Flexural Behavior Of Beams Research Articles

Flexural Behaviour of RC Beam with Pond Flyash and ESP FlyAsh

The use of Supplementary Cementitious Materials (SCM) such as Fly ash, Granulated Slag and Silica fume as a replacement for Portland cement in concrete presents one viable solution with multiple benefits for the sustainable development of the construction industry. Out of various supplementary materials, Fly ash is the most widely used material worldwide. Fly ash has excellent structural and durability characteristics. The pore filling effect and pozzolanic properties of Flyash improves the properties of fresh and hardened concrete. In addition to the cost saving bythe replacement amount of cement; it reduces co2emission during the manufacture of Portland cement. In the present investigation, a controlled beam and six number of ESP flyash and Pond flyash beams of size 200 x 100 x 1700 mm were cast. This paper deals with the investigation on the flexural behaviour of beam with pond flyash and ESP (Electro static precipitated) flyash at various cement replacement levels of 4%, 6%, and 8% and the results are compared with controlled beam. The flexural test was conducted to determine the ultimate load carrying capacity of the beams and their corresponding mid span deflection, load point deflection, crack pattern, Stress vs strain are measured. The flexural strength of ESP flyash is increased 24.76% for 8% replacement level and pond flyash is increased 10.97 % for 6% replacement level than controlled beam respectively. This study revealed that the replacement of cement by flyash concrete provides higher compressive strength & flexural strength compared with controlled concrete.

Effect of alkali-silica reaction on the flexural behavior of beams with tensile lap splices

A series of 19 beam specimens, with varying stirrup spacing and tensile lap splice lengths, were tested at the National Institute of Standards and Technology (NIST) under four-point loading to investigate the impact of alkali silica reaction (ASR) on the flexural strength and bond behavior of reinforced concrete members. The beams contained highly reactive aggregates, were cured in an environmental chamber at high relative humidity and temperature, and were tested in batches at regular intervals in time. The development of strains in the deformed bar reinforcement was monitored in five beam specimens to provide an assessment of the level of ASR expansion achieved prior to testing. The strain development in the tensile reinforcement bars and stirrups was generally similar between the specimens, despite differences in stirrup spacing and lap splice length. Strains in the transverse stirrups due to ASR-induced expansion at the time of testing were roughly twice the strains recorded in the longitudinal tensile reinforcement, reaching a maximum value of approximately 0.002 mm/mm prior to testing. The concrete mixture studied exhibited expansions in the range of 0.2% and the tested beams exhibited randomly oriented surface cracking with no localized spalling or general loss of section at the time of testing. The effects of ASR included reductions in the compressive strength and modulus of companion cylinders of up to 15% and 50%, respectively. A rigorous statistical analysis of the measured data was performed to quantify the influence of ASR-induced expansion, splice length, and stirrup spacing on the beams’ flexural capacity and the maximum achieved average bond strength. Results indicated that in the range of expansions, stirrup spacings, and lap splice lengths studied, there was no evidence that the moment capacity or the maximum average bond strength was reduced by the effects of ASR. Tested beams constructed with ACI 318 code compliant splice lengths achieved or exceeded the nominal flexural strength of the section, regardless of the degree of ASR-induced expansion observed.

Flexural behavior of SFRC-NC composite beams: An experimental and numerical analytical study

In this study, the flexural behavior of SFRC-NC composite beams cast with normal concrete (NC) and steel fiber-reinforced concrete (SFRC) were investigated. Nine SFRC-NC composite beams were designed and tested through four-point bending (FPB) experiments, including one reference beam with normal concrete (NC) and eight beams with different SFRC layer thicknesses. The effect of the designed parameters, including the SFRC layer thickness, diameter of steel rebar, and fiber content, on the flexural behavior of the beams was investigated experimentally. Compared to beams cast with normal concrete, the experimental results showed that the application of SFRC can effectively improve the bearing capacity of RC beams. These improvements include the crack-initial load, yield load, ultimate load, and ductility. Based on the experimental results, an FE macro-model was developed, and a series of numerical analyses were conducted to investigate the flexural behavior of SFRC-NC composite beams.

Steel cable bonding in fresh mortar and 3D printed beam flexural behavior

This paper presents an approach for enhancing the path-following capability of concrete printing by integrating steel cables into the center of printed mortar strips during the print process, thus satisfying the synchronous and continuous requirements of 3D printing construction. To investigate the impact of steel cables on buildability of printed composites, the bonding strength between mortars and three types of steel cables with different diameters (0.5 mm, 1 mm, and 1.5 mm) was examined through pull-out tests. Moreover, four-point bending tests were conducted to examine the flexural performance of printed mortar beams reinforced with varying numbers and diameters of steel cables. Experimental results demonstrate that mortar filaments reinforced with 0.5 mm and 1 mm diameter steel cables can meet the buildability requirements within the designated open-time, while 1.5 mm diameter steel cables tend to rebound out of the fresh printed mortar due to their rebound force exceeding the grip strength of the mortar, rendering reinforced 3D printing unfeasible. Pull-out tests reveal that bonding strength between steel cables and 3D printed mortars is between 1.4 and 2.4 MPa. Due to steel cable's bundle structure and printing methods, this bonding strength is lower than that of traditional reinforced concrete. In addition, the flexural strength of printed beams reinforced with steel cables is increased by up to around 90%, and the ductile fracture mode trend was observed. This paper confirms the feasibility and effectiveness of this enhancement approach, providing a reference for other reinforcement methods in 3D printed building structures.

Deformation-based design of hollow coarse-aggregate ultra-high-performance-concrete beams reinforced with CFRP bars

This study aims to develop a novel type of beams strengthened with carbon fiber-reinforced polymer (CFRP) bars and cast using ultra-high-performance concrete (UHPC) with coarse aggregates (CA-UHPC) to address issues such as poor ductility, extensive cracking, and significant deflection observed in FRP-reinforced concrete (FRP-RC) beams. Six hollow beams were fabricated and tested via a four-point-bending test under cycle loading to study the effects of parameters, including CFRP reinforcement ratios, hollow shapes, and hollow ratio on the deformation performances of the beams. The results show that the deformation of all hollow beams under service loads met the requirements of the GB50610 code for deformation. Increasing hollow ratio had a negative impact on the flexural behaviors of beams, and this effect was more pronounced in beams with higher hollow ratios than in beams with lower hollow ratios. The flexural performances of square hollow beams were better than that of circular hollow beams with the same hollow ratio. Compared to other hollow beams, square hollow beams with a hollow ratio of 44.44% demonstrated superior flexural performance and optimal cost-effectiveness. Ultimately, leveraging the computational framework for steel fiber reinforcement and residual deflection, predictive models for deflection were formulated for CFRP-CA-UHPC beams with various hollow configurations under both static and cyclic loading conditions.

Analysis of beams prestressed with hybrid (Steel/Carbon Fiber-Reinforced Polymer) tendons using the conservation of energy approach

Durability of post-tensioned concrete members is greatly enhanced by using Carbon Fiber-Reinforced Polymer (CFRP) tendons in lieu of, or in combination with, unbonded and bonded steel tendons. However, current design and analysis methods are limiting the use of hybrid (i.e., a combination of unbonded and bonded steel and CRFP) tendons since they are only applicable to either bonded or to the rather complicated post-tensioned unbonded steel tendons. This paper presents an analytical approach developed to predict the overall response of concrete beams prestressed with hybrid tendons. The model is based on a structural idealization that uncouples the concrete beam and the unbonded tendon behaving as a trussed-beam system. The approach utilizes equilibrium equations, compatibility of deflection between beam and tendon, and the conservation of energy approach (CEA) applied at various limit states. Additionally, a simplified CEA is also presented at characteristic points for various cases including unbonded as well as hybrid tendons. Results are validated using experimental tests available in the literature indicating that CEA is a versatile and rational procedure that can accurately predict the overall flexural behavior of beams with hybrid tendons. A simplified version of the CEA using hand calculations is also developed for directly analyzing such beams with comparably accurate results.

Post-heating flexural behavior of reinforced concrete beam with lap-spliced bar and feasibility of improving flexural performance by adding hybrid fibers

Using bar splices in reinforced concrete structures is inevitable due to transportation and construction limitations. On the other hand, executing lap splices in flexural members such as beams allows these members to potentially fail at the splice zone before reaching their ultimate flexural capacity. The failure of the beam at the splice location results from different factors, one of which is the exposure of concrete members to elevated temperatures. To address this, the flexural behavior of beams with lap-spliced bars after exposure to heat was examined, and the feasibility of improving their flexural performance by incorporating hybrid steel-polypropylene fibers was studied in the work. Here, 24 reinforced concrete beam specimens were constructed in 12 groups and exposed to the four-point bending test. Variables considered in the manufacturing and testing of these specimens included the splicing method (continuous reinforcement, simple lap splice, and hooked-end lap splice), concrete mix type (plain and fiber-reinforced), and exposure temperature (25 and 600 °C). Parameters under study included the load–deflection behavior, crack pattern, cracking load, ultimate load, failure mode, initial stiffness, effective stiffness, energy-absorption capacity, and ductility of the beams. The results indicated that exposing the spliced concrete beams to elevated temperatures changed the failure mode from flexural to splitting; however, adding hybrid fibers to the concrete mix improved the behavior of these members, with a more pronounced improvement in the specimens with the hooked-end splice. In addition, the simultaneous use of the hooked-end splice and hybrid fibers in the beams that had been exposed to heat prevented the splitting failure mode in these members. Furthermore, splicing the bar in the heated and unheated beam specimens lowered the energy-absorption capacity and ductility of the beams. The addition of fibers improved the energy absorption and ductility of the heated and unheated specimens, and the beams with the hooked-end splice showed a more significant improvement.

An Investigation on Eco Friendly Self-Compacting Concrete Using Spent Catalyst and Development of Structural Elements

The theme of this initiative is "Waste to Wealth." Construction materials, particularly concrete, need to have better qualities, including strength, rigidity, durability, and ductility, because Oman's construction industry is expanding. Self-compacting concrete (SCC) has more benefits than regular concrete, including better workability. The major focus of this study is the C30-grade SCC for the control mix, spent catalyst (zeolite catalyst)-based SCC, and the development of the RC beam's flexural behavior employing control and spent catalyst-based SCC. The preliminary study and the main study are the two study outcomes included in this project. Preliminary research involves creating four mixtures with various dosages of 3%, 6%, 9%, and 12% in order to optimize spent catalyst in C30 grade concrete. All of the cubes undergo a 28-day curing test. The cubes' compressive strength is tested in order to establish the ideal dosage, which is 9%. Develop a C30 grade control modified design mix in accordance with SCC and optimize chemical admixtures such as superplasticizer (SP) at different dosages, like 2, 2.5, 3, and 3.5%, using various trials and tests (slump flow, L-box, J-ring, V-funnel, and U-box tests), as well as the optimized dosage of spent catalyst (SC). The main study includes six singly reinforced RC beams with dimensions of 750 (L)×100 (B)×150 mm (D) that were cast and tested in the laboratory. After a 28-day curing period, two specimens were placed under a two-point loading setup, with the remaining two samples receiving the optimum dosages of spent catalyst and superplasticizer. All of the beams were tested using a Universal Testing Machine (UTM) with a 1000 kN capability. From the preliminary study, partial substitution of cement in control concrete of grade C30 using spent catalyst (SC), it was found that the 9% optimum dosage produces greater compressive strength compared to other doses, which are almost 10% rises at 28 days of curing period. Based on a different test, it was discovered that the optimum dose of 3% SP gave closer agreement and satisfied the need for SCC as per the BS standard. The load-carrying capability of the SCC beams is almost 21.7% higher than that of the control beams. Comparing the SCC beams to the control beams, their deflection was reduced by about 26% at the same load level, and their ductility rose by almost 33%. Comparatively to the control beam, the stiffness of 21.6% of SCC also rises. According to test results, the SCC beam performs better in every way when superplasticizer and spent catalyst are used at the recommended dosage. Doi: 10.28991/CEJ-2023-09-05-08 Full Text: PDF

Flexural behavior of concrete beams reinforced with high-strength steel bars after exposure to elevated temperatures

To study the flexural behavior of concrete beams reinforced with high-strength steel bars after exposure to elevated temperatures, flexural tests were conducted on twelve concrete beams reinforced with high-strength steel bars. The influences of exposure temperatures (room temperature, 200, 400, 600, 800, and 1000 °C), holding times (0, 1, and 2 h), yield strength grades of steel bars (600 and 500 MPa), and the number of heating sides (2 and 3 sides) on the flexural behavior of beams, including failure mode, load–deflection response, flexural bearing capacity, ductility, and concrete strain, were investigated. The results showed that all beam specimens presented flexural failure mode. When the exposure temperatures were below 600 °C, the flexural capacities changed negligibly, decreasing significantly when the exposure temperatures exceeded 800 °C. The peak loads of specimens with HRB600 bars after exposure to 800 and 1000 °C decreased by 12.9% and 38.7% relative to that under room temperature. The flexural capacities decreased more significantly when the holding time was 2 h relative to that was 0 h and 1 h, of which peak load decreased by 2.4% and 9.4%, respectively. The number of heating sides had no obvious effects on the load - deflection response of the specimens. The load - deflection curves were similar in the elastic stage and yield stage between the specimens were heated on two and three heating sides. At last, combining the temperature distribution on the cross-section obtained by the elevated temperature tests, the calculation methods on the flexural capacities of concrete beams reinforced with high-strength steel bars after exposure to elevated temperatures were proposed based on the equivalent section reduction method and the material reduction method, respectively. Comparing the calculated results with test results, a good agreement could be noted.

An experimental investigation on strength properties and flexural behaviour of ternary blended concrete

Depletion of natural resource materials has resulted from an increase in the consumption of component materials in the manufacturing of concrete. Recycling is the most effective method for dealing with the effective management of waste for preservation of the environment. Recently researchers are being conducted to utilize industrial waste by product as an admixture in the concrete production. In this study silica flour which is a waste from silica industry and waste glass powder from glass industry used for the replacement of cement. The concrete mixes were cast with replacement level such as 20%, 30% for OPC in this study. The target compressive strength of 40 MPa for the grade of M40 Concrete and specimens were casted such as cubes and beams and tested after the completion of curing to find the characteristic compressive strength and flexural behavior of beams. The compressive strength at the age of 7,14 and 28 days of curing were determined in the Compressive Testing Machine of 2000kN capacity and the results were compared and also discussions are presented on the trend of strength gain for such Ternary Blend Concrete (TBC) mixes. The RC Beams were tested in the loading frame of 500 kN Capacity and the results obtained from the testing of beam, the load versus deflection pattern were drawn and compared for various beams cast with different TBC mixes. The ductility index of the beam was calculated from load versus deflection curve. The results obtained from the investigation compared with the test specimens cast with normal concrete tested in the laboratory. From the result it is found that the TBC shall be an alternative to the conventional cement concrete and found well suitable for structural applications.

Curvature Ductility Factor of Reinforced Concrete Beams with Confinement under Different Strain Rates of Loading

The purpose of this work is to investigate the influence of confinement on the curvature ductility factor of reinforced concrete beams at low and high strain rates of loading. The curvature ductility of beams is affected by the tension reinforcement ratio, the compression-reinforced ratio, the compression strength of concrete <img src=image/14828877_01.gif>, and the yield strength of steel <img src=image/14828877_02.gif>. The degree of transverse reinforcement is another component that determines beam flexural behavior. A model of steel and restricted concrete under varying strain rates of loading was utilized to compute the curvature ductility factor. The reinforced concrete section is studied in this research to determine the confinement of the beam and the different strain rates of loading. The ratio of the volume of rectangular steel hoops to the volume of the concrete core, <img src=image/14828877_03.gif>, represents the confinement. Six values of <img src=image/14828877_03.gif> are investigated to ensure an acceptable degree of ductility capacity. It is concluded that the ACI-Code balanced reinforcement ratio is impacted by confinement, and that it is lower than the ratio achieved when confinement is present. In this work, specific values of the curvature ductility factor for beam sections constructed with the ACI code were reported for <img src=image/14828877_02.gif>=60 ksi (414 MPa), <img src=image/14828877_01.gif>=4 ksi (27.6 MPa). Furthermore, the maximum quantity of tension reinforcement max influences the curvature ductility factor.

Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

Flexural Behavior of Reinforced Concrete Beams with FRP Bars Exposed to Elevated Temperature

The present study aims to evaluate the performance of concrete beams with different Fiber Reinforced Polymer (FRP) and steel bars exposed to elevated temperatures through a detailed experimental investigation. Flexural behavior of beams is analyzed with Carbon Fiber Reinforced Polymer bars (CFRP), Basalt Fiber Reinforced Polymer bars (BFRP), Glass Fiber Reinforced Polymer bars (GFRP), and steel bars tests. Beams were exposed to elevated temperature 925 °C (1 hr) following standard fire curve, and subsequently cooled by either natural or forced water spraying. After the cooling, beam specimens were tested under four-point loading up to the failure load. Ultimate load and deflection profile of heated and unheated beams are evaluated. At higher temperatures (925 °C), the steel and GFRP specimens show a higher strength loss of about 60–80% with higher deformation values. The load carrying capacity of CFRP beams is found to be higher as compared to other types of beams. Specimens cooled by water shows higher strength loss of about 7–12% than air cooled specimens. The failure pattern of beams with FRP and steel beams are different, and it is based on heating cooling regime.

Flexural behavior of GFRP bars reinforced seawater sea sand concrete beams exposed to marine environment: Experimental and numerical study

Experimental and numerical investigations were conducted on the flexural behavior of GFRP bars reinforced seawater sea sand concrete (GFRP-reinforced SWSSC) beams after exposed to marine environment. A total of eight beams were tested by using a four-point static loading facility. Variables included the exposure environment, the exposure duration, the water for mixing and curing, and the sea sand replacement ratio. The failure process and failure modes of the specimens were observed, the load versus deflection curves and the deflection versus maximum width crack curves were obtained. The effects of various parameters on the ultimate bearing capacity, initial stiffness, and ductility coefficient were analyzed. In addition, the finite element analysis (FEA) method was used to simulate the flexural behavior of GFRP-reinforced SWSSC beams, and the parametric analysis was then conducted to investigate the effect of reinforcement ratio and shear-to-span ratio on the flexural behavior of the beam. The test results show that, after 270 days of exposure, compared with the general atmospheric environment, the ultimate bearing capacity of the specimen is increased by 28.0 % after being exposed to salt-spray environment while decreased by 13.0 % after being exposed to tidal environment. During a 270-day exposure duration to tidal environment, with the increase of the exposure duration, the ultimate bearing capacity increases first and then decreases, while both the initial stiffness and ductility coefficient of specimens decrease. The use of seawater for mixing and curing is detrimental to the initial stiffness and ductility coefficient of the specimens. The increase in sea sand replacement ratio is detrimental to specimens' ultimate bearing capacity and initial stiffness. Besides, FEA results indicate that increasing the longitudinal reinforcement ratio can obviously improve the ultimate bearing capacity and the post-cracking stiffness of the specimen. Based on the current China, America, and Canada codes, the calculation method of the flexural capacity of GFRP-reinforced SWSSC beams exposed to marine environment is discussed and the prediction value of long-term ultimate bearing capacity is given.

Flexural behavior of precast concrete beams in-span assembled with bolt-steel plate joints

The assembly of precast concrete structural components is primarily concentrated at the splicing joints of the components. Wet connections involving additional stirrups and detailing cause casting difficulties and possibly deficient joints. Herein, a new type of precast beam in-span assembled with bolt–steel plate joints (PBSPB) is proposed. A significant unique feature is the discontinuous longitudinal reinforcement in the midspan, where the U-shaped steel plate covers the web and tensile zone of the concrete beam. The steel plates and bolts are used to connect the two assembled short beams to resist both flexure and shear owing to the external effects. To investigate the effects of the steel-plate thickness and span–depth ratio on the flexural behavior of beams, a static behavior test was conducted on six PBSPBs and one cast-in-situ beam. The failure mechanisms of the PBSPBs and cast-in-situ beam were examined and compared with regard to the crack propagation, load–displacement characteristics, and strain responses. All the PBSPBs exhibited excellent performance with limited cracks under identical conditions; only minor damage was observed, which consisted of small amounts of concrete spalling and edge warping of the steel plates. Finite-element analysis (ABAQUS) models of the proposed PBSPBs were developed to verify the ultimate load and damage situations of each specimen, a simplified flexural-capacity calculation formula for the PBSPB was developed, and the theoretical results were consistent with the experimental results. The results indicated that the new precast concrete beams had favorable flexural capacities. The beam with thicker steel plates in the span had a higher strength owing to the higher stiffness. Increasing the span–depth ratio increased the ultimate load and barely affected the failure mechanism.

Flexural behavior of monolith and hybrid concrete beams produced through the partial replacement of coarse aggregate with PET waste

This study was conducted to compare the structural performance of monolith and hybrid reinforced concrete beams produced by partially replacing the coarse aggregates with polyethylene terephthalate (PET) shredded wastes. The process involved casting and testing a total of 6 beams with a dimension of 3300x150x250 mm under a four-point bending moment. The control specimens were cast using normal concrete and PET monolith specimens were fabricated using PET waste concrete. Moreover, the hybrid specimens were cast using normal concrete to a depth of 150 mm from the top and PET waste concrete at the remaining 100 mm depth at the bottom. The flexural behavior of the beams was then analyzed based on the load–deflection behavior, cracking behavior, failure mode, stiffness, and ductility. The test on the hardened concrete showed that the addition of the PET waste in the mixture reduced the compressive and tensile strength of the concrete. Moreover, the hybrid specimens were also observed to have better performance than PET monolith specimens. It was also discovered that the failure mode did not change in both PET waste monolith and hybrid specimens. Furthermore, the ultimate moment capacity of the PET waste monolith and hybrid specimens was predicted using the simple analytical model for under-reinforced concrete beams and good accuracy was obtained. The findings also showed that there is a need to consider the changes in the compressive and tensile stress distribution of concrete sections for monolith PET beams in order to extend the accuracy of the analytical model.

A Review on Flexural Behaviour of RC Beam with Nano-Silica

The partial replacement of cement with nanomaterials such as nano-silica(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 compressive strength, failure mechanisms, load-carrying capacity, and load-deflection behavior. 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 behavior 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.

Experimental and analytical investigation of using externally bonded, hybrid, fiber-reinforced polymers to repair and strengthen heated, damaged RC beams in flexure

PurposeThis study aims to conduct an experimental study and finite element model (FEM) to investigate the flexural behavior of heat-damaged beams strengthened/repaired by hybrid fiber-reinforced polymers (HFRP).Design/methodology/approachTwo groups of beams of (150 × 250 × 1,200) mm were cast, strengthened and repaired using different configurations of HFRP and tested under four-point loadings. The first group was kept at room temperature, while the second group was exposed to a temperature of 400°C.FindingsIt was found that using multiple layers of carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) enhanced the strength more than a single layer. Also, the order of two layers of FRP showed no effect on flexural behavior of beams. Using a three-layer scheme (attaching the GFRP first and followed by two layers of CFRP) exhibited increase in ultimate load more than the scheme attached by CFRP first. Furthermore, the scheme HGC (heated beam repaired with glass and carbon, in sequence) allowed to achieve residual flexural capacity of specimen exposed to 400°C. Typical flexural failure was observed in control and heat-damaged beams, whereas the strengthened/repaired beams failed by cover separation and FRP debonding, however, specimen repaired with two layers of GFRP failed by FRP rupture. The FEM results showed good agreement with experimental results.Originality/valueFew researchers have studied the effects of HFRP on strengthening and repair of heated, damaged reinforced concrete (RC) beams. This paper investigates, both experimentally and analytically, the performance of externally strengthened and repaired RC beams, in flexure, with different FRP configurations of CFRP and GFRP.

Flexural performance of layered PET fiber reinforced concrete beams

In recent years, plastic wastes represents one of the main threats to the environment. However, the use plastic fibers in concrete could be a sustainable solution to the problem of plastic waste accumulation. Moreover, the use of fibers in the production of concrete is one attempt to remedy this brittleness and to enhance other properties such as toughness and ductility. In this study, polyethylene terephthalate (PET) fibers produced from waste plastic bottles was used in reinforced concrete RC beams. PET fibers were included in concrete at two percentages (0.5% and 1% by volume). The influence of layered distributions of PET fibers in concrete on the flexural behavior of beams was also evaluated. For each mix, three layered PET fibers RC beams were prepared. Comparison with beam containing the same PET fiber percentage (full section) was presented as well. The flexural test parameters included the determination of first cracking, the yield, and the ultimate load, in addition to the deflections related to these loads. Furthermore, failure modes, toughness, and ductility were also evaluated. The use of PET fiber concrete with a layered distribution enhanced the ultimate load considerably. Moreover, the load–deflection relationships illustrated a tendency of layered PET fibers concrete beams to exhibit further deflections before failure. The toughness capacity approximately doubled for beams reinforced with 1% PET fibers concrete in the bottom quarter, bottom half, and top half sections of layered RC beams. This impressive enhancement of the flexural toughness and ductility using the layered distribution is a promising finding that could promote this type of sustainable concrete in various structural applications.

Flexural Behavior of Natural Hybrid FRP-Strengthened RC Beams and Strain Measurements Using BOTDA.

Experimental and finite element analysis results of reinforced concrete beams under monotonic loading were presented in this study. In the experimental program, one beam was tested in an as-built condition. The other two beams were strengthened using natural hybrid FRP layers in different configurations. The natural hybrid FRP composite was developed by using natural jute FRP and basalt FRP. One of the most appealing advantages of natural fiber is its beneficial impact on the environment, which is necessary for the sustainability recognition as an alternative to synthetic FRP. The hybrid FRP was applied to the bottom concrete surface in one beam, while a U-shaped strengthening pattern was adopted for the other beam. The flexural behavior of each beam was assessed through strain measurements. Each beam was incorporated with conventional strain gages, as well as the Brillouin Optical Time Domain Analysis (BOTDA) technique. BOTDA has its exclusive advantages due to its simple system architecture, easy implementation, measurement speed, and cross-sensitivity. The experimental results revealed that the beam strengthened with the U-shaped hybrid FRP composite pattern had a better flexural response than the other counterpart beams did both in terms of peak loads and maximum bottom longitudinal steel bar strains. Beams B-01 and B-02 exhibited 20.5% and 28.4% higher energy dissipation capacities than the control beam did, respectively. The ultimate failure of the control beam was mainly due to the flexural cracks at very low loads, whereas the ultimate failure mode of FRP composite-strengthened beams was due to the rupture of the hybrid FRP composite. Further, strain measurements using BOTDA exhibited similar patterns as conventional strain gage measurements did. However, it was concluded that BOTDA measurements were substantially influenced by the bottom flexural cracks, ultimately resulting in shorter strain records than those of conventional strain gages. Nonlinear structural analysis of the beams was performed using the computer program ATENA. The analytical results for the control beam specimen showed a close match with the corresponding experimental results mainly in terms of maximum deflection. However, the analytical peak load was slightly higher than the corresponding experimental value.