Hybrid Reinforced Concrete Beam Research Articles

Optimal Shape and Size of Holes in Hybrid Reinforced Concrete Beams

Optimal Shape and Size of Holes in Hybrid Reinforced Concrete Beams

Fracture mechanics approach to minimum reinforcement design of fibre-reinforced and hybrid-reinforced concrete beams

The problem of the minimum reinforcement condition in fibre-reinforced and hybrid-reinforced concrete flexural elements is addressed in the framework of fracture mechanics by means of the Updated Bridged Crack Model (UBCM). The model describes the crack propagation process occurring in the critical cross-section of the reinforced member, by assuming the composite as a multiphase material, whereby the toughening contribution of the cementitious matrix and of the reinforcements are independently evaluated. The key-point of the discussion is that, when the influence of the matrix nonlinearities on the response is neglected, the minimum reinforcement condition is defined by a linear relationship between the critical values of two dimensionless numbers: (i) the bar- reinforcement brittleness number, NP , proportional to the steel-bar area percentage, ρ; (ii) the fibre- reinforcement brittleness number, NP,f, proportional to the fibre volume fraction, Vf. The model is applied to several experimental campaigns of the literature, in order to assess its suitability in the minimum reinforcement design of reinforced members in a unified fracture mechanics-based framework.

Impact of developed hybrid polypropylene fiber inclusion on the flexural performance of concrete beams reinforced with innovative hybrid bars

This paper investigates the impact of incorporating a hybrid combination of structural polypropylene fibers on the flexural behavior of concrete beams reinforced with steel, GFRP, and innovative hybrid bars. A new ductile hybrid bar with equivalent bilinear stress-strain characteristics has been developed to address steel corrosion and FRP ductility issues. Fourteen half-scale RC beams were fabricated and tested under four-point loading configuration to study the flexural response. The tensile reinforcement types (steel, GFRP, and hybrid), hybrid reinforcement ratios (0.85 %, 1.26 %, and 1.70 %), reinforcement hybridization schemes (hybrid-hybrid, hybrid-GFRP, and GFRP-steel), and hybrid fiber ratio (0.0 %, 1.0 %, and 2.0 %) are the major parameters studied. The test results were recorded and analyzed in terms of mid-span deflection, cracking load, flexural capacity, and failure mechanism. The results demonstrated that the addition of hybrid fibers and using hybrid bars significantly improved the peak strength, ductility index, and bending stiffness. Moreover, the hybrid-reinforced concrete beams exhibit large inelastic deformations similar to steel-reinforced concrete beams. The inclusion of hybrid fibers improves the post-peak response of the tested beam due to fiber bridging capabilities. For design purposes, a simplified formula proposed by ACI 544 for predicting the nominal flexural capacity of hybrid fiber concrete beams reinforced with hybrid bars was presented, compared with experimental results and validated with 44 specimens from other studies. The predicted and test results were in good agreement with a standard deviation of 0.12. Additionally, 3D nonlinear finite element analysis was developed to validate the test results, demonstrating reasonable accuracy in predicting the flexural behavior of the beams.

Flexural property and design method evaluation of BFRP and steel bars hybrid reinforced concrete beams

AbstractFiber reinforced polymer (FRP) bars have been widely used as a replacement for steel bars in civil engineering due to their high strength and superior durability. However, compared to steel reinforced concrete (RC) beams, FRP RC beams have insufficient ductility and are more expensive. Therefore, a hybrid beam reinforced with steel and FRP bars has been proposed recently. In this study, the flexural properties of steel bar RC beam, basalt FRP (BFRP) bar RC beam, and BFRP steel bars hybrid RC beams were studied based on numerical simulation. The effect of As/Af on the stress of longitudinal reinforcements, load–midspan curves, ductility, and overall performance of the hybrid RC beams is analyzed. Results indicated that the hybrid RC beams exhibited a second‐order stiffness after the steel bars yielded owing to the contribution of the BFRP bars. As As/Af increases, the ductility of the hybrid RC beam and the strength utilization of BFRP bars increase, and a preferable ductility and overall performance can be achieved when As/Af was close to 1.0. The theoretical calculation results of hybrid RC beams based on ACI, CSA, and GB codes are compared with the simulation results, and the accuracy of the ultimate flexural strength of the prediction results is verified. In addition, equations for predicting the deflection of hybrid RC beams are proposed, and they exhibit higher prediction accuracy compared to the prediction models based on the ACI code.

Evaluation of Flexural Behavior and Service Condition of GFRP and CFRP Hybrid Reinforced Concrete Beams

Evaluation of Flexural Behavior and Service Condition of GFRP and CFRP Hybrid Reinforced Concrete Beams

Contribution of strain-hardening cementitious composites (SHCC) to shear resistance in hybrid reinforced concrete beams

Strain Hardening Cementitious Composite (SHCC) is an innovative type of fibre-reinforced cement-based composite that has superior tensile properties. Because of this, it holds the potential to enhance the shear capacity of reinforced concrete (RC) beams, if applied properly. This paper presents the general and distinctive properties of SHCC as well as a literature review of topics related to the contribution of SHCC layers to the shear resistance of RC beams with and without shear reinforcement. Based on the analysed results, it is concluded that the main characteristics of SHCC are its microcracking behaviour, high ductility, and increased tensile strength (between 2 and 8 MPa) at large deformations. When used in structural elements, SHCC develops multiple parallel cracks compared to concentrated cracks in conventionally reinforced concrete. The biggest disadvantage of SHCC is its significant drying shrinkage. Although showing high variability, using SHCC as laminates with a thickness of 10 mm improves the shear capacity of hybrid RC beams, but debonding of interfaces in a hybrid system occurs in some cases.

Design Provisions for Flexural Strength of Hybrid Reinforced Concrete Beams with Fiber-Reinforced Polymer and Steel Bars

Design Provisions for Flexural Strength of Hybrid Reinforced Concrete Beams with Fiber-Reinforced Polymer and Steel Bars

Response of hybrid concrete incorporating eco-friendly waste PET fiber: Experimental and analytical investigations

• Eco-friendly high strength concrete containing waste PET fiber was used as a repair material for deteriorated normal concrete. • Structural and material performance of hybrid RC beams, made with normal concrete and PET fiber HSC, were examined. • Interfacial surface roughened by sand blast technique provided proper bonding between normal concrete and PET fiber HSC. • Analytical solution for the behavior of RC hybrid beams, with PET fiber, was developed considering aspect ratio and content of fiber used. High Strength Concrete (HSC) has the ability to strengthen deteriorated concrete members. The performance of HSC incorporating waste polyethylene terephthalate (PET) fibers as a repair material for concrete structures has not been examined extensively in current literature. Thus, more investigations are considered essential in this direction. This endeavor is devoted to examining the flexural behavior of hybrid reinforced concrete beams (HRCB) made with normal concrete (NC) repaired by or bonded to HSC containing waste PET fibers (FRC). The workability and mechanical properties of fresh and hardened FRC were investigated. Moreover, the efficiency of HSC overlay as a repair material for NC substrate was evaluated through a slant shear test (SST) which considered four modes of roughening of the NC interfacial surface. A third-point load test was used to evaluate the structural behavior of the HRCB. The results of the slant shear and flexural tests indicated that the highest bond strength among all of the members was achieved by employing sandblasted and grooved interfacial surfaces between NC and HSC. The flexural capacity for the beams was also predicted via modification of the ACI 318–19 and Jarquio’s models, using regression analysis of present experimental records. Good matching was observed between the predicted and experimental ultimate load of the hybrid beams. Finally, the testing observations are noteworthy in the direction of using FRC as a repair material.

A fracture mechanics approach to the design of hybrid-reinforced concrete beams

The Updated Bridged Crack Model (UBCM) is proposed as a fracture mechanics tool to thoroughly predict the structural behaviour of hybrid-reinforced concrete (HRC) beams. The cementitious matrix is assumed to be linear-elastic perfectly-brittle, whereas nonlinear constitutive laws are used to describe the toughening action of the reinforcing phases, which is due to the yielding of steel-bars and to the pull-out of the short fibres.Under these assumptions, the model predicts different HRC post-cracking structural behaviours that can be synthetically described by three scaling dimensionless numbers: the bar-reinforcement brittleness number, NP, which is directly related to the steel-bar reinforcement percentage, ρ; the fibre-reinforcement brittleness number, NP,f, which depends on the fibre volume fraction, Vf; and the pull-out brittleness number, Nw, which is a function of the critical embedded length of the fibre-reinforcement, wc. An effective relationship between the two reinforcement brittleness numbers is proved to define the minimum reinforcement conditions for HRC beams. All the other parameters being the same, it can be translated into a relationship between the steel-bar and the short-fibre reinforcement ratios, thus providing an effective and straightforward tool for the minimum reinforcement design of HRC structures.

A comparative study of the flexural performance of hybrid-reinforced (glass fiber reinforced polymer and steel bars) concrete beams before and after exposure to chloride environment

To investigate the flexural performance of hybrid-reinforced concrete (HRC) beams before and after exposure to chloride environment comparatively, 12 HRC beams with two types of reinforcements of glass fiber reinforced polymer (GFRP) bars and steel bars, and four steel-reinforced concrete (SRC) beams were fabricated. Based on definitions of the balanced reinforcement ratio and the appropriate HRC beam, the calculation model of the flexural capacity of HRC beams after exposure to chloride environment was proposed in this study. The experimental results verified the validity of the plane section assumption on all test HRC beams. It is found that the deflection of unconditioned HRC beams increases faster than that of unconditioned SRC beams but slower than that of conditioned HRC beams exposed to chloride environment. Besides, the flexural capacity of conditioned HRC beams decreases due to the exposure and the retention ratio of flexural capacity correlates positively with the ratio of nominal reinforcement ratio converted by the elastic modulus to balanced reinforcement ratio converted by the elastic modulus ( ρnom,E/ ρb,E). The good agreement between the predicted values of flexural capacity and measured ones shows the applicability of the calculation model proposed for HRC beams.

Experimental study on the seismic behavior of seawater sea sand concrete beams reinforced with steel-FRP composite bars

This study offers a new solution to improve the durability of steel-reinforced seawater sea sand concrete (SWSSC) beams without reducing their energy-dissipation capacity under seismic loads. Thus, an investigation of beams reinforced with steel-FRP composite bars (SFCBs), hybrid reinforced with SFCB bars and basalt fiber reinforced polymer (BFRP) bars was conducted. The effects of incorporating 1% minibar in concrete on the seismic behavior of reinforced concrete (RC) beams were also studied. These behaviors included the failure mode, hysteretic response, stiffness degradation, energy-dissipation capacity, strain variation, and curvature of the pedestal. Results showed that chloride ions in seawater and sea sand concrete caused steel bars to corrode and adversely affected the seismic response of RC beams. In addition, the SFCB bars and hybrid RC beams exhibited a more pronounced pinching effect and smaller residual displacement as compared with the steel RC beams. The total cumulative dissipated energy of the SFCB RC beams was approximately the same as that of the steel bar RC beams due to increased deformation. The seismic behaviors of the SFCB bar reinforced minibar-concrete beams were significantly improved under low cyclic loads due to a stable confinement of minibar on concrete. Their load-carrying capacity and energy consumption increased by 27.0% and 36.5%, respectively, as compared with those of the steel RC beams. Similar improvements could be observed in the response of the lateral load versus curvature in the pedestal relationship. Based on these seismic behaviors, structures reinforced by SFCB bars and hybrid reinforced by SFCB and BFRP bars are recommended as means of reinforcement for seawater and sea sand concrete structures.

Experimental and Theoretical Analysis of Cracking Moment of Concrete Beams Reinforced with Hybrid Fiber Reinforced Polymer and Steel Rebars

This study aims at experimentally and theoretically investigating the cracking moment (Mcrc) of hybrid Fiber Reinforced Polymer (FRP)/steel Reinforced Concrete (RC) beams. Six hybrid Glass FRP (GFRP)/steel and three GFRP RC beams with various GFRP and steel reinforcement ratios are tested in four-point bending scheme. Experimental results indicate that both GFRP and steel rebars affect Mcrc, but the effect of steel reinforcement is more significant. When the steel reinforcement ratio increases to 1.17%, Mcrc goes up to 15.9%, while the same value for GFRP is only 9.7%. An analytical method is proposed based on the plain section assumption and nonlinear behavior of materials for estimating Mcrc. The proposed model shows a good agreement with the experimental data conducted in this study and collected from the literature. The results of the parametric study give evidence of the positive effects of hybrid reinforcement ratios and elastic modulus of FRP on Mcrc of hybrid RC beams.

Experimental and analytical study of the mechanical and flexural behavior of hybrid fiber concretes

The use of fibers in Reinforced Concrete (RC) structures may improve the properties of concrete; like reducing the shrinkage strain and increasing the tensile, flexural, and bond strength. This article presents an experimental and Finite Element (FE) analysis of hybrid fiber concretes. Three types of hybrid fibers were utilized, namely, hybrid steel-glass, steel-basalt, and glass-basalt fibers. For compressive and tensile strength tests, a total of forty-eight cubes and forty-eight cylinders were casted. The result obtained shows that fibers addition to concrete improves the compressive and tensile strengths. An increasing of the compressive strengths of 48% was recorded when compared with concrete without fibers. For flexural strength test, two RC beams were casted and tested up to failure under two-point loading. The beams have an identical size of 1500 × 150 × 200 mm. A nonlinear FE models were developed using ANSYS software to analyze the two hybrid RC beams. Nonlinear material properties, resulted from the experimental test, were defined in the FE models. The results obtained from FE and experimental analyses were compared and close correlations were found between them.

Performance of Concrete Beams Reinforced with Various Ratios of Hybrid GFRP/Steel Bars

This paper aims to study the flexural behavior of concrete beams reinforced with hybrid combinations of GFRP/steel bars. To this purpose an experimental program was carried out on four concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) and twelve hybrid GFRP/steel Reinforced Concrete (RC) beams. Flexural behavior of the tested beams such as stages of response, failure modes, crack patterns, stiffness, toughness and ductility were analyzed. The experimental results showed that depending on GFRP/steel reinforcement configurations, the behavior of hybrid GFRP/steel RC beams undergoes three or four stages, namely: pre-cracking stage; after concrete cracking and before steel yielding; post-yield stage of the steel bar until peak load and failure stage. Totally six failure modes of hybrid RC beams are reported depending on reinforcement rations and configuration. The effect of reinforcement configuration and ratio of GFRP to steel (ρg) on the crack patterns, stiffness, ductility and toughness of hybrid RC beams are significant. Based on the non-linear deformation model, an analytical model has been developed and validated to determine the steel yielding moment and ultimate moment of hybrid GFRP/steel RC beams. It could be seen that the experimental values were in good agreement with the predicted values.

Çelik, Cam FRP ve Hibrit Donatılı Betonarme Kirişlerin Eğilme Performansının İncelenmesi

Elyaf takviyeli polimer (FRP) donatılar korozyona karşı direnç, ağırlıkça yüksek mukavemet oranı, iyi yorulma özellikleri ve kullanım kolaylığı gibi avantajlar nedeniyle, alternatif olarak tercih edilmekte ve kullanımı giderek artmaktadır. İnşaat mühendisliği uygulamalarında düşük maliyetlerinden dolayı en yaygın olarak Cam-FRP (GFRP) donatılar kullanılmaktadır. Son zamanlarda, kiriş ve kolonlarda kullanılan çelik donatılar yerine Cam FRP donatılar ve çelik ile Cam FRP donatının birlikte kullanıldığı “Hibrit” donatı düzeni üzerinde birçok araştırma yapılmıştır. Bu çalışmada; Cam FRP ve Hibrit donatıların betonarme kirişlerde geleneksel çelik donatılara göre avantajları araştırılmıştır. Çelik çubuklardan ve farklı sayıda cam çubuklardan oluşan betonarme kirişler üretilmiştir. Üretilen betonarme kirişlere dört nokta eğilme testleri yapılmıştır. Deney sonucu her üç numune için yaklaşık eşit maksimum yük taşıma kapasitesi elde edilmiştir. Bununla birlikte, çelik donatılı ve hibrit donatılı kiriş, gevrek bir davranış sergilerken, GFRP donatılı kiriş sünek bir davranış sergilemiştir. Tamamen GFRP donatılı numunenin enerji emme kapasitesi diğer numunelere göre ciddi oranda artış gösterdi. Numunelerde oluşan hasarları açıklamak için hasar analizi sunuldu.

Behavior of hybrid Reinforced Concrete Beams made with two types of concrete (Normal Weight and Reactive Powder Concrete)

This research confirms the use of finite element modeling using volume 16 ANSYS package to represent the non pre stressed concrete beams reinforced with steel bars, reactive powder concrete beams and hybrid reinforced concrete beams. This work focused on two main purposes: the first one is for economic purpose to check the effects of inclusion of fresh reactive powder concrete with the fresh normal weight concrete beams body at compression and tension stress concentration regions to improve the ultimate load resistance and to control mid span deflection of simply supported beams or any great structural elements. The second purpose is to check effects of using steel fibers with different volume fractions (Vf = 0%, Vf = 1%, Vf = 1.5% and Vf = 2%) in reactive powder concrete beams with fixing all other mechanical properties of concrete to show clearly its effect on controlling of mid span deflection with applied loads or in other words, on beam ductility. The used beam was simple supported reinforced concrete beam with dimensions (110 X 200 X 1500)mm width, height and length, respectively, reinforced with bottom 2 main bars of 12mm diameter and 8mm diameter stirrups spaced at 50mm. Each beam was loaded up-to maximum load which makes failure under the effect of two concentrated parallel loads for beam used as a case study and one central concentrated load for parametric study beams to assign the load and deflection values at beams mid-span locations.The proposed nonlinear finite element solutions are compared with the experimental data obtained from other researcher [1], which gives a good agreement between the obtained results.Parametric studies are carried out by using the proved nonlinear ANSYS (version 16) model to investigate the effects of adding expensive RPC with cheap NWC in structural elements bodies to obtain an economic construction material and to reduce weight and volumes especially for great structural elements.

Experimental study of flexural behavior and serviceability of hybrid concrete beams reinforced by steel and G/BFRP bars

In this paper, the flexural behavior and serviceability performance of concrete beams reinforced with hybrid glass/basalt fiber-reinforced polymer (G/BFRP) bars and steel bars were investigated. From the viewpoint of reducing the risk of steel corrosion, two kinds of hybrid reinforced beams were designed, eleven concrete beams including 3 steel-reinforced beams and 8 hybrid-reinforced beams were tested. The effect of the hybrid reinforcement ratio on the flexural performance was analyzed and the applicability of replacing steel bars with GFRP or BFRP bars in concrete beams was discussed. The results show that the ultimate bending moment of hybrid-reinforced concrete beam was about 91-97% of that of steel-reinforced concrete beam with the same reinforcement ratio. Since the reduction of the bearing capacity of hybrid-reinforced beam was small, it can be proved that it is feasible to replace the corner steel bar of concrete members with G/BFRP bars. For the serviceability performance of beams hybrid-reinforced with G/BFRP bars and steel bars, however, their deflection and maximum crack width were 20%-60% higher than that of steel-reinforced beams under the same load levels within the limit state of serviceability. It showed that the stiffness and crack resistance of hybrid beams weakened greatly. Finally, it was found that the FRP-to-steel ratio of bar areas had great influence on the flexural behavior and serviceability performance of concrete beams hybrid-reinforced with FRP and steel bars.

Study on the Flexural Performance of Hybrid-Reinforced Concrete Beams with a New Cathodic Protection System Subjected to Corrosion.

Steel corrosion is considered as the main factor for the insufficient durability of concrete structures, especially in the marine environment. In this paper, to further inhibit steel corrosion in a high chloride environment and take advantage of the dual-functional carbon fiber reinforced polymer (CFRP), the impressed current cathodic protection (ICCP) technique was applied to the hybrid-reinforced concrete beam with internally embedded CFRP bars and steel fiber reinforced polymer composite bar (SFCB) as the anode material while the steel bar was compelled to the cathode. The effect of the new ICCP system on the flexural performance of the hybrid-reinforced concrete beam subjected to corrosion was verified experimentally. First, the electricity-accelerated precorrosion test was performed for the steel bar in the hybrid-reinforced beams with a target corrosion ratio of 5%. Then, the dry–wet cycles corrosion was conducted and the ICCP system was activated simultaneously for the hybrid-reinforced concrete beam for 180 days. Finally, the three-point bending experiment was carried out for the hybrid-reinforced concrete beams. The steel bars were taken out from the concrete to quantitatively measure the corrosion ratio after flexural tests. Results showed that the further corrosion of steel bars could be inhibited effectively by the ICCP treatment with the CFRP bar and the SFCB as the anode. Additionally, the ICCP system showed an obvious effect on the flexural behavior of the hybrid-reinforced concrete beams: The crack load and ultimate load, as well as the stiffness, were enhanced notably compared with the beam without ICCP treatment. Compared with the SFCB anode, the ICCP system with the CFRP bar as the anode material was more effective for the hybrid-reinforced concrete beam to prevent the steel corrosion.

Flexural behavior investigation of steel-GFRP hybrid-reinforced concrete beams based on experimental and numerical methods

Due to their superior corrosion resistance and strength-to-weight ratio, GFRP (glass fiber reinforced polymer) rebar are widely used as reinforcement for concrete structures, but the brittleness of GFRP and their inferior bonding performance with concrete needs to be addressed. Hybrid reinforcement is a strategy to address the brittleness of GFRP rebar, but the inferior bonding performance may cause inaccuracy in the performance prediction. To determine the effects of bonding performance on the flexural behavior of GFRP- and hybrid-reinforced concrete beams and compare their flexural behaviors, both types of beams were prepared and subjected to four-point bending tests in this research. Their flexural capacities from the experimental results were then compared with the theoretical results. Additionally, the bond-slip relation between the GFRP rebars and concrete was obtained by means of pull-out tests, and an FE model based of the bond-slip results was developed to simulate the flexural behavior of the beams. From the experimental results, the hybrid reinforcement was shown to be able to control the beginning of cracking and reduce the maximum crack width by over 50% in concrete compared that of to GFRP reinforcement at the same load level. The flexural behavior of the hybrid-reinforced beam can be accurately predicted by the theoretical and FE methods. For the GFRP-reinforced beams, the theoretical method overestimates the flexural capacity by 9%; according to the results from the FE simulation, inclusion of the nonlinear bond-slip constitutive relation between the GFRP rebar and concrete helps to mitigate the underestimation of the mid-span deflection from 14.4% to 2.1%.

Finite Element Analysis of Normal Strength, High Strength and Hybrid Reinforced Concrete Beams

This paper presents the numerical study to simulate the flexural behavior of normal strength, high strength and hybrid reinforced concrete beams, under two points load with two different reinforcement ratio. The hybrid beam consists of two layers: the compressive layer is made of high strength concrete, and the tension layer is made of normal strength concrete. The simulation was done with a finite element model using the commercial finite element code, ANSYS (v.9.0). The concrete component material is modeled, the internal steel reinforcement modeled using ''LINK'' elements. The modeled behavior shown a good agreement with the experimental data. The maximum percentage difference in ultimate load-carrying capacity is 8% at the ultimate load level.Analytical study also included the effect of increasing the depth of the normal strength concrete for the hybrid reinforced concrete beam and the effect of increasing the compressive strength for high strength concrete and normal strength concrete respectively on the behavior and the load carrying capacity of the hybrid reinforced concrete beams.