete beams containing forta-ferro fibers in acidic environment

The present study is dedicated to investigating the effects of Forta-Ferro (FF) fiber and calcium aluminate cement (CAC) on the flexural behavior of concrete beams reinforced with glass fiber-reinforced polymer (GFRP) rebars subjected to acid attack. Bending tests were designed to assess the effects of the acidic environment, replacement of ordinary Portland cement (OPC) with CAC, and the addition of FF fibers on the flexural strength, the load-deflection curve, and the cracking behavior of the beam specimens. Based on the results, the optimum content of FF fibers for improving the mechanical properties of concrete, as well as the flexural behavior of beams, is 0.4%. Further, using 0.7% FF fibers proved to be very effective in controlling the mechanical strength reduction of concrete and the flexural strength of beams immersed in acid. In addition, substituting CAC for OPC enhanced the ultimate flexural capacity of the beams with and without immersion in acid. With regard to cracking behavior, the presence of FF fibers, the exposure of specimens to acid, and the replacement of OPC with CAC reduced the average width and spacing of cracks and increased the number of cracks in the beams.

Experimental and Numerical Comparison of Prestressed Perforated Concrete Rafters of Different Configurations

This paper demonstrates an experimental and numerical study aimed to compare the influence of openings of different configurations on the flexural behavior of prestressed concrete rafters. The experimental program consisted of testing six simply supported prestressed concrete rafters; 5 rafters are perforated, and the other one is solid as a reference. All rafters were tested under monotonic midpoint load. The variable which has been investigated in this work was the opening’s configuration (quadrilateral or circular) with the same upper and lower chords depths. The results indicate improvement in the beam flexural behavior using the circular openings compared to the quadrilateral openings, represented by increase the ultimate load capacity and decrease in deflection at the service limit. The experimental results of the tested rafters were confirmed by the non-linear finite element software (ABAQUS13.6.1). Comparisons are offered and the good agreement appears between the experimental results and the predictions of finite element analysis in terms of load-deflection and failure loads relationships.

Quality Assessment of Strengthened Concrete by FRP Laminates using Non Destructive Testing

A non-destructive testing program has been designed to evaluate the integrity of the bond strength of plain concrete beams strengthened by Glass Fiber Reinforced Polymer (GFRP) Laminates. A series of concurrent static load and non-destructive testing experiments were carried out in the materials and testing laboratory at the college of engineering, Mataria, Helwan University, Cairo, Egypt. A total of 90 plain concrete standard beam specimens of dimensions 150 mm x 150 mm x 750 mm were constructed in the laboratory with three different design strength categories (38, 45, and 50) MPa. The beam specimens were strengthened by externally bonded GFRP laminates with various number of layers namely (3, 5 and 7) layers. In addition, the effect of debonding of the GFRP laminates was investigated by simulating it by variation in voids between concrete and laminates namely, (0, 30 and 60%). This study investigates the effectiveness of externally bonded GFRP laminates on the flexural strength of plain concrete beams by using Ultrasonic Pulse Velocity (UPV) device before and during loading until failure and their effect on the p-wave velocities. Four-point flexural tests were performed on the concrete beams, strengthened with different layouts of GFRP laminates and different percentage of voids at the concrete-laminate interface. The capacity of the beams and p-wave velocity were investigated. It was found that as the percentage of voids decreased, the capacity of strengthened concrete beams increased linearly. The reduction in voids enhanced the beam flexural behavior and controlled tension crack propagation. In addition, it was observed that use of GFRP laminates were more effective with higher concrete characteristic strength provided that debonding is not present. Finally, it was evident that the UPV technique was successful in detecting the variation in concrete p-wave velocity with strength and laminate layers variation.

Effect of Manufactured Sand on Flexural Behavior of Geopolymer RCC Beams: A review

In recent days, the continuous running down of the ozone coat and global warming problem has greater than before, it is necessary to get the consciousness of the construction industries in using new recyclable construction materials. To suit this, geopolymer concrete has begun to boost massive concern from the research scholars and construction practitioners, because of its beneficial in utilizing byproduct materials to replace cement and diminishing ozone depleting substance release all through its generation. It is also having superior mechanical and durability properties compared to conventional concrete. On the other hand river sand is becoming scare day by day and costlier. So the manufactured sand turns out to be alternative material for river sand. In spite of its benefits, the use of geopolymer concrete in realistic is significantly narrow, this is primarily due to the deficiency in the studies in terms of structural elements, design and application. This paper objective is to identify the research gaps in this area and develop future research investigations in the materials and structural elements performance of geopolymer concrete. Many researchers from their analysis on flexural behavior of beams concluded that geopolymer concrete could replace conventional concrete.

Flexural Behavior of Bamboo Reinforced Concrete Beam with Steel Stirrups

The flexural behavior of concrete beams reinforced with bamboo was studied experimentally. Bamboo was used as the main reinforcement with different bonding materials in place of steel. A nominal mix of M20 grade concrete was adopted for the beam design. The Bamboo surface was treated with common binding materials like Araldite and Bitumen. Araldite and Bitumen are good binding materials used to connect materials like steel, carbon and many different materials. Two specimens were casted with bitumen coating, two specimens were coated with araldite, two specimens were casted without any binder coating and a specimen was casted using normal steel reinforcement. Beams were casted with bamboo reinforcement and cured for 28 days. Deflection and flexural behavior of the beams were monitored. The test results imply that araldite coating in concrete beams with bamboo reinforcement increased the flexural strength to that of bamboo reinforced concrete using bitumen which is lesser strength to that of steel reinforced concrete beam.

Flexural Behavior of Cement Concrete Beams Containing Recycled Waste Glass as Coarse Aggregate

Waste glass can be a non-biodegradable substance and at this its drop on a land that becomes a very world organisation property selection. To look out a far higher response to cut back the ecological issues caused by disposable of waste glass is used as concrete manufacturing. Recycled glass as coarse mixture is used to prepare for various grade of concrete mix like M 20, M 40 and M 60 as an alternate for typical crushed stone for creating concrete. The physical and chemical characterize of recycled waste glass coarse mixture is examine and note the similarities with typical crushed stone aggregate. For each mix to hunt out out the mechanical strength of control concrete and RWGCA mixture concrete. Six numbers of cube size 100 × a hundred × 100 metric linear unit are cast. To check flexural behaviour, a hundred twenty five × two hundred × 1100 metric linear unit size of the beams are cast. Beam sections are created as below strengthened sections. For on prime of grade mix, three beams are created with typical crushed stone mixture & alternative 3 beams are created with RWG coarse mixture. All the beams are tested under two point loading. The flexural behaviour of beams are obtained. ANSYS software is used for finite element modeling and the results of experimental values are compared with ANSYS modeling.

Experimental evaluation of bamboo reinforced concrete beams

The paper presents the experimental study on flexural behaviour of concrete beams reinforced with “bamboo strips”. Total 30 beam specimens were tested under four point bending test (pure bending). Three different types of concrete beams were investigated experimentally. They were concrete beams reinforced with bamboo strips, concrete beams reinforced with conventional steel and concrete beams with no reinforcement. The flexural behaviour of these beams was studied through linear stiffness, ultimate load, energy absorption capacity, shear strength and flexural strength.There are two types of BRC (Bamboo reinforced concrete) beams having both longitudinal as well as shear reinforcement (stirrups) in the form of bamboo strips. First is with 2.8% and second with 3.8% longitudinal bamboo reinforcement with respect to the beam cross section. Analysis and comparison of different performance parameters against RCC (steel reinforced cement concrete) as well as PCC (plain cement concrete) beams is carried out. It is observed that both types of BRC beams have shown significantly higher shear as well as flexural strength than PCC beams.However, BRC beams with 2.8% bamboo reinforcement shown less shear and flexural capacity compared to that of RCC beams. The effect of additional 1% bamboo reinforcement on shear as well as flexural strength can be clearly observed in second type of BRC beam. Failure mode observed in both type of BRC beams were different from that of PCC and RCC beams.

Flexural Behaviour of Geopolymer Concrete Beams using Recycled Waste Glass as Fine Aggregate

Cement substitutes and concrete alternatives are currently on the market to help in creating concrete a very ecofriendly material. In cement concrete production, heating and compounding method need large amounts of energy and emits minacious amounts of CO2 into the atmosphere. There has been an increasing significant interest in the development of cement less concrete called geopolymer concrete. In this study, cement is replaced entirely by ash and GGBS for making of geopolymer concrete. Now a days, the scarcity of river sand can have an effect on the development trade and hence there's a requirement of finding a replacement different material to switch the river sand. Non-reactive recycled waste glass is chosen as alternative to the river sand. Various grades of concrete including M 20, M 40 and M 60 grades are developed in GP concrete and also same proportion is used for making GP concrete with glass aggregate. In geopolymer preparation, NaOH of 8 molarity concentration is used. Flexural behaviour of beams is studied by casting of nine beams of size 125 mm × 200 mm × 1100 mm. The beams are designed as under reinforced sections. Out of nine beams, three beams of M 20, M 40 and M 60 grade conventional cement concrete beams, three beams of GP beams and the remaining three beams are made with RWGFA in GP. Beams are tested under two point loading for flexure. The ultimate load carrying capability of all beams is obtained. The crack and deflections of the beams are studied. The experimental results are compared with finite element modeling using ANSYS software

보-기둥 접합부에서 GFRP 보강근을 휨 철근으로 사용한 보의 휨 거동

이 연구의 목적은 철근콘크리트 보의 휨 거동에 대한 주철근으로 사용된 유리섬유보강폴리머(GFRP)의 정착길이 결함의 영향을 평가하는 데 있다. 보의 자유단에서 반복하중을 받는 4개의 보-기둥 접합부 실험체의 구조실험을 수행하였다. 주철근으로서 GFRP 보강근을 사용한 보의 휨 거동은 보-기둥 접합부 내에 충분한 정착이 이루어지지 않을 경우 뽑힘파괴로 지배되었다. 결과적으로 주철근으로서 GFRP 보강근을 사용한 보는 주철근으로서 일반 철근으로 배근된 보보다 휨 내력 및 연성이 낮았다. 이 경향에 대한 콘크리트 압축강도와 주철근 항복강도의 영향은 미미하였다. 특히, GFRP 보강근이 충분한 정착이 이루어지지 않은 보의 휨강도는 ACI 440.1R-15 기준에서 산정된 예측값보다 낮았다.

Effects of trapezoidal cross-section dimensions on the behaviours of CFRP SCC beams

This study investigates the behaviour of trapezoidal cross-sections self-compacting reinforced concrete beams under flexural failure, with and without strengthening with carbon fibre reinforced polymer CFRP. The studied beams were divided into two groups according to their cross-sections; each group included five beams, and the first group (T20) were those with trapezoidal cross-sections with dimensions length 1,600 × height 260 × width of 160 mm at the bottom and 200 mm at the top, while second group (T24) consisted of those with trapezoidal cross-sections with dimensions length 1,600 × height 260 × width of 160 mm at the bottom and 240 mm at the top. The experimental programme included studying the effects of top width on the flexural behaviour of beams with trapezoidal cross-sections, in addition to studying the effect of reinforcing those beams with varying numbers, locations, and methods of placement of CFRP strips. The experimental results showed that trapezoidal cross-sections with 240 mm top width gave higher ultimate load capacity by 4 to 11.54%, as well as offering lower deflection, compared to trapezoidal cross-sections with 200 mm top width. In addition, strengthening beams with CFRP strips leads to an increase in the ultimate load capacity by 4 to 24% in trapezoidal cross-section beams, reducing their deflection and delaying the appearance of the first crack in the concrete. It was found that applying CFRP strips to the maximum moment region increased the ultimate load capacity by an average of 4.17 to 7.7 % in comparison to beams strengthened with strips applied along the beam

Finite element modeling of corroded RC beams using cohesive surface bonding approach

The modeling of loss of bond between reinforcing bars (rebars) and concrete due to corrosion is useful in studying the behavior and prediction of residual load bearing capacity of corroded reinforced concrete (RC) members. In the present work, first the possibility of using different methods to simulate the rebars-concrete bonding, which is used in three-dimensional (3D) finite element (FE) modeling of corroded RC beams, was explored. The cohesive surface interaction method was found to be most suitable for simulating the bond between rebars and concrete. Secondly, using the cohesive surface interaction approach, the 3D FE modeling of the behavior of non-corroded and corroded RC beams was carried out in an ABAQUS environment. Experimental data, reported in literature, were used to validate the models. Then using the developed models, a parametric study was conducted to examine the effects of some parameters, such as degree and location of the corrosion, on the behavior and residual capacity of the corroded beams. The results obtained from the parametric analysis using the developed model showed that corrosion in top compression rebars has very small effect on the flexural behaviors of beams with small flexural reinforcement ratio that is less than the maximum ratio specified in ACI-318-14 (singly RC beam). In addition, the reduction of steel yield strength in tension reinforcement due to corrosion is the main source of reducing the load bearing capacity of corroded RC beams. The most critical corrosion-induced damage is the complete loss of bond between rebars and the concrete as it causes sudden failure and the beam acts as un-reinforced beam.

Flexural Behaviour of RC beams using GFRP Composites

Reinforced Concrete (RC) structures damaged by sudden accidental loads due to earthquake and severe environmental exposure. Traditional strengthening methods are not meeting the service life of the structure for long time. Recently, FRP strengthening is used successfully in all kind of exposure with minimum cost and less duration. In this paper RC beams were strengthened by GFRP sheets in two different orientations. Two specimens are control beams, two specimens are wrapped with U wrapping and the remaining beams are bottom wrapping. The size of the beam is 1700mm long, 150mm wide and 250mm depth. The test specimens consit of 2 nos of 10mm dia rods as longitudinal reinforcement in compression zone and 2 nos of 10mm dia steel rods in tension zone. 2-legged stirrups of 8mm diameter were used with a centre-to-centre spcaing of 150mm. All beams were tested under four-point loading. Experiments will be undertaken until beams fails so that the influence of GFRP characteristics on the Flexural behaviour of beams which includes Flexural behaviour, Ultimate load carrying capacity, Deformation and Stress-strain behaviour. Evaluation of the results will lead to optimum GFRP jacketing /wrapping arrangements for the concrete beams are considered here.

Flexural Behavior of RC Beams Strengthened by NSM-CFRP Laminates or Bars

The strengthening and enhancing the structures represents an important aspect in the construction industry due to the growing need to increase the tolerability of origin to a specific level and within the required rehabilitation and maintenance work. This paper assessed the performance and effectiveness of the Near Surface Mounted (NSM) strengthening technique for the reinforced concrete beams. Three (140x260x2700 mm) reinforced concrete beams were strengthened in flexure with NSM strengthening systems using Carbon Fiber Reinforced Polymer (CFRP) strips, bars, and cement-based adhesive as a binding materials. The flexural behaviour of the beams was evaluated by testing the specimens under three-point loading to failure. The structural performance, deflection, ductility, stiffness, and modes of failure of the tested beams are presented and discussed in this paper. The test results indicate that using NSM-CFRP strips and bars is practical and significantly improves the stiffness and increases the flexural capacity of reinforced concrete beams. The strength increments were 48, 42, and 15 percent recorded with CFRP bars, rough strips, and smooth strips respectively. The deflection of the strengthened beams was reduced by about 66, 48, and 58 percent for CFRP smooth strips, rough strips, and CFRP bars respectively, compared with the control beam due to the increased stiffness of the strengthened beams.

Effect of Types of Concrete on Flexural Behavior of Beams Reinforced with High-Strength Steel Bars

Effect of Types of Concrete on Flexural Behavior of Beams Reinforced with High-Strength Steel Bars